CS5531-AS Просмотр технического описания (PDF) - Cirrus Logic

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CS5531-AS

16-bit and 24-bit ADCs withUltra-low-noise PGIA

Cirrus Logic 

CS5531/32/33/34-AS

2.2.4. Serial Port Interface

The CS5531/32/33/34’s serial interface consists of

four control lines: CS, SDI, SDO, SCLK. Figure 7

details the command and data word timing.

CS, Chip Select, is the control line which enables

access to the serial port. If the CS pin is tied low,

the port can function as a three-wire interface.

SDI, Serial Data In, is the data signal used to trans-

fer data to the converters.

SDO, Serial Data Out, is the data signal used to

transfer output data from the converters. The SDO

output will be held at high impedance any time CS

is at logic 1.

SCLK, Serial Clock, is the serial bit-clock which

controls the shifting of data to or from the ADC’s

serial port. The CS pin must be held low (logic 0)

before SCLK transitions can be recognized by the

port logic. To accommodate optoisolators SCLK is

designed with a Schmitt-trigger input to allow an

optoisolator with slower rise and fall times to di-

rectly drive the pin. Additionally, SDO is capable

of sinking or sourcing up to 5 mA to directly drive

an optoisolator LED. SDO will have less than a 400

mV loss in the drive voltage when sinking or sourc-

ing 5 mA.

CS

SCLK

SDI

MSB

LSB

Command Time

8 SCLKs

Data Time 32 SCLKs

Write Cycle

CS

SCLK

SDI

Command Time

8 SCLKs

SDO

MSB

LSB

Data Time 32 SCLKs

Read Cycle

CS

SCLK

SDI

SDO

Command Time

8 SCLKs

td*

8 SCLKs Clear SDO Flag MSB

MCLK /OWR

Clock Cycles

LSB

Data Conversion Cycle

Data Time 32 SCLKs

* td is the time it takes the ADC to perform a conversion. See the Single

Conversion and Continuous Conversion sections of the data sheet for more

details about conversion timing.

Figure 7. Command and Data Word Timing

22

DS289F5

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