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UC3842AL-S08-T [UTC]

CURRENT MODE PWM CONTROL CIRCUITS; 电流模式PWM控制电路
UC3842AL-S08-T
型号： UC3842AL-S08-T
厂家： Unisonic Technologies    Unisonic Technologies
描述：

CURRENT MODE PWM CONTROL CIRCUITS
电流模式PWM控制电路

稳压器 开关式稳压器或控制器 电源电路 开关式控制器 光电二极管
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UNISONIC TECHNOLOGIES CO., LTD  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
CURRENT MODE PWM  
CONTROL CIRCUITS  
SOP-8  
ꢀ
DESCRIPTION  
The UTC UC3842A/3843A provide the necessary functions to  
implement off-line or DC to DC fixed frequency current mode ,  
controlled switching circuits with minimal external components.  
ꢀ
FEATURES  
*Low start up current ( Typical 0.12mA )  
*Automatic feed forward compensation  
*Pulse-by-Pulse current limiting  
DIP-8  
*Under-voltage lockout with hysteresis  
*Double pulse Suppression  
*High current totem pole output to drive MOSFET directly  
*Internally trimmed band gap reference  
*500kHz operation  
*Pb-free plating product number: UC3842AL  
UC3843AL  
ꢀ
ORDERING INFORMATION  
Ordering Number  
Package  
Packing  
Normal  
Lead Free Plating  
UC3842A-D08-T  
UC3842A-S08-R  
UC3842A-S08-T  
UC3843A-D08-T  
UC3843A-S08-R  
UC3843A-S08-T  
UC3842AL-D08-T  
UC3842AL-S08-R  
UC3842AL-S08-T  
UC3843AL-D08-T  
UC3843AL-S08-R  
UC3843AL-S08-T  
DIP-8  
SOP-8  
SOP-8  
DIP-8  
Tube  
Tape Reel  
Tube  
Tube  
SOP-8  
SOP-8  
Tape Reel  
Tube  
UC3842AL-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 © 2005 Unisonic Technologies Co., Ltd  
1 of 9  
QW-R103-002,D  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
PIN CONFIGURATION  
V
REF  
COMP  
1
2
3
4
8
7
6
5
V
CC  
VFB  
Current Sense  
RT/CT  
Output  
GND  
ꢀ
BLOCK DIAGRAM  
7
5
7
Vcc  
GND  
Vcc  
VREF  
8
5V REF  
S/R  
Internal  
Bias  
U.V.L.O  
V
REF  
Good  
Logic  
1/2VREF  
CURRENT  
SENSE  
1/3VREF  
COMPARATOR  
VFB  
2
1
3
R
1V  
ERROR  
AMPLIFIER  
PWM  
LATCH  
6
5
OUTPUT  
GND  
COMP  
S
CURRENT SENSE  
RT/CT  
4
OSCILLATOR  
UNISONIC TECHNOLOGIES CO., LTD  
2 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
ABSOLUTE MAXIMUM RATINGS (Ta=25  
℃)  
PARAMETER  
SYMBOL  
VCC  
RATINGS  
30  
UNIT  
Supply Voltage(Low Impedance Source)  
Supply Voltage(ICC<30mA)  
V
V
A
VCC  
Self Limiting  
±1  
Output Current ( Peak )  
IO(PEAK)  
Output Energy (capacity Load)  
Analog Inputs(pin 2,3)  
5
-0.3 ~ +6.3  
10  
µJ  
V
VI(ANA)  
Error Amplifier Output Sink Current  
ISINK(EA)  
mA  
W
DIP-8  
1.0  
Power Dissipation( Ta≦25°C)  
PD  
SOP-8  
0.5  
W
Derated at Ta>25  
°
C
PD  
TJ  
8
mW/°C  
Junction Temperature  
Storage Temperature  
+150  
-65 ~ +150  
°
°
C
C
TSTG  
Note Absolute maximum ratings are those values beyond which the device which the device could be permanently  
damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied.  
