ADT7516 datasheet(22/44 Pages) AD

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ADT7516/ADT7517/ADT7519

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BIAS

DIODE

INTERNAL

SENSE

TRANSISTOR

VDD

TO ADC

VOUT+

VOUT–

× I

IBIAS

Figure 46. Top Level Structure of Internal Temperature Sensor

Table 7. Thermal Voltage Output (0 V to 2VREF)

O/P Voltage (V)

Default °C

Max °C

Sample °C

–40

–128

0.25

–26

–114

+14

0.5

+12

–100

+28

0.75

–85

+43

+17

–71

+57

1.12

+23

–65

+63

1.47

+43

–45

+83

1.5

+45

–43

+85

+73

–15

+113

2.25

+88

+127

2.5

+102

+14

UDB

∗

2.75

+116

+28

UDB

∗

UDB

∗

+42

UDB

∗

3.25

UDB

∗

+56

UDB

∗

3.5

UDB

∗

+70

UDB

∗

3.75

UDB

∗

+85

UDB

∗

UDB

∗

+99

UDB

∗

4.25

UDB

∗

+113

UDB

∗

4.5

UDB

∗

+127

UDB

∗

Negative temperatures:

()

(

) 128

Temp

Code

Offset

where:

D7 of Offset Register Code is set to 1 for negative temperatures.

Example:

() ()

58h

Code

Offset

−

128

Since a negative temperature has been inserted into the

equation, DB7 (MSB) of the offset register code is set to 1.

Therefore 58h becomes D8h.

58h + DB7(1) = D8h

Positive temperatures:

Offset Register Code (d) = 0 V Temp

Example:

Offset Register Code (d) = 10d = 0Ah

The following equation is used to work out the various

temperatures for the corresponding 8-bit DAC output:

(

) (

)

Temp

LSB

DAC

Temp

Bit

−

For example, if the output is 1.5 V, VREF-IN = 2.25 V, 8-bit DAC

has an LSB size = 2.25 V/256 = 8.79 × 10–3, and 0 V temp is at

–128°C, then the resultant temperature is

(

) ()

−

128

The following equation is used to work out the various

temperatures for the corresponding 10-bit DAC output:

10-Bit Temp = ((DAC O/P ÷ 1 LSB) × 0.25) + (0 V Temp)

For example, if the output is 0.4991 V, VREF-IN = 2.25 V, 10-bit

DAC has an LSB size = 2.25 V/1024 = 2.197 × 10–3, and 0 V

temp is at –40°C, then the resulting temperature is

(((0.4991 ÷ 2.197 × 10–3) × 0.25) + (–40) = +16.75°C

Figure 47 shows a graph of the DAC output versus temperature

for a VREF-IN = 2.25 V.

TEMPERATURE (

°C)

0.15

–128–110 –90 –70 –50 –30 –10 10

90 110 127

0.30

0.45

0.60

0.75

0.90

1.05

1.20

1.35

1.50

1.65

1.80

1.95

2.10

2.25

0V = –128

°C

0V = –40

°C

0V = 0

°C

Figure 47. DAC Output vs. Temperature VREF-IN = 2.25 V

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