RT8287A

RT8287A RICHTEK | Alldatasheet

Document overview

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Technical content

Features

zzzzz Adjustable Soft-Start zzzzz 120mΩΩΩΩΩ/40mΩΩΩΩΩ Internal Power MOSFET Switch zzzzz Internal Compensation Minimizes External Parts Count zzzzz Fixed 500kHz Frequency zzzzz Thermal Shutdown Protection zzzzz Cycle-by-Cycle Over Current Protection zzzzz Wide 4.5V to 21V Operating Input Range zzzzz Adjustable Output from 0.808V to 15V zzzzz Small 14-Lead WDFN Package zzzzz RoHS Compliant and Halogen Free

Ordering Information

Note : Richtek products are : \ RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. \ Suitable for use in SnPb or Pb-free soldering processes. WDFN-14L 4x3

Applications

z Distributive Power Systems z Battery Charger z DSL Modems z Pre-Regulator for Linear Regulators VIN SW SW SW AGND GND GND SS VCC SW BOOT PGOOD EN FB GND 1578 Package Type QW : WDFN-14L 4x3 (W-Type) RT8287A Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free) Marking Information 01 YM DNN 01 : Product Code YMDNN : Date Code

©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.

1 VIN

suitably large capacitor to eliminate noise on the input to the IC. from SW to BOOT to power the high side switch.

6 BOOT

90% low to high and 70% high to low of regulation value. SS to GND to set the soft-start period. Table 1. Recommended Components Selection

DS8287A-03 June 2012 www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Function Block Diagram Pin No. Pin Name Pin Function 11 VCC Bias Supply. Decouple with 0.1μF to 0.22μF capacitor. The capacitance should be no more than 0.22μF. 12, 13 15 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 14 AGND Analog Ground. Connect this pin to the system ground in PCB layout. S Q R Driver Current Sense Amplifier PWM Comparator Oscillator 500kHz Ramp Generator Regulator Reference VC Error Amplifier SW BOOT FB EN VIN GND 10µA SS PGOOD VCC VA VA VC 400k30pF 1pF 1.2V 1.7V 1µA Lockout Comparator Shutdown Comparator

DS8287A-03 June 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 2) z ESD Susceptibility (Note 3) Recommended Operating Conditions (Note 4)

Electrical Characteristics

Parameter Symbol Test Conditions Min Typ Max Unit Shutdown Current I SHDN V EN = 0 -- 0 1 μA Quiescent Current I Q V EN = 2V, VFB = 1V -- 0.7 -- mA Upper Switch On Resistance R DS(ON)1 -- 120 -- m Ω Lower Switch On Resistance R DS(ON)2 -- 40 -- m Ω Switch Leakage I LEAK V EN = 0V, VSW = 0V or 12V -- 0 10 μA Current Limit I LIMIT V BOOT − VSW = 4.8V 6.2 7 -- A Oscillator Frequency f SW V FB = 0.75V 425 500 575 kHz Short Circuit Frequency V FB = 0V -- 150 -- kHz Maximum Duty Cycle D MAX V FB = 0.8V -- 90 -- % Minimum On Time t ON -- 100 -- ns Feedback Voltage V FB 4.5V ≤ VIN ≤ 21V 0.796 0.808 0.82 V Feedback Current I FB -- 10 50 nA Logic-High V IH 2 -- 5.5 EN Threshold Voltage Logic-Low V IL -- -- 0.4 V V EN = 2V -- 1 -- Enable Current V EN = 0V -- 0 -- μA (VIN = 12V, TA = 25°C unless otherwise specified)

DS8287A-03 June 2012 www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Parameter Symbol Test Conditions Min Typ Max Unit Power Good Rising Threshold -- 90 -- % Power Good Falling Threshold -- 70 -- % Power Good Delay -- 20 -- μs Power Good Sink Current Capability Sink 4mA -- -- 0.4 V Power Good Leakage Current -- 10 -- nA Under Voltage Lockout Threshold VUVLO V IN Rising 3.8 4 4.2 V Under Voltage Lockout Threshold Hysteresis ΔVUVLO -- 400 -- mV VCC Regulator -- 5 -- V VCC Load Regulation I CC = 5mA -- 5 -- % Soft-Start Period t SS C SS = 47nF -- 4.7 -- ms Thermal Shutdown T SD -- 150 -- °C Thermal Shutdown Hysteresis ΔTSD -- 30 -- °C Note 1. Stresses beyond those listed “Absolute Maximum Ratings ” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θ JA is measured at T A = 25 °C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.

