TPS54821 datasheet(13/42 Pages) TI2

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)

ENFALLING

STOP

ENFALLING

R1 V

R2 =

R1 I

ENFALLING

START

STOP

ENRISING

ENFALLING

ENRISING

R1 =

VIN

TPS54821

R 1

R 2

PVIN

TPS54821

R 1

R 2

VIN

TPS54821

R 1

R 2

TPS54821

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SLVSB14B – OCTOBER 2011 – REVISED FEBRUARY 2016

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Device Functional Modes (continued)

The EN pin has a small pull-up current Ip which sets the default state of the pin to enable when no external

components are connected. The pull-up current is also used to control the voltage hysteresis for the UVLO

function since it increases by Ih once the EN pin crosses the enable threshold. The UVLO thresholds can be

calculated using Equation 2 and Equation 3.

Figure 17. Adjustable VIN Undervoltage Lock Out

Figure 18. Adjustable PVIN Undervoltage Lock Out, VIN

≥ 4.5V

Figure 19. Adjustable VIN and PVIN Undervoltage Lock Out

(2)

(3)

Where Ih = 3.3 μA, Ip = 1.15 μA, VENRISING = 1.21 V, VENFALLING = 1.17 V

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