8.3.2 Enable and Programmable UVLO

The TPS61376 has a dual function enable and UVLO circuit. When the input voltage at the VIN pin is

above the input UVLO rising threshold of 2.8 V and the EN/UVLO pin is pulled above rising threshold, the

TPS61376 is enabled and starts switching. The EN/UVLO pin has an accurate UVLO voltage threshold to

support programmable input under-voltage lockout with hysteresis. A hysteresis current IUVLO_HYS is sourced out

of the EN/UVLO pin to provide hysteresis that prevents on/off chattering in the presence of input voltage noise.

By using resistor divider as shown in Figure 8-1 , the turn on threshold can be calculated by using Equation 1.

VINUVLO_ON =VUVLO× 1+R1R2

(1)

where

• VUVLO is the UVLO threshold of 0.813 V at the EN/UVLO pin

The hysteresis between the UVLO turn on threshold and turn off threshold is set by the upper resistor in the

EN/UVLO resistor divider and is given by Equation 2

ΔVINUVLO =IUVLO_HYS×R1

(2)

where

• IUVLO is the sourcing current from the EN/UVLO pin when the voltage at the EN/UVLO pin is above VUVLO

UVLO Comparator

R1

VIN

EN/UVLO

IUVLO_HYS 2 A

0.813V

Enable

R2

Figure 8-1. Programmable UVLO with Resistor Divider at EN/UVLO Pin

8.3.3 Soft Start and Inrush Current Control During Start-up

The TPS61376 has a soft-start and input average current limit function to prevent high inrush current during

start-up. When the EN pin is pulled high, the TPS61376 starts to ramp up the output voltage by ramping an

internal reference voltage from 0 V to the reference voltage within typical 4 ms. During start-up when Vin is

higher than Vout, the ISO FET between VP and SW pin will limit the current across the inductor. This current will

increase linearly as the Vin and Vout delta decreases. When Vout is higher than Vin, TPS61376 will regulate the

input average current programmed via ILIM pin.

8.3.4 Switching Frequency

The TPS61376 uses adaptive constant off-time peak current control topology to regulate the output voltage. In

moderate to heavy load conditions, the TPS61376 works in pulse width modulation (PWM) mode. The switching

frequency in PWM mode is 1.2 MHz (650 KHz for TPS613761). At light load conditions, the TPS61376 works

in power-save mode with pulse frequency modulation (PFM). The PFM mode brings high efficiency at the light

load.

8.3.5 Adjustable input average Current Limit

The TPS61376 has integrated input average current limit function internally, the average current limit can be

set by a resistor from the ILIM pin to AGND. The current limit can be programmed from 0.1 A to 3.0 A. It is

recommended to set ISEL pin logic low when setting input average current limit below 750 mA. With ISEL pin

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TPS61376

SLVSGQ1A – JANUARY 2022 – REVISED SEPTEMBER 2022

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Product Folder Links: TPS61376