MAS3504D datasheet(7/40 Pages) MICRONAS

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MAS 3504D

Micronas

2.5.2. DC/DC Converter

The DC/DC converter of the MAS 3504D is used to

generate a fixed power supply voltage even if the chip

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. The DC/DC converter is

switched on by activating the DCEN pin. Its output

power is sufficient for other ICs as well.

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 is

always connected to the output voltage at the low ESR

capacitor.

2.5.3. Stand-by Functions

The digital part of the MAS 3504D and the DC/DC con-

verter are turned on by setting WSEN. If only the DC/

DC converter should work, it can remain active byset-

ting DCEN alone to supply other parts of the applica-

tion even if the audio decoding part of the MAS 3504D

is not being used. The WSEN power-up pin of the digi-

tal part should be handled by the controller.

Please pay attention to the fact, that the I2C interface

is working only if the processor is powered up

(WSEN = 1).

Fig. 2–1: DC/DC converter connections

0...15

32...47

64...94

−

VSS

AVSS

AVDD

VDD

CLKI

DCSO

DCSG

DCEN

PUP

WSEN

VSENSE

47 k

Ω

47 k

Ω

Power-On

Push Button

10 k

Ω

10 nF

DC/DC

converter

voltage

monitor

Start-up

oscillator

µController

µH

VIN ≥ 0.9 V

COUT

330

µF

Low ESR

CIN

330

µF

DCCF

8ehex

optional

filter

Start-up

divider

+32

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