MC34025DWG View Datasheet(PDF) - ON Semiconductor
Part Name
Description
View to exact match
MC34025DWG Datasheet PDF : 20 Pages
| |||
MC34025, MC33025
PIN FUNCTION DESCRIPTION
Pin No.
DIP/SOIC
1
Function
Error Amp Inverting
Input
Description
This pin is usually used for feedback from the output of the power supply.
2
Error Amp
This pin is used to provide a reference in which an error signal can be produced on the output of the
Noninverting Input error amp. Usually this is connected to Vref, however an external reference 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.
5
RT
6
CT
The value of RT sets the charge current through timing Capacitor, CT.
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 current is
Limit/Shutdown
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 noise on the control circuitry.
14
Output B
This is a high current totem pole output.
15
VCC
16
Vref
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.
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.
Figure 22. Voltage 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.
Figure 23. Current Mode Operation
http://onsemi.com
10
|
|
Share Link: 