SLVSBC6C March 2013 – December 2019 TPS84A20
Many of the common power supply sequencing methods can be implemented using the SS/TR, INH and PWRGD pins. The sequential method is illustrated in Figure 38 using two TPS84A20 devices. The PWRGD pin of the first device is coupled to the INH pin of the second device which enables the second power supply once the primary supply reaches regulation. Figure 39 shows sequential turnon waveforms of two TPS84A20 devices.
Simultaneous power supply sequencing can be implemented by connecting the resistor network of R1 and R2 shown in Figure 40 to the output of the power supply that needs to be tracked or to another voltage reference source. The tracking voltage must exceed 750 mV before VOUT2 reaches its set-point voltage.Figure 41 shows simultaneous turnon waveforms of two TPS84A20 devices. Use and to calculate the values of R1 and R2.