MPR032 FREESCALE [Freescale Semiconductor, Inc], MPR032 Datasheet - Page 18

• Manufacturer Part Number: MPR032
• Description: Proximity Capacitive Touch Sensor Controller
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

MPR03X
18
Smaller amounts of change indicate increased sensitivity for the capacitance sensor. Some sample values are shown in
In the above cases, the capacitance is assumed to be in the middle of the range for specific settings. Within the capacitance
range the equation is nonlinear, thus the sensitivity is best with the lowest capacitance. This graph shows the sensitivity derivative
reading across the valid range of capacitances for a set I, T, and V
21 pF) and a nominal 1.8V supply the following graph is representative of this effect.
-0.5
-1.5
-2.5
-3.5
-4.5
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
-1
-2
-3
-4
-5
0
0.1
0
0
10
12
Sensitivity vs. Capacitance for V DD = 1.8 V and I =36 μA and T = .5 μS
500
Sensitivity vs. Midpoint Capacitance for V DD = 1.8 V
Table 11.
14
100
pF
10
16
dC/dADC @cmid (pF/1 ADC Count)
Minimum
Midpoint Capacitance (pF)
1000
Sensitivity (pF/ADC count)
18
Figure 23.
Figure 24.
C/ADC
Capacitance
-0.01953
-0.19531
20
DD
. For simple small electrodes (that are approximately
1500
22
24
2000
26
Maximum
28
Freescale Semiconductor
2500
30
Sensors
Table
11.