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SS8017TR 数据表(PDF) 8 Page - Silicon Standard Corp. |
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SS8017TR 数据表(HTML) 8 Page - Silicon Standard Corp. |
8 / 16 page www.SiliconStandard.com 8 of 16 In this way, most parasitic thermocouple errors are swamped out. Use wide traces. Narrow ones are more inductive and tend to pick up radiated noise. The 10 mil widths and spacing recommended on Figure 2 aren't absolutely necessary (as they offer only a minor improvement in leakage and noise), but try to use them where practi- cal. Keep in mind that copper can't be used as an EMI shield, and only ferrous materials such as steelwork will. Placing a copper ground plane between the DXP - DXN traces and traces carrying high-frequency noise signals do not help reduce EMI. PC Board Layout Checklist n Place the 8017 close to a remote diode. n Keep traces away from high voltages (+12V bus). n Keep traces away from fast data buses and CRTs. n Use recommended trace widths and spacing. n Place a ground plane under the traces n Use guard traces flanking DXP and DXN and con- necting to GND. n Route two DXPx-DXN pairs independently n Connect the common DXN as close as possible to the DXN pin on IC. n Place the noise filter and the 0.1µF Vcc bypass capacitors close to the 8017. Fig 2(a) Connect the common DXN as close as possible to the DXN pin on IC. Twisted Pair and Shielded Cables For remote-sensor distances longer than 8 in., or in particularly noisy environments, a twisted pair is rec- ommended. Its practical length is 6 feet to 12 feet (typi- cal) before noise becomes a problem, as tested in a noisy electronics laboratory. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. Connect the twisted pair to DXP and DXN and the shield to GND, and leave the shield's remote end unterminated. Excess capacitance at DX_ limits practical remote sen- sor distances (see Typical Operating Characteristics), For very long cable runs, the cable's parasitic capaci- tance often provides noise filtering, so the 2200pF ca- pacitor can often be removed or reduced in value. Ca- ble resistance also affects remote-sensor accuracy; 1 Ω series resistance introduces about + 1°C error. Low-Power Standby Mode Standby mode disables the ADC and reduces the sup- ply-current drain to less than 10µA. Enter standby mode via the RUN/STOP bit in the configuration byte register. In standby mode, all data is retained in mem- ory, and the SMB interface is alive and listening for reads and writes. This is valid for temperature sensor only. Standby mode is not a shutdown mode. With activity on the SMBus, extra supply current is drawn (see Typical Operating Characteristics). In software standby mode, the 8017 can be forced to perform temperature measurement via the one-shot command, despite the RUN/STOP bit being high. Supply-current drain during the 125ms conversion pe- riod is always about 500µA. Slowing down the conver- sion rate reduces the average supply current (see Typical Operating Characteristics). In between conver- sions, the instantaneous supply current is about 200µA due to the current consumed by the system resetting circuit. Reset Immunity Negative-Going VCC Transients In addition to issuing a reset to the microprocessor (µP) during power-up, power-down, and brownout conditions, the 8017 is relatively immune to short duration nega- tive-going VCC transients (glitches). Typically, for the 8017, a V CC transient that goes 100mV below the reset threshold and lasts 20µs or less will not cause a reset pulse. A 0.1µF bypass ca- pacitor mounted as close as possible to the VCC pin provides additional transient immunity. DXP1 DXN DXN DXP2 DXP1 DXN DXP2 GND Chip Boundary GND DXP1 DXN DXN DXP2 DXP1 DXN SS8017 DXP2 GND Chip Boundary GND GND DXP DXN GND 10 MILS MINIMUM 10 MILS 10 MILS 10 MILS GND GND DXP DXP DXN DXN GND GND 10 MILS MINIMUM 10 MILS 10 MILS 10 MILS Fig 2 (b) Recommended DXP/DXN PC SS8017 Rev.2.01 6/06/2003 |
类似零件编号 - SS8017TR |
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类似说明 - SS8017TR |
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