High Power Step-Down Synchronous DC/DC Controller Operates from I

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High Power Step-Down Synchronous DC/DC Controller Operates from I

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APW7057
High Power Step-Down Synchronous DC/DC Controller
Operates from Input 0.8V Internal Reference Voltage
±1.5% Accuracy Over Line, Load Temp.
General Description
APW7057 300kHz constant frequency voltage mode synchronous switching controller that drives external N-channel MOSFETs. When input supply drops close output, upper MOSFET remains achieving 100% duty cycle. Internal loop compensation optimized fast transient response, eliminating external compensation network. precision 0.8V reference makes this part suitable wide variety voltage applications. Soft start internally 2ms, limiting input in-rush current preventing output from overshoot during powering APW7057 over current short circuit protections. Over current protection achieved monitoring voltage drop across high side MOSFET, eliminating need current sensing resistor short circuit condition detected through pin. either fault conditions occur, APW7057 would initiate soft start cycle. After three cycles fault condition persists, controller will shut down. restart controller, either recycle supply momentarily pull OSCSET below 1.25V. APW7057 shutdown pulling OCSET below 1.25V. shutdown, both gate drive signals will low. controller available small SOP8 package.
0.8V Output Range Full Duty Cycle Range
100%
Internal Loop Compensation Internal Soft Start
Typical
Programmable Over-Current Protection
Lossless Sensing Using MOSFET (ON)
Under-Voltage Protection Drives External N-Channel MOSFETs Shutdown Control Small SOP-8 Package
Applications
Motherboard Graphics Cards Cable Modems, Boxes Supplies Memory Supplies Input DC-DC Regulators Distributed Power Supplies
Pinouts
SOP-8 (Top View
ANPEC reserves right make changes improve reliability manufacturability without notice, advise customers obtain latest version relevant information verify before placing orders. Copyright ANPEC Electronics Corp. Rev. Feb., 2004 www.anpec.com.tw
APW7057
Ordering Marking Information
APW7057
Lead Free Code Handling Code Temp. Range Package Code APW7057 XXXXX Package Code SOP-8 Operating Junction Temp. Range 70°C Handling Code
Tube Tape Reel Lead Free Code Lead Free Device
Blank Original Device
APW7057
XXXXX Date Code
Block Diagram
BOOT
nderVoltage Lockout
Shutdown
IOCSET
40uA parator Soft-Start Fault Logic
0.5V
Soft-Start
Inhibit ontrol
0.8V
COMP
Error plifier
300kH
scillator
Figure
Copyright ANPEC Electronics Corp. Rev. Feb., 2004 www.anpec.com.tw
APW7057
Typical Application
4148
8.2k
470pF
OCSET
BOOT
1000uF
0.1uF
3.3uH
hutdown
7057
+2.5V /10A 1000uF
5.1k
2.4k 0.1uF
2014N 2014N 7002
1000uF /10V 1000uF /6.3V
Figure
Absolute Maximum Ratings
Symbol BOOT Parameter Supply Voltage (VCC GND) BOOT Supply Voltage (BOOT GND) PHASE, OCSET Input Voltage Input Voltage Maxim Junction perature Storage perature Maxim Soldering perature, Seconds Minim Rating Rating -0.3 -0.3 -0.3 -0.3 +0.3 Unit
Thermal Characteristics
Symbol Parameter Junction-to-Ambient Resistance free (SOP-8)
Value
Unit
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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APW7057
Recommended Operating Conditions
Symbol Supply Voltage Output Voltage Switching Regulator (Note) Input Voltage Switching Regulator (Note) Ambient Temperature Junction Temperature Parameter Range Unit
Note Refer typical application circuit
Electrical Characteristics
Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V 0~70 Typical values TA=25oC.
Symbol Parameter Test Conditions APW7057 Unit
SUPPLY CURRENT IVCC IBOOT Nominal Supply Current BOOT Nominal Supply Current Rising Threshold Falling Threshold OSCILLATOR FOSC Free Running Frequency Ramp Upper Threshold Ramp Lower Threshold VREF Ramp Amplitude Reference Voltage Reference Voltage Accuracy ERROR AMPLIFIER Gain First Pole Frequency First Zero Frequency UGATE Duty Range Input Current
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
UGATE LGATE Open UGATE Open
Under Voltage Lockout(UVLO) 2.85 0.95 -1.5 +1.5 VP-P
REFERENCE VOLTAGE
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APW7057
Electrical Characteristics (Cont.)
Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V 0~70 Typical values TA=25oC.
