AAT1154 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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AAT1154 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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1MHz Buck DC/DC Converter General Description
AAT1154 SwitchRegis member AnalogicTechTM's Total Power ManagementIC product family. Step-down switching converter ideal applications where high efficiency, small size, ripple critical. Able deliver with internal power MOSFET, current-mode controlled provides high efficiency. Fully internally compensated, AAT1154 simplifies system design lowers external part count. AAT1154 available SOP-8 package, rated over 85°C.
AAT1154
SwitchReg
Range: 2.7-5.5Volts Fixed adjustable VOUT: 1.0V 4.2V output current efficiency Integrated resistance power switch Internally compensated current mode control 1MHz switching frequency Fixed adjustable VOUT: 4.2V Constant mode output ripple with light load Internal softstart Current limit protection Over-Temperature protection SOP-8 package 85°C Temperature Range
Applications
Computer Peripherals Boxes Network Cards Cable/DSL Modems High efficiency conversion from 3.3V supply
Typical Application
INPUT
10µF
AAT1154
1.5µH
ENABLE 0.1µF 120µF OUTPUT
1154.2004.08.1.2
1MHz Buck DC/DC Converter Descriptions
AAT1154
Symbol
Function
Feedback input pin. This must connected converter's output. used output converter regulate desired value. Ground connection. Enable input pin. When connected high, AAT1154 normal operation. When connected low, powered down. This should left floating. Power supply. supplies power internal circuitry. Input Supply Voltage converter power stage. Inductor connection pins. These pins should connected output inductor. Internally, pins connected drain P-channel switch.
Configuration
SO-8
1154.2004.08.1.2
1MHz Buck DC/DC Converter Absolute Maximum Ratings
Symbol
VCC, VESD
AAT1154
(TA=25°C unless otherwise noted) Value
-0.3 VP+0.3 -0.3 VCC+0.3 -0.3 VCC+0.3 3000
Description
VCC, Operating Junction Temperature Range Rating
Units
Note: Stresses above those listed Absolute Maximum Ratings cause permanent damage device. Functional operation conditions other than operating conditions specified implied. Only Absolute Maximum rating should applied time. Note Human body model 100pF capacitor discharged through 1.5K resistor into each pin.
Thermal Characteristics
Symbol
Description
Thermal Resistance Maximum Power Dissipation 25°C)
Value
Units
°C/W
Note Mounted demo board (FR4, still air). Note Derate 9.1mW/°C above 25°C.
Recommended Operating Conditions
Symbol
Description
Ambient Temperature Range
Rating
Units
1154.2004.08.1.2
1MHz Buck DC/DC Converter Electrical Characteristics
values 25°C) Symbol
VOUT VUVLO VUVLO(HYS) ISHDN ILIM RDS(ON)L VOUT (VOUT*VIN) VOUT/VOUT FOSC VEN(L) VEN(H) THYS
AAT1154
(VIN 85°C unless otherwise noted. Typical
Description
Input Voltage Range Output Voltage Tolerance Under Voltage Lockout Under Voltage Lockout Hysteresis Quiescent Supply Current Shutdown Current Current Limit High Side Switch Resistance Efficiency Load Regulation Line Regulation Oscillator Frequency Enable Threshold Enable Threshold High Over Temp Shutdown Threshold Over Temp Shutdown Hysteresis
Conditions
VOUT 5.5V, IOUT Rising Falling Load, VFB= VIN= 5.5V 25°C 25°C IOUT ILOAD VIN= 5.5V 25°C
Units
-5.0 ±2.6 0.75 1000
1154.2004.08.1.2
1MHz Buck DC/DC Converter Typical Characteristics
RDS(ON) Temperature
AAT1154
Oscillator Frequency Variation Supply Voltage
2.7V
4.2V Variation
0.25
RDS(ON)
3.6V
5.5V
-0.25
-0.5
Temperature (°C)
