SX8650 Datasheet, PDF (25/56 Pages) Semtech Corporation – World’s Lowest Power & Smallest Footprint 4-wire Resistive Touchscreen Controller with 15kV ESD

SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
By re-arranging z1 and z2 one obtains
R4
=
Rytot
⋅
Y_----p_---o_----s_-
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Which results in:
R_T = R4 ⋅
z_---2--
z1
–
1
R_T
=
Rytot
⋅
Y_----p_----o_---s_-
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⋅
z_---2--
z1
–
1
The touch resistance calculation above requires three channel measurements (Ypos, z2 and z1) and one specification data
(Rytot).
An alternative calculation method is using Xpos, Ypos, one z channel and both Rxtot and Rytot shown in the next
calculations.
R1 is inverse proportional to the X coordinate.
R1 = Rxtot ⋅
1 – ^X----^p----^o---^s-
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Substituting R1 and R4 into z1 and rearranging terms gives:
R_T
=
R_-----y_---t_--o_---t_---⋅_---Y_----p_---o_---s_-
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⋅
-4--0----9---5-
z1
–
1
– Rxtot ⋅
1
–
X_-----p_---o_---s_-
4095
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 24
www.semtech.com