The TPS7H3302 provides S3 support by an EN function. The EN pin could be connected to an SLP_S3 signal in the end application. Both VTTREF and VTT are on when EN = high (S0 state). VTTREF is maintained while VTT is turned off and discharged via an internal discharge MOSFET when EN = low (S3 state). Please notice that the EN signal controls only the output buffer for VTT and therefore, while in S3 state, VDDQSNS is present in order to maintain data in volatile memory. As a result, when EN is set high to exit the S3 state, it is desired to bring VTT into regulation as fast as possible. This causes an output current controlled by the current limit of the device and the output capacitors.

When EN = low and the VDDQSNS voltage is less than 0.75 V(typically), TPS7H3302 enters pseudo-S5 state. Both VTT and VTTREF outputs are turned off and discharged to GND through internal MOSFETs when pseudo-S5 support is engaged (S4/S5 state). Figure 8-3 shows a typical startup and shutdown timing diagram for an application that uses S3 and pseudo-S5 support.

Figure 8-3 Typical Timing Diagram for S3 and Pseudo-S5 Support