LP55231 datasheet(46/53 Pages) TI

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LP5523 INPUT

CURRENT 1 mA/DIV

PWM POWERSAVE

ENABLED

INPUT CURRENT ~50 éA

DURING PWM

POWERSAVE

LED CURRENT 5 mA/DIV

TIME 1 ms/DIV

LP55231

SNOSCR5 – MARCH 2013

www.ti.com

PWM Power-Save Mode

PWM cycle power-save mode is enabled when register 36 bit [2] PWM_PS_EN is set to “1”. In PWM power-save

mode analog blocks are powered down during the "down time" of the PWM cycle. Which blocks are powered

down depends whether the external or internal clock is used. While the Automatic Power-Save Mode (see

above) saves energy when there is no PWM activity at all, the PWM Power-Save mode saves energy during

PWM cycles. Like the Automatic Power-Save Mode, PWM Power-Save Mode also works during program

execution. Figure 27 shows the principle of the PWM power-save technique. An LED on D9 output is driven at

50%PWM, 5mA current (top waveform). After PWM Power-save enable, the LED-current remains the same, but

the LP55231 input current drops down to ~50 µA level when the LED is OFF, or to ~200 µA level when the

charge-pump-powered output(s) are used.

Figure 27. PWM Power-save Principle. External Clock, VDD = 3.6V

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LP55231 Datasheet(PDF) 46 Page - Texas Instruments