TC1303A Datasheet, PDF (22/36 Pages) Microchip Technology – 500 mA Synchronous Buck Regulator, + 300 mA LDO with Power-Good Output

TC1303A/TC1303B/TC1303C/TC1304
4.6 TC1304 Sequencing
The TC1304 device features an integrated sequencing
option. A sequencing circuit using only the SHDN input,
(Pin1), will turn on the LDO output (V_OUT2) and delay
the turn on of the Buck Regulator output (V_OUT1) until
the LDO output is in regulation. During power-down,
the sequencing circuit will turn off the Buck Regulator
output prior to turning off LDO output.
SHDN
V_OUT2
Enable
+
–
92% of V_OUT2
160 µs Delay*
To PG
Delay CKT.
V_OUT1
Enable
+
–
92% of V_OUT1
160 µs Delay*
* 160 µs delay on trailing edge
FIGURE 4-2:
TC1304 Sequencing Circuit.
V_IN1/V_IN2
TC1304
Power Up Timing From SHDN
SHDN
V_OUT1
500 µs
t_WK + t_S
V_OUT2
Power Good
300ms
4.7 Soft Start
Both outputs of the TC1303/TC1304 are controlled
during start-up. Less than 1% of V_OUT1 or V_OUT2 over-
shoot is observed during start-up from V_IN rising above
the UVLO voltage or either SHDN1 or SHDN2 being
enabled.
4.8 Overtemperature Protection
The TC1303/TC1304 has an integrated overtempera-
ture 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.
FIGURE 4-3:
from SHDN.
TC1304 Power-up Timing
DS21949B-page 22
© 2005 Microchip Technology Inc.