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UNISONIC TECHNOLOGIES CO., LTD UC3842G
HIGH PERFORMANCE CURRENT MODE CONTROLLER
DESCRIPTION
The UTC UC3842G of high performance current mode controller is specifically designed for off-line and DC-to-DC converter applications offering the designer a cost effective solution with minimal external components. This integrated circuit features approximately 300A start up current, a precision reference trimmed the error amplifier input. Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, and so on.
LINEAR INTEGRATED CIRCUIT
FEATURES
* Low startup and operating current * User defined switching frequency(Norm is 52kHz) * Power-saving mode for low power * Under voltage lockout with hysteresis * Over voltage protection * Latching PWM for Cycle-By-Cycle current limiting * Internally trimmed reference with undervoltage lockout *Pb-free plating product number: UC3842GL
ORDERING INFORMATION
Ordering Number Normal Lead Free Plating UC3842G-D08-T UC3842GL-D08-T UC3842G-S08-R UC3842GL-S08-R UC3842G-S08-T UC3842GL-S08-T Package DIP-8 SOP-8 SOP-8 Packing Tube Tape Reel Tube
UC3842GL-D08-T (1)Packing Type (2)Package Type (3)Lead Plating (1) T: Tube, R: Tape Reel (2) D08: DIP-8, S08: SOP-8 (3) L: Lead Free Plating, Blank: Pb/Sn
www.unisonic.com.tw Copyright (c) 2007 Unisonic Technologies Co., Ltd
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PIN CONFIGURATION
LINEAR INTEGRATED CIRCUIT
COMP 1
8 VREF
FB 2
7 VCC
CS 3
6 OUT
CT 4
5 GND
PIN DESCRIPTION
PIN NO. 1 2 3 4 5 6 7 8 PIN NAME COMP FB CS CT GND OUT VCC VREF I/O O I I I O O Function This pin is error amplifier output The error amplifier inverting input Current sense input The capacitor controlling switch frequency Ground Output to the gate of external power MOS Supply voltage Inter 5V reference voltage output
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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UC3842G
BLOCK DIAGRAM
LINEAR INTEGRATED CIRCUIT
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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ABSOLUTE MAXIMUM RATINGS (Ta 25C)
LINEAR INTEGRATED CIRCUIT
PARAMETER SYMBOL RATINGS UNIT Supply Voltage (Low Impedance Source) VCC 30 V Supply Voltage (ICC<30mA) VCC Self Limiting V Output Current (Peak) IO(PEAK) 1 A Output Energy (Capacity load) 5 J Junction Temperature TJ +150 C Operating Temperature TOPR -40 ~ +125 C Storage Temperature 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.
ELECTRICAL CHARACTERISTICS
(0C Ta 70C, VCC=15V, CT=3.3n , unless otherwise specified) PARAMETER SYMBOL TEST CONDITION STANDBY SECTION Reduce Frequency Point of Standby Mode VCOMP Right load REFERENCE SECTION Reference Output Voltage VREF IOUT=1.0mA Line Regulation VREF 12VVCC25V Load Regulation VREF IOUT=1.0mA to 20mA Output Short Circuit Current ISC OSCILLATOR SECTION Frequency fOSC1 Normal Frequency fOSC2 No load or right load Frequency Change fOSC/V 12VVCC25V VOSC(P-P) Oscillator Voltage VOSCL VOSCH ERROR AMPLIFIER SECTION Input Voltage VI(EA) VCOMP=2.5V Input Bias Current II(BIAS) VFB=5V AVOL 2VVOUT4V Unity Gain Bandwidth TJ=25C(Note1) PSRR 12VVCC25V Output Sink Current ISINK VFB=2.7V, VCOMP=1.1V Output Source Current ISOURCE VFB=2.3V, VCOMP=5V VOUT High VOH VFB=2.3V, RL=15K to GND VOUT Low VOL VFB=2.7V, RL=15K to VREF CURRENT SENSE SECTION Gain GV (Note2,3) Maximum Input Signal VI(MAX) VCOMP=5V(Note2) PSRR 12VVCC25V Input Bias Current IBIAS Delay to Output MIN TYP 2.2 4.95 5.0 3 8 -65 52 14 0.2 1.6 1.2 2.8 2.50 -0.3 90 1 70 4 -0.7 5.6 0.8 3 1 70 -2 150 5.05 20 25 -180 55 1.0 V V V 2.58 -2 V A dB MHz dB mA mA V V V/V V dB A nS MAX UNIT V V mV mV mA KHz KHz
-30 49
2.42 60 0.7 60 2 -0.5 5.0
1.1 3.15 1.1 -10 300
2.85 0.9
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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ELECTRICAL CHARACTERISTICS (Cont.)