Symbol Parameter Test Conditions APW7057 VOCSET=4.5V falling Unit
CONTROLLER GATE DRIVERS UGATE Source UGATE Sink LGATE Source LGATE Sink IOCSET UVFB Dead Time OCSET Sink Current Under-Voltage Level Under-Voltage Hysteresis SOFT-START SHUTDOWN Soft-Start Interval Shutdown Threshold OCSET Shutdown Hysteresis VOCSET Falling 1.25 PROTECTION VUAGTE=1V VUGATE=1V VLGATE=1V VLGATE=1V
Functional Description
BOOT (Pin This provides supply voltage high side MOSFET driver. voltage greater than connected this supply driver. driving logic level N-channel MOSEFT, bootstrap circuit create suitable driver's supply. UGATE (Pin This provides gate drive high-side MOSFET. (Pin Signal power ground voltage levels measured with respect this pin. this ground plane through lowest impedance connection available.
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
LGATE (Pin This provides gate drive signal side MOSFET. (Pin This main bias supply controller side MOSFET driver. Must closely decoupled (Pin apply voltage greater than 5.5V this pin. (Pin This inverting input error amplifier receives feedback voltage from exter-
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APW7057
Functional Description
resistive divider across output (VOUT). output voltage determined VOUT 0.8V(1+ ROUT RGND over current limit. internally generated 40uA current source will flow through this resistor, creating voltage drop. This voltage will compared with voltage across high side MOSFET. threshold over current limit therefore given where ROUT resistor connected between VOUT while RGND resistor connected from GND. OCSET (Pin This serves functions: shutdown control setting over current limit threshold. Pulling this below 1.25V shuts controller down, forcing UGATE LGATE signals soft start cycle will initiated upon release this pin. resistor (Rocset) connected between this drain high side MOSFET will determine PHASE (Pin This connected source high-side MOSFET used monitor voltage drop across high-side MOSFET over-current protection. 40uA ROCSET RDS(ON)
over current condition will cycle soft start function. After three consecutive cycles fault condition persists, controller will shut down. restart controller, either recycle supply momentarily pull OSCSET below 1.25V.
Typical Characteristics
Reference Voltage Junction Temperature
0.812
Switching Frequency Junction Temperature
Switching Frequency, FOSC (kHz)
Reference Voltage, VREF
0.808
0.804
0.800
0.796
0.792
0.788
Junction Temperature (oC)
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Junction Temperature (°C)
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APW7057
Typical Characteristics (Cont.)
OCSET Current Junction Temperature
OCSET Current IOCSET (µA)
Junction Temperature (oC)
Operating Waveforms
IOUT slew rate ±10A/µS IOUT
(Refer typical application circuit)
Load Transient Response IOUT
IOUT
VOUT
IOUT
VOUT
VOUT
VUGATE
VUGATE
IOUT
IOUT
IOUT
VOUT, 100mV/Div, Offset 2.50V VUGATE, 10V/Div, IOUT, 5A/Div Time 10µS/Div 20MHz
VOUT, 100mV/Div, Offset 2.50V IOUT, 5A/Div Time 100µS/Div 20MHz
VOUT, 100mV/Div, Offset 2.50V VUGATE, 10V/Div, IOUT, 5A/Div Time 10µS/Div 20MHz
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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APW7057
Operating Waveforms
UGATE LGATE UGATE Rising
IOUT=10A VUGATE IOUT=10A VUGATE
(Refer typical application circuit)
UGATE Falling
VLGATE
VLGATE
VUGATE, 2V/Div, Time 125nS/Div
VLGATE, 2V/Div, 500MHz
VUGATE, 2V/Div, Time 125nS/Div
VLGATE, 2V/Div, 500MHz
Powering Soft-start Powering
Powering
VOUT
VOUT
VIN, 2V/Div, Time 1mS/Div
VOUT, 1V/Div, 20MHz
VIN, 2V/Div, Time 5mS/Div
VOUT, 1V/Div, 20MHz
Short-Circuit Protection Under-Voltage (UVP) Over-Current Protection (OCP)
VOUT VOUT, 1V/Div, IOUT, 10A/Div Time 1mS/Div 20MHz
IOUT
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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APW7057
Application Information
Component Selection Guidelines
Output Capacitor Selection selection COUT determined required effective series resistance (ESR) voltage rating rather than actual capacitance requirement. Therefore select high performance capacitors that intended switching regulator applications. some applications, multiple capacitors have paralled achieve desired value. tantalum capacitors used, make sure they surge tested manufactures. doubt, consult capacitors manufacturer. Input Capacitor Selection input capacitor chosen based voltage rating current rating. reliable operation, select capacitor voltage rating least times higher than maximum input voltage. maximum current rating requirement approximately IOUT/2 where IOUT load current. During power input capacitors have handle large amount surge current. tantalum capacitors used, make sure they surge tested manufactures. doubt, consult capacitors manufacturer. high frequency decoupling, ceramic capacitor between 0.1uF connected between ground pin. Inductor Selection inductance inductor determined output voltage requirement. larger inductance, lower inductor's current ripple. This will translate into lower output