ML9058E datasheet(35/76 Pages) ETC2

35 / 76 page

FEDL9058E-01

LAPIS Semiconductor

ML9058E

35/76

is also used

It is possible to set the LCD drive power supply voltage V1 using fine adjustment of Ra' and Rb' by adding a

variable resistor to the case of using external resistors in the above case. Even in this case, it is possible to control

the LCD power supply voltage V1 and adjust the intensity of LCD display using commands if the electronic

potentiometer function is used.

The voltage V1 can be obtained by the following equation C-1 in the range of V1<VOUT by setting the external

resistors R1, R2 (variable resistor), and R3 appropriately and making fine adjustment of R2 (R2).

V1 = (1 + (R3 + R2 – R2)/(R1 + R2))  VEV

= (1 + (R3 + R2 – R2)/(R1 + R2))  (1 – (/324))  VREG (Eqn. C-1)

Fig. 11 V1 voltage adjustment circuit (equivalent circuit)

Setting example: Setting V1 in the range 5 V to 9 V using R2 at Tj = 25°C .

When the electronic potentiometer register value is set to (DB5, DB4, DB3, DB2, DB1, DB0) = (1, 0, 0, 0, 0, 0),

the value of

 will be 31 and that of VREG will be 3.0 V, and hence in order to make V1 = 9 V when R2 = 0, the

equation C-1 becomes as follows:

9 = (1 + (R3 + R2)/R1)  (1 – (31/324))  (3.0) (Eqn. C-2)

In order to make V1 = 5 V when

R2 = R2,

5 = (1 + R3/(R1+R2))  (1 – (31/324))  (3.0) (Eqn. C-3)

Further, if the current flowing between VSS and V1 is set as 5 µA, the value of R1 + R2 + R3 becomes-

R1 + R2 + R3 = 1.8 M (Eqn. C-4)

and hence,

R1 = 542 k, R2 = 436 k, R3 = 822 k.

In this case, the variability range of voltage V1 using the electronic potentiometer function and the increment size

will be as given in Table 13.

Table 14 Example 2 of V1 variable-voltage range using electronic potentiometer function and

variable resistor

Min

Typ

Max

Unit

Variable-voltage range

4.45 (

 = 63)

7.0 (

 = 31)

9.96 (

 = 0)

[V]

VEV (Constant voltage supply +

electronic potentiometer)

–

Rb'

Ra'

External R3

 R2

VSS

External R2

External R1

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