2-7. Reverse-current protection

The reverse-current blocking circuit blocks the current flowing in the reverse direction from the V_OUT pin to the V_IN pin when output voltage (V_OUT) > input voltage (V_IN).
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, V_IN becomes lower than V_OUT to prevent reverse current from flowing from the V_OUT pin to the V_IN 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 V_OUT pin to the V_IN pin regardless of whether the MOS pass transistor is on or off. The reverse-current blocking circuit is enabled when V_OUT becomes higher than V_IN by V_RB (reverse blocking voltage threshold) and is disabled when V_OUT becomes lower than V_IN by V_RBR (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), I_REVERSE increases as the difference between V_OUT and V_IN (V_OUT – V_IN) increases. Reverse-current blocking is enabled when V_OUT – V_IN reaches Point A at which it is approximately 40 mV, blocking I_REVERSE. When V_IN becomes higher than V_OUT 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 V_IN pin to the V_OUT pin.