Datasheet

UC1851
UC2851
UC3851
OPEN-LOOP CIRCUIT
High Peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass
capacitors should be connected close to pin 13 in a single ground point.
Programmable Soft Start and Restart Delay Circuit
For further application information see UC1840/UC1841
Data Sheets
UC1851 Power MOSFET Drive Interface
UNITRODE INTEGRATED CIRCUITS
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. [phone] • FAX [phone]
Nominal Frequency =
1
RTCT
= 50kHz
Start Voltage = 3



R1
+ R2 + R3
R2 + R3



+0.2R1 = 12V
UV Fault Voltage
= 3



R1
+ R2 + R3
R2 + R3



= 8V
OV Fault Voltage
= 3



R1
+ R2 + R3
R3



= 32V
Current Limit = 200mV
Current Fault Voltage = 600mV
Duty Cycle Clamp = 50%
@V
IN = 15V, Duty Cycle = 48%
@V
IN = 30V, Duty Cycle = 24%
6