MAX1021 datasheet(28/47 Pages) MAXIM

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10-Bit, Multichannel ADCs/DACs with FIFO,

Temperature Sensing, and GPIO Ports

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Unipolar/Bipolar Registers

The final 2 bits (LSBs) of the setup register control the

unipolar-/bipolar-mode address registers. Set

DIFFSEL[1:0] = 10 to write to the unipolar-mode regis-

ter. Set bits DIFFSEL[1:0] = 11 to write to the bipolar-

mode register. In both cases, the setup command byte

must be followed by 1 byte of data that is written to the

unipolar-mode register or bipolar-mode register. Hold

CS low and run 16 SCLK cycles before pulling CS high.

If the last 2 bits of the setup register are 00 or 01, nei-

ther the unipolar-mode register nor the bipolar-mode

as a new command byte. See Tables 6, 7, and 8 to pro-

gram the unipolar- and bipolar-mode registers.

Both registers power up at all zeros to set the inputs as

16 unipolar single-ended channels. To configure a

channel pair as single-ended unipolar, bipolar differen-

tial, or unipolar differential, see Table 8.

In unipolar mode, AIN+ can exceed AIN- by up to

VREF. The output format in unipolar mode is binary. In

bipolar mode, either input can exceed the other by up

to VREF/2. The output format in bipolar mode is two’s

complement (see the ADC Transfer Functions section).

ADC Averaging Register

Write a command byte to the ADC averaging register to

configure the ADC to average up to 32 samples for

each requested result, and to independently control the

number of results requested for single-channel scans.

Table 8. Unipolar/Bipolar Channel Function

UNIPOLAR-

MODE

BIPOLAR-MODE

CHANNEL PAIR

FUNCTION

Unipolar single-ended

Bipolar differential

Unipolar differential

Table 9. ADC Averaging Register*

BIT NAME

BIT

FUNCTION

—7 (MSB)

Set to zero to select ADC averaging register.

—6

Set to zero to select ADC averaging register.

—5

Set to one to select ADC averaging register.

AVGON

Set to one to turn averaging on. Set to zero to turn averaging off.

NAVG1

Configures the number of conversions for single-channel scans.

NAVG0

Configures the number of conversions for single-channel scans.

NSCAN1

Single-channel scan count. (Scan mode 10 only.)

NSCAN0

0 (LSB)

Single-channel scan count. (Scan mode 10 only.)

AVGON

NAVG1

NAVG0

FUNCTION

Performs one conversion for each requested result.

Performs four conversions and returns the average for each requested result.

Performs eight conversions and returns the average for each requested result.

Performs 16 conversions and returns the average for each requested result.

Performs 32 conversions and returns the average for each requested result.

NSCAN1

NSCAN0

FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED)

Scans channel N and returns four results.

Scans channel N and returns eight results.

Scans channel N and returns 12 results.

Scans channel N and returns 16 results.

*See below for bit details.

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