Datasheet
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TMP411-Q1
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TMP411-Q1
SBOS527F –DECEMBER 2010–REVISED NOVEMBER 2013
www.ti.com
LAYOUT CONSIDERATIONS
Remote temperature sensing on the TMP411-Q1
measures very small voltages using very low
currents; therefore, noise at the IC inputs must be
minimized. Most applications using the TMP411-Q1
have high digital content, with several clocks and
logic-level transitions creating a noisy environment.
Layout should adhere to the following guidelines:
1. Place the TMP411-Q1 as close to the remote
junction sensor as possible.
2. Route the D+ and D− traces next to each other
and shield them from adjacent signals through
the use of ground guard traces, as shown in
Figure 19. If a multilayer PCB is used, bury these
traces between ground or VDD planes to shield
them from extrinsic noise sources. Five-mil
(0.127-mm) PCB traces are recommended.
3. Minimize additional thermocouple junctions
A. 5-mil (0.127-mm) traces with 5-mil (0.127-
mm) spacing
caused by copper-to-solder connections. If these
junctions are used, make the same number and
Figure 19. Example Signal Traces
approximate locations of copper-to-solder
connections in both the D+ and D− connections
to cancel any thermocouple effects.
4. Use a 0.1-μF local bypass capacitor directly
between the V+ and GND of the TMP411-Q1, as
shown in Figure 20. Minimize filter capacitance
between D+ and D− to 1000 pF or less for
optimum measurement performance. This
capacitance includes any cable capacitance
between the remote temperature sensor and
TMP411-Q1.
5. If the connection between the remote
temperature sensor and the TMP411-Q1 is less
than 8 inches (20 cm), use a twisted-wire pair
Figure 20. Suggested Bypass Capacitor
connection. Beyond 8 inches (20 cm), use a
Placement
twisted, shielded pair with the shield grounded as
close to the TMP411-Q1 as possible. Leave the
remote sensor connection end of the shield wire
open to avoid ground loops and 60-Hz pickup.
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