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TC18C46
TC28C46
TC38C46
CMOS CURRENT MODE PWM CONTROLLER
FEATURES
GENERAL DESCRIPTION
■ Isolated Output Drive
■ Low Power CMOS Construction
The TC38C46 is a current mode CMOS PWM control
IC. It draws only 2 mA supply current, so it can be driven
without a costly 50-60 Hz transformer. The output drive
stage is capable of high drive currents, 300mA typical.
The TC38C46 is pin compatible with earlier bipolar
products so that designers can easily update older designs.
A number of improvements have been added.
This second generation part has been designed with an
isolated drive stage. Unlike its cousin, the TC170, the output
stage of the TC38C46 can be run from a separate power
supply such as a secondary winding on an output trans-
former. This allows for bootstrap start-up of the power
supply.
■ Low Supply Current ................................. 2mA Typ.
■ Wide Supply Voltage Operation .............. 8V to 18V
■ Latch-Up Immunity ................... 500mA on Outputs
■ Above and Below Rail Input Protection .............6V
■ High Output Drive ................................ 500mA Peak
■ Current Mode Control
■ Fast Rise/Fall Time ..................... 50nsec @ 1000pF
■ High Frequency Operation ..........................500kHz
■ UV Hysteresis Guaranteed
■ Programmable Current Limit
■ Shutdown Pin Available
■ Double Ended
■ Soft Start
ORDERING INFORMATION
■ Low Prop Delay Current Amp
Part No.
Configuration
Pkg./Temperature
to Output ......................................... < 350nsec Typ.
■ Low Prop Delay Shutdown
TC18C46MJE
Non-Inverting
16-Pin CerDIP
– 55°C to +125°C
16-Pin SOIC (Wide)
– 40 °C to +85°C
to Output ......................................... < 400nsec Typ.
■ TC38C46Pin Compatible with Unitrode UC3846
■ ESD Protected................................................. ±2 kV
TC28C46EOE Non-Inverting
TC28C46EPE
Non-Inverting 16-Pin Plastic DIP (Narrow)
– 40°C to +85°C
16-Pin SOIC (Wide)
TC38C46COE Non-Inverting
0°C to +70°C
TC38C46CPE Non-Inverting 16-Pin Plastic DIP (Narrow)
0°C to +70°C
FUNCTIONAL BLOCK DIAGRAM
V
REF
2
15
5.1 VOLT
REFERENCE
V
IN
13
9
8
V
R
DD
T
UNDER VOLTAGE
LOCKOUT
OUTPUT A
OSCILLATOR
11
C
T
D
C
Q
Q
10
SYNC
CURRENT SENSE
AMPLIFIER
PWM
COMPARATOR
R
– CURRENT
SENSE INPUT
3
4
–
.65V
14
12
OUTPUT B
GROUND
Q
+
x3
–
+
+
S
S
+ CURRENT
SENSE INPUT
–
PWM LATCH
7
COMPENSATION
+
+V
S
LIMIT BUFFER
AMPLIFIER
+
+ ERROR
AMP INPUT
100µA
5
6
Q4
1
CURRENT LIMIT
+
–
SOFT START ADJUST
SHUTDOWN
–
– ERROR
COMPARATOR
AMP INPUT
Q1
ERROR
AMPLIFIER
16
350mV
–
+
SHUTDOWN
350mV
+
–
LOCK-UP
AMPLIFIER
Q2
POSITIVE
FEEDBACK
6kΩ
Q3
TC18C46
TC28C46
TC38C46
3.5kΩ
TC38C46 OUTPUTS
LOW IN OFF STATE
TC18/28/28/C46-8 9/23/96
TELCOM SEMICONDUCTOR, INC.
4-101