PC87591L datasheet(173/437 Pages) NSC

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Embedded Controller Modules (Continued)

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4.11.3 Voltage Measurement

The ADC performs a linear conversion of the input voltage signal to a 10-bit, unsigned digital representation. The input signal

should be applied relative to the AGND pin and should range from 0V to VFS (Full Scale).

The equations in the folowing table should be used to calculate the input voltage based on the reading from the Voltage

Channel Data result (VCHDAT field in VCHiDAT register).

An input signal of zero (ground) is converted to 00016; an input signal equal to (1023/1024) * VFS is converted to 3FF16.

Changing the input selection for a new measurement requires switching between inputs at different voltage levels. The input

interface circuits of the ADC, together with the externally added noise-rejection filters (if applicable), require a settling time

to reach the new voltage value with a 10-bit accuracy (less than 1/2 LSB error). Therefore, the ADC waits for a programma-

ble delay time between the selection of the input to be measured and the beginning of the A/D conversion. This Voltage

Channel Delay is expressed in ADC clock cycles in ADC Delay Control register (ADLYCTL). The number of ADC clock cy-

cles should be converted to time using the following formula:

tVD = Number_of_ADC_clocks * (System_clock_cycle) * SCLKDIV(5-0)

To calculate the required delay value according to externally added components, see Section 4.11.7 on page 185.

4.11.4 Temperature Measurement

The ADC performs a linear conversion of the temperature, measured by a remote or a local diode, to an 8-bit, 2s complement

digital representation. The ADC generates a current that flows through the diode and measures the resulting voltage drop.

This differential voltage is converted to an 8-bit value, with the LSB equal to 1

°C, according to Table 22.

Input Channel

Scale

Calculation1

1. See Section 7.4.1 on page 378 for the dynamic range relevant for each input.

AD0 to AD9

Low

Vi = VCHDAT(9-0) * (1 / 1024) * VFSL

AD0 to AD9

High

Vi = VCHDAT(9-0) * (1 / 1024) * VFSH

AD10 to AD13

Low2,3

2. High Scale is undeﬁned for these inputs.

3. These inputs are scaled down by 4 at the input and compensated back at the result read phase.

Vi = VCHDAT(9-0) * (1 / 1024) * VFSV

Table 22. Temperature Format Conversion

Temperature

(

°C)

Temperature Channel Data

Binary

Hex

+1271

1. Values higher than +125

°C and lower than −40°C

are not within the speciﬁed operating temperature range.

0111 1111

7F16

+125

0111 1101

7D16

+100

0110 0100

6416

+40

0010 1000

2816

+25

0001 1001

1916

0000 0001

0116

0000 0000

0016

−1

1111 1111

FF16

−25

1110 0111

E716

−40

1101 1000

D816

−1281

1000 0000

8016

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