Input Voltage
RDS(ON) VIN,
Oscillator Frequency Variation Temperature
RDS(ON)
Variation
Input Voltage
Temperature (°C)
Enable Threshold Input Voltage
Output Voltage Temperature IOUT=2A
Enable Threshold
Variation
EN(H)
-0.2 -0.4 -0.6 -0.8
EN(L)
Input Voltage
Temperature (°C)
1154.2004.08.1.2
1MHz Buck DC/DC Converter Typical Characteristics
Line Regulation VOUT=3.3V
AAT1154
Over Temp Current Input Voltage VOUT 3.3V
Output Current
Output Voltge Error
0.3A
70°C
85°C 100°C
3.75 4.25 4.75 5.25
3.0A
Input Voltage
Input Voltage
Load Regulation 5.0V, 3.3V
-1.0
Non-Switching Operating Current Temperature
Operating Current (mA)
5.5V
5.0V
Output Error
-2.0 -3.0 -4.0 -5.0 -6.0 -7.0 -8.0 -9.0 -10.0 0.01
4.2V
3.6V 2.7V
Load Current
Temperature (°C)
Over Temp Shutdown Current Temperature VOUT 3.3V, 5.0V, 1.5µH
Inrush Output Overshoot Characteristic Load
Inductor Current
Output Current
Voltage (bottom traces)
Current (top trace)
Input Output
Temperature (°C)
Time (millisec)
1154.2004.08.1.2
1MHz Buck DC/DC Converter Typical Characteristics
Inrush Output Overshoot Characteristic Load
AAT1154
Output Ripple IOUT 3.0A, VOUT 3.3V, 5.0V
Inductor Current
Output Ripple (mV)
Voltage (bottom traces)
Inductor Current bottom
Current (top trace)
Input Output
6.3VCeramic C3325X5R0J107M
Time (millisec)
Time (µsec)
Output Ripple IOUT 3.0A, VOUT 3.3V, 5.0V
Output Ripple (top) (mV)
Tantalum Output Ripple IOUT 3.0A, VOUT 3.3V, 5.0V
-100 -120
Inductor Current (bottom)
Output Ripple (top) (mV)
Inductor Current (bottom)
6.3V Ceramic C3325X5R0J107M
6.3V Tantalum Vishay 594D127X96R3C2T
Time (µsec)
Time (µsec)
Loop Crossover Gain Phase
Loop Crossover Gain Phase
6.3V Tantalum Vishay 594D127X96R3C2T Phase
Phase (Degrees)
Phase (Degrees)
Phase
Gain (dB)
Gain (dB)
10000
100µF 100µF 100µF 6.3V Ceramic C3225X5R0J107M
-135 -180 100000
Gain
-135 -180 100000
10000
Frequency (Hz)
Frequency (Hz)
1154.2004.08.1.2
1MHz Buck DC/DC Converter Typical Characteristics
Transient Response IOUT 3.0A, VOUT 3.3V, 5.0V
100µF 6.3V Ceramic C3325X5R0J107M
AAT1154
Transient Response IOUT 3.0A, VOUT 3.3V, 5.0V
6.3V Ceramic C3325X5R0J107M
Inductor Current (bottom)
Inductor Current (bottom)
Output Voltage (top) (mV)
-200 -300 -400 -500 -600 -700
Output Voltage (top) (mV)
-100
-100 -200 -300 -400 -500 -600 -700
Time (µs)
Time (µs)
Tantalum Transient Response IOUT 3.0A, VOUT 3.3V, 5.0V
Inductor Current (bottom)
Output Voltage (top) (mV)
-100 -200 -300 -400 -500 -600 -700 120µF 6.3V Tantalum Vishay 594D127X96R3C2T
Time (µs)
1154.2004.08.1.2
1MHz Buck DC/DC Converter Functional Block Diagram
2.7V- 5.5V
AAT1154
LOGIC
Temp. Sensing
Applications Information
Main Control Loop
AAT1154 peak current mode buck converter. inner wide bandwidth loop controls inductor peak current. inductor current sensed flows through internal P-Channel MOSFET. fixed slope compensation signal then added sensed current maintain stability duty cycles greater than 50%. inner loop appears voltage programmed current source parallel with output capacitor. voltage error amplifier output programs current loop necessary inductor current force constant output voltage load line conditions. feedback resistive divider internal, dividing output voltage error amplifier reference voltage 1.0V. error amplifier limited gain. This eliminates need external compensation components while still providing sufficient loop gain good load regulation.
crossover frequency phase margin output capacitor value. Duty cycle extends 100% input voltage approaches output voltage. Thermal shutdown protection disables device event short circuit overload condition.
