SX8661 datasheet(20/88 Pages) SEMTECH

20 / 88 page

ADVANCED COMMUNICATIONS & SENSING

DATASHEET

Revision v3.2, January 2011

www.semtech.com

SX8661

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

Index

Width

Index

Width

Index

Width

Index

Width

Index

Width

Index

Width

Index

Width

Index

Width

111

112

143

144

175

176

207

208

239

240

112

113

144

145

176

177

208

209

240

241

113

114

145

146

177

178

209

210

241

242

114

115

146

147

178

179

210

211

242

243

115

116

147

148

179

180

211

212

243

244

116

117

148

149

180

181

212

213

244

245

117

118

149

150

181

182

213

214

245

246

118

119

150

151

182

183

214

215

246

247

119

120

151

152

183

184

215

216

247

248

120

121

152

153

184

185

216

217

248

249

121

122

153

154

185

186

217

218

249

250

122

123

154

155

186

187

218

219

250

251

123

124

155

156

187

188

219

220

251

252

124

125

156

157

188

189

220

221

252

253

125

126

157

158

189

190

221

222

253

254

126

127

158

159

190

191

222

223

254

255

127

128

159

160

191

192

223

224

255

256

Table 8 AOI Level index vs. PWM pulse width (normal polarity)

The AOI reports always one button. The AOI can be split over two GPIO pins (AOI-A, AOI-B). The AOI-A interface

is connected to pin GPIO7 and the AOI-B is connected to pin GPIO6. The user can map any button to either AOI-

A or AOI-B or both.

In case buttons are split to both AOI pins, multiple button touches are still resulting in one AOI reporting.

In most applications only one AOI pin will be selected. The two AOI pins allow the user a more coarse detection

circuitry at the host. Assuming a 3.3V supply and 8 buttons on one single AOI then the AOI levels could be

separated with around 0.3…0.4V. In case of using the two AOI pins, 4 buttons could be mapped on AOI-A

separated with around 0.8V (similar for 4 buttons on AOI-B) which step is about the double in case of a single

AOI.

In case of a single touch the reported button is straight forward (as in Figure 13).

If more than one button is touched the reported depends on the selected button reporting mode parameter (5.5).

Three reporting modes exist for the SX8661 (All, Single and Strongest).

The All reporting mode is applicable only for the I2C reporting (AOI is not available). In All-mode all buttons that

are touched are reported in the I2C buttons status bits.

In the Single-mode a single touched button will be reported on the AOI and the I2C. All touches that occur

afterwards will not be reported as long as the first touch sustains. Only when the first reported button is released

will the SX860 report another touch.

Figure 15 shows the Single-mode reporting in case of 2 touches occurring over time.

Figure 15

Single-mode reporting with 2 touches

At time t1 button0 is touched and reported on the AOI. At time t2 button1 is touched as well but not reported. At

time t3 the button0 is released and button1 will be reported immediately (or after one scan period at idle level).

At time t4 both buttons are released and the AOI reports the idle level.

The button with the lowest Cap pin index will be reported in case of a simultaneous touch (that means touches

occurring within the same scan period).

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