PCF8811USLASH2DASLASH1 datasheet(55/73 Pages) PHILIPS

55 / 73 page

2004 May 17

Philips Semiconductors

Product speciﬁcation

× 128 pixels matrix LCD driver

PCF8811

22 MODULE MAKER PROGRAMMING

The One Time Programmable (OTP) technology is

implemented on the PCF8811. It enables the module

maker to program some extended features of the

PCF8811 after it has been assembled on an LCD module.

Programming is made under the control of the interfaces

and the use of one special pin. This pin must be made

available on the module glass but need not to be accessed

by the set maker.

The PCF8811 features 3 module maker programmable

parameters:

• VLCD calibration

• Temperature coefficient selection

• Seal bit.

22.1

VLCD calibration

The first feature included is the ability to adjust the VLCD

voltage with a 5-bit code (MMVOPCAL). This code is

implemented in twos complement notation giving rise to a

positive or negative offset to the VPR register. This is in the

same manner as the on-glass calibration pins VOS.

In theory, both may be used together but it is

recommended that the VOS pins are tied to VSS when OTP

calibration is being used. This will set them to a default

offset of zero. If both are used then the addition of the two

5-bit numbers must not exceed a 5-bit result otherwise the

resultant value will be undefined. The final adder in the

circuit has underflow and overflow protection. In the event

of an overflow, the output will be clamped to 255; during an

underflow the output will be clamped to 0.

The final control to the high voltage generator, VOP, will be

the sum of all the calibration registers and pins. The VLCD

equation (4) or (5) given in Section 13.10 must be

extended to include the OTP calibration, as follows;

(7)

The possible MMVOPCAL[4:0] values are the same as the

VOS[4:0] values; see Table 12.

LCD TT

CUT

()

OS [4:0]

MMVOPCAL[4:0]

OP [7:0]

(

) b

handbook, full pagewidth

MGU287

OTP VLCD calibration: 5-bit offset

MMVOPCAL[4:0]

VOP[7:0]

range: 0 to

+255

range

−16 to +15

range

−16 to +15

range 0 to

+255

usable range

+32 to +255

to high voltage

generator

laser trim pins: 5-bit offset

VOS[4:0]

VPR register: 8-bit value

VPR[7:0]

Fig.47 VLCD calibration.

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