ZHCSFP2B October 2016 – September 2021 TPS3850
PRODUCTION DATA
The propagation delay from exceeding the threshold to RESET being asserted is dependent on two conditions: the amplitude of the voltage on the SENSE pin relative to the threshold, (ΔV1 and ΔV2), and the length of time that the voltage is above or below the trip point (t1 and t2). If the voltage is just over the trip point for a long period of time, then RESET asserts and the output is pulled low. However, if the SENSE voltage is just over the trip point for a few nanoseconds, then the RESET does not assert and the output remains high. The time required for RESET to assert can be changed by increasing the time that the SENSE voltage goes over the trip point. Equation 8 shows how to calculate the percentage overdrive.
In Equation 8, VITx corresponds to the SENSE threshold trip point. If VSENSE exceeds the positive threshold, then VIT+(OV) is used. VIT-(UV) is used when VSENSE falls below the negative threshold. In Figure 8-4, t1 and t2 correspond to the amount of time that the SENSE voltage is over the threshold. The response time versus overdrive for VIT+(OV) and VIT-(UV) is illustrated in Figure 6-14 and Figure 6-17, respectively.
The TPS3850 is relatively immune to short positive and negative transients on the SENSE pin because of the overdrive voltage curve; see Figure 6-20 and Figure 6-21.