Microchip Technology MCP3421DM-WS Data Sheet
© 2009 Microchip Technology Inc.
DS22003E-page 15
MCP3421
5.0
USING THE MCP3421 DEVICE
5.1
Operating Modes
The user operates the device by setting up the device
configuration register using a write command (see
configuration register using a write command (see
) and reads the conversion data using a read
and
). 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.
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 =
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.
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
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 =
(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.
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
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 39 µA (145 µA / 3.75
SPS = 39 µA), if the device performs only one
conversion per second (1 SPS) in 18-bit conversion
mode with 3V power supply.
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 39 µA (145 µA / 3.75
SPS = 39 µA), if the device performs only one
conversion per second (1 SPS) in 18-bit conversion
mode with 3V power supply.