Lcd controller operation modes, Lcd drive voltages, Figure 9. lcd drive voltage generation – Maxim Integrated MAXQ Family Users Guide: MAXQ2000 Supplement User Manual
Page 73: Selecting the lcd mode, Table 30. lcd display modes, Maxq family user’s guide: maxq2000 supplement
MAXQ Family User’s Guide:
MAXQ2000 Supplement
STATIC DISPLAY
R
R
V
LCD2
V
ADJ
R
V
LCD
V
LCD1
R
ADJ
GNDIO
LRIG
1/2 BIAS
R
R
V
LCD2
V
ADJ
R
V
LCD
V
LCD1
R
ADJ
GNDIO
LRIG
1/3 BIAS
R
R
V
LCD2
V
ADJ
R
V
LCD
V
LCD1
R
ADJ
GNDIO
LRIG
Figure 9. LCD Drive Voltage Generation
DUTY[1:0]
DUTY
CYCLE
BIAS
DISPLAY SEGMENT
DRIVE CAPACITY
COMMONS
V
LCD2
VOLTAGE*
V
LCD1
VOLTAGE*
00
Static
Static
36 (68-pin), 28 (56-pin)
COM0
—
—
01
1/2
1/2
70 (68-pin), 54 (56-pin)
COM0, COM1
V
ADJ
+ (1/2 x V
LCD
–
V
ADJ
)
V
ADJ
+ (1/2 x V
LCD
–
V
ADJ
)
10
1/3
1/3
102 (68-pin), 78 (56-pin)
COM0, COM1,
COM2
V
ADJ
+ (1/3 x V
LCD
–
V
ADJ
)
V
ADJ
+ (2/3 x V
LCD
–
V
ADJ
)
11
1/4
1/3
132 (68-pin), 100 (56-pin)
COM0, COM1,
COM2, COM3
V
ADJ
+ (1/3 x V
LCD
–
V
ADJ
)
V
ADJ
+ (2/3 x V
LCD
–
V
ADJ
)
* For 1/2 bias mode, this assumes an external shunt in place between V
LCD1
and V
LCD2
.
Table 30. LCD Display Modes
LCD Controller Operation Modes
The LCD controller defaults to suspended mode (OPM = 0, DPE = x) on power-up. In this mode, the LCD controller is completely shut
down to conserve power. Any pins that are configured for LCD operation (as well as any dedicated LCD segment/common pins) are
driven by a weak pullup to V
DDIO
.
Setting the OPM bit to 1 places the LCD controller in normal operating mode. In this mode, the LCD segment and common drivers gen-
erate waveforms to display the contents of display register memory if the DPE bit is set to 1. If DPE is set to 0, the LCD controller gen-
erates waveforms to turn all segments OFF.
LCD Drive Voltages
The LCD controller provides internal voltage-divider resistors to generate the voltage bias levels needed for the LCD control. The top
voltage level, V
LCD
, must be provided by an external supply. As shown in Figure 9, no external connections (other than the power sup-
ply to V
LCD
) are needed for static and 1/3 bias modes. For 1/2 bias mode, V
LCD1
and V
LCD2
must be shunted together externally.
Selecting the LCD Mode
The DUTY1 and DUTY0 bits select one of four possible display modes for the LCD controller as Table 30 shows. The display mode
required for a given application depends on the number of segments needed and the multiplexing and voltage bias requirements for
a given LCD display.
Maxim Integrated
73