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Fairchild
Fairchild

KA3842B Datasheet

SMPS Controller


KA3842B Datasheet Preview


www.fairchildsemi.com
KA3842B/KA3843B/KA3844B/KA3845B
SMPS Controller
Features
• Low Start Up Current
• Maximum Duty Clamp
• UVLO With Hysteresis
• Operating Frequency Up To 500KHz
Description
The KA3842B/KA3843B/KA3844B/KA3845B are fixed
frequency current-mode PWM controller. They are spe-
cially designed for Off - Line and DC-to-DC converter
applications with minimum external components. These
integrated circuits feature a trimmed oscillator for precise
duty cycle control, a temperature compensated reference,
high gain error amplifier. current sensing comparator, and a
high current totempole output Ideally suited for driving a
power MOSFET. Protection circuity Includes built in
under-voltage lockout and current limiting. The KA3842B
and KA3844B have UVLO thresholds of 16V (on) and
10V (off) The KA3843B and KA3845B are 8.5V (on) and
7.9V (off) The KA3842B and KA3843B can operate within
100% duty cycle. The KA3844B and KA3845B can operate
with 50% duty cycle.
8-DIP
14-SOP
1
1
©2000 Fairchild Semiconductor International
Rev. 5.0
Page 1

KA3842B/KA3843B/KA3844B/KA3845B
Internal Block Diagram
Absolute Maximum Ratings
Parameter
Supply Voltage
Output Current
Analog Inputs (Pin 2.3)
Error Amp Output Sink Current
Power Dissipation (TA = 25°C)
Symbol
VCC
IO
V(ANA)
ISINK (E.A)
PD
Value
30
±1
-0.3 to 6.3
10
1
Unit
V
A
V
mA
W
2
Page 2

KA3842B/KA3843B/KA3844B/KA3845B
Electrical Characteristics
(VCC=15V, RT=10K, CT=3.3nF, TA= 0°C to +70°C, unless otherwise specified)
Parameter
REFERENCE SECTION
Reference Output Voltage
Line Regulation
Load Regulation
Short Circuit Output Current
OSCILLATOR SECTION
Oscillation Frequency
Frequency Change with Voltage
Oscillator Amplitude
ERROR AMPLIFIER SECTION
Input Bias Current
Input Voltage
Open Loop Voltage Gain
Power Supply Rejection Ratio
Output Sink Current
Output Source Current
High Output Voltage
Low Output Voltage
CURRENT SENSE SECTION
Gain
Maximum Input Signal
Power Supply Rejection Ratio
Input Bias Current
OUTPUT SECTION
Low Output Voltage
Symbol
VREF
VREF
VREF
ISC
f
f/VCC
VOSC
IBIAS
VI(E>A)
GVO
PSRR
ISINK
ISOURCE
VOH
VOL
GV
VI(MAX)
PSRR
IBIAS
VOL
High Output Voltage
VOH
Rise Time
tR
Fall Time
tF
UNDER-VOLTAGE LOCKOUT SECTION
Start Threshold
VTH(ST)
Min. Operating Voltage
(After Turn On)
VOPR(MIN)
Conditions
Min.
TJ = 25°C, IREF = 1mA
12VVCC25V
1mAIREF20mA
TA = 25°C
4.90
-
-
-
TJ = 25°C
12VVCC25V
-
47
-
-
-
V1 = 2.5V
2VVO 4V
12VVCC 25V
V2 = 2.7V, V1 = 1.1V
V2 = 2.3V, V1 = 5V
V2 = 2.3V, RL = 15Kto GND
V2 = 2.7V, RL = 15Kto Pin 8
-
2.42
65
60
2
-0.6
5
-
(Note 1 & 2)
V1 = 5V(Note 1)
12VVCC 25V (Note 1)
-
2.85
0.9
-
-
ISINK = 20mA
ISINK = 200mA
ISOURCE = 20mA
ISOURCE = 200mA
TJ = 25°C, CL= 1nF (Note 3)
TJ = 25°C, CL= 1nF (Note 3)
-
-
13
12
-
-
KA3842B/KA3844B
KA3843B/KA3845B
KA3842B/KA3844B
KA3843B/KA3845B
14.5
7.8
8.5
7.0
Typ.
5.00
6
6
-100
52
0.05
1.6
-0.1
2.50
90
70
7
-1.0
6
0.8
3
1
70
-3
0.08
1.4
13.5
13.0
45
35
16.0
8.4
10.0
7.6
Max. Unit
5.10
20
25
-180
V
mV
mV
mA
57 KHz
1%
- VP-P
-2
2.58
-
-
-
-
-
1.1
µA
V
dB
dB
mA
mA
V
V
3.15
1.1
-
-10
V/V
V
dB
µA
0.4 V
2.2 V
-V
-V
150 ns
150 ns
17.5
9.0
11.5
8.2
V
V
V
V
3
Page 3
Part Number KA3842B
Manufactur Fairchild
Description SMPS Controller
Total Page 12 Pages
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KA3842 , KA3842 , KA3842A , KA3842AC , KA3842AE , KA3842AM , KA3842AMM , KA3842AMN , KA3842AN , KA3842B , KA3842BD ,

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