DS8287A-03 June 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Output Voltage vs. Output Current 1.210 1.212 1.214 1.216 1.218 1.220 1.222 1.224 1.226 00 . 511 . 522 . 533 . 54 Output Current (A) Output Voltage (V) VIN = 12V, VOUT = 1.22V, IOUT = 0A to 4A Reference Voltage vs. Input Voltage 0.790 0.795 0.800 0.805 0.810 0.815 0.820 0.825 0.830 4 6 8 10 12 14 16 18 20 22 Input Voltage (V) Reference Voltage (V) Reference Voltage vs. Temperature 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84 - 5 0- 2 5 0 2 5 5 0 7 51 0 0 1 2 5 Temperature (°C) Reference Voltage (V) Typical Operating Characteristics Efficiency vs. Output Current 100 00 . 511 . 522 . 533 . 54 Output Current (A) Efficiency (%) VIN = 12V VIN = 21V VOUT = 1.22V, IOUT = 0A to 4A Switching Frequency vs. Temperature 350 375 400 425 450 475 500 525 550 - 5 0- 2 5 0 2 5 5 0 7 51 0 0 1 2 5 Temperature (°C) Switching Frequency (kHz) 1 VIN = 12V, VOUT = 1.22V, IOUT = 1A Switching Frequency vs. Input Voltage 350 375 400 425 450 475 500 525 550 4 6 8 10 12 14 16 18 20 22 Input Voltage (V) Switching Frequency (kHz) 1 VOUT = 1.22V, IOUT = 0.8A

DS8287A-03 June 2012 www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Current Limit vs. Input Voltage 4 6 8 10 12 14 16 18 20 22 Input Voltage (V) Current Limit (A) Current Limit vs. Temperature - 5 0- 2 5 0 2 5 5 0 7 51 0 0 1 2 5 Temperature (°C) Current Limit (A) VIN = 12V, VOUT = 1.22V Output Voltage Ripple Time (1 μs/Div) IL (2A/Div) VOUT (50mV/Div) VLX (10V/Div) VIN = 12V, IOUT = 4A Output Voltage Ripple Time (1 μs/Div) IL (2A/Div) VOUT (50mV/Div) VLX (10V/Div) VIN = 12V, IOUT = 1A VIN = 12V, VOUT = 1.22V, IOUT = 0A to 4A Load Transient Response Time (100 μs/Div) IOUT (2A/Div) VOUT (200mV/Div) VIN = 12V, VOUT = 1.22V, IOUT = 1A to 4A Load Transient Response Time (100 μs/Div) IOUT (2A/Div) VOUT (200mV/Div)

DS8287A-03 June 2012www.richtek.com ©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Power On from EN Time (2.5ms/Div) IL (5A/Div) VOUT (1V/Div) VEN (5V/Div) VIN = 12V, VOUT = 1.22V, IOUT = 4A VPGOOD (5V/Div) Power Off from EN Time (50 μs/Div) IL (5A/Div) VOUT (1V/Div) VEN (5V/Div) VIN = 12V, VOUT = 1.22V, IOUT = 4A VPGOOD (5V/Div) Power On from V IN Time (5ms/Div) IL (5A/Div) VOUT (1V/Div) VIN (10V/Div) VIN = 12V, VOUT = 1.22V, IOUT = 4A VPGOOD (5V/Div) Power Off from V IN Time (50ms/Div) IL (5A/Div) VOUT (1V/Div) VIN (10V/Div) VIN = 12V, VOUT = 1.22V, IOUT = 4A VPGOOD (5V/Div)

©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Table 2. Suggested Inductors for Typical trapezoidal current at the source of the high side MOSFET. meet size or height requirements in the design. capacitor, please refer to Table 3 for more detail. for COUT selection to ensure that the control loop is stable. Table 3. Suggested Capacitors for CIN and COUT

©Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Figure 7. PCB Layout Guide \` Connect feedback network behind the output capacitors.

DS8287A-03 June 2012www.richtek.com Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnish ed by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringeme nts of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of R ichtek or its subsidiaries. Outline Dimension W-Type 14L DFN 4x3 Package 1 122 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. DETAIL A Pin #1 ID and Tie Bar Mark Options Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 3.900 4.100 0.154 0.161 D2 3.250 3.350 0.128 0.132 E 2.900 3.100 0.114 0.122 E2 1.650 1.750 0.065 0.069 e 0.500 0.020 L 0.350 0.450 0.014 0.018