JAJS177F November 2003 – February 2020 TPS2490 , TPS2491
PRODUCTION DATA.
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The TIMER pin charges CT as long as limiting action continues, and discharges at a 1/10 charge rate when limiting stops. If the voltage on CT reaches 4 V before the output is charged, Q1 is turned off and either a latch-off or restart cycle commences, depending on the part type. The open-drain PG output provides a deglitched end-of-charge indication which is based on the voltage across Q1. PG is useful for preventing a downstream DC/DC converter from starting while CO is still charging. PG goes active (open drain) about 9 ms after CO is charged. This delay allows Q1 to fully turn on and any transients in the power circuits to end before the converter starts up. The resistor pullup shown on pin PG in 代表的なアプリケーション only demonstrates operation; the actual connection to the converter depends on the application. Timing can appear to terminate early in some designs if operation transitions out of the power limit mode into a gate charge limited mode at low VDS values.