sx8675iwltrt Semtech Corporation, sx8675iwltrt Datasheet - Page 17

• Manufacturer Part Number: sx8675iwltrt
• Description: Haptics Enabled Multitouch 4/5-wire Resistive Touchscreen Controller With Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
When using a 5-wire touchscreen, the pen detection pull-up resistor R
monitor the X+/BR pin as in 4-wire mode. The top panel is grounded via the WIPER pin to provide the grounding
path for a screen touch event. When a touch occurs, a current path is created and will bring BR to the level
defined by the resistive divider determined by R
R
R
Pen detection uses a bias time of POWDLY/8 (digital comparator => less precision required vs analog
conversion). Increasing POWDLY can improve the detection on panels with high resistance.
A pen touch will set the PENSTAT bit of the RegStat register which will generate an interrupt if enabled in
RegIrqMsk.
A pen release will reset PENSTAT bit of the RegStat register which will generate an interrupt if enabled in
RegIrqMsk.
4.5
SX8674/75/76 support up to two simultaneous touches on any standard 4-wire touchscreen.
The simplified model for dual-touch is given in figure below.
Rev 1 – 25
PNDT
PNDT
can be configured to 4 different values to accommodate different screen resistive values.
should be set to a value greater than 7x(Rxtot + Rytot), it is recommended to set it to max value.
Multitouch Measurement (4-wire only)
th
July 2011
Figure 15 – 4-wire Touchscreen Pen Detection
Figure 16 – 5-wire Touchscreen Pen Detection
PNDT
Resistive Touchscreen Controller with Proximity Sensing
and the sum of R1, RT and RW.
17
SX8674/SX8675/SX8676
PNDT
Haptics Enabled Multitouch 4/5-Wire
and digital comparator continue to
www.semtech.com