Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
16 L PDIP & SO Wide
1
SYNC
A positive going pulse applied to this input will synchronize the
oscillator. A DC voltage within the range of 2.4V to 5.5V will
inhibit the oscillator.
2
3
4
CT
RT
Timing capacitor CT connects pin to ground setting oscillator
frequency.
Resistor RT connects to ground setting the charge current for CT.
Its value must be between 4.0kΩ and 16kΩ.
VFB
The inverting input of error amplifier 1. Normally it is connect-
ed to the switching power supply output.
1
5
6
COMP1
Sense1
The output of error amplifier 1, for loop compensation.
Output 1 pulse by pulse current limit.
Drives the power switch at output 1.
7
VOUT
1
8
Gnd
Logic ground
9
Pwr Gnd
Power ground. Power device return is connected to this pin.
Drives the power switch at output 2.
10
11
12
13
VOUT
2
Sense2
Output 2 pulse by pulse current limit.
Output of error amplifier 2, for loop compensation.
COMP2
VFB
Inverting input of error amplifier 2. Normally it is connected to
the switching power supply output.
2
14
15
16
ENABLE2
VREF
Output 2 disable. A logic low at this pin disables VOUT .
2
5.0V reference output. It can source current in excess of 30mA.
VCC
The positive supply of the IC. The minimum operating voltage
range after start-up is 9V.
Typical Performance Characteristics
Timing Resistor vs. Oscillator Frequency
Max. Output Duty Cycle vs. Oscillator Frequency
16
50
14
12
48
46
44
10
42
40
38
VCC = 15V
8.0
VCC
15V
=
R
C
T = 4.0kΩ to 16kΩ
L = 15pF
6.0
T
A = 25°C
30k 50k
OSC OSCILLATOR FREQUENCY (Hz)
TA=25°C
4.0
10k
10k
100k
300k 500k 1.0M
30k 50k
100k
300k 500k 1.0M
f
OSC OSCILLATOR FREQUENCY (Hz)
f
Error Amp Open-Loop Gain & Phase vs. Frequency
Current Sense Input Threshold vs. Error
Amp Output Voltage
0
100
80
1.2
VCC = 15V
O = 1.5V TO 2.5V
L = 100kΩ
VCC = 15V
1.0
30
60
90
120
GAIN
V
R
TA = 25°C
60
40
20
0
0.8
TA = 125°C
TA = 25°C
0.6
PHASE
TA = -55°C
0.4
0.2
0
150
180
-20
10k
100k
1.0k
10k
100k
1.0M
10M
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
f, FREQUENCY (Hz)
ERROR AMP OUTPUT VOLTAGE (V)
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
