JW1621 GENERAL DESCRIPTION FUNCTION APPLICATION PACKAGE REFERENCE

Transcription

1 GENERAL DESCRIPTION is a PWM controller for step down switching regulator with constant voltage and constant current modes, It uses a synchronous rectified buck Technology and Conversion efficiency is up to 90%. built in cable compensation function and provides stable output voltage, meanwhile, with output current limiting function, and it can be used in DC switching power supply. built in multiple protection functions, for example: VDD OVP, VDD UVLO, over temperature protect, over current protect and short output circuit protect, it available in ESOP-8 package, and provides a very compact solution with minimal external components. FUNCTION Input voltage range:8v to 30V. Fixed work frequency:150k. Maximum output current is up to 3.1A. Output voltage precision: 2%. Output current precision: 15%. Programmable cable drop compensation Built in VDD over voltage protect. Built in VDD under voltage protect. Built in soft-start protect. Built in over temperature protect. Built in over current protect. Built in output short circuit protect. Available in ESOP-8 package. APPLICATION Car charger for single channel output. DC-DC power supply. LED backlight driver. PACKAGE REFERENCE VIN SW VDD CS+ 6 COMP CS- GND FB 5

2 PIN DESCRIPTION PIN NO. NAME FUNCTION DESCRIPTION 1 VIN Source of P-MOS switch 2 VDD Power supply input 3 COMP Frequency compensation terminal, connect the RC circuit to GND. GND Ground 5 VSEN The built-in voltage reference terminal, adjustment of external divider resistors can adjust the output voltage 6 CS- The negative input for Current detection 7 CS+ The positive input for Current detection 8 SW Regulator output pin, connect to inductor 9 SW Regulator output pin, connect to inductor TYPICAL APPLICATION CIRCUIT Vin C1 100uF/35V C2 22uF/35V R1 200K R1 10K U1 VIN SW 8 7 VDD CS+ 6 COMP CS- GND FB 5 L1 33uH/5A C5 220F/10V D1 SS5 R2 0mR C6 330pF R3 32K R 10K C7 22uF/25V Vo+ GND C 10nF Vo- ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL MIN MAX UNITS VDD to GND VDD V VIN to GND VIN V VSEN PIN to GND VFB V CS-(CS+) PIN to GND VCS-(+) V COMP PIN to GND VCOMP V MAX output current IMAX.0 A MAX power dissipation PD 0.75 W ESD HBM 2000 V Operation Junction Temperature TJ Storage Temperature TSTG

3 ELECTRICAL SPECIFICATIONS (Vin=12V, Ta=25, Io=2.0A, unless otherwise specified) Parameter Symbol Test conditions MIN TYP MAX UNIT INPUT SECTION Input Voltage VDD / 8 / 30 V Standby Current INO_LOAD IOUT=0A / / 10 ma OSCILLATOR SECTION Operating Frequency FOSC1 FOSC2 VIN=12V,VOUT=5V, IOUT=2A,TA=25 VIN=12V,VOUT=5V, IOUT=2A,TA= KHz MAX Duty Cycle D_MAX 95 % REFERENCE SECTION Reference Voltage VFB VIN=12V V Reference Voltage of the over voltage protect Reference Voltage of the output short circuit protect VFB_OVP V VFB_OSP V ERROR AMPLIFIER SECTION Reference Voltage of the current error amplifier VCS mv VCS mv OVER TEMPERATURE PROTECTION SECTION Thermal shut-down temperature TOTP_R Temperature rise 150 TOTP_F Temperature fall 100 MOSFET SECTION Drain-Source Breakdown voltage Drain-Source On-State Resistance BVDSS VGS=0V,ID=250uA -30 V RDS(ON) VIN=2V,ID=1.0A 80 mr

4 FUNCTIONAL DESCRIPITION The is a synchronous buck PWM controller, with constant current and constant voltage mode, integrated 30V P-channel power MOSFET for delivering output current, the maximum of conversion efficiency can reach 90%. operation voltages from 8V to 30V and output voltage as low as 1.2V, and supplies up to 3.1A of load current. Dual-Channeling CV/CC mode control The with CV/CC function. The CV function is implemented to deliver a regulated output voltage for the output terminal, and the CC function is to limit output current to be a limited value to prevent the device damaged due to output short circuit or over current condition. Soft Start function The is composed of built-in internal soft start function to prevent a large surge current happening when during start-up period due to the surge current charging output filter capacitors. Output Over-Voltage Protection The provides built-in output over voltage protection function. When output over-voltage happens, the shuts down and recovers to normal state automatically if output over-voltage is released. Output Short-Circuit Protection The provides output short circuit protection function. When output over voltage happens, the shuts down and recovers to normal state automatically if output short-circuit is released. APPLICATION INFORMATION COMPONENT SELECTION Setting the Output Voltage The output voltage is set using a resistor voltage divider from the output voltage to FB pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio: R VFB V OUT R R 3 Where VFB is the feedback voltage and VOUT is the output voltage. Thus the output voltage is: R3 R VOUT V FB VFB=1.2V R

5 INDUCTOR SECLECTION The inductor is required to supply constant current to the output load while being driven by the switch input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and lower saturation current. A good rule for determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. Also, make sure that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by: VOUT VOUT L (1 D); D F I V S L Where VOUT is the output voltage, VIN is the input voltage, FS is the switching frequency, and ΔIL is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated by: VOUT ILP ILOAD (1 D); 2 F L Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price, Size and any EMI requirements. INPUT CAPACTIOR SELECTION The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the converter. A low ESR electrolytic capacitor is highly recommended. Since large current flows in and out of this capacitor during switching, its ESR also affects efficiency. The input capacitance needs to be higher than 100uF.The RMS ripple current rating needs to be higher than 50% of the output current. The input capacitor should be placed close to the VIN and GND pins of the,with the shortest traces possible. The input capacitor can be placed a little bit away if a small parallel 0.1uF ceramic capacitor is placed right next to the. The 100uF_35V electrolytic capacitor and 22uF ceramic capacitor are recommend as input capacitance. OUTPUT CAPACITOR SELECTION The output capacitor also needs to have a low ESR to keep low output ripple voltage.in the case of ceramic output ceramic output capacitors, RESR is very small and does not contribute to the ripple. Therefore, a lower capacitance value can be used for ceramic capacitors. In the case of tantalum or electrolytic capacitors, the ripple is dominated by RESR multiplied by the ripple current. In that case, the output capacitor is chosen to have sufficiently low ESR. The 220uF_10V electrolytic capacitors are recommend as output capacitance. S IN

6 PACKAGE INFORMATION: EESOP-8