Data Sheet

© 2009 Microchip Technology Inc. DS22088C-page 17
MCP3422/3/4
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 and Figure 5-5).
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 Mode (single conver-
sion) 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 18 bit
conversion data once a second in One-Shot
Conversion mode, the device draws only about one
fourth of its total operating current. In this example, the
device consumes approximately 36 µA (135 µA /
3.75 SPS = 36 µA), if the device performs only one
conversion per second (1 SPS) in 18-bit conversion
mode with 3V power supply.