MC34023 ON Semiconductor, MC34023 Datasheet - Page 11

• Manufacturer Part Number: MC34023
• Description: (MC33023 / MC34023) High Speed Single-Ended PWM Controller
• Manufacturer: ON Semiconductor

Amplifier from 0% to 90% duty cycle is from 2.25 V to 4.05 V.
DIP/SOIC
In voltage mode operation, the control range on the output of the Error
Pin
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
Feedback Input
Output Voltage
Figure 22. Voltage Mode Operation
C
Reference Input
Inverting Input
Power Ground
T
Current Limit/
Noninverting
Current Limit
Ramp Input
Error Amp
Error Amp
Error Amp
Soft−Start
Shutdown
Function
Ground
Output
Output
Clock
Input
V
V
R
C
V
V
CC
ref
ref
C
T
T
4
5
6
7
3
1
2
This pin is usually used for feedback from the output of the power supply.
This pin is used to provide a reference in which an error signal can be produced on the output of the
error amp. Usually this is connected to V
This pin is provided for compensating the error amp for poles and zeros encountered in the power
supply system, mostly the output LC filter.
This is a bidirectional pin used for synchronization.
The value of R
In conjunction with R
For voltage mode operation this pin is connected to C
connected through a filter to the current sensing element.
A capacitor at this pin sets the Soft−Start time.
This pin has two functions. First, it provides cycle−by−cycle current limiting. Second, if the current is
excessive, this pin will reinitiate a Soft−Start cycle.
This pin is the ground for the control circuitry.
This pin voltage sets the threshold for cycle−by−cycle current limiting.
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.
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 noise
on the control circuitry.
This is a high current totem pole output.
This pin is the positive supply of the control IC.
This is a 5.1 V reference. It is usually connected to the noninverting input of the error amplifier.
1.25 V
Oscillator
T
PIN FUNCTION DESCRIPTION
sets the charge current through timing Capacitor, C
MC34023, MC33023
T
, the timing Capacitor sets the switching frequency.
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11
to filter the leading edge spike caused by turn−on of a power MOSFET.
In current mode control, an RC filter should be placed at the ramp input
Sense Element
ref
From Current
Feedback Input
, however an external reference can also be used.
Output Voltage
Figure 23. Current Mode Operation
Description
T
. For current mode operation this pin is
C
T
V
ref
T
4
5
6
7
3
1
2
.
1.25 V
Oscillator