When VIN is powered but the TPS7H2201 is disabled (EN is low), the internal FETs are disabled, creating a high impedance path from VIN to VOUT. However, there are parasitic leakage paths that can cause VOUT to slowly charge. The forward leakage current, I_F, indicates how much current flows from VIN to VOUT during this situation. The maximum forward of the TPS7H2201-SP current is specified at 250 μA across voltage, temperature and radiation.

Some applications need to pay particular attention to this behavior. Is particularly relevant when VOUT is a high impedance node (and therefore the leakage current goes entirely to charging VOUT instead of being dissipated). By using the basic capacitor equation shown in Equation 11, the time for the voltage to rise to a given value can be theoretically calculated.

where

• Δt = time to charge to final value
• ΔV_OUT = change in output voltage; for a 0 V starting voltage, use V_IN

For example, with a 7-V input voltage and a 220-µF output capacitance, VOUT typically charge to 7 V in approximately 6.2 seconds (using I_F = 150 μA, ΔV_OUT = 7 V, C_OUT = 220 µF).

If the output voltage must remain below a certain value, a pull-down resistor can be utilized with a value as calculated by using Equation 12.

where

• VOUT_{LKG_MAX} = maximum output voltage due to leakage current, I_F
• R_{PULL_DOWN} = external pull-down resistor from VOUT to GND

For example, placing a 2.6-kΩ resistor between VOUT and ground makes sure VOUT does not rise above 0.65-V worse case due to the I_F current. The resistor need to be able to handle the worst case power dissipation when the switch is enabled and VOUT ≈ VIN.