3

S1

S2

S3

S4

S5

S6

S7

S8

S9

S1 0

SDI

SCK

EL1 Control

Latches

in Data

MSB of

EL1

LSB of

EL1

MSB of

EL2

LSB of

EL2

MSB of

EL3

LSB of

EL3

PWR_ON

EL2 Control

EL3 Control

Logic Input Conditions

The serial data input consists of a 10-bit string, three bits of

the power converter. The power converter runs if any of the

EL lamps has a non-zero brightness value or if the PWR_ON

bit is high while the other nine bits are low.

1.

SDI may be H or L if SCK is H.

2.

SCK may be H or L if SDI is H.

3.

While inputting serial data to the shift register, SDI can

change value only when SCK is L.

4.

The previous ten bits of serial input will be latched

when SDI makes L to H transition while SCK is H.

EL Lamp Brightness Control

The EL lamp brightness control is a 3-bit binary number stored

in a latch, which is provided by a serial to parallel conversion

shift register.

1.

If all the three bits for a designated EL lamp are L, the

differential voltage across that lamp will be zero.

2.

If any of the three bits for a designated EL lamp is H:

a.The 3-bit value sets the average number of cycles

for which the EL lamp voltage is non-zero.

b.The EL lamp brightness is linearly proportional

to the binary lamp control code.

Logic Input Diagram

Note:

1. Serial data is latched when SDI makes L to H transition and while SCK is H.

2. S1 is the first serial data input being fed.

HV856

Symbol Parameter

Min

Typ

Max

Units

Conditions

D

MAX

Maximum PWM switch duty

cycle

80

88

94

%

V

f

CLK

SCK speed

-

-

1

MHz

---

T

SU

SDI setup time before SCK

rises

30

-

-

ns

---

T

H

SDI hold time before SCK

rises

30

-

-

ns

---

Specifications (cont.)