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V

A

V

F

V

DX

TPS60255

Vin

Gear Down

Gear Up

Vout

Vin

1.5 Mode

Operating Area

´

1 Mode

Operating Area

´

VB

VC

Vhys

TPS60255

SLVS825 – MARCH 2008

Figure 10. Input Voltage Hysteresis Between 1

× and 1.5× Modes

As shown in Figure 10, there is input hysteresis voltage between 1

× and 1.5× modes to ensure stable operation

during mode transition. For the single-cell Li-ion battery input voltage range, the TPS60255 operates in 1

× mode

operates in the 1.5

× mode. Once in 1.5× mode with the same LED current condition, the battery voltage must

there is some input voltage fluctuation at the 1

×/1.5× mode transition.

where

is

the

1

× mode output impedance and I

O

is

the

total

output

current.

See the ELECTRICAL CHARACTERISTICS table for output impedance specifications.

The TPS60255 switches to 1.5

× mode when the input voltage is below V

impedance and WLED current.

characteristics curve.

Copyright © 2008, Texas Instruments Incorporated

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