TPS22917DBVT datasheet(16/29 Pages) TI

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• QOD pin is unused and left floating. Using this method, there is no quick output discharge functionality, and

the output remains floating after the switch is disabled.

The fall times of the device depend on many factors including the total discharge resistance (RDIS) and the

output capacitance (CL). To calculate the approximate fall time of VOUT use Equation 4.

tFALL = 2.2 × (RDIS || RL) × CL

(4)

Where:

• tFALL = output fall time from 90% to 10% (μs)

• RDIS = total QOD + RQOD resistance (Ω)

• RL = output load resistance (Ω)

• CL = output load capacitance (μF)

9.3.3.1 QOD When System Power is Removed

The adjustable QOD can be used to control the power down sequencing of a system even when the system

power supply is removed. When the power is removed, the input capacitor discharges at VIN. Past a certain VIN

level, the strength of the RPD is reduced. If there is still remaining charge on the output capacitor, this results in

longer fall times. For further information regarding this condition, see the Setting Fall Time for Shutdown Power

Sequencing section.

9.4 Full-Time Reverse Current Blocking

In a scenario where the device is enabled and VOUT is greater than VIN there is potential for reverse current

to flow through the pass FET or the body diode. When the reverse current threshold (IRCB) is exceeded, the

switch is disabled within tRCB. The Switch remains off and block reverse current as long as the reverse voltage

condition exists. After VOUT has dropped below the VRCB release threshold the device turns back on with slew

rate control.

9.5 Device Functional Modes

Table 9-2 describes the connection of the VOUT pin depending on the state of the ON pin as well as the various

QOD pin configurations.

Table 9-2. VOUT Connection

QOD CONFIGURATION

TPS22917 VOUT

TPS22917L VOUT

QOD pin connected to VOUT with RQOD

GND (via QOD + RQOD)

VIN

QOD pin tied to VOUT directly

GND (via QOD)

VIN

QOD pin left open

Floating

VIN

QOD pin connected to VOUT with RQOD

VIN

GND (via QOD + RQOD)

QOD pin tied to VOUT directly

VIN

GND (via QOD)

QOD pin left open

VIN

Floating

TPS22917

SLVSDW8B – SEPTEMBER 2017 – REVISED DECEMBER 2021

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