MIC2584/MIC2585 Dual-Channel Swap Controller/Sequencer Gener

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MIC2584/MIC2585 Dual-Channel Swap Controller/Sequencer Gener

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MIC2584/2585
MIC2584/MIC2585
Dual-Channel Swap Controller/Sequencer
General Description
MIC2584 MIC2585 dual-channel positive voltage swap controllers designed facilitate safe insertion boards into live system backplanes. MIC2584 MIC2585 available 16-pin 24-pin TSSOP packages, respectively. Using external discrete components controlling gate drives external NChannel MOSFET devices, MIC2584/85 provides inrush current limiting output voltage slew rate control harsh, critical power supply environments. Additionally, MIC2585 provides output turn-on sequencing output tracking during turn-on turn-off. combination, devices' many features provide simplified, robust solution many network applications meet power sequencing protection requirements multiple-voltage logic systems.
Features
1.0V 13.2V supply voltage operation Surge voltage protection Current regulation limits inrush current regardless load capacitance Programmable inrush current limiting Electronic circuit breaker Dual-level overcurrent fault sensing eliminates false tripping Fast response short circuit conditions 1µs) sequenced output mode selections (MIC2585 only) 250mV supply tracking mode during turn-on/turn-off (MIC2585 only) Overvoltage undervoltage output monitoring (Overvoltage MIC2585 only) Undervoltage lockout protection /FAULT status output Power-On Reset Power-Good status output (Power-Good MIC2585 only)
Applications
RAID systems Network servers Base stations Network switches Hot-board insertion
Ordering Information
Standard Part Number Pb-Free MIC2584-xYTS MIC2585-1xYTS MIC2585-2xYTS Output Sequencing OUT2 follows OUT1 OUT1 follows OUT2 Fast Circuit Breaker Threshold 100mV 150mV 200mV Package 16-pin TSSOP 24-pin TSSOP
MIC2584-xBTS MIC2585-1xBTS MIC2585-2xBTS
Contact Micrel availability.
Micrel, Inc. 2180 Fortune Drive Jose, 95131 (408) 944-0800 (408) 474-1000 http://www.micrel.com
March 2005
MIC2584/2585
MIC2584/2585
Typical Application
BACKPLANE EDGE CONNECTOR CONNECTOR VCC1 **BZX84Cxx 0.47µF RSENSE2 0.020
RSENSE1 0.006
Si7892DP (PowerPAKSO-8) CLOAD1 330µF 10.7k Si7892DP (PowerPAKSO-8)
VOUT1
VCC2 3.3V
0.47µF
CLOAD2 330µF 0.01µF
VOUT2 3.3V 1.5A
VCC2
SENSE2
VCC1
SENSE1
GATE2
105k
GATE1 OUT2 DIS2
0.01µF 4.42k 14.7k
/FAULT Signal 130k 0.047µF 30.9k
/FAULT CDLY
MIC2585-1
OUT1
DIS1 /POR
DOWNSTREAM CONTROLLER(S) Downstream Control Signals
8.06k
CPOR
CFILTER
0.02µF
0.033µF
Undervoltage (Output1) 10.5V Undervoltage (Output2) 2.95V Overvoltage (Input1) 13.2V Overvoltage (Input2) 3.65V START-UP Delay 2.5ms Delay 10ms Circuit Breaker Response Time 16ms (optional) used delay VOUT2 with respect VOUT1 VOUT2 Delay 9.5ms **D1 BZX84C18 BZX84C8V2 Resistor tolerances unless specified otherwise.
Figure Typical Application Circuit
MIC2584/2585
March 2005
MIC2584/2585
VCC2 SENSE2 GATE2 VCC1 SENSE1 GATE1 OUT1 DIS1 /POR /FAULT
Configuration
VCC2 SENSE2 GATE2 OUT2 CPOR CFILTER
VCC1 SENSE1 GATE1 OUT1 /POR /FAULT
OUT2 DIS2 CPOR CFILTER CDLY
MIC2584 16-Pin TSSOP (TS)
MIC2585 24-Pin TSSOP (TS)
Description
Number MIC2584 Number MIC2585 Name VCC1 Function Positive Supply (Input), Channel This input main supply internal circuitry must range 2.3V 13.2V. GATE1 held internal undervoltage lockout circuit until VCC1 VCC2 exceed their respective undervoltage lockout threshold 2.165V 0.8V. This input protected 20V. Positive Supply (Input), Channel GATE2 held internal undervoltage lockout circuit until VCC1 VCC2 exceed their respective undervoltage lockout threshold 2.165V 0.8V. This input must range 1.0V 13.2V less than equal VCC1. This input protected 20V. Circuit Breaker Sense (Inputs): resistor between this VCC1 VCC2 sets current limit threshold each channel. Whenever voltage across either sense resistor exceeds slow trip current limit threshold (VTRIPSLOW), GATE voltage adjusted ensure constant load current. VTRIPSLOW (50mV) exceeded longer than time period tOCSLOW, then circuit breaker tripped both GATE outputs immediately pulled low. voltage across either sense resistor exceeds fast trip circuit breaker threshold, VTRIPFAST, point fast, high amplitude power supply faults, then both GATE outputs immediately brought without delay. disable circuit breaker either channel, SENSE pins tied together. default VTRIPFAST either device 100mV. Other fast trip thresholds available: 150mV, 200mV, (VTRIPFAST disabled). Please contact factory availability other options. Enable (Input): Active High. pin, input Schmitt-triggered comparator used enable/disable controller, compared 1.235V reference with 25mV hysteresis. When logic high applied (VON 1.235V), start-up sequence begins when GATE1 GATE2 pins begin ramping towards their final operating voltage. When receives logic signal (VON 1.21V), GATE pins grounded /FAULT remains high both inputs above their respective UVLO thresholds. must least 20µs order initiate start-up sequence. Additionally, toggling HIGH resets circuit breaker.
