Data Sheet

© 2009 Microchip Technology Inc. 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 or
(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 is 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 a second in One-Shot
Conversion mode, the device draws only about one-
fifteenth of the operating currents for the continuous
conversion mode. In 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.