SLVAFO4 august   2023 TPS61299

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Overview
  5. 2Load Connected to Input Voltage
    1. 2.1 Body Diode Pass (TPS61288)
    2. 2.2 Force Pass Through (TPS61253)
    3. 2.3 Bypass (TPS61291)
    4. 2.4 Summary
  6. 3Load Disconnected to Input Voltage
    1. 3.1 Synchronous HSD FET With Switchable Body Diode (TPS61299)
    2. 3.2 Extra ISO FET to Cut-Off Leakage Path
  7. 4Summary
  8. 5References

2.2 Force Pass Through (TPS61253)

To reduce voltage drop and power loss in the diode, force pass through function (standby mode) is proposed. As Figure 2-3 shows, during shutdown, the high side P-MOS can still turn on by pulling the gate to ground.

GUID-20230807-SS0I-L2VT-RQJF-DCKNCHSM92NX-low.svg Figure 2-3 Force Pass Through During Shutdown

The output voltage equals the input voltage minus the voltage drop across the DCR of the inductor and the Rdson of the P-MOS. Output voltage follows input voltage.

Equation 3. V O U T = V I N - I O U T × ( D C R + R d s o n )
Equation 4. Ploss=IOUT2×(DCR+Rdson)

The TPS61253 integrates force pass through mode. Figure 2-4 shows the shutdown waveforms of the TPS61253. Compared to body diode pass operation, there is less voltage drop and power loss in the P-MOS than the body diode. However, inductor power loss still exists because the inductor is in the connecting path. With a 50-Ω resistor load, there is inductor current during shutdown.

GUID-20230728-SS0I-0SMS-CZNH-9HSRHH7SSZSR-low.svg Figure 2-4 TPS61253 Shutdown Waveforms