Datasheet

UDG-09205
t – Time
t
RS
TS_FAULT
V
SS
Persistent FAULT
FAULT SetFAULT Reset
2.5 V
300 mV
TPS40170
SLUS970A –MARCH 2011–REVISED NOVEMBER 2013 www.ti.com
Over-Temperature Fault
Figure 23 shows the over-temperature protection scheme. If the junction temperature of the device reaches the
thermal shutdown limit of t
SD(set)
(165°C, typ) and SS charging is completed, an over-temperature FAULT is
declared. The soft-start capacitor begins to be discharged. During soft-start discharging period, the PWM
switching is terminated; therefore both HDRV and LDRV are driven low, turning off both MOSFETs.
The soft-start capacitor begins to charge and over-temperature fault is reset whenever the soft-start capacitor is
discharged below V
SS(flt,low)
(300 mV, typ.). During each restart cycle, PWM switching is turned on. When SS is
fully charged, PWM switching is terminated. These restarts repeat until the temperature of the device has fallen
below the thermal reset level, t
SD(reset)
(135°C typ). PWM switching continues and system returns to normal
regulation.
Figure 23. Over-Temperature Fault Restart Timing
The soft-start timing during over-temperature fault is the same as the soft-start timing during overcurrent fault.
See the Equations for Soft-Start and Re-Start Time section.
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