ꢀ
ELECTRICAL CHARACTERISTICS  
(0°  
C≦  
T
a≦70°C, VCC=15V, RT=10kΩ, CT=3.3nF, unless otherwise specified)  
PARAMETER  
SYMBOL  
TEST CONDITIONS  
MIN  
4.9  
TYP MAX UNIT  
Reference Section  
Output Voltage  
VREF  
TJ=25  
°
C,IOUT=1mA  
VIN25V  
5
6
5.1  
20  
25  
V
12≦  
Line Regulation  
Load Regulation  
Temperature Stability  
Total Output Variation  
Output Noise Voltage  
Long Term Stability  
Output Short Circuit  
Oscillator Section  
Initial Accuracy  
∆
∆
VREF  
VREF  
mV  
mV  
1
≦IOUT=20mA  
6
(Note 1)  
0.2  
0.4 mV/°C  
Line, Load, Temp(Note 1)  
4.82  
5.18  
V
10Hz  
≦
f
≦
10kHz,TJ=25°C (Note 1)  
Vosc  
ISC  
f
50  
5
µV  
mV  
mA  
Ta=25  
°
C,1000Hrs(Note 1)  
25  
-30  
47  
-100 -180  
TJ=25  
12 VCC  
Tmin Ta  
°
C
52  
0.2  
5
57  
1
kHz  
%
≦
≦
25V  
Voltage Stability  
Temperature Stability  
Amplitude  
∆f/∆Vcc  
≦
≦Tmax(Note 1)  
%
Vosc  
Vpin 4 peak to peak  
1.7  
V
Error Amplifier Section  
Input Voltage  
VI(EA)  
Vpin 1=2.5V  
2.42  
2.50  
-0.3  
90  
1
2.58  
-2  
V
Input Bias Current  
AVOL  
II(BIAS)  
µA  
2
≦
VOUT  
TJ=25 C (Note 1)  
I2 VCC 25V  
≦4V  
60  
0.7  
60  
2
dB  
MHz  
dB  
mA  
mA  
V
Unity Gain Bandwidth  
PSRR  
°
≦
≦
70  
6
Output Sink Current  
Output Source Current  
VOUT High  
IO(SINK) Vpin 2=2.7V,Vpin 1=1.1V  
IO(SOURCE) Vpin 2=2.3V,Vpin 1=5V  
-0.5  
5
-0.8  
6
VOH  
VOL  
Vpin 2=2.3V, RL=15k  
Ω to GND  
VOUT Low  
Vpin 2=2.7V,Vpin 1=1.1V  
0.7  
1.1  
V
UNISONIC TECHNOLOGIES CO., LTD  
3 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
ELECTRICAL CHARACTERISTICS(Cont.)  
PARAMETER  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP MAX UNIT  
Current Sense section  
Gain  
GV  
(Note 2,3)  
2.85  
0.9  
3
1
3.15  
1.1  
V/V  
V
Maximum Input signal  
PSRR  
VI(MAX) Vpin 1=5V( Note 2)  
12 VCC 25V  
≦
≦
70  
-2  
dB  
Input Bias Current  
Delay to Output  
Output Section  
IBIAS  
-10  
µA  
ns  
Vpin 3=0 to 2V  
150  
300  
IO(SINK)=20mA  
0.1  
1.5  
13.5  
13.5  
50  
0.4  
2.2  
V
V
Low  
VOL  
VOH  
IO(SINK)=200mA  
IO(SOURCE)=20mA  
IO(SOURCE)=200mA  
Output Level  
13  
12  
V
High  
V
Rise Time  
Fall Time  
tR  
tF  
TJ=25  
°
°
C,CL=1nF(Note 1)  
C,CL=1nF(Note 1)  
150  
150  
ns  
ns  
TJ=25  
50  
Under-Voltage Lockout Output Section  
3842A  
14.5  
7.8  
8.5  
7
16  
8.4  
10  
17.5  
9
V
V
V
V
Start Threshold  
VTH(ST)  
3843A  
3842A  
3843A  
11.5  
8.2  
Min. Operating Voltage  
PWM Section  
VOPR(MIN) After Turn On  
7.6  
MAX  
Min  
D(MAX)  
D(MIN)  
95  
97  
100  
0
%
%
Duty Cycle  
Total Standby Current  
Start-up Current  
IST  
0.12  
11  
0.3  
17  
mA  
mA  
V
Operating Supply Current  
VCC Zener Voltage  
ICC(OPR) Vpin 2=Vpin 3=0V  
Vz  
ICC=25mA  
34  
Note:1.These parameters, although guaranteed ,are not 100% tested in production.  
2. Parameters measured at trip point of latch with Vpin 2=0.  
3. Gain defined as:  
∆Vpin 1  
A=  
; 0  
≦
Vpin3 0.8V  
≦
∆Vpin 3  
4. Adjust VCC above the start threshold before setting at 15V.  
UNISONIC TECHNOLOGIES CO., LTD  
4 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
OPEN-LOOP LABORATORY TEST FIXTURE  
VREF  
RT  
1
8
7
6
5
A
Vcc  
Error  
Amp  
Adjust  
2
3
4
1kΩ  
/ 1W  
OUTPUT  
5kΩ  
CT  
High peak current associated with capacity loads necessitate careful grounding techniques. Timing and bypass  
capacitors should be connected close to pin 5 in single point GND. The transistor and 5k  
to sample the oscillator waveform and apply an adjustable Ramp to Pin 3.  
