ADA4523-1

Data Sheet

Rev. 0 | Page 22 of 29

To minimize thermocouple induced errors, attention must be

given to circuit board layout and component selection. It is good

practice to minimize the number of junctions in the input signal

path of the op amp and to avoid connectors, sockets, switches, and

relays whenever possible. If such components are required,

select these components for low thermal EMF characteristics.

Furthermore, match the number, type, and layout of junctions

for both inputs with respect to thermal gradients on the circuit

board, which can involve deliberately introducing dummy

junctions to offset unavoidable junctions.

Air currents can also lead to thermal gradients and cause

significant noise in measurement systems. It is important to

prevent airflow across sensitive circuits because doing so often

reduces thermocouple noise substantially.

A summary of techniques is shown in Figure 70.

POWER DISSIPATION

Because the ADA4523-1 can operate at a 36 V total supply, take

care with respect to power dissipation in the amplifier. When

driving heavy loads at high voltages, use the θJA of the package

to estimate the resulting die temperature rise and ensure that

the resulting junction temperature does not exceed specified

limits. In addition, consider PCB metallization and heat sinking

when high power dissipation is expected.

The ADA4523-1 LFCSP features lower package thermal

resistances compared to its standard counterparts. The LFCSP

exposed pad facilitates heat sinking. The exposed bottom pad

must be soldered to the PCB, and due to its internal connection

to V−, connecting the exposed pad to V− is a requirement. For

more efficient heat sinking, it is recommended that the exposed

pad have as much PCB metal connected to the pad as reasonably

available.

Thermal information for the ADA4523-1 packages can be

found in the Thermal Resistance section.

HEAT SOURCE/

POWER DISSIPATOR

THERMAL

GRADIENT

1CUT SLOTS IN PCB FOR THERMAL ISOLATION.

2INTRODUCE DUMMY JUNCTIONS AND COMPONENTS TO OFFSET UNAVOIDABLE JUNCTIONS OR CANCEL THERMAL EMFS.

3ALIGN INPUTS SYMMETRICALLY WITH RESPECT TO THERMAL GRADIENTS.

4INTRODUCE DUMMY TRACES AND COMPONENTS FOR SYMMETRICAL THERMAL HEAT SINKING.

5LOADS AND FEEDBACK CAN DISSIPATE POWER AND GENERATE THERMAL GRADIENTS. BE AWARE OF THEIR THERMAL EFFECTS.

6COVER CIRCUIT TO PREVENT AIR CURRENTS FROM CREATING THERMAL GRADIENTS.

5

3

2

2

RELAY

MATCHING RELAY

VTHERMAL

VTHERMAL

VIN

6

4

RF

RG

ADA4523-1

–IN

+IN

RG

RF

NC

5

RL

1

Figure 70. Techniques for Minimizing Thermocouple Induced Errors