PARAMETER OUTPUT SECTION Output Voltage With UVLO Active Output Voltage VOH Output Voltage Rise and Fall time tR tF SYMBOL VOL(UVLO) VOL
LINEAR INTEGRATED CIRCUIT
TEST CONDITION VCC=6V,ISINK=1mA ISINK=20mA ISINK=200mA ISOURCE=20mA ISOURCE=200mA CL=1.0nF(Note1) CL=1.0nF(Note1)
MIN
TYP 0.8 0.1 1.6 14.5 14.6 100 100 15 10 94
MAX UNIT 1.1 0.4 2.2 V V V V V nS V V % % V mA A
13 12
150 150 16.5 11.5
UNDER VOLTAGE LOCKOUT SECTION Startup Threshold VTH(STAR-UP) Min Operating Voltage VOPR(MIN) After Turn-ON PWM SECTION Max Duty Cycle DMAX Minimum Duty Cycle DMIN TOTAL DEVICE Power Supply Zener Voltage VZ ICC=25mA Power Operating Supply Current ICC Note2 Startup Current ISTART-UP VCC=14V,UVLO Active Note: 1.These parameters, although guaranteed, are not 100% tested in production. 2.Parameters measured at trip point of latch with VFB=0. 3.Gain defined as: A= VCOMP/ VCS; 0 VCS 0.8V
13.5 8.5 92
0 30 39 7 150
10 300
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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UC3842G
OPEN-LOOP TEST CIRCUIT
LINEAR INTEGRATED CIRCUIT
VCOMP Ra 100k Rb 100k VFB Vpwl adjust 5K
1 COMP
10p
VREF 8 VCC 7
VCC
VIN or
2 FB 3 CS 4 CT
CIN 470
Output 6 GND 5
CT 3.3n
High peak current associated with capacity loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to pin5 in single point GND.
UNDER-VOLTAGE LOCKOUT
During Under-Voltage Lockout, the output driver is biased to a high impedance state. Pin6 should be shunt to GND with a bleeder resistor to prevent activing the power switch with output leakage currents.
ERROR AMPLIFIER CONFIGURATION
Error amplifier can source or sink up to 0.5mA
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www.unisonic.com.tw
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CURRENT SENSE CIRCUIT
Error Amplifier 2R 1 R Rs C 3 5 R
LINEAR INTEGRATED CIRCUIT
Is
1V Current Sense Comparator
Peak current (IS) determined by the formula: ISMAX=1V/Rs. A small RC filter be required to suppress switch transients
OSCILLATOR AND STANDBY MODE
We can judge the state of output load through the voltage of PIN1. In order to reduce the standby power, it will reduce the OSC frequency at right load. When VCOMP 2.2V, the OSC frequency begins to reduce. The normal frequency is 52KHz, the minimum frequency is 14KHz.
VCOMP 2.2V Increase
1.2V Normal Frequency: 52KHz Standby mode Minimum frequency :14KHz Normal Frequency: 52KHz
OSC triangle wave
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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SHUTDOWN TECHNIQUE
LINEAR INTEGRATED CIRCUIT
1k
8
Shutdown
1
330
3
500 To current Sense resistor
Shutdown
Shutdown UTC UC3842G can be accomplished by two methods; either raise pin 3 above 1V or pull Pin 1 below a voltage two diode drops above ground.
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
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