Ω potentio-meter are used  
ꢀ
UNDER-VOLTAGE LOCKOUT  
Icc  
Vcc  
<15mA  
ON/OFF Command  
to rest of IC  
7
Von=16V  
Voff=10V  
<1mA  
Voff  
Von  
Vcc  
During Under-Voltage Lockout, the output driver is biased to a high impedance state. Pin 6 should be shunt to  
GND with a bleeder resistor to prevent activating the power switch with output leakage currents.  
ꢀ
ERROR AMPLIFIER CONFIGURATION  
2.5V  
0.5mA  
Zi  
2
1
Zf  
Error amplifier can source or sink up to 0.5mA  
UNISONIC TECHNOLOGIES CO., LTD  
5 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
CURRENT SENSE CIRCUIT  
Error Amplifier  
2R  
Is  
R
1V  
1
3
Current Sense Comparator  
R
Rs  
C
5
Peak current (Is) determined by the formula: Ismax=10V/Rs.  
A small RC filter be required to suppress switch transients.  
ꢀ
SLOPE COMPENSATION  
8
4
3
RT  
CT  
Isense  
R1  
R2  
Rsense  
C
A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope  
compensation for converts requiring duty cycles over 50%.Note that capacitor C, forms a filter with R2 to suppress  
the leading edge switch spikes.  
ꢀ
OSCILLATOR SECTION  
V4  
Large RT  
Small CT  
8
4
5
INTERNAL CLOCK  
V4  
RT  
CT  
Small RT  
Large CT  
INTERNAL CLOCK  
Dead time vs. CT(RT>5k  
Ω)  
Timing Resistance vs. Frequency  
100  
10  
100  
10  
1
CT=2.2nF  
CT=4.7nF  
CT=10nF  
CT=22nF  
1
CT=47nF  
CT=100nF  
0.1  
1
10  
CT (nF)  
100  
2
3
4
6
10  
5
10  
10  
10  
Frequency (Hz)  
10  
UNISONIC TECHNOLOGIES CO., LTD  
6 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
SHUTDOWN TECHNIQUES  
1kΩ  
1
8
3
Shutdown  
Shutdown  
To current  
Sense resistor  
Shutdown UTC UC3842A can be accomplished by two methods; either raise pin 3 above 1V or pull Pin 1 below a  
voltage two diode drops above ground. Either method caused the output of PWM comparator to be high(refer to  
block diagram).The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the  
shutdown condition at pins 1 and/or 3 is removed . In one example, an externally latched shut –down may be  
accomplished by adding an SCR which be reset by cycling VCC below the lower UVLO threshold. At this point the  
reference turns off allowing the SCR to reset  
.
UNISONIC TECHNOLOGIES CO., LTD  
7 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
ꢀ
TYPICAL CHARACTERISTICS  
Output Saturation Characteristics  
4
Error Amplifier Open-Loop Frequency Response  
100  
Vcc=15V  
Ta=+25℃  
Ta=-40℃  
80  
60  
40  
20  
0
0
3
2
1
0
-45  
-90  
-135  
-180  
0.01  
0.1  
Output Current  
(Sourse or Sink Current) (A)  
1
7
2
3
4
5
6
10  
10 10 10  
10 10  
10  
Frequency (Hz)  
Istart Temperature Drift  
Vcc=9V  
V
REF Temperature Drift  
Vcc=15V  
5.02  
5.01  
550  
500  
I
OUT=1mA  
5.00  
4.99  
450  
400  
4.98  
350  
4.97  
4.96  
300  
250  
-50 -25 0 25 50 75 100 125 150  
-50 -25 0 25 50 75 100 125 150  
Temperature (℃)  
Temperature (℃)  
Icc Temperature Drift  
Vcc=15V  
15  
14  
IOUT=1mA  
13  
12  
11  
10  
9
-50 -25  
0
25 50 75 100 125 150  
Temperature (℃)  
UNISONIC TECHNOLOGIES CO., LTD  
8 of 9  
QW-R103-002,D  
www.unisonic.com.tw  
UC3842A/3843A  
LINEAR INTEGRATED CIRCUIT  
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  
9 of 9  
QW-R103-002,D  
www.unisonic.com.tw  

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