UNISONIC TECHNOLOGIES CO., LTD P1786 LINEAR INTEGRATED CIRCUIT PWM CONTROL 3A STEP-DOWN CONVERTER DESCRIPTION UTC P1786 consists of 3A step-down switching regulator control which includes a reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc with PWM. UTC P1786 can provide low-ripple power, high efficiency, and excellent transient characteristics. An enable function, an over current protect and short circuit protect function are built inside, so the operation frequency can be reduced from 300KHz to 30KHz when OCP or SCP happens. The PWM control circuit can vary the duty ratio linearly from 100 down to 0%. This converter also includes an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. Also, to minimum external component counts for an internal compensation block is built in. These ICs can work as step-down switching regulators with the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally. They provide such outstanding features: low current consumption. It is also suitable for the operation via an AC adapter because this converter accommodate an input voltage up to 23V. FEATURES * Input voltage: 4.0V ~ 23V * Output voltage: 0.8V ~ VCC * Duty ratio: 0% to 100% PWM control * Oscillation frequency: 300KHz typ. * Soft-start, current limit, enable function * Thermal shutdown function * Built-in internal SW P-channel MOS ORDERING INFORMATION Ordering Number Lead Free Halogen Free P1786L-S08-R P1786G-S08-R www.unisonic.com.tw Copyright © 2009 Unisonic Technologies Co., Ltd Package Packing SOP-8 Tape Reel 1 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT PIN CONFIGURATION PIN DESCRIPTIONS PIN NO. 1 PIN NAME FB I/O I I 2 EN 3 4 OCSET VCC I 5, 6 Output O 7, 8 VSS DESCRIPTION Feedback pin. Chip enable, H: enable step-down function L: chip disable Add an external resistor to set max output current. IC power supply pin Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI. GND Pin UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT BLOCK DIAGRAM UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL RATING UNIT VCC Pin Voltage VCC VSS - 0.3 ~ VSS + 25 V Feedback Pin Voltage VFB VSS - 0.3 ~ VCC V EN Pin Voltage VEN VSS - 0.3 ~ VIN + 0.3 V Switch Pin Voltage VOUT VSS - 0.3 ~ VIN + 0.3 V Power Dissipation PD Internally limited Operating Temperature TOPR -20 ~ +125 °C Storage Temperature TSTG -40 ~ +150 °C Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. THERMAL DATA PARAMETER Junction to Ambient SYMBOL θJA MIN TYP 65 MAX UNIT °C/W ELECTRICAL CHARACTERISTICS (VIN = 12V, Ta=25°C, unless otherwise specified) PARAMETER Input Voltage Feedback Voltage Feedback Bias Current Switch Current Standby Current Line Regulation Load Regulation Oscillation Frequency Frequency of Current Limit or Short Circuit Protect EN Pin Input Voltage EN Pin Input Leakage Current SYMBOL VIN VFB IFB(BIAS) ISC ISTN-BY ΔVOUT VOUT ΔVOUT VOUT fOSC VEN =0V VIN = 5V~23V, IOUT=0.2A IOUT = 0.1 to 3A 1 2 % 0.2 0.5 % 240 300 360 KHz fOSC1 Measure waveform at SW pin 10 30 60 KHz VSH Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin 2.0 VSL Internal MOSFET RDS(ON) RDS(ON) η UNISONIC TECHNOLOGIES CO., LTD 75 0.3 VIN=5V, VFB=0V VIN=12V, VFB=0V VIN = 12V, VOUT = 5V, IOUT = 3A V 0.8 ISH ISL IOCSET TSS www.unisonic.com.tw IOUT=0.1A IOUT=0.1A MIN TYP MAX UNIT 4 23 V 0.784 0.8 0.816 V 0.1 0.5 μA 3.5 A 10 μA Measure waveform at SW pin OCSET Pin Bias Current Soft-Start Time Efficiency CONDITIONS 20 -10 90 2 110 70 91 105 5 150 100 V μA μA μA ms mΩ mΩ % 4 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT FUNCTION DESCRIPTION PWM Control The UTC P1786 consists of DC/DC converters which employ a PWM system. In this DC/DC converter, the pulse width varies in a range from 0 to 100% which is according to the load current. Cause the switching frequency remains constant the ripple voltage which produced by the switching can be removed easily through a filter. Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current. Under Voltage Lockout The under voltage lockout circuit makes sure that the outputs of high-side MOSFET driver remain in the off state after the supply voltage drops below 3.3V. When VCC rises above 3.5V normal operation resumes. RDS(ON) Current Limiting The current limit threshold is fixed by the external resistor which is connected from VCC supply to OCSET. An over-current condition is triggered when the PWM voltage is less than the voltage at OCSET. ILOAD × RDS(ON) = IOCSET × ROCSET above formula is setting the current limit value. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT TYPICAL APPLICATION CIRCUIT VOUT L1 Value VIN=12V, IMAX=3A 2.5V 3.3V 15uH 18uH UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw + TEST CIRCUITS - 5V 22uH 6 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT TYPICAL CHARACTERISTICS Input Voltage vs. Frequency Input Voltage vs. FB 0.84 345 0.83 340 0.82 335 0.81 330 0.80 FB (V) Oscillation Frequency, Fosc (KHz) 350 325 320 315 0.79 0.78 0.77 310 0.76 VOUT=3.3V IOUT=0.2A 305 300 0 0.74 10 5 VOUT=3.3V IOUT=0.2A 0.75 15 20 25 0 5 Input Voltage, VIN (V) 10 20 15 Input Voltage, VIN (V) Line Regulation 25 Load Regulation 3.40 5.10 Output Voltage, VOUT (V) Output Voltage, VOUT (V) 5.09 3.35 3.30 3.25 3.20 3.15 VOUT=3.3V IOUT=0.2A 5 5.07 5.06 5.05 5.04 5.03 5.02 5.01 3.10 0 5.08 10 15 20 25 1.0 2.0 3.0 4.0 Output Current, IOUT (A) Efficiency (%) Input Voltage, VIN (V) 5.00 0.0 VIN=12V UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 8 QW-R103-038.B P1786 LINEAR INTEGRATED CIRCUIT TYPICAL CHARACTERISTICS(Cont.) UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 8 QW-R103-038.B