YOUDA INTEGRATED CIRCUIT
YD3842
CURRENT MODE PWM CONTROL CIRCUITS--YD3842
DESCRIPTION
The YD3842 provides the necessary features to implement off-line or DC fixed frequency current mode control
schemes with a minimal external parts count.
FEATURES
*Optimized For Off-line and DC to DC Converts
*Low Start up Current
*Automatic Feed Forward Compensation
*Pulse-by-Pulse Current Limiting
*Under-voltage Lookout with Hysteresis
*Double Pulse Suppression
*High Current Totem Pole Output
*Internally Trimmed Band-gap Reference
*500kHz Operation
BLOCK DIAGRAM
8
7
6
1/2
1/3
VCC
5V
REF
S/R
UVL
5
1
2
3
4
R S
OSC
+
-
EA
1V
WuXi YouDa Electronics Co., Ltd
Add: No.5 Xijin Road, National Hi-Tech Industrial Development Zone, Wuxi Jiangsu China
Tel: 86-510-85205117 86-510-85205106 Fax: 86-510-85205110 Website: www.e-youda.com
SHENZHEN OFFICE Tel 86-755-83740369 Fax 86-755-83741418
Ver 5.0 1 of 4 2006-7-10
YOUDA INTEGRATED CIRCUIT
YD3842
ABSOLUTE MAXIMUM RATINGS
(Tamb=25)
PARAMETER SYMBOL
VALUE
UNIT
Supply Voltage (Low impedance Source)
V
CC
30 V
Output Current
Io
1 A
Analog Inputs(pin 2, 3)
V
I(ANA)
-0.3 to +6.3
V
Error Amplifier Output Sink Current
l
SINK(EA)
10 mA
Power Dissipation
P
D
1.0
W
ELECTRICAL CHARACTERISTICS
(Tamb=25, V
CC1
=10V, Vcc2=9.5V, unless otherwise specified)
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Reference Section
Output Voltage
V
REF
Tj=25, Io=1mA
4.90
5.00
5.10
V
Line Regulation
V
REF
12
V
IN
25
V
6 20
mV
Load Regulation
V
REF
1lo=20mA
6
25
MV
Output Noise Voltage
Vose
10Hzf10kHz,
Tj=25(note 2)
50 6 mV
Long Term Stability
Ta=25, 1000Hrs
(note 2)
5 25
mV
Output Short Circuit
lsc
-30
-100
-180
mA
Oscillator Section
Initial Accuracy
f
Tj=25 47
52
57
kHz
Voltage Stability
f/
Vcc 12Vcc25V
0.2
1
%
Temp Stability
TminT
A
Tmax
(note 2)
5 %
Amplitude
Vosc
Vpin 4 peak to peak
1.7
V
Error Amplifier Section
Input Voltage
V
I(EA)
Vpin
1=2.5V
2.42
2.50
2.58
V
Input Bias Current
l
BIAS
-0.3
-2
A
A
VOL
2Vo4V 60
90
dB
Unity Gain
Bandwidth
Tj=25(note 2)
0.7
1
6.0
mHz
PSRR
12Vcc25V 60
70
dB
Output Sink Current
lsink
Vpin2=2.7V,
Vpin 1=1.1V
2 6 mA
Output Source
Current
lsource
Vpin 2=2.3V, Vpin
1=5V
-0.5 -0.8 mA
Vout High
V
OH
Vpin 2=2.3V, R
L
=15k
to GND
5 6 V
Vout Low
V
OL
Vpin 2=2.7V, Vpin
1=1.1V
0.7
1.1 V
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YOUDA INTEGRATED CIRCUIT
YD3842
Current Sense Section
Gain
Gv
(note 3, 4)
2.85
3
3.15
V/V
Maximum Input Signal
V
I(MAX)
Vpin 1=5V(note 3)
0.9
1
1.1
V
PSRR
12Vcc25V 70 dB
Input Bias Current
l
BIAS
-2
-10
A
Delay to Output
Vpin 3=0 to 2V
150
300
ns
Output Section
lsink=20mA
0.1
0.4
V
Output Low Level
V
OL
lsink=200mA
1.5
2.2
V
lsource=20mA 13
13.5
V
Output High Level
V
OH
lsource=200mA 12
13.5
V
Rise Time
t
R
Tj=25, C
L
=1nF
(note 2)
50
150
ns
Fall Time
t
F
Tj=25, C
L
=1nF(note 2)
50
150
ns
UVLO Saturation
Vcc=5V, lsink=10mA
0.7
1.2
V
Under-Voltage lockout Output Section
Start Threshold
V
TH(ST)
14.5
16
17.5
V
Min. Operating Voltage
After Turn On
V
OPR
(min
)
8.5
10
11.5
V
PWM Section
Maximum Duty Cycle
D
(MAX)
95 07 100 %
Minimum Duty Cycle
D
(MIN)
0 %
Total Standby Current
Start-up Current
l
ST
0.5
1
mA
Operating Supply
Current
Icc
(OPR)
Vpin 2=Vpin 3=0V
11
17
mA
Vcc
Zener
Voltage Vz
Icc=25mA
34 V
APPLICATION CIRCUIT
1
/1
OUTPUT
VCC
0.
1
A
Vref
Adjust
Isense
CT
5
4
3
2
7
6
5
4.
7
Error Amp
Adjust
10
0
1
8
RT
4.
7
0.
1
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