AD28MSP02 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD28MSP02

Voiceband Signal Port

Analog Devices 

AD28msp02

Serial Output Startup Time

The AD28msp02 begins transmitting data to the host processor

after it is taken out of powerdown. To take the AD28msp02 out

of powerdown, the host processor writes a control word to the

AD28msp02.

The start-up time (from the start of this control word write)

before the AD28msp02 begins transmitting data is shown in

Figure 11.

PC Board Layout Considerations

Separate analog and digital ground planes should be provided

for the AD28msp02 in order to ensure the characteristics of the

device’s ADC and DAC. The two ground planes should be con-

nected at a single point—this is often referred to as a “Star” or

“Mecca” grounding configuration. The point of connection may

be at the system power supply, at the PC board power connec-

tion, or at any other appropriate location. Because ground loops

increase susceptibility to EMF, multiple connections between

the analog and digital ground planes should be avoided.

The ground planes should be designed such that all noise-

sensitive areas are isolated from one another and critical signal

traces (such as digital clocks and analog signals) are as short as

possible.

Each +5 V digital supply pin, VDD, of the AD28msp02 (SOIC

Pins 20, 21) should be bypassed to ground with a 0.1 µF capaci-

tor. These capacitors should be low inductance, monolithic, ce-

ramic, and surface-mount. The capacitor leads and PC board

traces should be as short as possible to minimize inductive ef-

fects. In addition, a 10 µF capacitor should be connected be-

tween VDD and ground, near the PC board power connection.

MCLK Frequency

The sigma-delta converters and digital filters of the AD28msp02

are specifically designed to operate at a master clock (MCLK)

frequency of 13.0 MHz. MCLK must equal 13.0 MHz to guar-

antee the filter characteristics and sample rate of the ADC and

DAC. The AD28msp02 is not tested or characterized at any

other clock frequency.

A low cost crystal with a different frequency, for example

12.288 MHz, can be used for the master clock input; in this

case, however, the AD28msp02 is not guaranteed to meet the

specifications listed in this data sheet.

SCLK

DATA/

CNTRL

SDIFS

SDI

SDOFS

SDO

MSB

2nd MSB

POWERUP CONTROL WORD

WRITTEN TO AD28msp02

410 SCLK CYCLES

(2050 MCLK CYCLES)

Figure 11. Serial Output Startup Time

MSB

2nd MSB

FIRST DATA WORD

TRANSMITTED

FROM AD28msp02

REV. 0

–9–

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