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 fre-
quency.
Resistor RT connects to ground setting the charge current for CT. Its
value must be between 4.0k and 16k.
VFB
The inverting input of error amplifier 1. Normally it is connected 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.
The positive supply of the IC.
VCC
Typical Performance Characteristics
Timing Resistor vs. Oscillator Frequency
Max. Output Duty Cycle vs. Oscillator Frequency
50
16
14
48
OUT 2
46
12
10
OUT 1
44
42
40
38
VCC = 15V
8.0
VCC
15V
=
R
C
T = 4.0kΩ to 16kΩ
L = 15pF
6.0
TA = 25°C
TA=25°C
4.0
10k
10k
30k 50k
100k
300k 500k 1.0M
30k 50k
100k
300k 500k 1.0M
f
OSC OSCILLATOR FREQUENCY (Hz)
f OSC OSCILLATOR FREQUENCY (Hz)
Current Sense Input Threshold
vs. Error Amp Output Voltage
Error Amp Open-Loop Gain & Phase vs. Frequency
0
100
80
0.6
VCC = 15V
VCC = 15V
O = 1.5V TO 2.5V
RL = 100kΩ
30
60
90
120
GAIN
V
0.5
0.4
TA = 25°C
60
40
20
0
TA = 125°C
TA = 25°C
0.3
0.2
0.1
0
PHASE
TA = -55°C
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 ]
