www.fairchildsemi.com
KA3502
PC SMPS Supervisory IC
Features
• • • • • • • • • • Complete Housekeeping Circuit Few Ext...
www.fairchildsemi.com
KA3502
PC SMPS Supervisory IC
Features
Complete Housekeeping Circuit Few External Components Over
Voltage Protection for 3.3V/5V/12V/Adj. Output Over Current Protection for 3.3V/5V/12V Output Open-Collector Output and Remote On/Off Function Remote On/Off Delay Time Control Precision
Voltage Reference for Outputs, 5V/12V Uncommitment Precision
Voltage Reference for +5Vs Power Good Signal Generator with Hysteresis Disable Logic of 3.3V, 5V, 12V for Complete Shutdown
Descriptions
The KA3502 is complete housekeeping circuitry for use in the secondary side of SMPS(Switched Mode Power Supply). It contains various functions, which are two Precision
Voltage References, Over
Voltage/Current Protection, Remote On/Off Control, Power Good Signal Generator, Disable Logic and etc.
20-DIP
1
Internal Block Diagram
V33 V5 V12 1 2 3
PWM FB1 VREF1 UV 14 11 6 15
VCC 5
R3
R1
R5
Vcc Adj 4
R2 R4
R6
+ + + + 1.26V
COMP1 Ion
R8 1k
R10 39k
Ichg R15 5.1k 9
R9 10k
R13 Vcc
5.2V + COMP9 Q3
PG
Tsur 17 2.7V IS5 19 -+ 50mV IS33 20 -+ 135mV IS12 18 Vcc + COMP2 Vcc + COMP3 Vcc + - + - COMP4 65mV Vcc + 2V
S Vcc Q R
Q1 REFERENCE1
+ COMP7 Vcc + COMP8 R12 1.28V↔1.24V
2V↔1.3V Q2
COMP5 Vcc Vcc + COMP6 1.4V Ion+ Ioff 2.8V + 2V↔0.7V R11 5.4k
12 FB2
R14 REFERENCE2 13 VREF2
R7 7 REM 8 Trem 16 GND 10 Topr
Rev. 5.0
©2000 Fairchild Semiconductor International
KA3502
Pin Assignments
#1 V33
#20 IS33
V5
IS5
V12
IS12
Adj
Tsur
VCC
PWM
K A 3 5 0...