sx150x_89b-datasheet

ADVANCED COMMUNICATIONS & SENSING
Rev 4 – 26
th
April 2011 20 www.semtech.com
SX1508B/SX1509B
World’s Lowest Voltage Level Shifting GPIO
with LED Driver and Keypad Engine
13 1 45 7 77 18 109 36 141 65 173 104 205 157 237 225
14 1 46 7 78 19 110 38 142 65 174 104 206 157 238 225
15 1 47 7 79 19 111 38 143 65 175 104 207 157 239 225
16 2 48 8 80 20 112 39 144 69 176 110 208 165 240 235
17 2 49 8 81 20 113 39 145 69 177 110 209 165 241 235
18 2 50 8 82 21 114 41 146 69 178 110 210 165 242 235
19 2 51 8 83 21 115 41 147 69 179 110 211 165 243 235
20 2 52 9 84 22 116 42 148 73 180 116 212 172 244 245
21 2 53 9 85 22 117 42 149 73 181 116 213 172 245 245
22 2 54 9 86 23 118 44 150 73 182 116 214 172 246 245
23 2 55 9 87 23 119 44 151 73 183 116 215 172 247 245
24 3 56 10 88 24 120 46 152 78 184 122 216 181 248 255
25 3 57 10 89 24 121 46 153 78 185 122 217 181 249 255
26 3 58 10 90 25 122 46 154 78 186 122 218 181 250 255
27 3 59 10 91 25 123 46 155 78 187 122 219 181 251 255
28 3 60 11 92 26 124 49 156 83 188 129 220 189 252 255
29 3 61 11 93 26 125 49 157 83 189 129 221 189 253 255
30 3 62 12 94 27 126 49 158 83 190 129 222 189 254 255
31 3 63 12 95 27 127 49 159 83 191 129 223 189 255 255
Table 7 – LED Driver Linear vs Logarithmic Function (I)
0
50
100
150
200
250
300
1 10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 172 181 190 199 208 217 226 235 244 253
RegIOn (4xRegOff[2:0])
IOn (IOff)
Linear mode
Log mode
Figure 18 – LED Driver Linear vs Logarithmic Function (II)
4.8.6 Synchronization of LED Drivers across several ICs
When several GPIO expanders are used in the same application it may be useful that their LEDs drivers are
synchronous for coherent global operation.
In this case all ICs should share their fOSC through their OSCIO pins and have their reset connected together.
When RegMisc of each IC is set accordingly, NRESET signal can then be used to reset all devices’ internal
counters (but not the register settings) and allow synchronous LED operation (blinking, fading) across multiple
devices.
4.8.7
Tutorial
Below are the steps required to use the LED driver with the typical LED connection described §6.2:
- Disable input buffer (RegInputDisable)
- Disable pull-up (RegPullUp)