CS51221 Datasheet, PDF (1/12 Pages) Cherry Semiconductor Corporation – Enhanced Voltage Mode PWM Controller

CS51221
Enhanced Voltage Mode PWM Controller
Description
The CS51221 fixed frequency
feed forward voltage mode
PWM controller contains all of
the features necessary for basic
voltage mode operation. This
PWM controller has been opti-
mized for high frequency prima-
ry side control operation. In
addition, this device includes
such features as: Soft Start, accu-
rate duty cycle limit control, less
than 50µA startup current, over
and under voltage protection,
and bidirectional synchroniza-
tion. The CS51221 is available in
16 lead PDIP and SO narrow
surface mount packages.
Application Diagram
36V-72V to 5V/5A converter
1µF
SYNC
VIN (36V to 72V)
BAS21
100
51k
11V
22µF
FZT688
18V
160k
10
0.1µF
24.3k
0.22µF
10k
200
2200pF
330pF
0.01µF
VC
VCC
VREF
UV
COMP
OV
VFB
ISET
RT/CT
FF
SYNC
SS
LGnd
GATE
ISENSE
U1 ^PGnd
470pF
20.25k
1µF
510k
4.3k
13k
10
T3
100:1
10k
T1 MBRB2545CT
4:1
D11
BAS21
10
680pF
100pF
D13
V33MLA1206A23
IRF634
62
10
T2
2:5
100µF
0.1µF 5.1k
5.6k
150
4700pF
1k
180
MOC81025
1k TL431
2k
2k
VOUT
(5V/5A)
SGnd
Features
s 1MHz Frequency Capability
s Fixed Frequency Voltage
Mode Operation, with Feed
Forward
s Thermal Shutdown
s Under Voltage Lock-out
s Accurate Programmable Max
Duty Cycle Limit
s 1A Sink/Source Gate Drive
s Programmable Pulse by
Pulse Over Current
Protection
s Leading Edge Current Sense
Blanking
s 75ns Shutdown Propagation
Delay
s Programmable Soft Start
s Under Voltage Protection
s Over Voltage Protection with
Programmable Hysteresis
s Bidirectional
Synchronization
s 25ns GATE Rise and Fall
Time (1nF load)
s 3.3V 3% Reference Voltage
Output
Package Options
16 Lead SO Narrow & PDIP
GATE 1
I_SENSE
SYNC
FF
UV
OV
R_TC_T
I_SET
VC
PGnd
V_CC
V_REF
LGnd
SS
COMP
V_FB
Rev. 3/26/99
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: [phone] Fax: [phone]
Email: [e-mail]
Web Site: www.cherry-semi.com
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® Company