SX8654ICSTRT SEMTECH [Semtech Corporation], SX8654ICSTRT Datasheet - Page 17

• Manufacturer Part Number: SX8654ICSTRT
• Description: Haptics Enabled 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing
• Manufacturer: SEMTECH [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
The chip offers 4 types of data processing which allows the user to make trade-offs between data throughput,
power consumption and noise rejection.
The parameter FILT is used to select the filter order Nfilt. The noise rejection will be improved with a high order
to the detriment of power consumption. Each channel can be sampled up to 7 times and then processed to get a
single consolidated coordinate.
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.
Digital Processing
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
SX8654/SX8655/SX8656
PNDT
and digital comparator continue to
Haptics Enabled 4/5-Wire
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