UNISONIC TECHNOLOGIES CO., LTD UC3666 Preliminary CMOS IC DUAL CHANNEL 800mA HIGH EFFICIENCY STEP-DOWN DC/DC CONVERTER 1 DESCRIPTION SON-10 The UTC UC3666 is a dual channel high efficiency step-down DC/DC converter with constant frequency and current mode. A main switch and a synchronous rectifier for high efficiency are contained in each converter, and thus an external Schottky diode is saved. Supply current is only 300μA during normal operation and is reduced to less than 1μA in shutdown mode. The output voltage can be adjusted to as low as 0.6V. With input voltage range from 2.5V ~ 5.5V , each converter can deliver 800mA current to the load. Due to the internally fixed 1.8MHz switching frequency , small surface mount inductors and capacitors can be used. It can also run 100% duty cycle for low dropout applications. The UTC UC3666 is generally used in digital still cameras, portable instruments, slim-type DVD, microprocessors and DSP core supplies, wireless and DSL card, PDAs, smart phones, cellular telephones and so on. FEATURES * high efficiency * Current mode operation * Low quiescent current less than 300uA (Active mode) * Input voltage varying from 2.5V to 5.5V * Output current on each channel: 800mA * Fixed frequency operation * 0 - 100% full duty ratio in dropout * 0.6V reference allows low output voltages * Over-temperature protection circuit * Shutdown current less than 0.1μA * RoHS Compliant (100% green available) * Halogen Free ORDERING INFORMATION Ordering Number Lead Free Halogen Free UC3666L-B10-R UC3666G-B10-R Package Packing SON-10 Tape Reel Note: xx: Output Voltage, refer to Marking Information. www.unisonic.com.tw Copyright © 2010 Unisonic Technologies Co., Ltd 1 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC PIN CONFIGURATION Top View EN1 1 10 SW1 FB1 2 9 GND1 VIN2 3 8 VIN1 GND2 4 7 FB2 SW2 5 6 EN2 Exposed Pad On Backside PIN DESCRIPTION PIN NO. PIN NAME 1 EN1 2 3 4 5 FB1 VIN2 GND2 SW2 6 EN2 7 8 9 10 FB2 VIN1 GND1 SW1 DESCRIPTION Channel 1 Regulator Enable Control Input Pin. Drive EN1 above 1.5V to turn on channel1. Drive EN1 below 0.3V to turn it off (shutdown current < 0.1uA). Channel 1 Voltage Feedback Pin Channel 2 Supply Pin Channel 2 Ground Pin Channel 2 Power Switch Output Channel 2 Regulator Enable Control Input Pin. Drive EN2 above 1.5V to turn on channel2. Drive EN2 below 0.3V to turn it off (shutdown current < 0.1uA). Channel 2 Voltage Feedback Pin Channel 1 Supply Pin Channel 1 Ground Pin Channel 1 Power Switch Output UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC BLOCK DIAGRAM VIN1 VIN2 EN1 EN2 EN Logic UVLO Reference + + Current Sense Amplifier Slop Comp Soft Start - M1 UG FB1 FB2 0.6V + - + Error Amplifier PWM Comparator PWM Logic SW1 SW2 RS & Drive M2 Oscillator LG Clock DCC + GND1 GND2 Zero-Current Comparator UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC ABSOLUTE MAXIMUM RATING PARAMETER SYMBOL RATINGS UNIT Input Supply Voltage VIN GND-0.3 ~ +6.5 V SW Voltage -0.3 ~ VIN +0.3 V ENB, VFB Voltage -0.3 ~ VIN V SW Peak Current 1.5 A ESD Classification Class 2 Junction Temperature TJ 125 °C Operating Temperature Torp -20 ~ +85 °C Storage Temperature Range TSTG -65 ~ +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. The IC has a protection circuit against static electricity. Do not apply high static electricity or high voltage that exceeds the performance of the protection circuit to the IC. THERMAL DATA PARAMETER SYMBOL θJA Junction ambient TYP MAX 50 UNIT °C/W ELECTRICAL CHARACTERISTICS (Recommended Operating Conditions, unless otherwise specified; VIN=3.6V, TA=0 ~ 70°C (typical=25°C)) PARAMETER Supply Voltage Feedback Current Regulated Feedback Voltage Reference Voltage Line Regulation Output Voltage Line Regulation Output Voltage Load Regulation Shutdown Current SW Leakage Current PMOSFET On Resistance NMOSFET On Resistance SYMBOL VIN IVFB VFB ΔVFB ΔVOUT VLOADRGE IS ILEAK RDSONP RDSONN PMOSFET Current Limit IPCL Oscillator Frequency Thermal Shutdown Threshold EN High Level Input Voltage EN Low Level Input Voltage EN Input