Datasheet

© 2009 Microchip Technology Inc. DS22072B-page 13
MCP3425
5.0 USING THE MCP3425 DEVICE
5.1 Operating Modes
The user operates the device by setting up the device
configuration register using a write command (see
Figure 5-2) and reads the conversion data using a read
command (see Figure 5-3). 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 recommended for
low power operating applications. During the low
current standby mode, the device consumes less than
1 µA typical. For example, if the device converts only
one time per second with 16 bit resolution, the total
current draw is only about one fourth of the draws in
continuous mode. In this example, the device
consumes approximately 9.7 µA (= ~145 µA/15 SPS),
if the device performs only one conversion per second
(1 SPS) in 16-bit conversion mode with 3V power
supply.