AS3722 datasheet(24/198 Pages) AMSCO

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[v1-01] 2015-Sep-07

AS3722 − Detailed Descriptions- Power Management Functions

It’s possible to switch between these two modes during

operation.

Power Save Operation (Automatically Controlled)

As soon as the output voltage stays above the desired target

value for a certain time, some internal blocks will be powered

down leaving the output floating to lower the power

consumption. Normal operation starts as soon as the output

drops below the target value for a similar amount of time. To

minimize the accuracy error some internal circuits are kept

powered to assure a minimized output voltage ripple.

Two addition guard bands, based on comparators, are set at

±5% of the target value to react quickly on large

over/under-shoots by immediately turning on the output

drivers without the normal time delays. This ensures a

minimized ripple also in very extreme load conditions.

Fast Regulation Mode

This mode can be used to react faster on sudden load changes

and thus minimize the over-/undershoot of the output voltage.

This mode needs a bigger output capacitor to guarantee the

stability of the regulator. The mode is enabled by setting

sdX_fast =1.

Selectable Frequency Operation

Especially for very low load conditions, e.g. during a sleep mode

of a processor, the switching frequency can be reduced to

achieve a higher efficiency. The frequency for SD2, SD3, SD4

and SD5 can be set to 3 or 4MHz. This mode is selected by setting

sdX_freq to the appropriate value.

100% PMOS ON Mode for Low Dropout Regulation

For low input to output voltage difference the DCDC converter

can use 100% duty cycle for the PMOS transistor, which is then

in LDO mode.

Step-Down Converter Configuration Modes

The step down dc/dc converters have two configuration modes

to deliver different output currents for the applications. The

operating mode is selected by setting the bit sd3_slave,

sd4_slave and sd5_slave (the default is set by the Boot-OTP). It’s

not allowed to set sd3_slave and sd4_slave at the same time.

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