hd66717 Renesas Electronics Corporation., hd66717 Datasheet - Page 57

• Manufacturer Part Number: hd66717
• Description: Low-power Dot-matrix Liquid Crystal Display Controller/driver -
• Manufacturer: Renesas Electronics Corporation.

Contrast Adjuster
Multiplexing Drive System
Contrast for an LCD controlled by the multiplexing drive method can be adjusted by varying the liquid-
crystal drive voltage (potential difference between V
instruction (electron volume function). See Figure 35 and Table 20. The value of a variable resistor (VR)
can be adjusted within the range from 0.4R through 6.4R, where R is a reference resistance obtained by
dividing the total resistance between V
The HD66717 incorporates a voltage-follower operational amplifier for each of V1 to V5 to reduce
current flowing through the internal bleeder-resistors, which generate different levels of liquid-crystal
drive voltages. Thus, potential differences between V
greater. Note that the OPOFF pin must be grounded when using the operational amplifiers.
Static Drive System
Contrast for a statically-driven LCD, that is, annunciator display, can be adjusted through the AGND pin.
The annunciators are driven statically by the potential difference between V
pin level must be equal to or greater than the GND level.
1/6 bias (V2 and V3 pins left open)
1/4 bias (V2 and V3 pins short-circuited)
LCD drive voltage VLCD: 6R
to 6.4R)
VLCD adjustable range: 0.484
Potential difference between V
Potential difference between V5 and V
LCD drive voltage VLCD: 4R
to 6.4R)
VLCD adjustable range: 0.385
Potential difference between V
Potential difference between V5 and V
CC
CC
CC
(V
(V
(V
(V
and V1: R
and V1: R
and V5.
CC
CC
CC
CC
– V
– V
– V
– V
EE
EE
: VR
: VR
EE
EE
EE
EE
)/(6R + VR) (VR = a value within the range from 0.4R
)/(4R + VR) (VR = a value within the range from 0.4R
)
)
CC
(V
(V
CC
VLCD
VLCD
(V
(V
and V5) through the CT bits of the contrast control
CC
CC
and V1 and between V
CC
CC
– V
– V
– V
– V
EE
EE
0.938
0.909
)/(6R + VR)
)/(4R + VR) ³ 0.4 (V)
EE
EE
)/(6R + VR)
)/(4R + VR) ³ 0.4 (V)
(V
(V
CC
CC
– V
– V
0.4 (V)
CC
EE
0.4 (V)
EE
EE
and AGND. The AGND
and V5 must be 0.4V or
)
)
HD66717
509