VCC2
SENSE2, SENSE1
March 2005
MIC2584/2585
MIC2584/2585
Number MIC2584 Number MIC2585 Name GATE2, GATE1 Function
Gate Drive (Outputs): Connect each output gates external N-Channel MOSFETs. When asserted, 14µA current source activated begins charge gate N-Channel MOSFET connected this pin. internal clamp ensures that more than applied between GATE Source when VCC1 VCC2 above When circuit breaker trips when input undervoltage lockout condition detected, GATE1 GATE2 pins immediately brought low. Ground: analog ground. Power-On Reset Timer (Input): capacitor connected between this ground sets start-up delay (tSTART) power-on reset interval (tPOR). Once lagging supply rises above UVLO threshold asserts, capacitor connected CPOR begins charge. When voltage CPOR crosses 0.3V, start-up threshold (VSTART), start cycle initiated GATE outputs begin ramp while capacitor CPOR immediately discharged ground. When voltage lagging rises above threshold (VFB), capacitor CPOR begins charge again. When voltage CPOR rises above power-on reset delay threshold (VPOR) 1.235V, timer resets pulling CPOR ground /POR deasserted. CPOR then tSTART defaults 20µs. Current Limit Response Timer (Input): capacitor connected this defines period time, tOCSLOW, which overcurrent event must last signal fault condition trip circuit breaker. When overcurrent condition occurs, 2.5µA current source begins charge this capacitor. voltage this reaches 1.235V, circuit breaker tripped, both GATE pins immediately shut off, /FAULT asserted. CFILTER then tOCSLOW defaults 20µs. Power-Good Threshold Input (Undervoltage Detect): internally compared 1.235V 0.80V references with 25mV hysteresis, respectively. External resistive divider networks used voltage these pins. either input momentarily goes below threshold, then /POR activated timing cycle, tPOR, indicating output undervoltage condition. /POR signal deasserts timing cycle after exceeds power-good threshold 25mV. filter these pins prevents glitches from inadvertently activating /POR signal. Circuit Breaker Fault Status (Output): Active-Low, weak pull-up VCC1 open-drain. Asserted when circuit breaker tripped overcurrent, undervoltage lockout, overvoltage event. When deasserted, MIC2585 will initiate start cycle toggling pin. Power-On Reset (Output): Active Low, weak pull-up VCC1 open drain. This remains asserted during start-up until time period (tPOR) after lagging threshold (VFB1 VFB2) exceeded. timing capacitor CPOR determines tPOR. When output voltage monitored either falls below VFB, /POR asserted minimum timing cycle (tPOR). Output Voltage Monitor (Inputs): output tracking, connect these pins their respective output sense output voltage. Output Sequence Delay Timer (Input): This internally clamped capacitor connected this sets timer delay, tDLY, between VOUT1 VOUT2 shown Figure With this pulled VCC1 through resistor, CGATE1 CGATE2, both VOUT1 VOUT2 ramp down with same dv/dt depicted Tracking Mode diagram while maintaining maximum voltage differential between VOUT1 VOUT2. Discharge Tracking Mode (Input): this OUT1 OUT2 enable tracking during turn-off cycle. Ground this disable tracking during turn-off. used digital input.
CPOR
CFILTER
FB2,
/FAULT
/POR
OUT2, OUT1 CDLY
MIC2584/2585
March 2005
MIC2584/2585
Number MIC2584 Number MIC2585 Name OV2, Function
Overvoltage Detect Inputs: Whenever threshold voltage (VOV1, VOV2) either input exceeded, circuit-breaker tripped while /FAULT asserted GATE1 GATE2 outputs immediately brought low. Discharge Outputs: When receives logic signal (deasserts), these pins provide impedance path ground order allow discharging load capacitance. pins assert less than 0.3V once been deasserted. typical resistance varies between dependent upon input supply voltage (see Electrical Table). external resistor required. "Fast Output Discharge Capacitive Load" section Applications Information more detail. Power-Good Outputs: Active-HIGH, weak pull-up VCC1 open-drain. These outputs asserted whenever thresholds exceeded will asserted when below their thresholds.
DIS2, DIS1
PG2,
March 2005
MIC2584/2585
MIC2584/2585
Absolute Maximum Ratings (Note1)
voltages referred GND) Supply Voltage (VCC1/VCC2) -0.3V SENSE1/SENSE2 pins -0.3V VCC1/2 TRK, DIS1, DIS2, OUT1, OUT2, /POR, /FAULT, PG1, pins -0.3V GATE1/GATE2 -0.3V other input pins -0.3V DIS1/DIS2 current ±25mA Junction Temperature 125°C Rating Human body model 1500V Machine model 100V
Operating Ratings (Note
Supply Voltage VCC1 2.3V 13.2V VCC2 1.0V 13.2V Operating Temperature Range -40°C +85°C Package Thermal Resistance R(JA), 16-pin TSSOP 99.1°C/W R(JA), 24-pin TSSOP 83.8°C/W
Electrical Characteristics (Note
2.3V VCC1 13.2V, 1.0V VCC2 13.2V, 25°C unless otherwise noted. Bold values indicate -40°C 85°C. Symbol VCC1 ICC1 VCC2 ICC2 VUV1 VUV1HYS VUV2 VUV2HYS VTRIPSLOW VTRIPHYS VTRIPFAST Parameter Supply Voltage Supply Current Supply Voltage Supply Current VCC1 Undervoltage Lockout Threshold VCC1 Undervoltage Lockout Hysteresis VCC2 Undervoltage Lockout Threshold VCC2 Undervoltage Lockout Hysteresis Slow Trip Overcurrent Threshold Slow Trip Overcurrent Hysteresis Fast Trip Overcurrent Threshold VCC1 VCC2 VGATE IGATE IGATEOFF RDIS External Gate Drive (GATE1 GATE2) GATE Pull-up Current GATE Sink Current Start cycle /FAULT asserted Turn deasserted) Discharge Resistance deasserted 0.3V VCCx 2.3V VCCx 5.0V VCCx 13.2V ITMR Overcurrent Timer Charge Current Overcurrent Timer Discharge Current VTMR Overcurrent Timer Threshold VCCx VSENSEx 50mV VCCx VSENSEx 25mV -3.5 1.190 VGATEx VCCx VCC1 VCC2 VCC1 VCC2 VCCx VSENSEx, VCC1 VCC2 42.5 2.050 VCC2 VCC1 0.05 2.165 -2.5 1.235 -1.5 1.290 57.5 Condition 13.2 13.2 0.15 2.275 Units
MIC2584/2585
March 2005
MIC2584/2585
Symbol ICPOR VPOR VPORHYS VSTART VTRK VTRKOFF VFB1 VFB1HYS VFB2 VFB2HYS VOV1 VOV1HYS VOV2 VOV2HYS IDELAY VDELAY VDLYHYS VONHYS Parameter Power-on Reset Current Condition VCC1 CPOR 0.5V Start-up cycle Charge current Sink current Power-on Reset Delay Threshold Power-on Reset Delay Threshold Hysteresis Start-up Threshold Threshold (MIC2585 only) Turn-off Voltage (MIC2585 only) Threshold Threshold Hysteresis Threshold Threshold Hysteresis Threshold (MIC2585 only) Threshold Hysteresis (MIC2585 only) Threshold (MIC2585 only) Threshold Hysteresis (MIC2585 only) Delay Timer Current (MIC2585 only) Delay Timer Threshold (MIC2585 only) Delay Timer Threshold Hysteresis (MIC2585 only) Input Threshold Hysteresis Input Current /FAULT /POR PG1, Output Voltage (PG1 MIC2585 only) /FAULT /POR PG1, Active Output Pull-up Current (PG1 MIC2585 only) GATE1 GATE2 ON/OFF Voltage Window (Tracking enabled) Note VCCX IOUT 1.6mA, VCC1 1.190 VCC1 VCC2 Timer charge current Timer discharge current 1.190 0.75 1.190 0.75 Start-up cycle deasserted, IGATE 10µA VCC1 VCC2 asserted, VSENSE2 VOUT2 VCC1 VCC2 0.25 0.25 1.190 1.190 -3.5 -2.5 1.235 0.30 0.30 1.235 0.80 1.235 0.80 1.235 1.235 1.290 1.290 0.85 1.290 0.85 0.35 0.35 1.290 1.290 -1.5
Units
IPULLUP
asserted, VFB1 1.25V, VFB2 0.8V /POR VCC1 Timing Diagram (Figure
VGATEWIN
Parameters tOCFAST tOCSLOW
Note Note Note Note
Fast Overcurrent Sense GATE Trip Time Slow Overcurrent Sense GATE Trip Time
VCCx VSENSEx 100mV, CGATE 10nF Timing Diagram (Figure VCCx VSENSEx 50mV, CFILTER
Exceeding absolute maximum rating damage device. device guaranteed function outside operating rating. MIC2584, VGATEWIN specified only when asserted. Specification packaged product only.
