GX3290 Datasheet, PDF (31/47 Pages) Semtech Corporation – 290 x 290 3.5Gb/s Crosspoint Switch

In addition to the diode temperature sensors, four ADCs, each with two selectable
temperature sensors, are also provided. Digitized temperatures can be read through the
device’s host interface.
thermo
ADC 1 _{Even Outputs 0 to 288}
thermo
ADC 2
Crosspoint Core
Legend:
ADC and “local” temperature sensors
“remote” temperature sensors
thermo
ADC 3
Odd Outputs 1 to 289
thermo
ADC 0
Package Top-view of Die
Figure 4-4: Map of Thermometer ADC Positions on Die
Table 4-10: Junction Temperature Registers
Thermometer ADC
0
1
2
3
Sensor Location Select
Register
ADC_IN_0
ADC_IN_1
ADC_IN_2
ADC_IN_3
Result Register
JNCTN_TEMP_0
JNCTN_TEMP_1
JNCTN_TEMP_2
JNCTN_TEMP_3
Digitized 10-bit temperature values can be read through the host interface from
registers JNCTN_TEMP_0 (register 0xA08h[9:0]) through JNCTN_TEMP_3 (register
0xA0Bh[9:0]). The temperature word in each register will be updated every 2¹³ clock
cycles, provided the value of the respective COUNT_PD_[3:0] bit remains LOW. When
a COUNT_PD_[3:0] bit goes HIGH, the ADC is reset and the corresponding
JNCTN_TEMP_[3:0] register retains its last updated value. The clock rate can be
selected between 211kHz or 844kHz through the corresponding
ADC_CTRL_CLK_SEL_[3:0] bits (registers 0xA04h, 0xA05h, 0xA06h and 0xA07h).
The junction temperature at each temperature sensor in terms of the ADC output code
is given by:
T_j = 0.5489 × JNCTN_TEMP_[3:0] – 263 + δ₃
Where δ₃ is the temperature uncertainty. The accuracy of the temperature sensors can
be improved by calibrating the GX3290 at a known junction temperature. Without
calibration, the temperature uncertainty, due to process variations and component
mismatch, can be as high as ±27°C. After calibration, the uncertainty can be reduced to
about ±2°C.
GX3290 290 x 290 3.5Gb/s Crosspoint
Final Data Sheet Rev. 2
GENDOC-053317 March 2013
www.semtech.com
31 of 47
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