SS8017TR SSC [Silicon Standard Corp.], SS8017TR Datasheet - Page 8

• Manufacturer Part Number: SS8017TR
• Description: Two Remote Temperature Sensors with SMBus Serial Interface and System Reset
• Manufacturer: SSC [Silicon Standard Corp.]

Rev.2.01 6/06/2003
GND
GND
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
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10 MILS
10 MILS
10 MILS
10 MILS
Fig 2(a) Connect the common DXN as close as
capacitors close to the 8017.
Place the 8017 close to a remote diode.
Keep traces away from high voltages (+12V bus).
Keep traces away from fast data buses and CRTs.
Use recommended trace widths and spacing.
Place a ground plane under the traces
Use guard traces flanking DXP and DXN and con-
necting to GND.
Route two DXPx-DXN pairs independently
Connect the common DXN as close as possible to
the DXN pin on IC.
Place the noise filter and the 0.1µF Vcc bypass
Fig 2 (b) Recommended DXP/DXN PC
DXP2
DXP2
DXP1
DXP1
DXN
DXN
DXN
DXN
possible to the DXN pin on IC.
GND
GND
GND
GND
GND
GND
DXP
DXP
DXP
DXN
DXN
DXN
www.SiliconStandard.com
DXP2
DXP2
GND
GND
DXP1
DXP1
DXN
DXN
Chip Boundary
Chip Boundary
10 MILS
10 MILS
10 MILS
10 MILS
SS8017
MINIMUM
MINIMUM
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
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 V
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 V
Typically, for the 8017, a V
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 V
provides additional transient immunity.
series resistance introduces about + 1°C error.
CC
transients (glitches).
CC
transient that goes
CC
Transients
SS8017
CC
8 of 16
pin