Soft Start/Enable
Soft-start controls current limit when input voltage enable applied. limits current surge seen input eliminates output voltage overshoot. enable input, when pulled low, forces device into power non-switching state. total input current during shutdown less than 1µA.
Power Signal Source
Separate small signal ground power supply pins isolate internal control circuitry from switching noise. addition, pass filter figure filters noise associated with power switching.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
Current Limit Over Temp Protection
AAT1154 over temp current limit circuitry protects AAT1154 well external Schottky diode during overload, short circuit excessive ambient temperature conditions. junction over temp threshold 140°C nominal 15°C hysteresis. Typical graphs over temp load current input voltage ambient temperature shown Typical Characteristics section.
AAT1154
factor fraction full load (30%) selected ripple current maximum input voltage. corresponding inductor current
IRMS
Inductor
output inductor selected limit ripple current 20-40% full load current maximum input voltage. Manufacturer's specifications list both inductor current rating, which thermal limitation, peak current rating, which determined inductor saturation characteristics. inductor should show appreciable saturation under normal load conditions. During overload short circuit conditions inductor exceed peak current rating without affecting converter performance. Some inductors have sufficient peak average current ratings result excessive losses high resistance (DCR). losses associated with affect total converter efficiency must considered. load ripple current maximum input voltage, maximum peak peak ripple current 0.9Amp. Assuming input voltage ripple output inductance required
VOUT VOUT VIN(MAX)
peak peak ripple current which fixed inductor selection above. peak peak current full load current peak current full load will 115% full load. 1.5µH inductor selected from Sumida CDRH6D38 series current rating with height full load inductor loss loss efficiency.
Schottky Freewheeling Diode
Schottky average current load current times minus duty cycle. Volts Vout Volts average diode current
3.3V 5.0V
With 125°C maximum junction temperature 120°C/W thermal resistance maximum average current
IAVG J(MAX)- 125°C 70°C 1.14A 0.4V
VFWD
3.3V 3.3V 3.0A 1MHz 5.25V
1.36µH
overload, short circuit, excessive ambient conditions AAT1154 enters over-temperature shutdown mode protecting AAT1154 well output Schottky. this mode output current limited internally until junction temperature reaches temperature limit (see over temp characteristics graphs). diode reverse voltage must rated withstand input voltage.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
Diodes Inc. ROHM Micro Semi B340LA RB050L-40 5820SM 0.45V@3A 0.45@3A 0.46V@3A
AAT1154
IRMS
VOUT+ VFWD) (VIN VOUT)
Surface Mount Schottky Diodes
Input Capacitor Selection
primary function input capacitor provide impedance loop edges pulsed current drawn AAT1154. ESR/ESL ceramic capacitor ideal this function. minimize stray inductance capacitor should placed close possible This also keeps high frequency content input current localized, minimizing radiated conducted while facilitating optimum performance AAT1154. proper placement input capacitor shown layout figure Ceramic capacitors ideal. size required will vary depending load, output voltage, input voltage source impedance characteristics. Typical values range from input capacitor current varies with input voltage output voltage. highest when input voltage double output voltage where half load current.
ceramic output capacitor dissipation current output ripple associated with negligible. Tantalum capacitors, with sufficiently meet output ripple requirements, generally have current rating much greater than that actually seen this application. maximum tantalum output capacitor
VRIPPLE
Where peak peak inductor ripple current. zero associated with tantalum capacitor, smaller values than those required with ceramic capacitors provide more phase margin with greater loop crossover frequency.
Layout
Figures display suggested layout AAT1154. following guidelines should used help insure proper layout. connection from input capacitor Schottky anode should short possible. input capacitor should connect closely possible VPOWER (pins (pin should connected closely possible. connection from cathode Schottky node should short possible. feedback trace (pin should separate from power trace connect closely possible load point. Sensing along high current load trace degrade load regulation. resistance trace from load return (pin should kept minimum. This will help minimize error regulation differences potential internal reference ground load rtn. required order provide cleaner power source AAT1154 control circuitry.
