PCF8545ATT datasheet(40/103 Pages) NXP

40 / 103 page

PCA8530

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Product data sheet

Rev. 2 — 25 September 2014

40 of 103

NXP Semiconductors

PCA8530

Automotive 102 x 4 Chip-On-Glass LCD segment driver

8.10.4 Temperature measurement and temperature compensation of VLCD

8.10.4.1

Temperature readout

The PCA8530 has a built-in temperature sensor which provides an 8-bit digital value

(TD[7:0]) of the ambient temperature. This value can be read by command (see

Section 8.2.6 on page 12 and Section 8.2.7 on page 13). The actual temperature is

determined from TD[7:0] using Equation 3.

(3)

TD[7:0] = FFh means that no temperature readout is available or was performed. The

measurement needs about 8 ms to complete. It is repeated periodically every second as

long as bit TME is set logic 1 (see Table 17 on page 17).

Due to the nature of a temperature sensor, oscillations may occur. To avoid this, a filter

has been implemented in PCA8530. A control bit, TMF, is implemented to enable or

disable the digital temperature filter (see Table 17 on page 17). The system is exemplified

in Figure 21.

The digital temperature filter introduces a certain delay in the measurement of the

temperature. This behavior is illustrated in Figure 22.

Fig 21. Temperature measurement block with digital temperature filter

C



0.6275

TD 7:0

 40

–



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