MCP3426 datasheet(17/56 Pages) MICROCHIP

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DS22226A-page 17

MCP3426/7/8

5.0

USING THE DEVICES

5.1

Operating Modes

The user operates the device by setting up the device

configuration register using a write command (see

Figure 5-3) and reads the conversion data using a read

command (see Figure 5-4 ). The device operates in two

modes:

(a)

Continuous

Conversion

Mode

(b) One-Shot Conversion Mode (single conversion).

This mode selection is made by setting the O/C bit in

the Configuration Register. Refer to Section 5.2

“Configuration Register” for more information.

5.1.1

CONTINUOUS CONVERSION

MODE (O/C BIT = 1)

The device performs a Continuous Conversion if the

O/C bit is set to logic “high”. Once the conversion is

completed, RDY bit is toggled to ‘0’ and the result is

placed at the output data register. The device

immediately begins another conversion and overwrites

the output data register with the most recent result.

The device clears the data ready flag (RDY bit = 0)

when the conversion is completed. The device sets the

ready flag bit (RDY bit = 1), if the latest conversion

result has been read by the Master.

• When writing configuration register:

- Setting RDY bit in continuous mode does not

affect anything.

• When reading conversion data:

- RDY bit = 0 means the latest conversion

result is ready.

- RDY bit = 1 means the conversion result is

not updated since the last reading. A new

conversion is under processing and the RDY

bit will be cleared when the new conversion

result is ready.

5.1.2

ONE-SHOT CONVERSION MODE

(O/C BIT = 0)

Once the One-Shot Conversion (single conversion)

Mode is selected, the device performs only one

conversion, updates the output data register, clears the

data ready flag (RDY = 0), and then enters a low power

standby mode. A new One-Shot Conversion is started

again when the device receives a new write command

with RDY = 1.

• When writing configuration register:

- The RDY bit needs to be set to begin a new

conversion in one-shot mode.

• When reading conversion data:

- RDY bit = 0 means the latest conversion

result is ready.

- RDY bit = 1 means the conversion result is

not updated since the last reading. A new

conversion is under processing and the RDY

bit will be cleared when the new conversion is

done.

This

One-Shot

Conversion

Mode

highly

recommended for low power operating applications

where the conversion result is needed by request on

demand. During the low current standby mode, the

device consumes less than 1 µA maximum (or 300 nA

typical). For example, if the user collects 16-bit

conversion

data

once

second

One-Shot

Conversion mode, the device draws only about one-

fifteenth of the operating currents for the continuous

conversion

mode.

this

example,

the

device

consumes

approximately

9 µA

(135 µA

15 SPS = 9 µA), when the device performs only one

conversion per second (1 SPS) in 16-bit conversion

mode with 3V power supply.

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