ZHCSBP7C October 2013 – December 2018 TPS24750 , TPS24751
UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.
A capacitor CT connected from the TIMER pin to GND determines the overload fault timing. TIMER sources 10 µA when an overload is present, and discharges CT at 10 µA otherwise. Internal FET is turned off when VTIMER reaches 1.35 V. In an application implementing auto-retry after a fault, this capacitor also determines the period before the internal FET is re-enabled. A minimum timing capacitance of 1 nF is recommended to ensure proper operation of the fault timer. The value of CT can be calculated from the desired fault time tFLT, using Equation 4.
Either latch mode (TPS24750) or retry mode (TPS24751) occurs if the load current exceeds the current limit threshold or the fast trip shutdown threshold. While in latch mode, the TIMER pin continues to periodically charge and discharge the attached capacitor. In retry mode, the internal MOSFET is disabled for sixteen cycles of TIMER charging and discharging. The TIMER pin is pulled to GND by a 2 mA current source at the end of the 16th cycle of charging and discharging. The internal MOSFET is then re-enabled. The TIMER pin capacitor, CT, can also be discharged to GND during latch mode or retry mode in the following way:
TIMER is not affected when the die temperature exceeds the OTSD threshold.