PCF8833USLASH2DA datasheet(57/112 Pages) PHILIPS

57 / 112 page

2003 Feb 14

Philips Semiconductors

Objective speciﬁcation

STN RGB - 132

× 132 × 3 driver

PCF8833

When the required bias system (a) is defined, the LCD

supply voltage for a display size N can be determined; see

equation (4).

(4)

The parameter P in equation (4) is the number of

simultaneous selected rows. For the maximum number of

rows of 132, P = 4 is chosen. When partial Display mode

is selected the P value is set to 1 internally.

The bias voltages needed in a MRA LCD driver depends

on the number of simultaneous selected rows (P). The

bias voltages of the PCF8833 are given for P = 4 and

P = 1; see Fig.32. In the PCF8833 the maximum column

voltage (GMAX) is always lower or equal to the row

voltage F.

LCD

N2a

()

---------------------------------------

handbook, full pagewidth

MGU941

VLCD2

V2H

V1H

V1L

V2L

VSS

P = 4

−F

Gmax

−Gmax

VLCD2

V2H

V2L

VSS

P = 1

−F

Gmax

−Gmax

Fig.32 Bias levels for a MRA system with P = 4 and P = 1.

The bias voltage levels are a function of the row voltage

F and a:

(5)

(6)

(7)

(8)

Depending on the value of p, the bias levels are set in the

ratio of:

p=1:

αR − 2R − 2R −αR

p=4:

αR − R − R − R − R −αR

Where the value of

α is in the range from 0 to 4.

The value of F is determined by (

α +2) × R and the value

of Gmax is determined by 2 × R.

The relationship between the ratio F/Gmax and α:

(9)

or:

(10)

The relation between a and

α for a given p is the following:

(11)

This leads to the following bias systems given in Table 70.

LCD

-------------

max

≥

max

-----------------------

max

--------------

---

max

--------------

---

α 2

() R

-----------------------------

α 2

()

------------------

---

max

-------------

–



 2

---



 p

---

–



 2

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