Datasheet

© 2008 Microchip Technology Inc. DS21949C-page 23
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.
FIGURE 4-2: TC1304 Sequencing Circuit.
FIGURE 4-3: TC1304 Power-up Timing
from SHDN
.
4.7 Soft Start
Both outputs of the TC1303/TC1304 are controlled
during start-up. Less than 1% of V
OUT1
or V
OUT2
overshoot 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
temperature 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.
Enable
Enable
V
OUT2
V
OUT1
+
–
+
–
160 µs Delay*
160 µs Delay*
92% of V
OUT2
92% of V
OUT1
To PG
Delay CKT.
SHDN
* 160 µs delay on trailing edge
V
IN1
/V
IN2
V
OUT1
V
OUT2
Power Good
Power Up Timing From SHDN
300 ms
t
WK
+ t
S
500 µs
TC1304
SHDN