
TC33025
4
TC33025-1 5/25/00
High Speed Double Ended Controller
Pin No.
DIP/SOIC
Symbol
Description
1
Error Amp
This pin is usually used for feedback from the output of the power supply.
Inverting Input
2
Error Amp
This pin is used to provide a reference in which an error signal can be produced on the
Noninverting
output of the error amp. Usually this is connected to VREF, however an external reference
Input
can also be used.
3
Error Amp Output
This pin is provided for compensating the error amp for poles and zeros encountered in the
power supply system, mostly the output LC filter.
4
Clock
This is a bidirectional pin used for synchronization.
5RT
The value of RT sets the charge current through timing Capacitor, CT.
6CT
In conjunction with RT, the timing Capacitor sets the switching frequency. Because this part
is a push–pull output, each output runs at one–half the frequency set at this pin.
7
Ramp Input
For voltage mode operation this pin is connected to CT. For current mode operation this pin
is connected through a filter to the current sensing element.
8
Soft–Start
A capacitor at this pin sets the Soft–Start time.
9
Current
This pin has two functions. First, it provides cycle–by–cycle current limiting. Second, if the
Limit/Shutdown
current is excessive, this pin will reinitiate a Soft–Start cycle.
10
Ground
This pin is the ground for the control circuitry.
11
Output A
This is a high current totem pole output.
12
Power Ground
This is a separate power ground return that is connected back to the power source. It is
used to reduce the effects of switching transient noise on the control circuitry.
13
VC
This is a separate power source connection for the outputs that is connected back to the
power source input. With a separate power source connection, it can reduce the effects of
switching transient noiseon the control circuitry.
14
Output B
This is a high current totem pole output.
15
VCC
This pin is the positive supply of the control IC.
16
VREF
This is a 5.1V reference. It is usually connected to the noninverting input of the error amplifier.