Datasheet

New_Average_Result=
7
8
(Previous_Average_Result)+
1
8
(Current_Result)
ADS8028
SBAS549B –MAY 2011–REVISED MARCH 2012 www.ti.com
TEMPERATURE SENSOR
The internal temperature sensor measures the ADS8028 die temperature. The temperature sensor can be
selected for conversion by setting the T
SENSE
bit in the Control Register to '1'. The TM_BUSY pin goes high as
soon as the temperature sensor is selected for conversion and remains high until the conversion is completed
(100 µs, max).
The operating temperature range for this internal temperature sensor is limited by the operating temperature
range of the ADS8028 (–40°C to +125°C).
Modes of Operation
The ADS8028 temperature sensor can operate in two modes: normal mode and averaging mode.
Normal Mode
To operate in normal mode (without the averaging feature), the TMP_AVG bit in the Control Register should be
set to '0' and the T
SENSE
bit in the Control Register should be set to '1'. Output data are the result of a single
conversion performed on the temperature sensor. This mode is the default mode of operation for the temperature
sensor. A single conversion on the temperature sensor takes 100 µs, max.
Averaging Mode
In this mode, the ADS8028 provides rolling average filtering to increase the accuracy of the temperature sensor
measurement. To activate this filter, the TMP_AVG bit in the Control Register should be set to '1'. This bit must
be set to '1' in subsequent write operations for the duration of the filter operation. Resetting the TMP_AVG bit to
'0' resets and deactivates the filter and places the ADS8028 in a normal mode of operation.
When the TMP_AVG and T
SENSE
bits are both set to '1', the temperature sensor is selected and the conversion
result is sent to the filter block. The filter block output is given by Equation 2:
(2)
This output can be read during the next conversion cycle. After enabling the averaging feature, the first ADS8028
output data are the same as the temperature sensor conversion result. Averaging starts taking effect from the
subsequent conversion performed on the temperature sensor.
Temperature Sensor Data Format
The temperature sensor, along with the ADC, gives 0.25°C resolution over the operating temperature range. The
temperature reading from the ADC is in 12-bit twos complement format, as shown in Table 1.
Table 1. Temperature Data Format
TEMPERATURE (°C) DIGITAL OUTPUT
–40 1111 0110 0000
–25 1111 1001 1100
–10 1111 1101 1000
–0.25 1111 1111 1111
0 0000 0000 0000
+0.25 0000 0000 0001
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