BU21026MUV Datasheet, PDF (5/23 Pages) Rohm – 4-wire Resistive Touch Screen Controller

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 2^nd 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