BU9728AKV_08 Datasheet, PDF (5/24 Pages) Rohm – For 128-140 Segment type LCD LCD Segment Driver

● Block Description (BU9728AKV)
◯ ADDRESS COUNTER
An address counter shows the address of DDRAM. Address data are transferred to the address
counter automatically when an address set is written in the command/data register.
After data are written in DDRAM, +1 or +2 is done automatically with an address counter. The
choice of +1 or +2 is done automatically by the next condition.
DDRAM 8bit writing (in the 8 clock of SCK, C/D= "L") → +2
DDRAM 4bit rewriting (in the 8 clock of SCK, C/D= "H") → +1
And, when it is counted to 1FH, an address becomes 00H with an address counter by the next count
up.
◯ DISPLAY DATA RAM (DDRAM)
A display data RAM (DDRAM) is used to store display data. That capacity is 32 address × 4 bits.
DDRAM and the relations of the display position are as the following.
DDRAM address
D0
BIT
D1
D2
D3
・・・・・・・
COM0
COM1
COM2
COM3
◯ TIMING GENERATER
It will be started to oscillate by connecting Rf between OSC1, OSC2, and generated display timing
signal. Also it will be able to do by external clock input.
OSC1
Rf
OSC2
(It is possible that Oscillating Frequency
is changed with Rf. )
Fig. BU9728AKV-7 Rf Oscillator Circuit
OSC1
EXTERNAL CLOCK INPUT
OSC2
OPEN
Fig. BU9728AKV-8 External Clock Input
◯ LCD DRIVE POWER SUPPLY
LCD drive power supply occurs by BU9728AKV. LCD voltage is given by VDD- V3, and it causes
V1=2・VLCD/3, V2=VLCD/3. When input LCD power supply by using external breeder register
etc.
Please keep below condition.
VDD≧V1≧V2≧V3≧VSS
VDD
VDD
V1
V1
V2
V2
V3
V3
VSS
Fig. BU9728AKV-9 Internal Power supply use
5/23
VSS
Fig. BU9728AKV-10 External Power supply use