MCP3421 datasheet(10/30 Pages) MICROCHIP

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MCP3421

DS22003B-page 10

5.0

USING THE MCP3421 DEVICE

5.1

Operating Modes

The user operates the device by setting up the device

configuration register and reads the conversion data

using serial I2C interface commands. The MCP3421

operates in two modes: (a) Continuous Conversion

Mode or (b) One-Shot Conversion Mode (single

conversion). The 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 MCP3421 device performs a Continuous

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

conversion is completed, the result is placed at the

output data register. The device immediately begins

another conversion and overwrites the output data

The device also 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.

5.1.2

ONE-SHOT CONVERSION MODE

(O/C BIT = 0)

Once the One-Shot Conversion (single conversion)

Mode is selected, the device performs a 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.

This One-Shot Conversion Mode is recommended for

low power operating applications. During the low

current standby mode, the device consumes less than

1 µA typical. For example, if user collects 18 bit

conversion data once a second in One-Shot Conver-

sion mode, the device draws only about one fourth of

its total operating current. In this example, the device

consumes approximately 39 µA (= ~145 µA/3.75 SPS),

if the device performs only one conversion per second

(1 SPS) in 18-bit conversion mode with 3V power

supply.

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