March 2005
MIC2584/2585
MIC2584/2585
Timing Diagrams
GATE1 GATE2
GATE1 GATE2 GATE1 GATE2
100mV
GATE1 GATE2
VOUT1 VOUT2
Asserted
GATE1 GATE2 GATE1 GATE2
100mV
GATE1 GATE2
VOUT1 VOUT2
Deasserted
Figure Gate Voltage Window Tracking Mode
VTRIPFAST 50mV (VCCx VSENSEx) tOCSLOW VGATEx 0.5V 0.5V tOCFAST
Figure Current Limit Response
VSTART CPOR tSTART VOUT[1,2] VPG[1/2]
VPOR
PG[1/2]
tPOR
/POR
Figure Start-Up Cycle Timing
VOUT1 V<0.25V VOUT2 Tracking Mode, VOUT1 VOUT2 VOUT1,VOUT2 (-1) (-2) VOUT2,VOUT1 (-1) (-2) V<0.25V V<0.25V
tDLY
Sequencing/Tracking Mode, VOUT1 VOUT2 (-1) VOUT2 follows VOUT1 (-2) VOUT1 follows VOUT2
Figure Sequencing Modes (MIC2585 only)
MIC2584/2585
March 2005
MIC2584/2585
Typical Characteristics
VTRIPSLOW1+ Temperature VTRIPSLOW1- Temperature VTRIPSLOW2+
VTRIPSLOW2+ (mV)
Temperature
VTRIPSLOW1+ (mV)
VCC1 5.0V
VTRIPSLOW1- (mV)
VCC1 13.2V
5.0V
VCC1 13.2V
VCC2 1.0V VCC2 5.0V VCC2 13.2V VCC2 2.3V
VCC1 2.3V TEMPERATURE (°C)
VCC1 2.3V
TEMPERATURE (°C)
TEMPERATURE (°C)
VTRIPSLOW2- (mV)
VTRIPSLOW2- Temperature
VTRIPFAST1 (mV)
VTRIPFAST1 Temperature
VCC1 13.2V VTRIPFAST2 (mV)
VTRIPFAST2 Temperature
VCC2 1.0V VCC2 5.0V VCC2 13.2V VCC2 2.3V
VCC2 13.2V
VCC1 5.0V
VCC1 2.3V
VCC2 5.0V
VCC2 2.3V
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
VGATE1
22.5 GATE VOLTAGE_1 17.5 12.5 TEMPERATURE (°C) VCC1 2.3V VCC1 5.0V
Temperature
VCC1 13.2V GATE VOLTAGE_2
VGATE2 Temperature
22.5 VCC2 13.2V VCC2 5.0V
UVLO1 UVLO2 Temperature
UVLO1+
UVLO THRESHOLD
17.5 12.5
2.25 1.75 1.25 0.75 UVLO2- TEMPERATURE (°C) UVLO2+ UVLO1-
VCC2 2.3V
TEMPERATURE (°C)
1.26
OVERCURRENT TIMER
Overcurrent Timer Threshold Temperature
CPOR THRESHOLD1
0.32 0.31 0.29 0.28
CPOR Threshold1 (Start-Up) Temperature
VCC1 13.2V CPOR THRESHOLD2
1.28 1.26
CPOR Threshold2 Temperature
1.25 1.24 1.23
13.2V 5.0V
VCC1 5.0V
VCC1 2.3V
2.3V 1.22 1.21 TEMPERATURE (°C)
VCC2 13.2V 1.24 1.22
VCC2 5.0V
VCC2 2.3V TEMPERATURE (°C)
0.27 TEMPERATURE (°C)
March 2005
MIC2584/2585
MIC2584/2585
1.25
OVERVOLTAGE1
Overvoltage1 Temperature
VCC1 13.2V
0.85 OVERVOLTAGE2 0.83 0.81 0.79 0.77
Overvoltage2 Temperature
1.25 THRESHOLD 1.24 1.23 1.22 1.21
Threshold Temperature
VCC1=13.2V FB1+ VCC1=2.3V
1.24
VCC2 13.2V
VCC1=5.0V VCC1=5.0V
1.23 VCC1 2.3V VCC1 5.0V
1.22
0.75 VCC2 5.0V 0.73
VCC2 2.3V
VCC1=13.2V FB1- VCC1=2.3V TEMPERATURE (°C)
1.21 TEMPERATURE (°C)
0.71 TEMPERATURE (°C)
0.81 THRESHOLD 0.79 0.77 0.75
Threshold Temperature
OUTPUT VOLTAGE VCC2=13.2V VCC2=5.0V FB2+ VCC2=2.3V VCC2=2.3V FB2-
Output Voltage Temperature
GATE1 CURRENT (µA)
Gate1 Current Temperature
2.3V 5.0V 13.2V TEMPERATURE (°C)
5.0V 13.2V
VCC2=13.2V VCC2=5.0V
0.73
2.3V
0.71 TEMPERATURE (°C)
TEMPERATURE (°C)
OVERCURRENT TIMER CURRENT (µA)
OVERCURRENT TIMER CURRENT (µA)
13.2V
-2.9 -2.8 -2.7 -2.6 -2.5 -2.4 -2.3 -2.2
POWER RESET CURRENT (µA)
Overcurrent Timer Discharge Current Temperature
Overcurrent Timer Charge Current Temperature
13.2V
Power Reset Current Temperature
13.2V 5.0V
5.0V 2.3V
5.0V 2.3V
2.3V
TEMPERATURE (°C)
-2.1 TEMPERATURE (°C)
TEMPERATURE (°C)
ACTIVE OUTPUT PULL-UP CURRENT (µA)
Active Output Pull-Up Current Temperature
SUPPLY CURRENT_1 (mA)
Supply Current_1 Temperature
Supply Current_2 Temperature
VCC1 13.2V VCC1 5.0V
SUPPLY CURRENT_2 (µA)
13.2V 5.0V
VCC2 13.2V
2.3V
VCC2 5.0V
VCC1 2.3V
VCC2 2.3V
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MIC2584/2585
March 2005
MIC2584/2585
Test Circuit
VINx+
RSENSEx 0.005
IRF7822 (SO-8)
IOUT VOUTx+ RLOAD
CINx 4.7µF VINx-
VCCx MIC2585 OUTx CDLY CPOR 0.1µF SENSEx 0.01µF
CLOAD VOUTx-
CDLY (optional)
CFILTER 8200pF
(Not pins shown simplicity)
March 2005
MIC2584/2585
MIC2584/2585
Functional Characteristics
Turn-On, Staggered Mode (MIC2585-1BTS)
VCC1 VCC2 3.3V CDLY 47nF OPEN
Turn-On Delay)
VOUT1 VOUT2 2V/div
/POR 5V/div
TIME (5ms/div.)
/POR 5V/div
VOUT1 VOUT2 2V/div
2V/div
VCC1 VCC2 3.3V 220µF
5V/div
TIME (10ms/div.)
Turn-On (Channel
Turn-On (Channel
5V/div
/FAULT 5V/div
IIN1 VOUT1 2A/div 2V/div
VCC1 VCC2 3.3V 220µF
VOUT2 1V/div
/FAULT 5V/div
5V/div
VCC1 VCC2 3.3V 220µF TIME (2.5ms/div.)
IIN2 1A/div
TIME (5ms/div.)
