Datasheet

2 2
Re sistors
Vdc 325
P 10.56mW
Rstart up 10M
= = =
- W
Rstart up 10M- = W
Vdc max 230Vac 2 325Vdc= · =
LM5023
OUT
QR
CS
VCC
GND
90-264 VAC
High
Voltage
Start-up
VSD
Depletion
Mode
FET
CVCC
R
VSD
LM5023
SNVS961D –APRIL 2013–REVISED JANUARY 2014 www.ti.com
Figure 8. Start-Up With a Depletion Mode FET
An alternative start-up circuit employs an Enhancement Mode FET with resistors connected from the rectified dc
bus to the Gate of the FET, Figure 9. After the input AC power is applied the Enhancement Mode FET supplies
the charging current to the VCC capacitor C
VCC
. After reaching the VCC
ON
threshold the LM5023 VSD open
Drain output, which is pulled up to VCC during start-up, goes low. This grounds the Gate of the start-up MOSFET
turning it off. The start-up resistors are always in the circuit, therefore the standby power consumed will be higher
than if a Depletion Mode FET were used.
• Vin = 230 Vac
• VCC = 10 V
•
•
•
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