UC3842B, 43B UC2842B, 43B
PIN FUNCTION DESCRIPTION
Pin
8–Pin
1
2
3
4
14–Pin
1
3
5
7
Function
F
i
Compensation
Voltage
Feedback
Current
Sense
RT/CT
Description
D
i i
This pin is the Error Amplifier output and is made available for loop compensation.
This is the inverting input of the Error Amplifier. It is normally connected to the switching power
supply output through a resistor divider.
A voltage proportional to inductor current is connected to this input. The PWM uses this
information to terminate the output switch conduction.
The Oscillator frequency and maximum Output duty cycle are programmed by
connecting resistor RT to Vref and capacitor CT to ground. Operation to 500 kHz
is possible.
This pin is the combined control circuitry and power ground.
This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are sourced
and sunk by this pin.
This pin is the positive supply of the control IC.
This is the reference output. It provides charging current for capacitor CT through resistor RT.
This pin 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.
The Output high state (VOH) is set by the voltage applied to this pin. With a separate power
source connection, it can reduce the effects of switching transient noise on the control circuitry.
This pin is the control circuitry ground return and is connected back to the power source ground.
No connection. These pins are not internally connected.
5
6
7
8
10
12
14
8
Gnd
Output
VCC
Vref
Power
Ground
VC
Gnd
NC
11
9
2,4,6,13
MOTOROLA ANALOG IC DEVICE DATA
7
ONSEMI [ ON SEMICONDUCTOR ]