Turn-Off (Tracking Off)
VCC1 VCC2 3.3V 2200µF 220µF
Turn-Off (Tracking
VCC1 VCC2 3.3V 2200µF 220µF
2V/div
VOUT1 /POR VOUT2 5V/div 2V/div
TIME (500µs/div.)
/POR 5V/div
VOUT1 VOUT2 2V/div
2V/div
TIME (1ms/div.)
MIC2584/2585
March 2005
MIC2584/2585
Turn-On Response (Hot Insert)
VCC1 VCC2 3.3V 250µF
Power-On Reset Response
FAULT 5V/div
VCC1 2V/div
VOUT1 2V/div
5V/div
IIN1 VOUT1 500mA/div 2V/div
22.5ms /POR 2V/div 2V/div
VCC1 VCC2 3.3V =3.5 220µF CPOR 47nF
TIME (5ms/div.)
TIME (5ms/div.)
Short-Circuit Crowbar Channel (SCR enabled through from pin-MIC2585-1BTS)
FAULT VOUT1 5V/div 5V/div
Short-Circuit Crowbar Channel (SCR enabled through from pin-MIC2585-1BTS)
/FAULT VOUT2 5V/div 2V/div
4.5A peak VCC1 VCC2 3.3V 220µF
3.88A peak
VCC1 VCC2 3.3V 220µF
IIN1 1A/div
TIME (25µs/div.)
IIN2 1A/div
TIME (10µs/div.)
Short-Circuit Response
VCC1 VCC2 3.3V open 2200µF 220µF
FAULT VGATE1 VOUT1 10V/div 10V/div 2V/div
6.04A peak
IIN1 2A/div
TIME (25µs/div.)
March 2005
MIC2584/2585
MIC2584/2585
Functional Diagram
MIC2585-J
Charge Pump SENSE1 VCC1 SENSE2 VCC2
(15) (16) (14)
GATE1
50mV 50mV 100mV 100mV 2.5µA ITMR UVLO2 0.8V UVLO1 2.165V VCC1 20µA
(10)
Charge Pump
GATE2
Down Tracking
(13)
OUT1 OUT2 DIS1
VCC1
DIS2
CFILTER
VREF 2.5µA
Logic
/FAULT
VCC1 20µA
(11)
/POR
(12)
VCC1 VREF Glitch Filter VCC1 0.8V Glitch Filter 20µA
20µA
CDLY
VCC1 2.5µA CPOR
VREF ICPOR 0.3V
0.3V
VREF
VREF
VREF
1.235V Reference numbers MIC2584 parenthesis where applicable
0.8V
MIC2584/2585
March 2005
MIC2584/2585
This second timing cycle (tPOR) begins when lagging voltage exceeds threshold (VFB). Figure "Timing Diagrams". When power supply already present (i.e., "hot swapping" condition) MIC2584/ device enabled applying logic high signal pin, GATE outputs begin ramping immediately first CPOR timing cycle bypassed. Active current regulation employed limit inrush current transient response during start-up regulating load current programmed current limit value (See "Current Limiting Dual-Level Circuit Breaker" section). following equation used determine nominal current limit value:
Functional Description
Swap Insertion When circuit boards inserted into live system backplanes supply voltages, high inrush currents result charging bulk capacitance that resides across supply pins circuit board. This inrush current, although transient nature, high enough cause permanent damage on-board components cause system's supply voltages regulation during transient period which result system failures. MIC2584 MIC2585 controller external N-Channel MOSFET devices which gate drive controlled provide inrush current limiting output voltage slew rate control during swap insertions. Power Supply VCC1 main supply input MIC2584/85 controller with voltage range 2.3V 13.2V. VCC2 supply input ranges from 1.0V 13.2V must less than equal VCC1 operation. Both inputs withstand transient spikes 20V. order ensure stability supplies, minimum capacitor from each ground recommended. Alternatively, pass filter, shown typical application circuit, used eliminate high frequency oscillations well help suppress transient spikes. Also, existence undetermined parasitic inductance absence bulk capacitance, placing Zener diode each controller ground order provide external supply transient protection strongly recommended. typical application circuit Figure Start-Up Cycle
Supply Contact Delay
ILIM
VTRIPSLOW RSENSE
50mV RSENSE
where VTRIPSLOW current limit slow trip threshold found electrical table RSENSE selected value that will desired current limit. There basic start-up modes MIC2584/85: 1)Start-up dominated load capacitance 2)start-up dominated total gate capacitance. magnitude inrush current delivered load will determine dominant mode. inrush current greater than programmed current limit (ILIM), then load capacitance dominant. Otherwise, gate capacitance dominant. expected inrush current calculated using following equation:
INRUSH IGATE
CLOAD CGATE
14µA
CLOAD CGATE
where IGATE GATE pull-up current, CLOAD load capacitance, CGATE total GATE capacitance (CISS external MOSFET external capacitor connected from MIC2584/85 GATE ground).
Load Capacitance Dominated Start-Up
During insert board into backplane when main supply (VCC1) powered from cold start, voltage rises above threshold (1.235V typical), MIC2584/85 first checks that both supply voltages above their respective UVLO thresholds. then device enabled internal 2.5µA current source begins charging capacitor CPOR 0.3V initiate start-up sequence. Once start-up delay (tSTART) elapses, CPOR pulled immediately ground separate 14µA current source begins charging each GATE output drive external MOSFET that switches VOUT. programmed contact start-up delay calculated using following equation:
this case, load capacitance (CLOAD) large enough cause inrush current exceed programmed current limit less than fast-trip threshold fast-trip threshold disabled, option). During start-up under this condition, load current regulated programmed current limit value (ILIM) held constant until output voltage rises final value. output slew rate equivalent GATE voltage slew rate computed following equation:
Output Voltage Slew Rate, dVOUT
ILIM CLOAD
START CPOR
VSTART ICPOR
0.12 CPOR (µF)
where start-up delay timer threshold (VSTART) 0.3V, Power-On Reset timer current (ICPOR) 2.5µA. Table some typical supply contact start-up delays using several standard value capacitors. each GATE voltage continues ramping toward final value (VCC VGS) defined slew rate (See Load Capacitance/Gate Capacitance Dominated Start-Up sections), second CPOR timing cycle begins 1)/FAULT high 2)CFILTER (i.e., overvoltage, undervoltage lockout, overcurrent state). March 2005
where ILIM programmed current limit value. Consequently, value CFILTER must selected ensure that overcurrent response time, tOCSLOW, exceeds time needed output reach final value. example, given MOSFET with input capacitance CISS CGATE 2000pF, CLOAD 1000µF, ILIM with input, then load capacitance dominates determined calculated INRUSH ILIM. Therefore, output voltage slew rate determined from Equation
Output Voltage Slew Rate, (dVOUT /dt)
100µF
MIC2584/2585
MIC2584/2585
resulting tOCSLOW needed achieve output approximately 2.5ms. (See "Power-On Reset, Overcurrent Timer, Sequenced Output Delays" section calculate tOCSLOW).
