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UNISONIC TECHNOLOGIES CO., LTD UC3844/45
HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS
DESCRIPTION
The UTC UC3844/3845 are high performance fixed frequency current mode controllers that specifically designed for Off-Line and DC to DC converter applications with minimal external parts count. The differences between UC3844 and UC3845 are the maximum duty cycle ranges and under-voltage lockout thresholds. The UC3844 ideally suited to off-line applications with UVLO thresholds of 16V(ON) and 10V(OFF), and UC3845 has UVLO thresholds of 8.5V(ON) and 7.6V(OFF) for lower voltage applications.
LINEAR INTEGRATED CIRCUIT
FEATURES
* Operation output switching frequency up to 500 kHz * Output deadtime adjustable from 50% to 70% * Automatic feed forward compensation * Latching PWM for cycle-by-cycle current limiting * High current totem pole output * Internally trimmed reference with under voltage lockout * UVLO with hysteresis * Low startup and operating current
*Pb-free plating product number: UC3844L/UC3845L
ORDERING INFORMATION
Order Number Normal Lead Free Plating UC3844-D08-T UC3844L-D08-T UC3844-S08-R UC3844L-S08-R UC3844-S08-T UC3844L-S08-T UC3845-D08-T UC3845L-D08-T UC3845-S08-R UC3845L-S08-R UC3845-S08-T UC3845L-S08-T Package DIP-8 SOP-8 SOP-8 DIP-8 SOP-8 SOP-8 Packing Tube Tape Reel Tube Tube Tape Reel Tube
www.unisonic.com.tw Copyright (c) 2005 Unisonic Technologies Co., Ltd
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PIN CONFIGURATION
LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTION
PIN NO 1 2 3 4 5 6 7 8 PIN NAME FUNCTION Compensation Error amplifier output, this pin is made available for loop compensation. Voltage Feedback, the inverting input of the Error Amplifier. It is normally connected to the VFB switching power supply output through a resistor divider. A voltage proportional to inductor current is connected to this input. The PWM uses this ISENSE information to terminate the output switch conduction. The Oscillator frequency and maximum output duty cycle are programmed by connecting RT/CT resistor RT to Vref and capacitor CT to ground. Operation to 1 MHz is possible. GND Power ground. This output directly drives the gate of a power MOSFET. Peak currents up to 1A are Output sourced and sunk by this pin. The output switches at one-half the oscillator frequency. VCC Positive supply. VREF Reference output, provides charging current for capacitor CT though resistor RT.
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BLOCK DIAGRAM
LINEAR INTEGRATED CIRCUIT
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ABSOLUTE MAXIMUM RATINGS (Ta=25C)
PARAMETER Total Power Supply and Zener Current Output Current, Source or Sink (Note 2) Output Energy (Capacitive Load per cycle) Current Sense and Voltage feedback Inputs Error Amp Output Sink Current SYMBOL (ICC+Iz) IOUT W VIN ISINK
LINEAR INTEGRATED CIRCUIT
RATINGS UNIT 30 mA 1.0 A 5.0 J -0.3 ~ +5.5 V 10 mA SOP-8 862 mW Power Dissipation PD DIP-8 1250 mW Junction Temperature TJ +150 C Operation Temperature Range TOPR 0 ~ 70 C Storage Temperature Range TSTG -65 ~ +150 C Note:1.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. 2.Maxmum package power dissipation limits must be observed.
