參數(shù)資料
型號: HD66726
廠商: Hitachi,Ltd.
英文描述: Graphics LCD Controller/Driver with Key Scan Function(帶鍵掃描功能的圖形LCD控制器/驅動器)
中文描述: 圖形液晶顯示控制器/鍵掃描功能(帶鍵掃描功能的圖形液晶顯示控制器/驅動器驅動程序)
文件頁數(shù): 69/117頁
文件大小: 1549K
代理商: HD66726
HD66726
69
When an Internal Booster and External Bleeder Resistors are Used
When internal operational amplifiers cannot fully drive the LCD panel used, V1 to V5 voltages can be
supplied through external bleeder resistors (figure 40). Here, the OPOFF pin must be set to the V
CC
level to
turn off the internal operational amplifiers. Since the internal contrast adjuster is disabled, contrast must be
adjusted externally. Connection of external bleeder-resistors can specify a given bias value from 1/2 to 1/7.
Figure 40 shows connection for 1/6-bias drive voltage generation. Internal boosters can be used as they are.
C1+
C1-
Vci
VLOUT
+
VLCD
V1OUT
V2OUT
V3OUT
V4OUT
V5OUT
+
-
+
-
+
-
+
-
+
-
GND
Booster
GND
+
0.47
μ
F
to 1
μ
F
0.47
μ
F
to 1
μ
F
HD66726
OPOFF = Vcc
VR
R
2R
R
R
R
C2+
C2-
+
0.47
μ
F
to 1
μ
F
Vci
GND
SEG1 to SEG96
COM1 to COM40
COMS1 to COMS2
Notes: 1.
2.
3.
4.
5.
6.
Resistance of each external bleeder resistor should be 4.7 k
to 25 k
.
When 0.1
μ
F to 0.5
μ
F capacitors are added in parallel with each external bleeder
resistor, resistance can be increased to 47 k
to 75 k
, and the through current in the
bleeder resistors can be considerably reduced (see figure 41).
The bias current value for driving LCDs can be varied by adjusting the resistance (2R)
between the V3OUT and V4OUT pins.
The internal contrast adjuster is disabled; contrast must be adjusted either by
controlling the external variable resistor between VLCD and V1 for the booster.
Vci is both a reference voltage and power supply for the booster; connect it to Vcc
directly or combine it with a transistor so that sufficient current can be obtained.
Vci must be smaller than Vcc.
V1
V2
V3
V4
V5
GND
LCD
driver
Figure 40 Circuit Using External Bleeder Resistors
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