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Datasheet 5A 350KHz 25V Buck DC to DC Converter Features
Wide 3.6V to 25V Input Voltage Range Output Adjustable from 0.8V to 23V
Maximum Duty Cycle 100% Minimum Drop Out 0.6V
General Description
The GS2678 is a 350 KHz fixed frequency PWM buck (step-down) DC/DC converter, capable of driving a 5A load with high efficiency, low ripple and excellent line and load regulation. Requiring a minimum number of external components, the regulator is simple to use and include internal frequency compensation and a fixed-frequency oscillator. The PWM control circuit is able to adjust the duty ratio linearly from 0 to 100%. An enable function, an over current protection function is built inside. When short protection function happens, the operation frequency will be reduced from 350KHz to 80KHz. An internal compensation block is built in to minimize external component count.
Fixed 350KHz Switching Frequency 5A Constant Output Current Capability Internal Optimize Power MOSFET High efficiency
Excellent line and load regulation TTL shutdown capability EN pin with hysteresis function
Built in thermal shutdown function Built in current limit function Built in output short protection function Available in TO-263 package
Applications
LCD Monitor and LCD TV Digital Photo Frame Set-up Box ADSL Modem Telecom / Networking Equipment
Figure1. Package Type of GS2678
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Pin Configurations
Figure2. Pin Configuration of GS2678 (Top View) Table 1 Pin Description Pin Number 1 Pin Name GND Description Ground Pin. Care must be taken in layout. This pin should be placed outside of the Schottky Diode to output capacitor ground path to prevent switching current spikes from inducing voltage noise into GS2678. Feedback Pin (FB). Through an external resistor divider network, FB senses the output voltage and regulates it. The feedback threshold voltage is 0.8V. Power Switch Output Pin (SW). SW is the switch node that supplies power to the output. Enable Pin. Drive EN pin high to turn on the device, drive it low to turn it off. Floating is default high. Supply Voltage Input Pin. GS2678 operates from a 3.6V to 25V DC voltage. Bypass Vin to GND with a suitably large capacitor to eliminate noise on the input.
2 3 4 5
FB SW EN VIN
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Function Block
Figure3. Function Block Diagram of GS2678
Typical Application Circuit
Figure4. GS2678 Typical Application Circuit 12V-5V/5A
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Ordering Information
Part Number Lead Free GS2678E1 GS2678TRE1 Marking ID Lead Free GS2678E1 GS2678E1 Packing Type Tube Tape & Reel
Package
Temperature Range
GSM Pb-free products, as designated with "E1"
suffix in the par number, are RoHS compliant.
Absolute Maximum RatingsNote1
Parameter Input Voltage Feedback Pin Voltage EN Pin Voltage Output Switch Pin Voltage Power Dissipation Thermal Resistance (TO263) (Junction to Ambient, No Heatsink, Free Air) Operating Junction Temperature Storage Temperature Lead Temperature (Soldering, 10 sec) ESD (HBM) Symbol Vin VFB VEN VOutput PD RJA TJ TSTG TLEAD Value -0.3 to 30 -0.3 to Vin -0.3 to Vin -0.3 to Vin Internally limited 50 -40 to 125 -65 to 150 260 2000 Unit V V V V mW C/W C C C V
Note1: Stresses greater than those listed under Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
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Datasheet 5A 350KHz 25V Buck DC to DC Converter GS2678 Electrical Characteristics
Ta = 25;unless otherwise specified. Symbol Parameter Test Condition Min. Typ. Max. Unit
System parameters test circuit figure4 VFB Efficiency Feedback Voltage Vin = 5V to 25V, Vout=5V Iload=0.5A to 5A Vin=12V ,Vout=5V Iout=5A 0.776 0.8 90 0.824 V %
Electrical Characteristics (DC Parameters)
Vin = 12V, GND=0V, Vin & GND parallel connect a 220uf/50V capacitor; Iout=500mA, Ta = 25; the others floating unless otherwise specified. Parameters Input operation voltage Shutdown Supply Current Quiescent Supply Current Oscillator Frequency Switch Current Limit EN Pin Threshold EN Pin Input Leakage Current Max. Duty Cycle Symbol Vin ISTBY Iq Fosc IL VEN IH IL DMAX VFB =0 High (Regulator ON) Low (Regulator OFF) VEN =2V (ON) VEN =0V (OFF) VFB=0V VEN=0V VEN =2V, VFB =Vin 298 Test Condition Min. 3.6 60 3 350 8 1.4 0.8 1 1 100 15 15 Typ. Max. 25 200 5 402 Unit V uA mA Khz A V uA uA %
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Datasheet 5A 350KHz 25V Buck DC to DC Converter
Test Circuit and Layout guidelines
Figure5. Standard Test Circuits and Layout Guides Select R1 to be approximately 2K, use a 1% resistor for best stability. C1 and CFF are optional; in order to increase stability and reduce the input power line noise, CIN and C1 must be placed near to PIN1 and PIN3; For output voltages greater than approximately 10V, an additional capacitor CFF is required. The compensation capacitor is typically between 100 pf and 33 nf, and is wired in parallel with the output voltage setting resistor, R2. It provides additional stability for high output voltage, low input-output voltages, and/or very low ESR output capacitors, such as solid tantalum capacitors. CFF=1/(31*1000*R2); This capacitor type can be ceramic, plastic, silver mica, etc. (Because of the unstable characteristics of ceramic capacitors made with Z5U material, they are not recommended.)
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Schottky Diode Selection Table
Current Surface Through VR (The same as system maximum input voltage) Mount Hole 20V 30V 40V 50V 1N5817 1N5818 1N5819 3A 5A SR302 1N5823 SR502 SB520 1N5820 MBR320 SK32 1N5821 MBR330 SK33 30WQ03 31DQ03 SR303 1N5824 SR503 SB530 50WQ03 1N5822 MBR340 MBR350 SK34 31DQ04 SR304 1N5825 SR504 SB540 SR505 SB550 SR506 SB560 SK35 31DQ05 SR305 SR306 30WQ04 30WQ05 MBR360 SK36
60V
1A
50WQ04 50WQ05
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Typical System Application for 24V ~ 12V/3A Version
Figure6. GS2678 System Parameters Test Circuit (24V ~ 12V/3A)
Typical System Application for 24V ~ 5V/5A
Figure7. GS2678 System Parameters Test Circuit (24V ~ 5V/5A)
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Datasheet 5A 350KHz 25V Buck DC to DC Converter Package Information
(2) TO263-5L
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