CS5651
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
frequency.
Resistor R
T
connects to ground setting the charge current for C
T
.
Its value must be between 4.0kΩ and 16kΩ.
The inverting input of error amplifier 1. Normally it is connect-
ed 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. The minimum operating voltage
range after start-up is 9V.
Typical Performance Characteristics
Timing Resistor vs. Oscillator Frequency
16
14
2.2n
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
MAXIMUM DUTY CYCLE (%)
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
R
T
TIMING RESISTOR (KΩ)
F
100p
1.0n
F
pF
220
pF
330
pF
500
3.3
12
C
T
=
F
10n
F
n
5.0
F
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)
Current Sense Input Threshold vs. Error
Amp Output Voltage
1.2
Vth, CURRENT SENSE
INPUT THRESHHOLD (V)
V
CC
= 15V
1.0
0.8
0.6
0.4
0.2
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 ]
