TPS1H100-Q1
ZHCSDD8D –OCTOBER 2014–REVISED DECEMBER 2019
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7.3.4.1 Short-to-GND and Overload Detection
In the on state, the short-to-GND fault is reported as the low status output or VCS,h on CS, when a current limit is
triggered. The lower one of the internal and external set values is applied for the actual current limit. It is in auto-
recovery when the fault condition is cleared. If not cleared, thermal shutdown triggers to protect the power FET.
7.3.4.2 Open-Load Detection
In the on state for version A, if the current flowing through the output is less than Iol,on, the device recognizes an
open-load fault. For version B, faults are diagnosed by reading the voltage on the CS pin and judged by the user.
A benefit of high-accuracy current sense down to a verylow current range, this device can achieve a very low
open-load detection threshold, which correspondingly expands the normal operation region. TI suggests 10 mA
as the upper limit for the open-load detection threshold and 25 mA as the lower limit for the normal operation
current. In Figure 35, the recommended open-load detection region is shown as the dark-shaded region and the
light-shaded region is for normal operation. As a guideline, do not overlap these two regions.
Normal Operation
Region
27.5 mA
10% Tolerance
25 mA
22.5 mA
18 mA
80% Tolerance
On State, Open Load/
Short to Battery
10 mA
2 mA
Figure 35. On-State Open-Load Detection and Normal-Operation Diagram
In the off state, if a load is connected, the output voltage is pulled to 0 V. In the case of an open load, the output
voltage is close to the supply voltage, VS – VOUT < Vol,off. For version A, the ST pin goes low to indicate the fault
to the MCU. For version B, the CS pin is pulled up to VCS,h. There is always a leakage current Iol,off present on
the output, due to the internal logic control path or external humidity, corrosion, and so forth. Thus, TI
recommends an external pullup resistor to offset the leakage current. This pullup current should be less than the
output load current to avoid false detection in the normal operation mode. To reduce the standby current, TI
recommends always to use a switch in series with? the pullup resistor. TI recommends Rpu ≤ 15 kΩ.
VBAT
VS
OPEN LOAD
Vol,off
ST/CS
FAULT
Rpu
OUT
Figure 36. Open-Load Detection Circuit
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