TC18C46
TC28C46
TC38C46
CMOS CURRENT MODE PWM CONTROLLER
FEATURES
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Isolated Output Drive
Low Power CMOS Construction
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
Low Prop Delay Current Amp
to Output ......................................... < 350nsec Typ.
Low Prop Delay Shutdown
to Output ......................................... < 400nsec Typ.
TC38C46Pin Compatible with Unitrode UC3846
ESD Protected .................................................
±
2 kV
1
GENERAL DESCRIPTION
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.
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3
4
5
6
ORDERING INFORMATION
Part No.
TC18C46MJE
TC28C46EOE
TC28C46EPE
TC38C46COE
TC38C46CPE
Configuration
Non-Inverting
Non-Inverting
Non-Inverting
Non-Inverting
Non-Inverting
Pkg./Temperature
16-Pin CerDIP
– 55°C to +125°C
16-Pin SOIC (Wide)
– 40
°C
to +85°C
16-Pin Plastic DIP (Narrow)
– 40°C to +85°C
16-Pin SOIC (Wide)
0°C to +70°C
16-Pin Plastic DIP (Narrow)
0°C to +70°C
FUNCTIONAL BLOCK DIAGRAM
VREF
2
VIN
RT
CT
SYNC
– CURRENT
SENSE INPUT
+ CURRENT
SENSE INPUT
COMPENSATION
15
9
8
10
3
4
7
+
+VS
+ ERROR
AMP INPUT
– ERROR
AMP INPUT
5
6
+
–
ERROR
AMPLIFIER
100µA
LIMIT BUFFER
AMPLIFIER
Q4
+
–
350mV
LOCK-UP
AMPLIFIER
Q3
TC18C46
TC28C46
TC38C46
3.5kΩ
Q1
–
+
POSITIVE
FEEDBACK
Q2
6kΩ
SHUTDOWN
COMPARATOR
+
–
350mV
16
CURRENT SENSE
PWM
AMPLIFIER
COMPARATOR
.65V
–
+
x3
– +
+
–
R
Q
S
S
PWM LATCH
14
12
OSCILLATOR
UNDER VOLTAGE
LOCKOUT
D Q
C Q
5.1 VOLT
REFERENCE
13
11
VDD
OUTPUT A
OUTPUT B
GROUND
1
7
CURRENT LIMIT
SOFT START ADJUST
SHUTDOWN
TC38C46 OUTPUTS
LOW IN OFF STATE
8
TC18/28/28/C46-8 9/23/96
TELCOM SEMICONDUCTOR, INC.
4-101
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
