CS5532 datasheet(36/50 Pages) CIRRUS

36 / 50 page

CS5532/34-BS

DS755F3

offset calibration on physical channel 2 and SDO

falls to indicate that the calibration is complete. To

perform additional calibrations, more commands

must be issued.

Note:

The CSRs need not be written. If they are not

initialized, all the Setups point to their default

settings irrespective of the conversion or

calibration mode (i.e conversions can be

performed, but only physical channel 1 will be

converted). Further note that filter

convolutions are reset (i.e. flushed) if

consecutive conversions are performed on

two different physical channels. If

consecutive conversions are performed on

the same physical channel, the filter is not

reset. This allows the ADCs to more quickly

settle full scale step inputs.

2.7. Using Multiple ADCs Synchronously

Some applications require synchronous data out-

puts from multiple ADCs converting different ana-

log channels. Multiple CS5532/34 parts can be

synchronized in a single system by using the fol-

lowing guidelines:

1) All of the ADCs in the system must be operated

from the same oscillator source.

2) All of the ADCs in the system must share com-

mon SCLK and SDI lines.

3) A software reset must be performed at the same

time for all of the ADCs after system power-up (by

selecting all of the ADCs using their respective CS

pins, and writing the reset sequence to all parts, us-

ing SDI and SCLK).

4) A start conversion command must be sent to all

of the ADCs in the system at the same time. The ±8

clock cycles of ambiguity for the first conversion

(or for a single conversion) will be the same for all

ADCs, provided that they were all reset at the same

time.

5) Conversions can be obtained by monitoring

SDO on only one ADC, (bring CS high for all but

one part) and reading the data out of each part indi-

vidually, before the next conversion data words are

ready.

An example of a synchronous system using two

CS5532 parts is shown in Figure 15.

2.8. Conversion Output Coding

The CS5532/34 output 24-bit data conversion

words. To read a conversion word the user must

read the conversion data register. The conversion

data register is 32 bits long and outputs the conver-

sions MSB first. The last byte of the conversion

data register contains data monitoring flags. The

channel indicator (CI) bits keep track of which

physical channel was converted and the overrange

flag (OF) monitors to determine if a valid conver-

sion was performed. Refer to the Conversion Data

Output Descriptions section for more details.

The CS5532/34 output data conversions in binary

format when operating in unipolar mode and in

two's complement format when operating in bipo-

lar mode. Table 4 shows the code mapping for both

unipolar and bipolar mode. VFS in the tables refers

to the positive full-scale voltage range of the con-

verter in the specified gain range, and -VFS refers

to the negative full-scale voltage range of the con-

verter. The total differential input range (between

AIN+ and AIN-) is from 0 to VFS in unipolar

mode, and from -VFS to VFS in bipolar mode.

CLOCK

SOURCE

CS5532

SDO

SDI

SCLK

OSC2

SDO

SDI

SCLK

OSC2

µC

Figure 15. Synchronizing Multiple ADCs

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