JAJSJK6D October 2007 – August 2020 LM5067
PRODUCTION DATA
During initial power up, the Power Good pin (PGD) is high until the operating voltage (VCC – VEE) increases above ≊2V. PGD then switches low, remaining low as the system voltage and the operating voltage increase. After Q1 is switched on, when the voltage at the OUT pin is within 1.23 V of the SENSE pin (Q1 VDS <1.23 V), PGD switches high indicating the output voltage is at, or nearly at, its final value. Any of the following situations will cause PGD to switch low within ≊10 µs:
A pull-up resistor is required at PGD as shown in Figure 9-12. The pull-up voltage (VPGD) can be as high as 80 V above VEE, with transient capability to 100 V, and can be higher or lower than the system ground.
If a delay is required at PGD, suggested circuits are shown in the following figure. In Figure 9-13, capacitor CPG adds delay to the rising edge, but not to the falling edge. In Figure 9-14, the rising edge is delayed by RPG1 + RPG2 and CPG, while the falling edge is delayed a lesser amount by RPG2 and CPG. Adding a diode across RPG2. Figure 9-15 allows for equal delays at the two edges, or a short delay at the rising edge and a long delay at the falling edge.