CS51221
CS51221
Enhanced Voltage Mode PWM Controller
Description
The CS51221 fixed frequency feed forward voltage mode ...
CS51221
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 optimized for high frequency primary side control operation. In addition, this device includes such features as: Soft Start, accurate duty cycle limit control, less than 50µA startup current, over and under
voltage protection, and bidirectional synchronization. The CS51221 is available in 16 lead PDIP and SO narrow surface mount packages.
s s
Features
1MHz Frequency Capability Fixed Frequency
Voltage Mode Operation, with Feed Forward Thermal Shutdown Under
Voltage Lock-out Accurate Programmable Max Duty Cycle Limit 1A Sink/Source Gate Drive Programmable Pulse by Pulse Over Current Protection Leading Edge Current Sense Blanking 75ns Shutdown Propagation Delay Programmable Soft Start Under
Voltage Protection Over
Voltage Protection with Programmable Hysteresis Bidirectional Synchronization 25ns GATE Rise and Fall Time (1nF load) 3.3V 3% Reference
Voltage Output
s s s s s
s s Application Diagram 36V-72V to 5V/5A converter s s s s s
BAS21 VIN (36V to 72V) 51k FZT688 11V
10
100
1µF 22µF 18V 160k T3 100:1 0.1µF 24.3k
VC VREF VCC UV OV ISET FF GATE ISENSE
U1
s
T2 2:5 VOUT (5V/5A) 100µF SGnd
510k
10k
T1 4:1
MBRB2545CT 10
CS51221/2
0.22µF 10k 1µF SYNC 330pF 0.01µF 200 2200pF
4.3k
D11 BAS21 100pF
COMP VFB RT/CT SYNC SS LGnd
680pF D13 V33...