PCF8811USLASH2DASLASH1 datasheet(54/81 Pages) NXP

54 / 81 page

PCF8811_4

Product data sheet

Rev. 04 — 27 June 2008

54 of 81

NXP Semiconductors

PCF8811

80 x 128 pixels matrix LCD driver

12.10.2 Extended command set

The VLCD at T = TCUT is calculated using Equation 5. In the extended command set

VPR[7:0] is the same value as VOP[7:0]. It can additionally be adjusted with the VLCD offset

pads VOS[4:0] to obtain the optimum optical performance.

Instead of using the VLCD offset pads (VOS[4:0]) the VLCD can be adjusted with the module

maker calibration setting MMVOPCAL[4:0]; see Section 18.

(5)

Where:

• TCUT is a reference temperature; see Section 12.11

• a is a ﬁxed constant value; see Table 27

• b is a ﬁxed constant value; see Table 27

• VPR[7:0] is the programmed VOP value

• VOS[4:0]/MMVOPCAL[4:0] is the value of the offset VLCD pads or the value stored in

the OTP cells

As the programming range for the internally generated VLCD allows values above the

maximum allowed VLCD (9 V) the user has to ensure while setting the VPR register and

selecting the Temperature Compensation (TC), that under all conditions and including all

tolerances the VLCD remains below 9.0 V. This is valid for the two different command sets.

12.11 Temperature control

Due to the temperature dependency of the liquid crystals’ viscosity, the LCD controlling

voltage VLCD might have to be increased at lower temperatures to maintain optimum

contrast.

LCD T

CUT

()

OS[4:0]

OP[7:0]

() b

VOP[7:0] programming, (00h to FFh).

Fig 36. VLCD programming of the PCF8811

mgt847

VLCD

VOP

. . .

. . . FD FE FF

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