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True Reverse Current Block Continued 2

True reverse current blocking is usually required for USB power path applications to avoid unwanted reverse current for all cases. The scope trace demonstrates this operation. The first section shows an initial state normally ON or VIN = VOUT without a load. The second section shows a transient higher voltage applied at VOUT inducing a reverse current creating a voltage drop from VOUT to VIN which reaches threshold for VT_RCB. After the time interval tBLANK the PMOS is turned OFF blocking the reverse current as shown in the third section. Please note that TRCB activation requires transient or continuous reverse current, which can develop voltage drop > VT_RCB. If VOUT > VIN and is applied slowly, then reverse current charges input capacitor and VIN will follow VOUT without TRCB activation.

PTM Published on: 2020-11-10