AS3909 datasheet(22/77 Pages) AMSCO

22 / 77 page

AS3909/AS3910 – 22

ams Datasheet, Confidential: 2013-Oct [3-02]

A p pl i c at io n I n f o r m at i o n

By writing Regulated Voltage Definition Register (#16) user

chooses between automatic and “manual” adjustment of

regulated voltage. Automatic mode is chosen when bit reg_s is

0 (default and also recommended state). When bit reg_s is

asserted to 1 regulated voltage is defined by bits rege_3 to

rege_1 of the same register.

Communication to External Microcontroller

The AS3909/10 is a slave device and the external

microcontroller initiates all communication. Communication is

done by a 4-wire Serial Peripheral Interface (SPI). The AS3909/10

asks microcontroller for its attention by sending an interrupt

(pin INTR).

In addition the microcontroller can use clock signal available

on pin MCU_CLK when the oscillator is running.

The microcontroller can also drive pin EN. Putting this pin high

has the same function as setting the Operation Control Register

bit en (entry in Ready mode).

Serial Peripheral Interface (SPI)

For details about SPI timing refer to Figure 8.

Figure 12:

Serial Peripheral Interface (4-wire Interface) Signal Lines

Name

Signal

Signal Level

Description

SEN

Digital Input with pull down

CMOS

SPI Enable

SDATAI

Digital Input

CMOS

Serial Data input

SDATAO

Digital Output with tristate

CMOS

Serial Data output

SCLK

Digital Input

CMOS

Clock for serial communication

AS3909 Datasheet(PDF) 22 Page - ams AG

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