GATE Capacitance Dominated Start-Up
GATE outputs shut down immediately, bypassing overcurrent timer period. disable current limit circuit breaker operation, each channel's SENSE pins together CFILTER ground. Output Undervoltage Detection MIC2584/85 employ output undervoltage detection monitoring output voltage through resistive divider connected pins. During turn while voltage either below threshold (VFB), /POR asserted low. Once both voltages cross their respective threshold (VFB), 2.5µA current source charges capacitor CPOR. Once CPOR voltage reaches 1.235V, time period tPOR elapses CPOR pulled ground /POR goes HIGH. voltage either drops below more than 10µs, /POR resets least timing cycle defined tPOR (See "Applications Information" example). Input/Output Overvoltage Protection MIC2585 monitors detects overvoltage conditions event excessive supply transients MIC2585 input(s)/output(s). Whenever voltage threshold exceeded either MIC2585, circuit breaker tripped both GATE outputs immediately brought low. Power-On Reset, Overcurrent Timer, Sequenced Output Delays Power-On Reset delay, tPOR, time period /POR HIGH once lagging voltage exceeds power-good threshold (VFB) monitored pin. capacitor connected CPOR sets interval determined using Equation with VPOR substituted VSTART. resulting equation becomes:
this case, value load capacitance relative GATE capacitance small enough such that during start-up output current never exceeds current limit threshold determined Equation minimum value CGATE that will ensure that current limit never exceeded given equation below:
CGATE (Min) GATE CLOAD ILIMIT
Where CGATE summation MOSFET input capacitance (CISS) specification value capacitor connected GATE MIC2584/85 (and MOSFET) ground. Once CGATE determined, following equation determine output slew rate dVOUT/dt gate capacitance dominated start-up:
dVOUT
IGATE CGATE
Table depicts output slew rate various values CGATE.
IGATE 14µA CGATE 0.001µF 0.01µF 0.1µF dVOUT/dt 14V/ms 1.4V/ms 0.14V/ms 0.014V/ms
Table Output Slew Rate Selection GATE Capacitance Dominated Start-Up Current Limiting Dual-Level Circuit Breaker Many applications will require that inrush steady state supply current limited specific value order protect critical components within system. Connecting sense resistor between SENSE pins each channel sets nominal current limit value each channel MIC2584/85 current limit calculated using Equation MIC2584/85 also features dual-level circuit breaker triggered 50mV 100mV current limit thresholds sensed across SENSE pins. first level circuit breaker functions follows. MIC2584/85, once voltage sensed across these pins exceeds 50mV either channel, overcurrent timer, duration capacitor CFILTER, starts ramp voltage CFILTER using 2.5µA constant current source. voltage CFILTER reaches overcurrent timer threshold (VTMR) 1.235V, then CFILTER immediately returns ground circuit breaker trips both GATE outputs immediately shut down. second level, voltage sensed across SENSE either channel exceeds 100mV option) time, circuit breaker trips both
tPOR CPOR
VPOR ICPOR
CPOR (µF)
where Power-On Reset threshold (VPOR) timer current (ICPOR) typically 1.235V 2.5µA, respectively. MIC2584/85, capacitor connected CFILTER used timer which activates circuit breaker during overcurrent conditions. When voltage across either sense resistor exceeds slow trip current limit threshold 50mV, overcurrent timer begins charge period, tOCSLOW, determined CFILTER. tOCSLOW elapses, then circuit breaker activated both GATE outputs immediately pulled ground. following equation used determine overcurrent timer period, tOCSLOW.
OCSLOW CFILTER CFILTER (µF) ITMR
where VTMR, overcurrent timer threshold, 1.235V ITMR, overcurrent timer current, 2.5µA. capacitor CFILTER used, then tOCSLOW defaults 20µs.
MIC2584/2585
March 2005
MIC2584/2585
sequenced output feature enabled MIC2585 placing capacitor from CDLY ground. option allows VOUT2 follow VOUT1 option allows VOUT1 follow VOUT2 during start-up (See "Timing Diagrams, Figure 5"). sequenced output delay time determined using following equation:
tDLY CDLY DELAY CDLY (µF) IDELAY
CFILTER 220pF 680pF 1000pF 3300pF 0.01µF 0.047µF 0.1µF 0.33µF tOCSLOW 110µs 340µs 500µs 1.6ms 23.5ms 50ms 165ms
where VDELAY, CDLY threshold, typically 1.235V, IDELAY, CDLY charge current, typically 6µA, CDLY capacitor connected CDLY. Tables provide quick reference several timer calculations using select standard value capacitors. Undervoltage Lockout Internal circuitry keeps both GATE output charge pumps until VCC1 VCC2 exceed 2.165V 0.8V, respectively. CPOR 0.01µF 0.033µF 0.05µF 0.1µF 0.33µF 0.47µF tSTART 1.2ms 12ms 40ms 56ms 120ms tPOR 16.5ms 25ms 50ms 165ms 235ms 500ms
Table Selected Overcurrent Timer Delays CDLY 4700pF 0.01µF 0.047µF 0.1µF 0.33µF 0.82µF 2.2µF tDLY 950µs 9.5ms 20ms 66ms 165ms 200ms 440ms
Table Selected Sequenced Output Delays
Table Selected Power-On Reset Start-Up Delays
March 2005
MIC2584/2585
MIC2584/2585
power-down independent load capacitance each supply. "Figure "Timing Diagrams". Wiring either OUT1 OUT2 MIC2585 enables tracking feature. OUT1 OUT2 pins provide output track sensing wired directly output (source) external MOSFET Channel Channel respectively. MIC2584/85 also used systems that support more than supplies. Figure illustrates generic separate controllers configured support four independent supply rails with associated output timing response. /POR) output first controller used enable second controller. configured, fault condition either VOUT1 VOUT2 will result channels being shut down. systems with multiple power sequencing requirements, controllers' output tracking sequencing features implemented order meet system's timing demands.
Applications Information
Output Tracking Sequencing MIC2585 equipped with optional supply settings: Tracking Sequencing. There many applications that require supplies track another within specified maximum potential difference time) during powerup power-down, such switching processor off. many other systems applications, supply sequencing during turn-on essential such when specific circuit block (e.g., system clock) requires available power before another block system circuitry. either supply configuration, MIC2585 requires only additional component used integrated solution traditional, most often complex, discrete circuit solutions. Additionally, optional supply settings combined provide supply sequencing during start-up supply tracking during turn-off (see Figure below). MIC2585 guarantees supply tracking within 250mV power-
VIN1
RSENSE1 0.007
**Q1 Si4922DY (SO-8) CLOAD1 1500µF RSENSE2 0.015
VOUT1 5V@5A
(8V)
VIN2 1.8V (6V)
**Q2 Si4922DY (SO-8)
8.06k CLOAD2 100µF
VOUT2 1.8V@2A
0.022µF
VCC1
SENSE1
VCC2
SENSE2
GATE2
39.2k
OUT2
CFILTER
0.01µF
MIC2585-1
10.5k GATE1
CDLY OUT1
0.022µF
0.1µF
15.8k
Undervoltage (OUT1) 4.4V Undervoltage (OUT2) 1.5V Circuit Breaker Response Time Sequenced Output Delay 20ms *Diodes BZX84C(x)V(x) **Si4922DY dual Power MOSFET Additional pins omitted clarity
Figure Output Sequencing/Tracking Combination
MIC2584/2585
March 2005
MIC2584/2585
Fast Output Discharge Capacitive Loads many applications where switch controller turned either removing from backplane reset, capacitive loading will cause output retain voltage unless `bleed' (low impedance) path place order discharge capacitance. MIC2585 equipped with internal MOSFET that allows discharging load capacitance ground through path. discharge feature configured wiring output (source) external MOSFET enabled below 0.3V after controller been disabled logic signal received Figure "Typical Application" circuit Figure series resistor required from VOUT that maximum current 25mA exceeded.