Current fOSC TS VEN VEN IEN TEST CONDITIONS TA=25°C -40°C≤TA≤85°C VIN=2.5V ~ 5.5V VIN=2.5V ~ 5.5V VEN=0V, VIN=5.5V VEN=0V, VIN=5.5V, VSW=0V or 5.5V ISW=100mA ISW=100mA Duty Cycle=100% Current Pulse Width<1ms -40°C≤TA≤+85°C -40°C≤TA≤+85°C VEN=0V ~ VIN UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw MIN 2.5 -30 0.588 0.582 TYP 0.5 0.6 0.6 0.04 0.04 0.5 0.01 -1 0.35 0.24 MAX UNIT 5.5 V 30 nA 0.612 V 0.618 V 0.4 %V 0.4 %V % 1 µA 1 µA Ω Ω 0.9 1.2 1.4 A 1.2 1.6 145 2.0 MHZ °C V V µA 0.9 -1 0.3 1 4 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC TYPICAL APPLICATION CIRCUIT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC FUNCTION DESCRIPTION The UC3666 is a dual channel constant frequency current mode PWM step-down converter. It is designed for low voltage, Li-Ion battery powered applications requiring high efficiency and small size. The output voltage can be adjusted from 0.6V to 5.5V by means of an external resistor divider. A main switch and a synchronous rectifier are integrated to provide high efficiency, thus an external Schottky diode is saved. This device can achieve 100% duty cycle. The duty cycle D of a step-down converter can be calculated as follows: D=TON×fOSC×100%≒VOUT/VIN×100% (Where TON is the main switch on time and fOSC is the oscillator frequency (1.6MHz)). Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. The UC3666 has a constant switching frequency of 1.6MHz and can adjust the output voltage. During each cycle, the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. The main switch is switched on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current exceeds the error voltage during normal operation. When the main switch is turned off, the synchronous rectifier will be turned on as soon as possible, and then stay on until either the inductor current drops to zero or the next cycle starts. To get a high efficiency, the device is skipped pulses at light load. Dropout Operation The UC3666 allows the main switch to keep for more than one switching cycle and increases the duty cycle while the input voltage decreases until nearly equal to the output voltage. When the duty cycle reaches 100%, the main switch is held on continuously to drive the output with current until it is equal to the P-MOSFET current limit. Thus, the output voltage can be calculated as the input voltage minus the voltage drop across the main switch and the inductor. Short Circuit Protection Short circuit protection is incorporated in UC3666. When the output is shorted to ground, the oscillator frequency is reduced to protect inductor current from being damaged due to it increasing beyond the P-MOSFET current limit. In order to make the short circuit current lower, the P-MOSFET current limit is also reduced. The values of frequency and current limit are restored until the short circuit condition is removed as well as the feedback voltage reaches 0.6V. Maximum Load Current The UC3666’s input voltage can be of as low as 2.5V, however, at lower input voltage, the maximum load current decreases because of the large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations as duty cycles become higher than 50%. Conversely the current limit increases as the duty cycle decreases match other diagrams in this datasheet. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC Soft Start/Enable Soft start limits the current surge seen at the input and eliminates output voltage overshoot. The enable pin is active high. When pulled low, the enable input (EN) forces the UTC UC3666 into a low-power, non-switching state. The total input current during shutdown is less than 1µA. Over-temperature Thermal protection completely disables switching when internal dissipation becomes excessive. The junction over-temperature threshold is 145℃ with 10℃ of hysteresis. Once an over-temperature condition is removed, the output voltage automatically recovers. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 8 QW-R502-489.a UC3666 Preliminary CMOS IC 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-R502-489.a