MAS3507D datasheet(9/60 Pages) MICRONAS

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PRELIMINARY DATA SHEET

MAS 3507D

Micronas

2.5. Clock Management

The MAS 3507D should be driven by a single clock at

a frequency of 14.725 MHz. It is possible to drive the

MAS 3507D with other reference clocks (see Section

3.7.2.1. on page 36).

The CLKI signal acts as a reference for the embedded

clock synthesizer that generates the internal system

clock. Based on the reference input clock CLKI

, a syn-

chronized output clock CLKO that depends on the

audio sample frequency of the decompressed bit

stream is generated and provided as ‘master clock’ to

external D/A converters. Some of them need master

clocks that have a fixed relation to the sampling fre-

quencies. A scaler can be switched on during start-up,

optionally, by setting the PI8 pin to 0. Then, the clock-out

will automatically be divided by 1, 2, or 4 as defined in

Table 2–2.

2.6. Power Supply Concept

The MAS 3507D offers an embedded controlled DC/

DC converter for battery based power supply con-

cepts. It works as an up-converter.

2.6.1. Internal Voltage Monitor

An internal voltage monitor compares the input voltage

at the VSENS pin with an internal reference value that

is adjustable via I2C bus. The PUP output pin becomes

inactive when the voltage at the VSENS pin drops

below the programmed value of the reference voltage.

It is important that the WSEN must not be activated

before the PUP is generated. The PUP signal thresh-

olds are listed in Table 3–8. The internal voltage moni-

tor will be activated with a high level at Pin DCEN.

2.6.2. DC/DC Converter

The DC/DC converter of the MAS 3507D is used to

generate a fixed power supply voltage even if the chip

set is powered by battery cells in portable applications.

The DC/DC converter is designed for the application of

1 or 2 batteries or NiCd cells as shown in Fig. 2–3

which shows the standard application circuit. The DC/

DC converter is switched on by activating the DCEN

pin. Its output power is sufficient for other ICs as well.

Note: Connecting DCEN directly to VDD leads to

unexpected states of the DCCF register.

The PUP signal should be read out by the system con-

troller.

A 22

µH inductor is required for the application. The

important specification item is the inductor saturation

current rating, which should be greater than 2.5 times

the DC load current. The DC resistance of the inductor

is important for efficiency. The primary criterion for

selecting the output filter capacitor is low equivalent

series resistance (ESR), as the product of the inductor

current variation and the ESR determines the high-fre-

quency amplitude seen on the output voltage. The

Schottky diode should have a low voltage drop VD for a

high overall efficiency of the DC/DC converter. The

current rating of the diode should also be greater than

2.5 times the DC output current. The VSENS pin has

to be always connected to the output voltage.

2.6.3. Stand-by Functions

The digital part of the MAS 3507D and the DC/DC

converter are turned on by setting WSEN. If only the

DC/DC converter should work, it can remain active by

setting DCEN alone to supply other parts of the appli-

cation even if the audio decoding part of the

MAS 3507D is not being used. The WSEN power-up

pin of the digital part may be handled by the controller.

Please pay attention to the fact, that I2C protocol is

working only if the processor and its interfaces works

(WSEN = 1)

Table 2–2: CLKO Frequencies

fs/kHz

CLKO/MHz

scaler on

CLKO/MHz

scaler off

48, 32

24.576

44.1

22.5792

24, 16

12.288

24.576

22.05

11.2896

22.5792

12, 8

6.144

24.576

11.025

5.6448

22.5792

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