TSI software configurations
KE15Z Touch Sensing Interface, User's Guide, Rev. 0, 12/2016
NXP Semiconductors
13
3.1.3. Sensitivity boost
The sensitivity boost configurations include: S_SEN Enable, S_CTRIM, and
Multiplier(S_XDN/S_XCH).
The capacitance actually removed is:
Cremoved = 𝑆_𝐶𝑇𝑅𝐼𝑀 ×
𝑆_𝑋𝐷𝑁
𝑆_𝑋𝐶𝐻
Attached below is an example for sensitivity boost configurations.
From the example above, we can find out that the Cremoved is the key configuration to the sensitivity
boost feature, as Cremoved increases, the sensitivity becomes better, which means it’s easier to
recognize touch event.
Variable
Register
Descriptions
S_SEN Enable
TSI_MODE[S_SEN]
Enable sensitivity boost
S_CTRIM
TSI_MODE[S_CTRIM]
Remove the parasitic capacitance virtually
TSI_MODE[S_XDN]
Sensitivity adjust
TSI_MODE[S_XCH]
Charge/discharge multiple
Setting: Sensitivity Boost
Multiplier:
S_XDN/S_XCH
S_XIN S_XCH
Current
Amplifier
(S_XIN*S_XCH)
S_SEN
Enable
S_XDN
S_Ctrim
(pF)
Cremoved
(pF)
1/4
1/2
1/8
OFF
1/2
2.5
0.0
12
10.5%
1/4
1/2
1/8
ON
1/2
2.5
2.5
12
11.9%
1/4
1/2
1/8
ON
1/2
5.0
5.0
12
19.4%
1/4
1/2
1/8
ON
1/2
7.5
7.5
12
30.2%
1/4
1/2
1/8
ON
1/2
10.0
10.0
12
66.9%
1/4
1/2
1/8
ON
1/2
12.5
12.5
12
0.0%
Sensitivity Boost
Intrinsic
Capacitcance
Calculated
Cx
Sensitivity
Calculated
Current Amplifier
10.5%
11.9%
19.4%
30.2%
66.9%
0.0%
20.0%
40.0%
60.0%
80.0%
OFF
2.5
5.0
7.5
10.0
Sen
si
tiv
ity
Key Configuration: Capacitance Removed (pF)
Sensitivity Boost / Key Configuration
TSI Channel 12
