SM8172A Datasheet, PDF (10/17 Pages) Nippon Precision Circuits Inc – 2-output Power Supply IC

SM8172A
12-5. Thermal Shutdown (TSD) Protection Circuit
When the chip temperature rises above approximately 170°C (typ) for any reason whatsoever, the thermal shut-
down circuit operates, stopping all outputs. When the chip temperature falls below 150°C (typ), the outputs
start again.
TSD
170 C (typ)
TSD-TSDHYS
150 C (typ)
Chip temperature
[ C]
VDCOUT
VLDOUT
LDOUT (regulator output)
DCOUT (DC/DC output)
800µsec (typ)^*1
70µsec (typ)^*1
DC/DC, regulator output stop
by thermal shutdown
DC/DC soft start time^*2
0.6msec (typ)
LDOUT (regulator output)
DCOUT (DC/DC output)
LDO soft start time^*2
1msec (typ)
VRESETN
(Pull-up)
Reset return delay time
65msec (typ)
*1. A time interval example for a typical application circuit with no load. The series regulator and DC/DC converter output voltage rise times may vary with
the load current, output capacitance, and other conditions.
*2. The soft start time is the interval during which the output current is limited internally in the IC, and is different from the series regulator and DC/DC con-
verter output raise time.
12-6. State of Each Output when Protection Function Operates
The output states of RESETN, DCOUT, and LDOUT when various circuit protection functions operate are
shown in the following table.
Pins
Normal
operation
RESET voltage
VIN2 ≤ 3.9V (typ)
RESETN
Hi-Z
L
DCOUT^*1
1.0V
1.0V
LDOUT
3.3V
3.3V
When various protection functions operate
Under voltage
lockout
VIN2 ≤ 3.2V (typ)
L
TSD
T_SD = 170°C (typ)
L
Series regulator
DC/DC converter
overcurrent protection overcurrent protection
I_OS = 700mA (typ) I_LIMITLX = 1.5A (typ)
Hi-Z
Hi-Z
0V (Disable)
0V (Disable)
1.0V
< 1.0V
0V (Disable)
0V (Disable)
< 3.3V
3.3V
*1. When the DC/DC converter output voltage is set to 1.0V.
Note. The RESETN output is unaffected by the overcurrent protection function.
The DCOUT and LDOUT outputs are unaffected by the reset voltage.
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