AS3543 datasheet(31/92 Pages) AMSCO

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AS3543 3v2

Data Sheet - D e t a i l e d D e s c r i p t i o n - P o w e r M a n a g e m e n t F u n c t i o n s

9 Detailed Description - Power Management Functions

9.1

Low Drop Out Regulators

9.1.1

General

These LDOs are designed to supply sensitive analogue circuits, audio devices, AD and DA converters, micro-control-

ler and other peripheral devices. The design is optimized to deliver the best compromise between quiescent current

and regulator performance for battery powered devices.

Stability is guaranteed with ceramic output capacitors of 1µF +/-20% (X5R) or 2.2µF +100/-50% (Z5U). The low ESR of

these caps ensures low output impedance at high frequencies. Regulation performance is excellent even under low

dropout conditions, when the power transistor has to operate in linear mode. Power supply rejection is high enough to

suppress high ripple on the battery at the output. The low noise performance allows direct connection of noise sensi-

tive circuits without additional filtering networks. The low impedance of the power device enables the device to deliver

up to 150mA even at nearly discharged batteries without any decrease of performance.

Figure 19. LDO Block Diagram

9.1.2

LDO1

This LDO generates the audio supply voltage used for the AFE itself.

Input voltage is VDD17IN

Output voltage is AVDD17 (typ. 1.7V)

Driver strength: 50mA

It is set to a default output voltage of 1.7V, 50mAmax. It supplies the analog audio blocks of the AFE. Additional external

loads are possible but most not exceed the supply ratings in total together with the operating internal blocks. Further

the external load must not induce noise to the sensitive AVDD17 supply pin.

9.1.3

LDO2

This LDO generates the digital and audio supply voltage used for the AFE itself.

Input Voltage is BVDD

Output Voltage is AVDD27 (typ. 2.7V)

Driver strength: 100mA, can be programmed to 200mA

It is set to a default output voltage of 2.7V, 100mAmax. It supplies the digital part of the AFE as well as all audio

switches and multiplexers. Additional external loads are possible but most not exceed the supply ratings in total

together with the operating internal blocks. Further the external load must not induce noise to the AVDD27 supply pin

but is not as critical as AVDD17.

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