TC1303B Datasheet, PDF (17/30 Pages) Microchip Technology – 500 mA Synchronous Buck Regulator, + 300 mA LDO with Power-Good Output

4.4 Power-Good
A power-good (PG) output signal is generated based
off of the LDO output voltage (V_OUT2). A fixed delay
time of approximately 300 ms is generated once the
LDO output voltage is above the power-good threshold
(typically 94% of V_OUT2). As V_OUT2 falls out of regula-
tion, the falling PG threshold is typically 92% of V_OUT2.
The PG output signal is pulled up to V_OUT2 indicating
that power is good and pulled low indicating that V_OUT2
is out of regulation. The typical quiescent current draw
for power-good circuitry is less than 10 µA.
If the LDO output voltage falls below the power-good
threshold, the power-good output will transition to the
low state. The power-good circuitry has a 165 µs delay
when detecting a falling output voltage. This helps to
increase the noise immunity of the power-good output
and avoiding false triggering of the PG signal during
line and load transients.
V_{TH_H}
V_OUT2
t_RPU
V_OH
PG
t_RPD
V_OL
FIGURE 4-1:
Power-Good Timing.
TC1303B
4.5 Soft Start
Both outputs of the TC1303B are controlled during
startup. Less than 1% of V_OUT1 or V_OUT2 overshoot is
observed during startup from V_IN rising above the
UVLO voltage or SHDN1 or SHDN2 being enabled.
4.6 Overtemperature Protection
The TC1303B has an integrated overtemperature
protection circuit that monitors the device junction
temperature and shuts the device off if the junction tem-
perature exceeds the typical 165°C threshold. If the
overtemperature threshold is reached, the soft start is
reset so that once the junction temperature cools to
approximately 155°C, the device will automatically
restart.
© 2005 Microchip Technology Inc.
DS21949A-page 17