SX8661I07AULTRT Semtech, SX8661I07AULTRT Datasheet - Page 19

• Manufacturer Part Number: SX8661I07AULTRT
• Description: IC, Capacitive Button Touch And Proximity Controller, 8 SENSOR, MLPQ-28
• Manufacturer: Semtech

Specifications of SX8661I07AULTRT

• Controller Type: Capacitive Touch Screen
• Ic Interface Type: I2C
• Supply Voltage Range: 2.7V To 3.6V
• Operating Temperature Range: -40°C To +85°C

ADVANCED COMMUNICATIONS & SENSING
3.8 Analog Output Interface
The Analog Output Interface outputs a PWM signal with a varying duty cycle depending on which button is
touched. By filtering (with a simple RC filter) the PWM signal results in a DC voltage, different for each button
touch. The host controller measures the DC voltage level and determines which buttons has been touched.
In the case of single button touches, each button produces its own voltage level as configured by the user (see
5.6 and
Figure 13 show how the AOI will behave when the user touches and releases different buttons.
The AOI will switch between the AOI idle level and the level for each button.
The PWM blocks used in AOI modes are 8-bits based and clocked at 2MHz typically.
The PWM period can be set to 256 (default) or 64. The 256 period offers a better granularity at a lower frequency,
while the 64 period is faster and with fewer steps.
Figure 14 shows the PWM definition of the AOI.
Table 8
the period is set to 255.
In case the period is set to 64 then the index from 0 to 63 applies.
Revision v3.2, January 2011
Index
10
11
12
13
14
0
1
2
3
4
5
6
7
8
9
Width
Table 8
10
11
12
13
14
15
0
2
3
4
5
6
7
8
9
describes the AOI level index versus the PWM pulse width. The user can select 256 steps (index) in case
Index
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
).
Figure 14
Width
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
PWM definition, (a) small pulse width, (b) large pulse width
Index
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
Width
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
Low Power, Capacitive Button Touch and Proximity Controller
© 2011 Semtech Corp.
Figure 13
Index
100
101
102
103
104
105
106
107
108
109
110
96
97
98
99
Width
100
101
102
103
104
105
106
107
108
109
110
111
97
98
99
AOI behavior
19
(8 sensors) with LED Drivers and Analog Output
Index
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
Width
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
Index
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
Width
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
Index
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
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DATASHEET
Width
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
Index
SX8661
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
Width
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239