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PDF BU21026MUV Data sheet ( Hoja de datos )
| Número de pieza | BU21026MUV | |
| Descripción | 4-wire Resistive Touch Screen Controller | |
| Fabricantes | ROHM Semiconductor | |
| Logotipo |  |
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Datasheet
Resistive touch screen controller LSI series
4-wire Resistive
Touch Screen Controller
BU21026MUV
General Description
BU21026MUV is a low power 4-wire resistive touch
screen controller. BU21026MUV measures coordinates
and touch pressures with a 12bit A/D converter.
BU21026MUV has a digital filter for noise reduction.
Features
4-wire resistive touch screen controller
Single 1.65V to 3.60V supply.
Low standby current ( 0.8uA max)
12bit SAR A/D converter
2-wire serial interface
Command base interface
Digital filter
Touch pressure measurement
Auto power down control
Built-in clock oscillation circuit
.
Key Specifications
Power supply voltage
Temperature range
Standby current
Operating current
Coordinate resolution
1.65V to 3.60V
-30℃ to 85℃
0.8uA (Max.)
120uA (Typ.)
12Bits
Package
VQFN020V4040
W(Typ) x D(Typ) x H(Max)
4.00mm x 4.00mm x 1.00mm
Applications
Equipment with a built in user interface of 4-wire
resistive touch screen
Portable device such as smart phone, tablet, PDA.
Digital still camera, digital video camera, portable TV.
PC / PC peripheral equipment such as laptop PC,
touch screen monitor, printer.
VDD
Typical Application Circuit(s)
3
1.0μF 0.1μF
GND
Auxilary Input
10Ω
10Ω
0.1μF
0.1μF
AUX
XP
YP
BU21026
2
SDA
2.2kΩ
2.2kΩ
Master
( 2-wire serial
interface )
SDA
SCL SCL
INT GPIO
Touch
Screen
1
10Ω
0.1μF
XN
10Ω
0.1μF
YN
5
GND
4
AD1
AD0
GND
GND
1. 4-wire resistive touch screen
2. Pull-up resistor for 2-wire serial interface
3. Bypass capacitors
4. Diodes for ESD protection
5. Low pass filter for noise reduction
〇Product structure : Silicon monolithic integrated circuit
.www.rohm.com
© 2016 ROHM Co., Ltd. All rights reserved.
TSZ22111 • 14 • 001
〇This product has no designed protection against radioactive rays
1/19
TSZ02201-0L5L0FF00890-1-2
4.Aug.2016 Rev.001
1 page  
BU21026MUV
Touch Detection
A touch detection function of BU21026MUV is automatically enabled after wakeup. BU21026MUV inform that touch screen
is touched or not by INT pin when touch detection is enabled. Output level of INT becomes low during screen is touched. In
this state, XP pin is pulled-up high by pull-up resistor (RPU) and YN pin is connected to GND. A resistance of RPU is
selectable from either 50 kohm (default) or 90 kohm by the setup command. When the screen isn’t touched, XP is
connected to VDD trough the pull-up resistor. When the screen is touched, XP is connected to GND trough the screen and
BU21026MUV detect touch.
When a received command is not setup (1011), the touch detection is disabled and RPU is disconnected from XP pin. And
output level of INT is fixed high or low by each command (see Table 3 for details about operation code).
When BU21026MUV receives software reset command (0101), touch detection is enabled after the 2nd acknowledge timing.
When BU21026MUV receives A/D conversion with PD=0 command touch detection is enabled after an A/D conversion is
finished.
When BU21026MUV receives a driving screen voltage or an A/D conversion with PD=1 command, touch detection is not
enable automatically. A method for re-enable the touch detection is sending new command that return to enable touch
detection. The set power command is almost same as an A/D conversion command.
VDD INT
XP OFF ON RPU
YP Control
logic
XN
YN
ON
GND
Touch Detection Circuit
Digital Filter
BU21026MUV has a Median Average Filter (MAF) as a digital filter for noise reduction. When the MAF is enabled,
BU21026MUV operates A/D conversion 7 times and stores converted data. Next, these stored data are sorted. An output
data of MAF is an average value of middle three values of the sorted data. An abnormal value becomes difficult to affect the
results. So noise reduction performance of MAF is higher than one of normal average filter. When the MAF is disabled,
BU21026MUV operates A/D conversion one times and output the converted data The MAF is enabled in defaults and is
changed by the setup command.
www.rohm.com
© 2016 ROHM Co., Ltd. All rights reserved.
TSZ22111 • 15 • 001
5/19
TSZ02201-0L5L0FF00890-1-2
4.Aug.2016 Rev.001
5 Page 
BU21026MUV
Write Protocol
An command write is started in BU21026MUV when the master sends the start condition, the slave address of
BU21026MUV, and zero in bit 0( 8th bit) for writing, as shown in Table 1. If the slave address is matched with its own,
BU21026MUV issues an acknowledge to the master. When the master receives the acknowledge from BU21026MUV, the
master send the command byte. When BU21026MUV received next 8 bits, it issues another acknowledge to the master.
After the acknowledge is received by the master, the master sends the stop or repeated start condition for ending write.
START
SCL
STOP or
Repeated START
Driving
Acquisition
Conversion
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Address Byte
Command Byte
SDA 1 0 0 1 0 AD1 AD0 0 0 C3 C2 C1 C0 O3 O2 O1 O0 0
SLAVE ADDR
R/WB ACK
FROM
BU21025
Figure 1. Write Protocol
ACK
FROM
BU21025
If a receiving command in BU21026MUV is not the software reset or setup, BU21026MUV starts driving screen voltage
when C0 is latched by rising edge of SCL. Next, if the received type of operation code is measurement, BU21026MUV
starts acquisition in A/D converter when next falling edge of SCL. BU21026MUV stops acquisition and starts A/D conversion
when BU21026MUV receive the stop or repeated start condition.
When BU21026MUV receives a command other than software reset during the A/D conversion, the command is ignored.
And if the command is ignored, BU21026MUV doesn’t return an acknowledge at the ACK timing behind the command byte.
(18th timing in Figure. 1)
www.rohm.com
© 2016 ROHM Co., Ltd. All rights reserved.
TSZ22111 • 15 • 001
11/19
TSZ02201-0L5L0FF00890-1-2
4.Aug.2016 Rev.001
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet BU21026MUV.PDF ] | |
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