zarric
Junior Member level 3
A On-chip regulator is designed with input volatage:12-25V ,Vout=5V. Current Limit=120mA.
The schematic is shows below,
Vout is connected to outside. Vin=12V, then connect a resistor RL=100ohm to Vout. Regulator can not start-up, Vout only 17mv. RL=200omh, Vout=36mv....If RL changed to 500ohm. then regulator can normally start . IF Vin=20V. then RL=300ohm, can start.
The pass device and current sense transistor all use thick oxide high volatage nmos.threshold is about 3V. pass device:60*80u/3u, sense device:7u/3u.
The schematic is shows below,
Vout is connected to outside. Vin=12V, then connect a resistor RL=100ohm to Vout. Regulator can not start-up, Vout only 17mv. RL=200omh, Vout=36mv....If RL changed to 500ohm. then regulator can normally start . IF Vin=20V. then RL=300ohm, can start.
The pass device and current sense transistor all use thick oxide high volatage nmos.threshold is about 3V. pass device:60*80u/3u, sense device:7u/3u.