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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
specially 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 for driving a power MOSFET.
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
Internal Block Diagram
1
14-SOP
1
©2002 Fairchild Semiconductor Corporation
Rev. 1.0.2
Page 1

KA3842B/KA3843B/KA3844B/KA3845B
Absolute Maximum Ratings
Parameter
Symbol
Value
Supply Voltage
Output Current
Analog Inputs (Pin 2.3)
Error Amp Output Sink Current
Power Dissipation at TA25°C (8DIP)
Power Dissipation at TA25°C (14SOP)
Storage Temperature Range
Lead Temperature (Soldering, 10sec)
VCC
IO
V(ANA)
ISINK (E.A)
PD(Note1,2)
PD(Note1,2)
TSTG
TLEAD
30
±1
-0.3 to 6.3
10
1200
680
-65 ~ +150
+300
Note:
1. Board Thickness 1.6mm, Board Dimension 76.2mm ×114.3mm, (Reference EIA / JSED51-3, 51-7)
2. Do not exceeed PD and SOA (Safe Operation Area)
Power Dissipation Curve
1200
1100
1000
900
800
700
600
500
400
300
0
8DIP
14SOP
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
AMBIENT TEMPERATURE ()
Thermal Data
Characteristic
Thermal Resistance Junction-ambient
Symbol
Rthj-amb(MAX)
Pin Array
8D8I-PD,I8PSOP
8-DIP
100
14SOP
14-SOP
180
COMP 1
8 VREF
COMP 1
14 VREF
VFB 2
7 VCC
N/C 2
13 N/C
CURRENT SENSE 3
6 OUTPUT
VFB 3
12 VCC
RT/CT 4
5 GND
N/C 4
11 PWR VC
CURRENT SENSE 5
10 OUTPUT
N/C 6
9 GND
RT/CT 7
8 PWR GND
Unit
V
A
V
mA
mW
mW
°C
°C
Unit
°C/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
Symbol
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
VREF
VREF
VREF
ISC
f
f/VCC
VOSC
IBIAS
VI(E>A)
GVO
PSRR
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
ISINK
ISOURCE
VOH
VOL
GV
VI(MAX)
PSRR
IBIAS
Low Output Voltage
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
TJ = 25°C, IREF = 1mA
12VVCC25V
1mAIREF20mA
TA = 25°C
TJ = 25°C
12VVCC25V
-
-
Vpin1 = 2.5V
2VVO 4V (Note3)
12VVCC 25V (Note3)
Vpin2 = 2.7V, Vpin1 = 1.1V
Vpin2 = 2.3V, Vpin1 = 5V
Vpin2 = 2.3V, RL = 15Kto GND
Vpin2 = 2.7V, RL = 15Kto Pin 8
(Note 1 & 2)
Vpin1 = 5V(Note 1)
12VVCC 25V (Note1,3)
-
ISINK = 20mA
ISINK = 200mA
ISOURCE = 20mA
ISOURCE = 200mA
TJ = 25°C, CL= 1nF (Note 3)
TJ = 25°C, CL= 1nF (Note 3)
KA3842B/KA3844B
KA3843B/KA3845B
KA3842B/KA3844B
KA3843B/KA3845B
Min. Typ. Max. Unit
4.90 5.00 5.10 V
- 6 20 mV
- 6 25 mV
- -100 -180 mA
47 52 57 KHz
- 0.05 1 %
- 1.6 - VP-P
- -0.1 -2 µA
2.42 2.50 2.58 V
65 90 - dB
60 70 - dB
2 7 - mA
-0.6 -1.0 - mA
5 6 -V
- 0.8 1.1 V
2.85 3 3.15 V/V
0.9 1 1.1 V
- 70 - dB
- -3 -10 µA
- 0.08 0.4 V
- 1.4 2.2 V
13 13.5 -
V
12 13.0 -
V
- 45 150 ns
- 35 150 ns
14.5 16.0 17.5
7.8 8.4 9.0
8.5 10.0 11.5
7.0 7.6 8.2
V
V
V
V
3
Page 3
Part Number KA3842B
Manufactur Fairchild
Description SMPS Controller
Total Page 10 Pages
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Related Datasheet

KA3842 , KA3842 , KA3842A , KA3842AC , KA3842AE , KA3842AM , KA3842AN , KA3842B , KA3842BD ,

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