Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
16 Lead 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
Timing capacitor CT connects pin to ground setting oscillator
frequency.
RT
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
COMP2
Output 2 pulse by pulse current limit.
Output of error amplifier 2, for loop compensation.
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
after start-up is 8.8V.
Typical Performance Characteristics
Timing Resistor vs. Oscillator Frequency
Max. Output Duty Cycle vs. Oscillator Frequency
16
14
50
48
12
10
46
44
8.0
42
40
38
VCC = 15V
VCC
15V
=
R
C
T = 4.0kΩ to 16kΩ
L = 15pF
6.0
T
A = 25°C
30k 50k
f OSC OSCILLATOR FREQUENCY (Hz)
TA=25°C
4.0
10k
30k 50k
100k
300k 500k 1.0M
10k
100k
300k 500k 1.0M
f
OSC OSCILLATOR FREQUENCY (Hz)
Current Sense Input Threshold
vs. Error Amp Output Voltage
Error Amp Open-Loop Gain & Phase vs. Frequency
1.2
0
100
80
VCC = 15V
1.0
VCC = 15V
O = 1.5V TO 2.5V
L = 100kΩ
30
60
90
120
GAIN
V
R
TA = 25°C
0.8
60
40
20
0
TA = 125°C
TA = 25°C
0.6
PHASE
TA
=
-55°C
0.4
0.2
0
150
180
-20
10k
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
100k
1.0k
10k
100k
1.0M
10M
ERROR AMP OUTPUT VOLTAGE (V)
f, FREQUENCY (Hz)
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