Output Turn-Off Sequencing Tracking There many applications where necessary desirable supply rails sequence during turn-on turnoff, case with some microprocessor requirements. MIC2585 configured allow output shut first, followed other output. Figure illustrates example circuit that sequences OUT1 OUT2 first last application. During start-up, capacitor CDLY allows VOUT1 turn followed VOUT2 20ms later. Once receives signal removing from backplane, external processor signal, DIS1 DIS2 will assert low. external crowbar circuit connected from DIS2 will immediately bring VOUT2 ground while VOUT1 will discharge ground through (680 external, internal) series path.
VIN1
MIC2585 GATE1
OUT1
VOUT1 VIN2
VOUT1/VOUT2 Short Circuit VOUT1
/FAULT GATE2 OUT2
VOUT2
VIN3
MIC2585 GATE1 OUT1
/FAULT
VOUT3 VIN4
VOUT3/VOUT4 System Timing
GATE2 /FAULT OUT2
VOUT4
Figure Supporting More Than Supplies
March 2005
MIC2584/2585
MIC2584/2585
RSENSE1 0.012
IRF7822 (SO-8) CLOAD1 220µF RSENSE2 0.012
VIN1 (8V)
VOUT1 5V@2.5A
VIN2 3.3V (8V)
IRF7822 (SO-8) CLOAD2 220µF 20.5k
VOUT2 3.3V@2.5A
VCC1
SENSE1
VCC2
SENSE2
GATE2
0.022µF
OUT2
8.66k
3.6k
39.2k
MIC2585-1
CFILTER
DIS2
1.5k
ZTX788A
0.01µF
0.033µF
TCR22-4
GATE1
CDLY DIS1 OUT1
0.1µF
0.022µF
Undervoltage (OUT1) 4.4V Undervoltage (OUT2) 2.85V Circuit Breaker Response Time Sequenced Output Delay (Turn-On) 20ms *Dual package Diode AZ23C8V2 Resistors unless specified otherwise Additional pins omitted clarity
15.8k
Figure First On-Last Application Circuit Output Undervoltage Detection output undervoltage detection, first consideration establish output voltage level that indicates "power good." this example, output value which supply will signal "good" 10.5V. Next, consider tolerances input supply threshold (VFB). this example, given supply Channel resulting output voltage 11.4V high 12.6V. Additionally, threshold ±50mV tolerance 1.19V high 1.29V. Thus, determine values resistive divider network (R12 R13) pin, shown typical application circuit page following iterative design procedure. Choose limit current through divider approximately 100µA less. Next, determine using output "good" voltage 10.5V following equation: (R12 R13) VOUT1(Good) VFB1(MAX) (10)
Using some basic algebra simplifying Equation isolate R12, yields:
OUT1(Good) VFB1(MAX)
(10.1)
1.29V 12.9k 100µA 100µA chosen 14.7k
VFB1(MAX)
where VFB1(MAX) 1.29V, VOUT1(Good) 10.5V, 14.7k. Substituting these values into Equation 10.1 yields 104.95k. standard 105k selected. Now, consider 11.4V minimum output voltage, lower tolerance higher tolerance R12, 14.55k 106.05k, respectively. With only 11.4V available, voltage sensed exceeds VFB1(MAX), thus /POR (MIC2585) signals will transition from HIGH, indicating "power good" given worse case tolerances this example. similar approach should used Channel March 2005
MIC2584/2585
MIC2584/2585
Input Overvoltage Protection similar design approach previous Undervoltage Detection example recommended overvoltage protection circuitry, resistors OV1, Figure input overvoltage protection, first consideration establish input voltage level that indicates overvoltage triggering system (output voltage) shut down. example, input value which Channel supply will signal "output shutdown" 13.2V (+10%). Similarly, from previous example: Choose satisfy 100µA condition.
voltage sensed below VOV1(MIN), MIC2584/85 will indicate overvoltage condition until VCC1 exceeds approximately 13.2V considering given tolerances. similar approach should used Channel Connection Sense There several configuration options MIC2584/85's detect been fully seated backplane before initiating start-up cycle. Figure MIC2584/85 mounted with resistive divider network connected pin. connected short edge connector. Until connectors mate, held which keeps GATE output charge pump off. Once connectors mate, resistor network pulled input supply, this example, voltage exceeds threshold (VON) 1.235V MIC2584/85 initiates start-up cycle. Figure connection sense consisting discrete logic-level MOSFET resistors allows interrupt control from processor other signal controller shut output MIC2584/85. pulls GATE held until connectors fully mated. Once connectors fully mate, logic /ON_OFF signal turns allows pull above threshold initiate start-up cycle. Applying logic HIGH /ON_OFF signal will turn short MIC2584/85 ground which turns GATE output charge pump.
1.19V 11.9k 100µA 100µA chosen 13.0k Thus, following previous example substituting R13, respectively, VOV1(MIN) VFB1(MAX), 13.2V overvoltage 10.5V output "good," same formula yields 131.2k. nearest standard value 130k. Now, consider 12.6V maximum input voltage (VCC1 +5%), higher tolerance lower tolerance 13.13k 128.7k, respectively. With 12.6V input,
VOV1(MIN)
Backplane Edge Connector Connector
VIN1
Long
RSENSE1 0.005
Si7892DP (PowerPAKSO-8)
VOUT1 5V@7A
CLOAD1 1000µF
VCC1
SENSE1 GATE1
/ON_OFF
0.01µF
27.4k
MIC2584 Short Connection Sense
OUT1
/FAULT
Medium Short
/FAULT CPOR
/POR
Downstream Signal
10.5k
CFILTER
Long
0.033µF
0.01µF
Undervoltage (Output) 4.45V /POR Delay 16.5ms START-UP Delay Circuit Breaker Response Time TN0201T (SOT-23) Channel additional pins omitted clarity.
Figure Connection Sense with ON/OFF Control March 2005 MIC2584/2585
MIC2584/2585
Higher UVLO Setting Once inserted into backplane (power supply), internal UVLO circuit MIC2584/85 holds GATE output charge pump until VCC1 exceeds 2.165V VCC2 exceeds 0.8V. VCC1 falls below 1.935V VCC2 falls below 0.77V, UVLO circuit pulls GATE output ground clears overvoltage and/or current limit faults. higher UVLO threshold, circuit Figure used delay output MOSFET from switching until desired input voltage achieved. circuit allows charge pumps remain until exceeds 1.235V provided that VCC2 exceeded threshold. Both GATE drive outputs will shut down when 1.21V example circuit VIN1 falls below rising UVLO threshold approximately 9.0V falling UVLO threshold established 8.9V. circuit consists external resistor divider that keeps both GATE output charge pumps until voltage exceeds threshold (VON) after startup timer elapses. Swap Power Control DSPs designing power supplies dual supply logic devices, such DSP, consideration should given system timing requirements core voltages powerup power-down operations. When power provided core circuit blocks unpredictable manner, effects detrimental life cycle logic device allowing unexpected current flow core isolation structures. Additionally, contention critical system-level issues supporting need power supply sequencing. Since core supplies logic control bus, powering before core result both attached peripheral device
VIN1 (18V) 154k
being simultaneously configured outputs. this case, output drivers each device contend control over sending data along which cause excessive current flow paths shown bidirectional port Figure Upon powering down system, core voltage supply should turn after control signal(s) enter indeterminate state core powered down first. Thus, power sequencing dual supply voltage implementing MIC2585 VCORE VI/O), circuit similar Figure recommended with core voltage supplied through Channel voltage supplied through Channel systems with VCORE VI/O, MIC2585-2 option with voltage through Channel core through Channel used implement first on-last application. Sense Resistor Selection MIC2584 MIC2585 low-value sense resistor measure current flowing through MOSFET switch (and therefore load). This sense resistor nominally 50mV/ILOAD(CONT). accommodate worst-case tolerances both sense resistor (allow over time temperature resistor with initial tolerance) still supply maximum required steady-state load current, slightly more detailed calculation must used. current limit threshold voltage (i.e., "trip point") MIC2584/85 42.5mV, which would equate sense resistor value 42.5mV/ILOAD(CONT). Carrying numbers through case where value sense resistor high yields:
RSENSE(MAX)
(1.03)(ILOAD(CONT)
42.5mV
41.3mV ILOAD(CONT) (11)
Once value RSENSE been chosen this manner, good practice check maximum ILOAD(CONT) which circuit through case tolerance build-up
IRF7822 (SO-8)
RSENSE1 0.010
VOUT1 12V@4A CLOAD1 1000µF
GATE1
VCC1
SENSE1
133k
0.01µF MIC2584
24.3k
16.2k
Undervoltage Lockout Threshold (rising) 9.0V Undervoltage Lockout Threshold (falling) 8.9V Undervoltage (Output) 11.4V Channel additional pins omitted clarity.