THERMAL DATA
PARAMETER Thermal Resistance(Junction-to-Air) SOP-8 DIP-8 SYMBOL JA RATINGS 145 100 UNIT C/W C/W
ELECTRICAL CHARACTERISTICS
(Ta=25C, VCC=15V, RT=10k, CT=3.3nF, 0C TA PARAMETER SYMBOL REFERENCE SECTION Reference Output Voltage VREF VOUT Line Regulation VOUT Load Regulation Temperature Stability Total Output Variation over Line, Load, Temperature Output Noise Voltage Long Term Stability Output Short Circuit Current OSCILLATOR SECTION Oscillator Voltage Swing Discharge Current Frequency Frequency Change with Voltage Frequency Change with Temperature ERROR AMPLIFIER SECTION Voltage Feedback Input High Output Voltage Swing Low Sink Output Current Source Input Bias Current Open Loop Voltage Gain Power Supply Rejection Ratio Unity Gain Bandwidth tS VREF eN S ISC VOSC IDSG fOSC fOSC/V fOSC/T VFB VOH VOL ISINK ISOURCE II(BIAS) GVO PSRR GBW f=10Hz ~ kHz, TJ=25C TA=125C for 1000 Hours -30 4.82 50 5 -85 1.6 10.8 52 0.2 5.0 2.42 5.0 2.0 -0.5 65 60 0.7 2.50 6.2 0.8 12 -1.0 -0.1 90 70 1.0 70C, unless otherwise specified) TEST CONDITIONS MIN IOUT=1.0mA,TJ=25 C VCC=12V ~ 25V IOUT=1.0mA ~ 20mA 4.9 TYP 5.0 2.0 3.0 0.2 MAX 5.1 20 25 5.18 UNIT V mV mV mV/C V V mV mA V mA 57 60 1.0 kHz % % V V mA -2.0 A dB dB MHz
-180
VOSC=2.0V, TJ=25C TJ=25C, 0C TA 70C VCC=12V ~ 25V 0C TA 70C VOUT=2.5V RL=15k to ground, VFB=2.3V RL=15k to VREF, VFB=2.7V VOUT=1.1V, VFB=2.7V VOUT=5.0V, VFB=2.3V VFB=2.7V VOUT=2.0V ~ 4.0V VCC=12V ~ 25V TJ=25C
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2.58 1.1
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ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER CURRENT SENSE SECTION Current Sense Input Voltage Gain (Note 2 & 3) Maximum Current Sense Input Threshold (Note 2) Input Bias Current Power Supply Rejection Ratio Propagation Delay OUTPUT SECTION Low Output Voltage High VOH SYMBOL GV VI(THR) II(BIAS) PSRR tPLH(IN/OUT) VOL
LINEAR INTEGRATED CIRCUIT
TEST CONDITIONS
MIN 2.85 0.9
TYP 3.0 1.0 -2.0 70 150 0.1 1.6 13.5 13.4 0.1 50 50
MAX 3.15 1.1 -10 300 0.4 2.2
UNIT V/V V A dB ns V V
VCC=12V ~ 25V (Note4)
Output Voltage with UVLO Activated VOL(UVLO) 1.1 V Output Voltage Rise Time tR 150 ns Output Voltage Fall Time tF 150 ns UNDERVOLTAGE LOCKOUT SECTION UC3844 14.5 16.0 17.5 Startup Threshold VTHR V UC3845 7.8 8.4 9.0 Minimum Operating UC3844 8.5 10.0 11.5 V VCC(MIN) Voltage After Turn-On 7.0 7.6 8.2 UC3845 PWM SECTION Max DCMAX 47 48 50 % Duty Cycle Min DCMIN 0 % TOTAL DEVICE Power Supply Zener Voltage VZ ICC=25mA 30 36 V UC3845 VCC=6.5V 0.5 1.0 Power Supply Current ICC mA (Note 4) VCC=14V UC3844 12 17 Note: 1. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. 2. This parameter is measured at the latch trip point with VFB=0V. 3. Comparator gain is defined as: V Output Compensation AV= V Current Sense Input 4. Adjust VCC above the startup threshold before setting to 15V.
ISINK=20mA ISINK=200mA ISINK=20mA ISINK=200mA VCC=6.0V, ISINK=1.0mA CL=1.0nF,TJ=25C CL=1.0nF,TJ=25C
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TYPICAL CHARACTERISTICS
Timing Resistor vs. Oscillator Frequency 100 50 Timing Resistor, RT (k) 20 75 Percent Output Deadtime, DT (%)
10 0p TA = 25 F 20 0p 50 F 0p F 1.0 2.0 nF nF 5.0 nF C T= 10 nF
VCC = 15V
LINEAR INTEGRATED CIRCUIT
Output Deadtime vs. Oscillator Frequency
1.0nF 70 5.0nF 65 CT = 10nF 2.0nF
10 5.0
60
2.0 Note: Output Switches At
One-Half The Oscillator Frequency
55 500pF 20k 50k 100k 200k Oscillator Frequency, IOSC (Hz)
100pF 200pF 1.0M
1.0 10k
20k
50k
100k
200k
500k 1.0M
50 10k
500k
Oscillator Frequency, IOSC (Hz)
Error Amp Open Loop Gain Phase vs. Frequency Current Sense Input Threshold, VIN(THR) (V) 100 Open Loop Voltage Gain, GV (dB) 80 Gain 60 40 Phase 20 0 -20 120 150 180 10M
VCC = 15V VOUT = 2.0V ~ 4.0V RL = 100k TA = 25
Current Sense Input Threshold vs. Error Amp Output Voltage 0 30 Excess Phase Degrees, 60 90 1.2 1.0
TA = 125
0.8
TA = 25
0.6 0.4
TA = -55
0.2 0
VCC = 15V
10
100
1.0k
10k
100k
1.0M
0
2.0
4.0
6.0
8.0
Frequency, f (Hz)
Error Amp Output Voltage, VOUT (V)
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TYPICAL CHARACTERISTICS(Cont.)
LINEAR INTEGRATED CIRCUIT
Output Saturation Voltage, VO(SAT) (V)
Supply Current, ICC (mA)
UCX845
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
UCX844
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