TPS25751AS datasheet(32/88 Pages) TI2

32 / 88 page

LDO

LDO_1V5

LDO

VREF

VIN_3V3

LDO_3V3

VBUS

RLDO_3V3

Figure 8-11. Power Supplies

The TPS25751A is powered from either VIN_3V3 or VBUS. The normal power supply input is VIN_3V3. When

powering from VIN_3V3, current flows from VIN_3V3 to LDO_3V3 to power the core 3.3V circuitry and I/Os.

A second LDO steps the voltage down from LDO_3V3 to LDO_1V5 to power the 1.5V core digital circuitry.

When VIN_3V3 power is unavailable and power is available on VBUS, the device is considered to be in the

dead-battery start-up condition. In a dead-battery start-up condition, the TPS25751A opens the VIN_3V3 switch

until the host clears the dead-battery flag through I2C. Therefore, the TPS25751A is powered from the VBUS

input with the higher voltage during the dead-battery start-up condition and until the dead-battery flag is cleared.

When powering from a VBUS input, the voltage on VBUS is stepped down through an LDO to LDO_3V3.

8.3.2.1 Power-On And Supervisory Functions

A power-on reset (POR) circuit monitors each supply. This POR allows active circuitry to turn on only when a

good supply is present.

8.3.2.2 VBUS LDO

The TPS25751A contains an internal high-voltage LDO which is capable of converting VBUS to 3.3V for

powering internal device circuitry. The VBUS LDO is used when in the dead-battery condition. (VIN_3V3 is low

and the dead-battery flag is active). The VBUS LDO is powered from VBUS.

8.3.3 Power Paths

The TPS25751A has internal sourcing power paths: PP_5V and PP_CABLE. TPS25751AD has a integrated

bidirectional high voltage load switch for sinking power path: PPHV.

TPS25751AS has a high voltage gate driver for power path control: PP_EXT. Each power path is described in

detail in this section.

8.3.3.1 Internal Sourcing Power Paths

Figure 8-12 shows the TPS25751A internal sourcing power paths available in both TPS25751AD and

TPS25751AS. The TPS25751A features two internal 5V sourcing power paths. The path from PP5V to VBUS is

called PP_5V. The path from PP5V to CCx is called PP_CABLE. Each path contains two back-to-back common

drain N-FETs, with current clamping protection, overvoltage protection, UVLO protection, and temperature

sensing circuitry. PP_5V can conduct up to 3A continuously, while PP_CABLE can conduct up to 315mA

continuously. When disabled, the blocking FET protects the PP5V rail from high-voltage that can appear on

VBUS.

TPS25751A

SLVSJG7 – MAY 2026

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