The reverse-current blocking circuit blocks the current flowing in the reverse direction from the VOUT pin to the VIN pin when output voltage (VOUT) > input voltage (VIN).
Toshiba’s load switch ICs are available with two types of reverse-current blocking circuit:
a) Reverse-current blocking activated only when a load switch IC is off
When the MOS pass transistor turns off, VIN becomes lower than VOUT to prevent reverse current from flowing from the VOUT pin to the VIN pin. Reverse-current blocking is disabled while the MOS pass transistor is on.
b) True reverse-current blocking
A true reverse-current blocking function prevents reverse current from flowing from the VOUT pin to the VIN pin regardless of whether the MOS pass transistor is on or off. The reverse-current blocking circuit is enabled when VOUT becomes higher than VIN by VRB (reverse blocking voltage threshold) and is disabled when VOUT becomes lower than VIN by VRBR (reverse blocking release voltage threshold).
The following figure shows the reverse-current characteristics of a load switch IC with a true reverse-current blocking function. As highlighted by the red line (#1), IREVERSE increases as the difference between VOUT and VIN (VOUT – VIN) increases. Reverse-current blocking is enabled when VOUT – VIN reaches Point A at which it is approximately 40 mV, blocking IREVERSE. When VIN becomes higher than VOUT by roughly 30 mV (at Point B) as highlighted by the green line (#2), reverse-current blocking is disabled, causing current to begin flowing again from the VIN pin to the VOUT pin.