CS3524A
CS3524A
Voltage Mode PWM Control Circuit
with 200mA Output Drivers
Description
The CS3524A PWM control circuit
retains the same versatile architecture
of the industry standard CS3524
(SG3524) while adding substantial
improvements.
The CS3524 is pin-compatible with
“non-A” versions, and in most applica-
tions can be directly interchanged. The
CS3524A, however, eliminates many of
the design restrictions which had pre-
viously required additional external
circuitry.
The CS3524A includes a precision 5V
reference trimmed to ±1% accuracy
(eliminating the need for potentiometer
adjustments), an error amplifier with
an output voltage swing extending to
5V, and a current sense amplifier use-
ful in either the ground or power sup-
ply output lines. The uncommitted
60V, 200mA NPN output pair greatly
enhances the output drive capability.
The CS3524A features an undervoltage
lockout circuit which disables all inter-
nal circuitry (except the reference) until
the input voltage has risen to 8V. This
holds standby current low until turn-
on, and greatly simplifies the design of
low power, off-line supplies. The turn-
on circuit has approximately 600mV of
hysteresis for jitter free activation.
Other improvements include a PWM
latch that insures freedom from multi-
ple pulsing within a period, even in
noisy environments; logic to eliminate
double pulsing on a single output, a
200ns external shutdown capability,
and automatic thermal protection from
excessive chip temperature. The oscil-
lator circuit is usable to 500kHz and is
easier to synchronize with an external
clock pulse.
Features
s
Precision Reference
Internally Trimmed to ±1%
s
Current Limit
s
Undervoltage Lockout
s
Start-up Supply Current
< 4mA
s
Output to 200mA
s
60V Output Capability
s
Wide Common-mode
Input Range for Error and
Current Limit Amplifiers
s
PWM Latch Insures Single
Pulse per Period
s
Double Pulse Suppression
s
200ns Shutdown
s
Guaranteed Frequency
s
Thermal Shutdown
Block Diagram
V
IN
5V Reference
Regulator
Power to
Internal
Circuitry
T
V
REF
Package Options
16 Lead PDIP & SO Wide
EA-
1
EA
+
2
16
15
14
13
12
11
10
9
SYNC
UV
Sense
CLOCK
V
OUTA
Flip
Flop
E
A
R
T
OSC
C
T
RAMP
V
REF
V
IN
E
B
V
OUTB
V
OUTA
E
A
SHUTDOWN
COMP
+
COMP
S
S
R
V
OUTB
PWM
Latch
E
B
SYNC
3
I
SENSE
+
4
I
SENSE
-
R
T
5
6
COMP
V
IN
EA-
EA+
200mV
I
SENSE
+
CL
I
SENSE
-
-
-
EA
+
V
IN
1kΩ
SHUTDOWN
10kΩ
Gnd
C
T
7
Gnd
8
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 10/28/96
1
A
®
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
