LTC2066/LTC2067/LTC2068

17

Rev. B

For more information www.analog.com

APPLICATIONS INFORMATION

RG**

RF

RF§

RL§

NC

‡

2066 F04

HEAT SOURCE/

POWER DISSIPATOR

THERMAL

GRADIENT

MATCHING RELAY

RELAY

* CUT SLOTS IN PCB FOR THERMAL ISOLATION.

** INTRODUCE DUMMY JUNCTIONS AND COMPONENTS TO OFFSET UNAVOIDABLE JUNCTIONS OR CANCEL THERMAL EMFs.

† ALIGN INPUTS SYMMETRICALLY WITH RESPECT TO THERMAL GRADIENTS.

‡ INTRODUCE DUMMY TRACES AND COMPONENTS FOR SYMMETRICAL THERMAL HEAT SINKING.

§ LOADS AND FEEDBACK CAN DISSIPATE POWER AND GENERATE THERMAL GRADIENTS. BE AWARE OF THEIR THERMAL EFFECTS.

# COVER CIRCUIT TO PREVENT AIR CURRENTS FROM CREATING THERMAL GRADIENTS.

VIN

VTHERMAL

VTHERMAL

LTC2066

+IN

OUT

–IN

RG

**

*

#

#

†

Figure 4. Techniques for Minimizing Thermocouple-Induced Errors

Figure 5. Example Layout of Inverting Amplifier with Leakage Guard Ring

‡

RF

OUT

VOUT

V–

V–

+IN

V+

V+

–IN

GUARD

RING

HIGH-Z

SENSOR

NO SOLDER MASK

OVER GUARD RING

LEAKAGE

CURRENT

VBIAS

‡ NO LEAKAGE CURRENT, V–IN = V+IN

§ AVOID DISSIPATING SIGNIFICANT AMOUNTS OF POWER IN THIS RESISTOR.

IT WILL GENERATE THERMAL GRADIENTS WITH RESPECT TO THE INPUT

PINS AND LEAD TO THERMOCOUPLE-INDUCED ERROR. THERMALLY

ISOLATE OR ALIGN WITH INPUTS IF RESISTOR WILL CAUSE HEATING.

§

2066 F05

+

–

GUARD RING

LTC2066

LEAKAGE

CURRENT

LEAKAGE CURRENT IS ABSORBED BY GROUND INSTEAD OF

CAUSING A MEASUREMENT ERROR.

VOUT

V+

V–

HIGH-Z SENSOR

RF

VBIAS

+

–

VIN

RIN