New_Average_Result= 7

8

(Previous_Average_Result)+ 1

8

(Current_Result)

ADS8028

SBAS549B – MAY 2011 – REVISED MARCH 2012

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TEMPERATURE SENSOR

The internal temperature sensor measures the ADS8028 die temperature. The temperature sensor can be

selected for conversion by setting the TSENSE 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 TSENSE 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 TSENSE 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

+10

0000 0010 1000

+25

0000 0110 0100

+50

0000 1100 1000

+75

0001 0010 1100

+100

0001 1001 0000

+105

0001 1010 0100

+125

0001 1111 0100

14

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