Datasheet

SDA
SCL
A0
A1
INT
IN0
ADC128D818
GND
V+
IN1
IN2
IN3
IN4
VREF
IN5
IN6
IN7
LM4140
+
(optional)
OUT
VDD
GND
LM94022
GS1
GS0
+
0.1 PF
Microcontroller
RA_top
GPO1
GPO2
GPO3
GPO4
R
R R
RA_bottom
1 PF
1 PF
0.1 PF
RA_top
RA_bottom
ADC128D818
www.ti.com SNAS483E –FEBRUARY 2010–REVISED MARCH 2013
Temperature Sensors
Figure 38. Temperature Sensor Applications
An external temperature sensor can be connected to any of ADC128D818's eight single-ended input for
additional temperature sensing. One such temperature sensor can be TI's LM94022, a precision analog
temperature sensor with selectable gains. The application diagram shows LM94022's gains (GS1 and GS0) both
grounded indicating the lowest gain setting. Four possible gains can be set using these GS1 and GS0 pins.
According to the LM94022 datasheet, the voltage-to-temperature output plot can be determined using the
method of linear approximation as follows:
V - V1 = (V2 - V1) / (T2 - T1) x (T - T1) (8)
Where V is in mV, T is in °C, V1 and T1 are the coordinates of the lowest temperature, and T2 and V2 are the
coordinates of the highest temperature.
For example, to determine the equation of a line over a temperature range of 20°C to 50°C, first find V1 and V2
relative to those temperatures, then use the above equation to find the transfer function.
V - 925 mV = (760 mV - 925 mV) / (50C - 20°C) x (T - 20°C) (9)
V = (-5.50 mV /°C) x T + 1035 mV (10)
For more information and explanation of this example, refer to the LM94022 datasheet.
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