AS3715 datasheet(23/159 Pages) AMSOSRAM

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[v1-03] 2015-Aug-10

AS3715 − Detailed Description – Power Management Functions

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.

Force PWM Mode Operation

Even in the case the load current gets so small that less than

the minimum ON-time of the PMOS would be needed to keep

the loop in regulation the regulator will still stay on the fixed

switching frequency without entering low power mode. To

guarantee a stable output voltage also negative coil currents

are possible. This mode guarantees the lowest possible ripple

and a fixed frequency over all load conditions for powering

noise sensitive RF circuits, but is compromising on the

efficiency. The mode is enabled by setting sdX_force_pwm =1.

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.

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.

DVM (Dynamic Voltage Management)

To minimize the over-/undershoot during a change of the

output voltage, the DVM can be enabled. With DVM the output

voltage will ramp up/down with a selectable slope after the new

value was written to the registers. Without DVM the slew rate

of the output voltage is only determined by external

components like the coil and load capacitor as well as the load

current.

DVM can be selected for all step-down controllers, but only for

one at a time. (see dvm_time and sd_dvm_select description).

AS3715 Datasheet(PDF) 23 Page - ams-OSRAM AG