ZHCSLQ5D October 2007 – August 2020 LM5067
PRODUCTION DATA
- Upon applying the system voltage (VSYS) to the circuit, the external MOSFET (Q1) is held off during the insertion time (t1 in Figure 8-2) to allow ringing and transients at VSYS to settle. Since each backplane’s response to a circuit card plug-in is unique, the worst case settling time must be determined for each application. The insertion time starts when the operating voltage (VCC-VEE) reaches the PORIT threshold, at which time the internal 6 µA current source charges CT from 0 V to 4 V. The required capacitor value is calculated from:
where
For example, if the desired insertion delay is 250 ms, CT calculates to 0.38 µF. At the end of the insertion delay, CT is quickly discharged by a 1.5 mA current sink.