Microchip Technology MCP3422, Manual

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©
2008 Microchip Technology Inc. DS22088B-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 immedi-
ately 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 conver-
sion, 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 recom-
mended for low power operating applications where the
conversion result is needed by request on demand.
During the low current standby mode, the device con-
sumes 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 approx-
imately 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.