CS3865C
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.
Timing capacitor C
T
connects pin to ground setting oscillator fre-
quency.
Resistor R
T
connects to ground setting the charge current for C
T
. Its
value must be between 4.0k and 16k.
The inverting input of error amplifier 1. Normally it is connected to
the switching power supply output.
The output of error amplifier 1, for loop compensation.
Output 1 pulse by pulse current limit.
Drives the power switch at output 1.
Logic ground
Power ground. Power device return is connected to this pin.
Drives the power switch at output 2.
Output 2 pulse by pulse current limit.
Output of error amplifier 2, for loop compensation.
Inverting input of error amplifier 2. Normally it is connected to the
switching power supply output.
Output 2 disable. A logic low at this pin disables V
OUT2
.
5.0V reference output. It can source current in excess of 30mA.
The positive supply of the IC.
Typical Performance Characteristics
Timing Resistor vs. Oscillator Frequency
16
MAXIMUM DUTY CYCLE (%)
R
T
TIMING RESISTOR (KΩ)
100p
1.0n
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C
T
R
T
V
FB1
COMP
1
Sense
1
V
OUT1
Gnd
Pwr Gnd
V
OUT2
Sense
2
COMP
2
V
FB2
ENABLE
2
V
REF
V
CC
Max. Output Duty Cycle vs. Oscillator Frequency
50
48
46
44
42
40
38
10k
V
CC
= 15V
R
T
= 4.0kΩ to 16kΩ
C
L
= 15pF
T
A
= 25°C
30k
50k
100k
300k
500k
1.0M
OUT 1
OUT 2
14
2.2n
p
220
330
F
F
500
F
3.3
pF
12
C
T
=
10n
F
pF
F
5.0
nF
nF
10
8.0
V
CC
=
6.0 15V
T
A
=25°C
4.0
10k
30k
50k
100k
300k
500k
1.0M
f
OSC
OSCILLATOR FREQUENCY (Hz)
f
OSC
OSCILLATOR FREQUENCY (Hz)
Error Amp Open-Loop Gain & Phase vs. Frequency
A
VOL
, OPEN-LOOP VOLTAGE GAIN (dB)
100
80
60
40
20
0
-20
10k
GAIN
V
CC
= 15V
V
O
= 1.5V TO 2.5V
R
L
= 100kΩ
T
A
= 25°C
PHASE
0
30
60
90
120
150
180
10M
Phase Margin (DEGREES)
Vth, CURRENT SENSE
INPUT THRESHHOLD (V)
0.6
Current Sense Input Threshold
vs. Error Amp Output Voltage
V
CC
= 15V
0.5
0.4
0.3
0.2
0.1
0
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
ERROR AMP OUTPUT VOLTAGE (V)
T
A
= 125°C
T
A
= 25°C
T
A
= -55°C
100k
1.0k
10k
100k
1.0M
f, FREQUENCY (Hz)
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