ripple voltage. ripple current ripple voltage approximated IRIPPLE VOUT VOUT VOUT IRIPPLE where switching frequency regulator. There tradeoff exists between inductor's ripple current regulator load transient response time smaller inductor will give regulator faster load transient response expense higher ripple current vice versa. maximum ripple current occurs maximum input voltage. good starting point choose ripple current approximately maximum output current. Once inductance value been chosen, select inductor that capable carrying required peak current without going into saturation. some type inductors, especially core that make ferrite, ripple current will increase abruptly when saturates. This will result larger output ripple voltage. MOSFET Selection selection N-channel power MOSFETs determined RDS(ON), reverse transfer capacitance (CRSS) maximum output current requirement.The losses MOSFETs have components: conduction loss transition loss. upper lower MOSFET, losses approximately given following PUPPER Iout TC)(RDS(ON))D (0.5)(Iout)(VIN)(tsw)FS PLOWER Iout TC)(RDS(ON))(1-D) where IOUT load current temperature dependency RDS(ON) switching frequency switching interval duty cycle
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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APW7057
Application Information
Note that both MOSFETs have conduction losses while upper MOSFET include additional transition loss.The switching internal, tsw, function reverse transfer capacitance CRSS. Figure illustrates switching waveform internal MOSFET. (1+TC) term factor temperature dependency RDS(ON) extracted from "RDS(ON) Temperature" curve power MOSFET. single point grounding. Figure illustrates layout, with bold lines indicating high current paths. Components along bold lines should placed close together. Below checklist your layout:
Keep switching nodes (UGATE, LGATE
PHASE) away from sensitive small signal nodes since these nodes fast moving signals. There fore keep traces these nodes short possible.
Layout Considerations
high power switching regulator, correct layout important ensure proper operation regulator. general, interconnecting impedances should minimized using short, wide printed circuit traces. Signal power grounds kept separate finally combined using ground plane construction
Decoupling capacitor provides bulk capaci
tance needs placed close since will provide MOSFET drivers transient current requirement.
ground return must return combine
COUT terminal.
Capacitor CBOOT should connected close
BOOT PHASE pins possible.
Voltage across drain source SFET
BOOT LGATE
7057 1UGATE
PHASE
VOUT
Figure Switching waveform across SFET
Figure Recommended Layout Diagram
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APW7057
Packaging Information
SOP-8 Reference JEDEC Registration MS-012)
0.004max.
Min. Min.
0.015X45
Inche
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APW7057
Physical Specifications
Terminal Material Lead Solderability Packaging Solder-Plated Copper (Solder Material 90/10 63/37 SnPb), 100%Sn Meets Specification RSI86-91, ANSI/J-STD-002 Category 2500 device reel
Reflow Condition
(IR/Convection Reflow)
ritical Zone
p-up
p-down Preheat
Peak
Classificatin Reflow Profiles
Profile Feature
Sn-Pb Eutectic Assembly Large Body Small Body
Pb-Free Assembly Large Body Small Body 3°C/second max. 150°C 200°C 60-180 seconds 3°C/second 217°C 60-150 seconds +0/-5°C +0/-5°C 10-30 seconds 20-40 seconds
Average ramp-up rate 3°C/second max. Preheat Temperature (Tsmin) 100°C Temperature (Tsmax) 150°C Time (min max)(ts) 60-120 seconds Tsmax Ramp-up Rate Tsmax Temperature(TL) 183°C Time (tL) 60-150 seconds Peak Temperature(Tp) +0/-5°C +0/-5°C Time within actual Peak 10-30 seconds 10-30 seconds Temperature(tp) Ramp-down Rate 6°C/second max. minutes max. Time 25°C Peak Temperature
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6°C/second max. minutes max.
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Note: temperatures refer topside package. Measured body surface.
APW7057
Reliability test program
Test item SOLDERABILITY HOLT Latch-Up Method MIL-STD-883D-2003 MIL-STD-883D-1005.7 JESD-22-B, A102 MIL-STD-883D-1011.9 MIL-STD-883D-3015.7 JESD Description 245°C 1000 Bias Hrs, 121°C -65°C 150°C, Cycles VHBM 2KV, 200V 10ms 100mA
Carrier Tape Reel Dimension
Application
330±1
12.75
12.4 +0.2
5.2±
1.75±
SOP-8
1.55±0.1 1.55+ 0.25
2.1± 0.3±0.013
(mm)
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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APW7057
Cover Tape Dimensions
Application SOP- Carrier Width Cover Tape Width Devices Reel 2500
Customer Service
Anpec Electronics Corp. Head Office Li-Hsin Road, SBIP, Hsin-Chu, Taiwan, R.O.C. 886-3-5642000 886-3-5642050 Taipei Branch 137, Lane 235, Chiao Rd., Hsin Tien City, Taipei Hsien, Taiwan, 886-2-89191368 886-2-89191369
Copyright ANPEC Electronics Corp. Rev. Feb., 2004
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High Power Step-Down Synchronous DC/DC Controller Operates from I

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