MC33023 데이터 시트보기 (PDF) - Motorola => Freescale
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MC33023 Datasheet PDF : 19 Pages
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MC34023 MC33023
Pin
DIP/SOIC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Function
Error Amp
Inverting
Input
Error Amp
Noninverting
Input
Error Amp
Output
Clock
RT
CT
Ramp Input
Soft–Start
Current Limit/
Shutdown
Ground
Current Limit
Reference
Input
Power Ground
VC
Output
VCC
Vref
PIN FUNCTION DESCRIPTION
Description
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 Vref, however an external reference can also be used.
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 RT sets the charge current through timing Capacitor, CT.
In conjunction with RT, the timing Capacitor sets the switching frequency.
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.
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.
Figure 21. Voltage Mode Operation
4
5
CT
6
Oscillator
7
1.25 V
3
1
Output Voltage
Feedback Input Vref 2
In voltage mode operation, the control range on the output of the Error
Amplifier from 0% to 90% duty cycle is from 2.25 V to 4.05 V.
10
Figure 22. Current Mode Operation
4
5
CT
6
Oscillator
From Current
Sense Element
7
1.25 V
3
1
Output Voltage
Feedback Input Vref 2
In current mode control, an RC filter should be placed at the ramp input
to filter the leading edge spike caused by turn–on of a power MOSFET.
MOTOROLA ANALOG IC DEVICE DATA
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