Figure Higher UVLO Setting MIC2584/2585 March 2005
MIC2584/2585
opposite direction. Here, worst-case maximum current found using 57.5mV trip voltage sense resistor that value. resulting equation
ILOAD(CONT,MAX)
MOSFET Voltage Requirements first voltage requirement MOSFET easily stated: drain-source breakdown voltage MOSFET must greater than VIN(MAX). instance, input reasonably expected high-frequency transients high 18V. Therefore, drain-source breakdown voltage MOSFET must least 19V. ample safety margin standard availability, closest minimum value will 20V. second breakdown voltage criterion that must subtler than simple drain-source breakdown voltage, hard meet. MIC2584/85 applications, gate external MOSFET driven approximately internal output MOSFET (again, assuming operation). same time, output external MOSFET (its source) suddenly subjected short, gate-source voltage will (20V 20V. This means that external MOSFET must chosen have gate-source breakdown voltage more, which available standard maximum value. However, operation above 12V, gate-source maximum will likely exceeded. result, external Zener diode clamp should used prevent breakdown external MOSFET when operating voltages above 10V. Zener diode with rating recommended shown Figure present time, most power MOSFETs with gate-source voltage rating have drain-source breakdown rating higher. general tip, choose surface-mount devices with drain-source rating starting point. Finally, external gate drive MIC2584/85 requires low-voltage logic level MOSFET when operating voltages lower than There 2.5V logic level MOSFETs available. Table "MOSFET Sense Resistor Vendors" suggested manufacturers.
(0.97)(RSENSE(NOM)
57.5mV
59.3mV RSENSE(NOM) (12)
example, output must carry continuous without nuisance trips occurring, Equation yields: RSENSE(MAX) 41.3mV 6.88m next lowest standard value other tolerance extremes output question, 59.3mV 9.88A Knowing this final da6.0m tum, determine necessary wattage sense resistor using I2R, where will ILOAD(CONT, MAX), will (0.97)(RSENSE(NOM)). These numbers yield following: PMAX (9.88A)2 (5.82m) 0.568W. this example, sense resistor sufficient. MOSFET Selection ILOAD(CONT,MAX) Selecting proper external MOSFET with MIC2584/85 involves three straightforward tasks: Choice MOSFET which meets minimum voltage requirements. Selection device handle maximum continuous current (steady-state thermal issues). Verify selected part's ability withstand peak currents (transient thermal issues).
CORE SUPPLY (VCC)
SUPPLY (VDD)
Data OUTPUT DRIVER CIRCUIT BLOCK OUTPUT DRIVER CIRCUIT BLOCK
Data
Data
Data
External Control CORE Dual Supply
TX_/RX
Peripheral
Figure Bidirectional Port Contention March 2005 MIC2584/2585
MIC2584/2585
MOSFET Steady-State Thermal Issues selection MOSFET meet maximum continuous current fairly straightforward exercise. First, yourself with following data: value ILOAD(CONT, MAX.) output question (see "Sense Resistor Selection"). manufacturer's data sheet candidate MOSFET. maximum ambient temperature which device will required operate. knowledge about heat sinking available device (e.g., heat dissipated into ground plane power plane, using surface-mount part? airflow available?). data sheet will almost always give value resistance given MOSFET gate-source voltage 4.5V, another value gate-source voltage 10V. first approximation, values together divide on-resistance part with enhancement. Call this value RON. Since heavily enhanced MOSFET acts ohmic (resistive) device, almost that's required determine steady-state power dissipation calculate I2R. addendum this that MOSFETs have slight increase with increasing temperature. good approximation this value 0.5% increase rise junction temperature above point which initially specified manufacturer. instance, selected MOSFET calculated 25°C, actual junction temperature ends 110°C, good first operating value would
10m[1 (110 25)(0.005)] 14.3m final step make sure that heat sinking available MOSFET capable dissipating least much power (rated °C/W) that with which MOSFET's performance specified manufacturer. Here practical tips: heat from surface-mount device such SO-8 MOSFET flows almost entirely drain leads. drain leads soldered down square inch more, copper will heat sink part. This copper must same layer board MOSFET drain. Airflow works. Even (linear feet minute) will cool MOSFET down substantially. can, position MOSFET(s) near inlet power supply's fan, outlet processor's cooling fan. best test surface-mount MOSFET application (assuming above tips show likely fit) empirical one. Check MOSFET's temperature actual layout expected final circuit, full operating current. thermocouple drain leads, infrared pyrometer package, will then give reasonable idea device's junction temperature. MOSFET Transient Thermal Issues Having chosen MOSFET that will withstand imposed voltage stresses, worse case continuous power dissipation which will see, remains only verify MOSFET's ability handle short-term overload power dissipation without overheating. MOSFET handle much
IRF7822 (SO-8)
(18V)
RSENSE1 0.006
1N5240B CLOAD1 220µF
VOUT 12V@6A
VCC1
SENSE1 GATE1
100k
0.01µF MIC2584
/POR CPOR
DOWNSTREAM SIGNAL
13.3k
0.05µF Undervoltage (Output) 11.0V /POR Delay 25ms START-UP Delay *Recommended MOSFETs with gate-source breakdown less catastrophic output short circuit protection. (IRF7822 VGS(MAX) 12V) Channel additional pins omitted clarity.
