PCF8833 datasheet(54/112 Pages) PHILIPS

54 / 112 page

2003 Feb 14

Philips Semiconductors

Objective speciﬁcation

STN RGB - 132

× 132 × 3 driver

PCF8833

Temperature compensation is implemented by adding an

offset to the VOP value. Previously, in Section 6.2.31, VOP

was calculated by adding VPR, VCON and MMVOPCAL

settings together. Now, an additional offset VT is added.

The final result for VLCD calculation is a 9-bit positive

number. Care must be taken by the user to ensure that the

ranges of VPR, MMVOPCAL, VCON and temperature

compensation do not cause clipping, and hence undesired

results (see Fig.24). The adders will not permit overflow or

underflow and will clamp results to either end of the range

(VOP = 0 or 445). Also, temperatures outside the range

−40 to +79 °C will be clamped to the last valid offset.

The temperature readout generates an 8-bit result TD[7:0].

This temperature readout number is used for temperature

compensation.

The resolution of the readout is

(

−40 to +80 °C)/128 = 0.9375 °C/LSB; where 0

represents

−40 °C and 127 represents +79 °C;

see Section 6.2.44.

The temperature readout function can also be used to read

back the temperature value via the interface;

see equation (12).

The offset value may be calculated from Table 67. The

effect on VLCD can be calculated by multiplying the offset

value with the value of b.

For example T =

−8 °C: TD = 34 and MB = 0.5:

VLCD(OS) =40mV × (64 − 34) × 0.5 = 600 mV.

A complete overview of the programming range of VLCD

can be found in Section 15.1.

handbook, full pagewidth

MGU939

SLA

SLB

SLC

SLD

TEMPERATURE

READOUT

VPR[8:0]

VOP[8:0]

OFFSET

VLCD

MMVOPCAL[5:0]

VCON[5:0]

T (

°C)

−40

zero

offset

+80

Fig.30 Segmented temperature compensation.

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