PCF8566 Просмотр технического описания (PDF) - NXP Semiconductors.
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PCF8566 Datasheet PDF : 48 Pages
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NXP Semiconductors
PCF8566
Universal LCD driver for low multiplex rates
Table 5. Preferred LCD drive modes: summary of characteristics
LCD drive mode Number of:
Backplanes Bias levels
LCD bias
configuration
V------oV--f--f-L-(--RC----MD----S----)
static
1
2
static
0
1:2 multiplex
2
3
1⁄2
0.354
1:2 multiplex
2
4
1⁄3
0.333
1:3 multiplex
3
4
1⁄3
0.333
1:4 multiplex
4
4
1⁄3
0.333
V------oV--n---L(--R-C--M-D----S---)
1
0.791
0.745
0.638
0.577
D = V-V-----oo--f-n-f--((-R-R---M-M---S-S---)-)
∞
2.236
2.236
1.915
1.732
A practical value for VLCD is determined by equating Voff(RMS) with a defined LCD
threshold voltage (Vth), typically when the LCD exhibits approximately 10 % contrast. In
the static drive mode a suitable choice is VLCD > 3Vth.
Multiplex drive modes of 1:3 and 1:4 with 1⁄2 bias are possible but the discrimination and
hence the contrast ratios are smaller.
Bias is calculated by 1-----+1-----a-- , where the values for a are
a = 1 for 1⁄2 bias
a = 2 for 1⁄3 bias
The RMS on-state voltage (Von(RMS)) for the LCD is calculated with the equation
V on(RMS)
=
V LCD
-1n- + (n – 1) × 1-----+1-----a-- 2
-----------------------------n-------------------------------
(1)
where VLCD is the resultant voltage at the LCD segment and where the values for n are
n = 1 for static mode
n = 2 for 1:2 multiplex
n = 3 for 1:3 multiplex
n = 4 for 1:4 multiplex
The RMS off-state voltage (Voff(RMS)) for the LCD is calculated with the equation:
V off (RMS) = V LCD -a-n--2---×-–---(--(-1-2----a+-----+a---)-n--2--)
(2)
Discrimination is the ratio of Von(RMS) to Voff(RMS) and is determined from the equation:
V-V-----oo--fn--f-(-(-R-R--M-M---S-S--)-) = (-(--aa-----+–-----11---)-)--22----++-----((--nn----–-–----11----))
(3)
Using Equation 3, the discrimination for an LCD drive mode of
• 1:3 multiplex with 1⁄2 bias is 3 = 1.732
PCF8566_7
Product data sheet
Rev. 07 — 25 February 2009
© NXP B.V. 2009. All rights reserved.
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