Microchip Technology MCP3422EV Data Sheet

© 2009 Microchip Technology Inc.

DS22088C-page 33

The MCP3422/3/4 devices can be used for broad
ranges of sensor and data acquisition applications. 

 shows a circuit example measuring both the

battery voltage and current using the MCP3422 device.
Channels 1 and 2 are measuring the voltage and the
current, respectively. 

When the input voltage is greater than the internal ref-
erence voltage (V

REF

 = 2.048V), it needs a voltage

divider circuit to prevent the output code from being
saturated. In the example, R

1

 and R

2

 form a voltage

divider. The R

1

 and R

2

 are set to yield V

IN

 to be less

than the internal reference voltage (V

REF

 = 2.048V).

For the current measurement, the device measure the
voltage across the current sensor, and converts it by
dividing the measured voltage by a known resistance
value. 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 device 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 determines the
direction of the current, which identifies the charging or
the discharging current. 

   

5 k

Ω

V

DD

 V

SS

0.1 µF

10 µF

To MCU

(MASTER)

SCL

SDA

5 k

Ω

CH2+

SCL

CH2-

R

1

R

2

Battery

(Rechargeable)

2

3
4

5

6

7

CH1-

SDA

1

8

CH1+

 V

DD

Current Sensor

To Load

To Battery

Discharging Current

Charging 
Current

R

1

 and R

2

 = Voltage Divider

2

1

2

+

------------------

×

=

V

IN

V

BAT