IRMS
high tantalum with value about times input ceramic capacitor also required when using 10µF smaller ceramic input bypass capacitor. This dampens input oscillations that occur source inductance resonating with converter input impedance
Output Capacitor
With external compensation components, output capacitor strong effect loop stability. Larger output capacitance will reduce crossover frequency with greater phase margin. 200µF ceramic capacitor provides sufficient bulk capacitance stabilize output during large load transitions characteristics necessary very output ripple. ripple current given
1154.2004.08.1.2
1MHz Buck DC/DC Converter
AAT1154
Figure AAT1154 Fixed Output Side Layout
Figure AAT1154 Fixed Output Bottom Side Layout
Thermal
losses associated with AAT1154 output switching MOSFET switching losses conduction losses. conduction losses associated with RDS(ON) characteristics output switching device. full load condition, assuming continuous conduction mode (CCM), accurate calculation RDS(ON) losses derived from following equations.
RMS2 RDS(ON)
Once total losses have been determined junction temperature derived. thermal resistance (JA) SO-8 package mounted printed circuit board still 110°C/W. TAMB TAMB maximum ambient temperature resultant maximum junction temperature.
Design Example
IOUT IRIPPLE full load VOUT 3.3V 1MHz TMAX 70°C Inductor Selection
RDS(ON) losses
IRMS
Internal switch current duty cycle forward drop Schottky diode.
VOUT VOUT
peak peak inductor ripple current. simplified form calculating RDS(ON) switching losses given
3.3V 1.25µH
standard value
DS(ON)
where AAT1154 quiescent current.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
Sumida inductor Series CDRH6D38.
AAT1154
Given case ambient thermal resistance 120°C/W from manufacturer's data sheet, TJ(MAX) diode
3.3V 3.3V 0.82A 1.5µH 1MHz 5.25V
IOUT
J(MAX) 70°C 120°C 0.354W 112°C
0.41A 3.41A
Output Capacitor
output capacitor value required sufficient loop phase margin depends type capacitor selected. ceramic capacitor minimum value 200µF required. tantalum capacitor lower values acceptable. While relatively higher associated with tantalum capacitor will give more phase margin more damped transient response, output voltage ripple will higher. 120µF Vishay 594D tantalum capacitor ripple current rating 1.48 Arms case size. Although smaller case sizes sufficiently rated this ripple current, their level would result excessive output ripple. requirement tantalum capacitor estimated
AAT1154 Junction Temperature
RDS(ON)
3.3V 20ns 1MHz 750µA 0.539 Watts
TJ(MAX)= TAMB 70°C 110°C 0.54W 129°C
Diode
IDIODE= 3.3V 1.02A
0.35V
DIODE IDIODE
0.35V 1.01A .354W
VRIPPLE 0.82A
IRMS
(VOUT+ VFWD) (VIN VOUT)
3.65V 240mArms 1.5µH 1MHz
three 1812 100uF 6.3V ceramic capacitors parallel also provide sufficient phase margin. associated with ceramic capacitors also reduces output ripple significantly over that seen with tantalum capacitors. Temperature rise ripple current dissipation also reduced.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
Input Capacitor
input capacitor ripple
AAT1154
IRMS
1.42 Arms
examples shown ceramic capacitor located close possible. provides impedance path sharp edges associated with input current.
required depending upon impedance characteristics looking back into source. serves dampen input oscillations that arise from source that highly inductive. most applications where source sufficient bulk capacitance directly AA1154 through large traces planes required. When operating AAT1154 evaluation board bench required inductance wires running from laboratory power supply evaluation board.
3.5V-5.5V Vout
Efficiency Load Current 5.0V, VOUT 3.3V
100µF
100k
AAT1154-3.
