MCP3422 datasheet(33/58 Pages) MICROCHIP

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DS22088C-page 33

MCP3422/3/4

6.2

Application Examples

The MCP3422/3/4 devices can be used for broad

ranges of sensor and data acquisition applications.

Figure 6-5 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 (VREF = 2.048V), it needs a voltage

divider circuit to prevent the output code from being

saturated. In the example, R1 and R2 form a voltage

divider. The R1 and R2 are set to yield VIN to be less

than the internal reference voltage (VREF = 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.

FIGURE 6-5:

Battery Voltage and Charging/Discharging Current Measurement.

VDD

VSS

0.1 µF

10 µF

To MCU

(MASTER)

SCL

SDA

CH2+

SCL

CH2-

Battery

(Rechargeable)

CH1-

SDA

CH1+

VDD

Current Sensor

To Load

To Battery

Discharging Current

Charging

Current

R1 and R2 = Voltage Divider

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

BAT

VIN

VBAT

MCP3422

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