ADBMS1818ASWAZ-R7 datasheet(88/92 Pages) AD

88 / 92 page

Data Sheet

ADBMS1818

APPLICATIONS INFORMATION

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Rev. B | 88 of 92

READING EXTERNAL TEMPERATURE

PROBES

Figure 110 shows the typical biasing circuit for a negative tempera-

ture coefficient (NTC) thermistor. The 10 kΩ at 25°C is the most

popular sensor value and the VREF2 output stage is designed to

provide the current required to bias several of these probes. The

biasing resistor is selected to correspond to the NTC value so the

circuit provides 1.5 V at 25°C (VREF2 is 3 V nominal). The overall

circuit response is approximately –1%/°C in the range of typical cell

temperatures, as shown in the chart of Figure 110.

Expanding the Number of Auxiliary

Measurements

The ADBMS1818 has nine GPIO pins that can be used as ADC

inputs. In applications that need to measure more than nine signals,

a mux circuit can be implemented to expand the analog measure-

ments to 16 different signals (Figure 111). The GPIO1 ADC input

is used for measurement and mux control is provided by the I2C

port on GPIO4 and GPIO5. The buffer amplifier is selected for fast

settling and increases the usable throughput rate.

Figure 110. Typical Temperature Probe Circuit and Relative Output

Figure 111. Mux Circuit Supports 16 Additional Analog Measurements

ADBMS1818ASWAZ-R7 Datasheet(PDF) 88 Page - Analog Devices