10µF 0.1µF
B340LA 120µF
Efficiency
1.5µH
0.01
Murata 10µF 6.3V GRM42-6X5R106K6.3 Vishay120µF 6.3V 594D127X96R6R3C2T 0603ZD104M Vishay Sprague 100µF 595D107X0016C 100µF B340LA Diodes Inc. CDRH6D28-1.5µH Sumida Options MuRata 100µF 6.3V GRM43-2 107M 100µF 6.3V (two three parallel 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two three parallel)
Output Current
Figure Volt Output
Figure Volt Input Volt Output accurate results (less than error outputs) select 10k. Once been selected calculated. 1.25 Volt output with 2.5k. 0.25 2.5k
Adjustable Output
applications requiring output other than fixed outputs available, version programmed externally. Resistors figure force output regulate higher than Volt.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
2.7V-5.5V VOUT 1.25V 2.55k
AAT1154
100µF
100k
AAT1154-1. 1.5µH
10µF 0.1µF 10.0k
B340LA
120µF
Murata 10µF 6.3V GRM42-6X5R106K6.3 Vishay 120µF 6.3V 594D127X96R6R3C2T 0603ZD104M Vishay Sprague 100µF 595D107X0016C 100µF B340LA Diodes Inc. CDRH6D28-1.5µH Sumida Options MuRata 100uF 6.3V GRM43-2 107M 100µF 6.3V (two three parallel) 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two three parallel)
Figure AAT1154 Evaluation Board with adjustable output
Figure Evaluation Board Side
Figure Evaluation Board Bottom Side
1154.2004.08.1.2
1MHz Buck DC/DC Converter
Capacitors Part Number
C4532X5ROJ107M GRM43-2 107M GRM43-2 476K GRM42-6 106K 594D127X_6R3C2T 595D107X0016C
AAT1154
Manufacturer
MuRata MuRata MuRata Vishay Vishay
Capacitance (µF)
Voltage
Temp
Case
1812 1812 1812 1206 case case
Inductors Part Number
CDRH6D38-4763-T055 N05D B1R5M NP06DB B1R5M LQH55DN1R5M03 LQH66SN1R5M03
Manufacturer
Sumida Taiyo Yuden Taiyo Yuden MuRata MuRata
Inductance (µH)
(Amps)
.014 .025 .022 .022 .016
Height (mm)
shielded shielded shielded shielded shielded
Diodes Manufacturer
Diodes Inc. ROHM Micro Semi
Part Number
B340LA RB050L-40 5820SM
Vfwd
0.45V 0.45 0.46V
1154.2004.08.1.2
1MHz Buck DC/DC Converter Ordering Information
Output Voltage 1.0V (Adj. VOUT 1.0V) 1.8V 2.5V 3.3V Package SO-8 SO-8 SO-8 SO-8 Marking Part Number (Tape Reel) AAT1154IAS-1.0-T1 AAT1154IAS-1.8-T1 AAT1154IAS-2.5-T1 AAT1154IAS-3.3-T1
AAT1154
Package Information
SO-8
3.90 0.10 4.90 0.10
6.00 0.20
0.375 0.125
1.55 0.20
0.175 0.075
0.235 0.045 0.825 0.445
0.42 0.09
1.27
dimensions millimeters.
1154.2004.08.1.2
1MHz Buck DC/DC Converter
AAT1154
AnalogicTech cannot assume responsibility circuitry other than circuitry entirely embodied AnalogicTech product. circuit patent licenses, copyrights, mask work rights, other intellectual property rights implied. AnalogicTech reserves right make changes their products specifications discontinue product service without notice, advise customers obtain latest version relevant information verify, before placing orders, that information being relied current complete. products sold subject terms conditions sale supplied time order acknowledgement, including those pertaining warranty, patent infringement, limitation liability. AnalogicTech warrants performance semiconductor products specifications applicable time sale accordance with AnalogicTech's standard warranty. Testing other quality control techniques utilized extent AnalogicTech deems necessary support this warranty. Specific testing parameters each device necessarily performed.
Advanced Analogic Technologies, Inc.
Arques Avenue, Sunnyvale, 94085 Phone (408) 737-4600 (408) 737-4611
1154.2004.08.1.2

AAT1154 SwitchRegis member AnalogicTechTM's Total Power ManagementIC p

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