MCP3421DM-BFG Microchip Technology, MCP3421DM-BFG Datasheet - Page 29

• Manufacturer Part Number: MCP3421DM-BFG
• Description: BOARD DEMO FOR MCP3421
• Manufacturer: Microchip Technology

Specifications of MCP3421DM-BFG

• Main Purpose: Power Management, Battery Gauge
• Utilized Ic / Part: MCP3421
• Processor To Be Evaluated: MCP3421
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

6.2
6.2.1
The MCP3421 device can be used in a broad range of
sensor and data acquisition applications.
Figure 6-5
battery voltage. When the input voltage is greater than
the internal reference voltage (V
a voltage divider circuit to prevent the output code from
being saturated. In the example, R
age divider. The R
less
(V
If the input voltage range is much less than the internal
reference voltage, the voltage divider at the input pin is
not needed, and the user may use the internal PGA
with a gain of up to 8.
When the voltage divider or internal PGA is used for the
input signal, these factor must be taken into account
when the user converts the output codes to the actual
input voltage.
Find the Microchip Application Note AN1156 for the
input voltage and current measurement using the
MCP342X device family. The MCU firmware is well
documented in the reference.
FIGURE 6-5:
Measurement.
© 2009 Microchip Technology Inc.
REF
V
Measured Analog Input Voltage
Input Voltage Calculation from Output Code:
BAT
V
R
= 2.048V).
IN
1
than
and R
Application Examples
=
shows a circuit example measuring the
VOLTAGE MEASUREMENT
=
------------------ -
R
(V)
Battery
1
2
Output Code LSB
R
+
the
= Voltage Divider
2
R
1
2
R
R
×
and R
2
1
V
internal
Battery Voltage
BAT
2
×
are set to yield V
V
V
IN
IN
REF
-
+
×
reference
1
R
------------------ -
= 2.048V), it needs
and R
MCP3421
1
R
+
2
R
To Load
V
2
2
DD
form a volt-
×
---------- -
PGA
IN
1
voltage
to be
6.2.2
Figure 6-6
measurement. For the current measurement, the
device measures the voltage across the current sensor,
and converts it to current by dividing the measured
voltage by a known resistance value of the current
sensor. The voltage drops across the sensor is waste.
Therefore, the current measurement often prefers to
use a current sensor with smaller resistance value,
which, in turn, requires high resolution ADC device.
The high precision MCP342x devices from Microchip
Technology
measurement with low resistive current sensors. These
devices can measure the input voltage as low as 2 µV
range (or current in ~ µA range) with 18 bit resolution
and PGA = 8 settings. The MSB (= sign bit) of the
output code indicates the direction of the current.
FIGURE 6-6:
Measurement.
Discharging Current
Current
Battery
(V)
Current Calculation from Output Code:
CURRENT MEASUREMENT
Charging
Current
shows a circuit example of current
=
Inc.
Output Code LSB
----------------------------------------------------
R Sensor
are
Current Sensor
(
Battery Current
suitable
MCP3421
×
V
V
)
IN
IN
-
+
×
for
DS22003E-page 29
MCP3421
----------- - A ( )
PGA
To Load
1
the
V
DD
current