Figure Zener Clamped MOSFET Gate MIC2584/2585 March 2005
MIC2584/2585
higher pulsed power without damage than continuous dissipation ratings would imply. reason this that, like everything else, thermal devices (silicon die, lead frames, etc.) have thermal inertia. terms related directly specification power MOSFETs, this known "transient thermal impedance," Z(J-A). Almost power MOSFET data sheets give Transient Thermal Impedance Curve. example, take following case: 12V, tOCSLOW been 100msec, ILOAD(CONT. MAX) 1.2A, slow-trip threshold 50mV nominal, fast-trip threshold 100mV. output accidentally connected load, output current from MOSFET will regulated 1.2A 100ms (tOCSLOW) before part trips. During that time, dissipation MOSFET given EMOSFET [12V-(1.2A)(6)] 4.8V PMOSFET (4.8V 1.2A) 5.76W 100msec. first glance, would appear that really hefty MOSFET required withstand this sort fault condition. This where transient thermal impedance curves become very useful. Figure shows curve Vishay (Siliconix) Si4410DY, commonly used SO-8 power MOSFET. Taking simplest case first, we'll assume that once fault event such question occurs, will long time, minutes more, before fault isolated channel reset. such case, approximate this "single pulse" event, that say, there's significant duty cycle. Then, reading from X-axis point where "Square Wave Pulse Duration" equal 0.1sec (=100msec), that Z(J-A) this MOSFET highly infrequent event this duration only continuous R(J-A). This particular part specified having R(J-A) 50°C/W intervals seconds less. Thus: Assume 55°C maximum, square inch copper drain leads, airflow.
Recalling from previous approximation hint, part (0.0335/2) 25°C. Assume been carrying just about 1.2A some time. When performing this calculation, sure highest anticipated ambient temperature (TA(MAX)) which MOSFET will operating starting temperature, find operating junction temperature increase (TJ) from that point. Then, shown next, final junction temperature found adding TA(MAX) Since this closedform equation, getting close approximation take iterations, it's hard calculation perform, tends converge quickly. Then starting (steady-state)TJ TA(MAX) TA(MAX) [RON (TA(MAX) TA)(0.005/°C)(RON)] R(J-A) 55°C [17m (55°C-25°C)(0.005)(17m)] (1.2A)2 (50°C/W) (55°C (0.02815W)(50°C/W) 54.6°C Iterate calculation once this value within percent expected final value. this iteration will start with equal already calculated value 54.6°C: [17m (54.6°C-25°C)(0.005)(17m)] (1.2A)2 (50°C/W) 55°C (0.02832W)(50°C/W) 56.42°C original approximation 56.4°C very close correct value. will 56°C. Finally, (5.76W)(50°C/W)(0.08) 23°C steady-state TJ(TRANSIENT MAX.) 79°C. This acceptable maximum junction temperature this part.
Normalized Thermal Transient Impedance, Junction-to-Ambient
Normalized Effective Transient Thermal Impedance
Duty Cycle
Notes:
0.05
Duty Cycle, Unit Base RthJA
0.02 Single Pulse 0.01 10-4 10-3 10-2 10-1
PDMZthJA(t) Surface Mounted
Square Wave Pulse Duration (sec)
Figure Transient Thermal Impedance
March 2005
MIC2584/2585
MIC2584/2585
Layout Considerations Because values sense resistors used with MIC2584/85 controllers, special attention layout must used order device's circuit breaker function operate properly. Specifically, 4-wire Kelvin connection accurately measure voltage across RSENSE highly recommended. Kelvin sensing simply means making sure that voltage drops power traces connecting resistors does picked traces themselves. Additionally, these Kelvin connections should isolated from other signal traces avoid introducing noise onto these sensitive nodes. Figure illustrates recommended, multi-layer layout RSENSE, Power MOSFET, timer(s), feedback network connections. feedback network resistor values selected
application. Many swap applications will require load currents several amperes. Therefore, power (VCC Return) trace widths need wide enough allow current flow while rise temperature given copper plate (e.g., 1oz. 2oz.) kept maximum 10°C 25°C. Also, these traces should short possible order minimize drops between input load. starting point, there many trace width calculation tools available such following link: Finally, plated-through vias will needed make circuit connections power ground planes when utilizing multi-layer boards.
Current Flow Load *SENSE RESISTOR (2512)
Current Flow Load *POWER MOSFET (SO-8)
**RGATE **CGATE
plane
SENSE1
VCC1
OUT1
GATE1
/POR
DRAWING SCALE Similar considerations should used Channel *See Table part numbers vendors. **Optional components. Trace width guidelines given "PCB Layout Recommendations" section datasheet.
Figure Recommended Layout Sense Resistor, Power MOSFET Feedback Network
MIC2584/2585
MIC2584
Current Flow from Load
/FAULT
12.4k plane
93.1k
March 2005
MIC2584/2585
MOSFET Sense Resistor Vendors Device types manufacturer contact information power MOSFETs sense resistors provided Table Some recommended MOSFETs include metal heat sink bottom side package that connected drain
leads. recommended trace MOSFET gate Figure must redirected when using MOSFETs packaged this style. Contact device manufacturer package information.
MOSFET Vendors Vishay (Siliconix)
MOSFET Type(s) Si4420DY (SO-8 package) Si4442DY (SO-8 package) Si3442DV (SO-8 package) Si7860DP (PowerPAKSO-8) Si7892DP (PowerPAKSO-8) Si7884DP (PowerPAKSO-8) SUB60N06-18 (TO-263) SUB70N04-10 (TO-263) IRF7413 (SO-8 package) IRF7457 (SO-8 package) IRF7822 (SO-8 package) IRLBA1304 (Super220TM) FDS6680A (SO-8 package) FDS6690A (SO-8 package) PH3230 (SOT669-LFPAK) HAT2099H (LFPAK)
*Applications IOUT IOUT 10A-15A, IOUT IOUT IOUT IOUT IOUT 20A, IOUT 20A, IOUT IOUT IOUT 10A-15A, IOUT 20A, IOUT IOUT 10A, IOUT IOUT
Contact Information www.siliconix.com (203) 452-5664
International Rectifier
www.irf.com (310) 322-3331
Fairchild Semiconductor Philips Hitachi
www.fairchildsemi.com (207) 775-8100 www.philips.com www.halsp.hitachi.com (408) 433-1990
These devices limited these conditions many cases, these conditions provided helpful reference customer applications.
Resistor Vendors Vishay (Dale)
Contact Information (203) 452-5664 "OARS" Series "LR" Series www.irctt.com/pdf_files/LRC.pdf (second source "WSL") (828) 264-8861 Table MOSFET Sense Resistor Vendors
Sense Resistors "WSL" Series
March 2005
MIC2584/2585
MIC2584/2585
Package Information
Rev.
16-Pin TSSOP (TS)
4.50 (0.177) (0.252) 4.30 (0.169)
DIMENSIONS: (INCH)
0.30 (0.012) 0.19 (0.007) 7.90 (0.311) 7.70 (0.303)
1.10 (0.043)
0.20 (0.008) 0.09 (0.003)
0.65 (0.026)
0.15 (0.006) 0.05 (0.002)
1.00 (0.039) 0.70 (0.028) 0.50 (0.020)
24-Pin TSSOP (TS)
MICREL, INC. 2180 FORTUNE DRIVE JOSE, 95131
(408) 944-0800
(408) 474-1000
http://www.micrel.com
information furnished Micrel this datasheet believed accurate reliable. However, responsibility assumed Micrel use. Micrel reserves right change circuitry specifications time without notification customer. Micrel Products designed authorized components life support appliances, devices systems where malfunction product reasonably expected result personal injury. Life support devices systems devices systems that intended surgical implant into body support sustain life, whose failure perform reasonably expected result significant injury user. Purchaser's sale Micrel Products life support appliances, devices systems Purchaser's risk Purchaser agrees fully indemnify Micrel damages resulting from such sale. 2005 Micrel, Incorporated.
MIC2584/2585
March 2005

MIC2584/MIC2585 Dual-Channel Swap Controller/Sequencer Gener

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