Datasheet

Temperature=V
EXT_REF
ADC_Code
10
+109.3
- 273.15
Temperature = V
EXT_REF
ADC_Code 4096-
10
+ 109.3
- 273.15
Positive Temperature =
ADC_Code
4
Negative Temperature =
4096 ADC_Code-
4
ADS8028
www.ti.com SBAS549B –MAY 2011–REVISED MARCH 2012
If the output data MSB is ‘0’, the temperature can be calculated with Equation 3:
where:
V
EXT_REF
is the value of the external reference voltage (3)
If the output data MSB is ‘1’, the temperature can be calculated with Equation 4:
where:
V
EXT_REF
is the value of the external reference voltage (4)
For a 2.5-V reference (internal or external), Equation 3 and Equation 4 simplify to Equation 5 and Equation 6,
respectively.
(5)
(6)
REFERENCE
The ADS8028 can operate with either an internal voltage reference or an optional external reference. The type of
reference used is set by the EXT_REF bit in the Control Register.
The internal reference is selected when the EXT_REF bit is set to '0'. A 2.5-V output of the internal reference is
available on the REF pin. A 10-µF decoupling capacitor is recommended between the REF and AGND pins. The
reference circuit requires 5.5 ms to charge the decoupling capacitor. The internal reference is capable of
sourcing up to 2 mA of current and is designed to drive the ADS8028. It is recommended to buffer this output for
use elsewhere in the system.
The ADS8028 can operate with an external reference when the EXT_REF bit is set to '1'. An external reference
can be supplied through the REF pin. By default, the ADS8028 powers up in internal reference mode and must
be programmed to function with an external reference. Until such a time, the ADS8028 draws additional current
from the external reference source. This current is limited to 20 mA, using internal protection circuitry. Texas
Instruments' REF5025 can be used as external reference source for the ADS8028.
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Product Folder Link(s): ADS8028