TPS62870 datasheet(20/66 Pages) TI2

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Because there is an internal open-drain transistor connected to the EN pin, do not drive this pin directly from a

low-impedance source. Instead, use a resistor to limit the current flowing into the EN pin (see Section 9).

When power is first applied to the VIN pin, the device pulls the EN pin low until the device has loaded the

default register settings from nonvolatile memory and read the state of the VSEL, FSEL, and SYNC_OUT pins.

The device also pulls EN low if a fault, such as thermal shutdown or overvoltage lockout, occurs. In stacked

configurations, all devices share a common enable signal, which means that the DC/DC converters in the stack

cannot start to switch until all devices in the stack have completed the initialization. Similarly, a fault in one or

more devices in the stack disables all converters in the stack (see Section 7.3.17).

In standalone (nonstacked) applications, the user can disable the active pulldown of the EN pin if the user sets

SINGLE = 1 in the CONTROL3 register. Fault conditions have no effect on the EN pin when SINGLE = 1 (the EN

pin is always pulled down during device initialization). In stacked applications, make sure that SINGLE = 0.

When the internal SYSTEM_READY signal is low (that is, initialization is complete and there are no fault

conditions), the internal open-drain transistor is high impedance and the EN pin functions like a standard input. A

high level on the EN pin enables the DC/DC converter in the device. A low level disables the DC/DC converter

(the I2C interface is enabled as soon as the device has completed the initialization and is not affected by the

state of the internal ENABLE or SYSTEM_READY signals).

A low level on the EN pin forces the device into shutdown. During shutdown, the MOSFETs in the power stage

are off, the internal control circuitry is disabled, and the device consumes only 20µA (typical).

The rising threshold voltage of the EN pin is 1.0V and the falling threshold voltage is 0.9V. The tolerance of the

threshold voltages is ±30mV, which means that the user can use the EN pin to implement precise turn-on and

turn-off behavior.

When power is applied to the VIN pin, the toggling of the EN pin does not reset the loaded default register

settings.

7.3.4 Start-Up

When the voltage on the VIN pin exceeds the positive-going UVLO threshold, the device initializes as follows:

• The device pulls the EN pin low.

• The device enables the internal reference voltage.

• The device reads the state of the VSEL, FSEL, and SYNC_OUT pins.

• The device loads the default values into the device registers.

When initialization is complete, the device enables I2C communication and releases the EN pin. The external

circuitry controlling the EN pin now determines the behavior of the device:

• If the EN pin is low, the device is disabled. The user can write to and read from the device registers, but the

DC/DC converter does not operate.

• If the EN pin is high, the device is enabled. The user can write to and read from the device registers and,

after a short delay, the DC/DC converter starts to ramp up the output.

Figure 7-7 shows the start-up sequence when the EN pin is pulled up to VIN.

TPS62870, TPS62871, TPS62872, TPS62873

SLVSGC5E – JANUARY 2023 – REVISED OCTOBER 2025

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TPS62870 Datasheet(PDF) 20 Page - Texas Instruments