SX8650 Datasheet, PDF (27/56 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
4.5. Data Processing
The SX8650 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 N_filt as seen in Figure 7. The noise rejection will be improved with a
high order to the detriment of the power consumption. The effective coordinate throughput will remain the same for all filter
configurations as the ADC will be enabled more often. For very high coordinate throughput rates the filter needs to be set
to FILT=0 (see Table 7).
FILT
N_filt
0
1
1
3
2
5
3
7
Table 7. Filter order
Figure 23 shows the SX8650 configuration (FILT = 0) in which the ADC output samples, s_n are sent directly to the I2C
interface. The FILT parameter can be setup through the I2C registers
.
s_n,s_n-1,s_n-2,....
ADC
= c_n,c_n-1,c_n-2,....
I2C
Figure 23. data processing, FILT = 0
In the case of FILT=1 three output samples of the ADC are averaged and the result is sent to the I2C.
ADC
s_n,s_n-1,s_n-2
∑ ^{1 ⋅ 2 sn − i}
c_n
3 _i=0
Figure 24. data processing, FILT = 1
I2C
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 26
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