ROHM BU9728AKV Datasheet
1
Standard ICs
LCD driver for segment-type LCDs
BU9728AKV
The BU9728AKV is a segment-type LCD system driver which can accommodate microcomputer control and a serial
interface. An internal 4-bit common output and LCD drive power supply circuit enable configuration of a display system at low cost.
•
Applications
Movie projectors, car audio systems, telephones
•
Features
1) Serial interface. (8-bit length)
2) Display RAM: Internal, 128 bits. (up to 128 segments can be displayed)
3) Internal power supply circuit for LCD drive.
4) Display duty: 1 / 4
5) Can be driven with low voltage and low current dissipation.
•
Absolute maximum ratings (Ta = 25°C, VSS = 0V)
Parameter Symbol Limits Unit
V
DD
– 0.3 ~ + 7.0 V
V
LCD
– 0.3 ~ + VDD
V
Pd 400
∗
mW
Tstg – 55 ~ + 125 °C
Topr – 20 ~ + 75 °C
Power supply voltage 1
Power supply voltage 2
Power dissipation
Operating temperature
Storage temperature
∗
Reduced by 4.0mW for each increase in Ta of 1°C over 25°C .
•
Recommended operating conditions (Ta = 25°C, VSS = 0V)
Parameter
V
DD 2.5 5.5 V—
—
V
LCD 0VDD V
The following relationship should
be maintained: V
DD
⭌ V1 ⭌ V2 ⭌ V3 ⭌ VSS.
Rf = 470kΩ
—
f
OSC — — kHz36
Symbol Min. Typ. Max. Unit
Conditions
Power supply voltage 1
Power supply voltage 2
(V
DD - V3)
Oscillation frequency
2
Standard ICs BU9728AKV
•
Block diagram
Serial
Interface
Display Data RAM
(DD RAM)
LCD Driver
Bias Circuit
LCD
Segment
Driver
32bits
LCD
Common
Driver
4bits
SD
SCK
C / D
CS
RESET
V
DD
V1
V2
V3
VSS
COM0
COM1
COM2
COM3
SEG0
SEG1
SEG31
OSC1
OSC2
Timing
Generator
Address
Counter
Common
Counter
Command
Decoder
Command / Data
Register
•
Pin assignments
SEG20
SEG21
SEG22
SEG23
SEG24
SEG25
SEG26
SEG27
SEG28
SEG29
SEG30
SEG31
37
38
39
40
41
42
43
44
45
46
47
48
24
23
22
21
20
19
18
17
16
15
14
13
SEG19
SEG18
SEG17
SEG16
SEG15
SEG14
SEG13
SEG12
SEG11
SEG10
SEG9
SEG8
OSC1
OSC2
V1V2V3
VSS
VDD
SCK
SD
CS
C / D
COM
0
SEG7
SEG6
SEG5
SEG4
SEG3
SEG2
SEG1
SEG0
RESET
COM
3
COM2
COM1
252627282930313233343536
121110987654321
BU9728AKV
3
Standard ICs BU9728AKV
•
Pin descriptions
OSC1
OSC2
1
2
I
O
SD 9 I
CS 10 I
I
—
—
—
SCK 8
V
1 ~ V3 3 ~ 5
V
SS 6
V
DD 7
C / D 11 I
COM
0
COM3
12 ~ 15 O
RESET 16 I
SEG
0
SEG31
17 ~ 48 O
Pin NO. I / OPin name Function
Input / output pins for the internal oscillator. Resistance is connected between
these pins when the internal clock is running. When an external clock is
running, the clock is input from OSC
1 and OSC2 is left open.
This is the reset input pin. When this pin is LOW, the BU9728AKV is initialized.
It resets the address counter and turns the display off.
This is the serial data input pin, used to input display data and commands.
Display data is displayed when this is "1" and not displayed when it is "0".
This is the chip select signal input pin. When this pin is LOW, SD input can be
received. The SCK counter is reset when the CS pin goes from HIGH to LOW.
This signal detects whether the SD input is command or display data. If the pin
is LOW at the rising edge of the 8th SCK pulse, the input is recognized as
display data, and if HIGH, the input is recognized as command data.
These are power supply pins for LCD drive.
The following relationship must be satisfied: V
DD ⭌ V1 ⭌ V2 ⭌ V3 ⭌ VSS (Low) .
These are the segment output pins for LCD drive. They are connected to the
LCD panel segments.
These are the common output pins for LCD drive. They are connected to the
LCD panel commons.
This is the shift clock input pin for serial data. The contents of the SD pin are
read one bit at a time at the rising edge of SCK.
This is the V
SS power supply pin.
This is the V
DD power supply pin.
•
Input / output equivalent circuits
VDD
GND
GND
VDD
V
DD
GND
GND
OUT
V
LCD
VLCD
IN
OSC1
IN
OSC
2
I / O
SD
SCK
C / D
CS
I
—
OSC
1
OSC2
RESET I
I / O
SEG
0
SEG31
COM0
COM3
O
~ ~
Pin name
Equivalent Circuit
Pin name
Equivalent Circuit
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