Applications Information

Self-Heating and Error

Applying a voltage across terminals P1 and P2 causes

the device to heat up due to power dissipation. In high-

voltage applications, consider the error in resistance-

ratio temperature coefficient caused by self-heating.

The worst-case self-heating occurs when the operating

voltage attains its maximum value. Approximate the

result of power dissipation under this condition as:

The thermal resistance from junction to ambient,

for a 3-pin SOT23 package is 141°C/W. Calculate the

resulting temperature rise as:

∆T = 83.3mW x 141°C/W = 11.7°C

If the ratio temperature coefficient is 2ppm/°C (typ), the

total error introduced by self-heating is:

11.7

°C x 2ppm/°C = 23.4ppm

P

V

R

V

k

mW

DISS

MAX

.

=

22

50

30

83 3

Ω

Precision-Matched Resistor-Divider in SOT23

4

_______________________________________________________________________________________

IN

P1

P2

P3

MAX5491

OUT

Figure 3. Buffered Attenuator

MAX5491

P1

P2

P3

IN

OUT

Figure 1. Inverting Amplifier Configuration

P1

P2

P3

MAX5491

OUT

IN

Figure 4. Attenuator with Buffer

MAX5491

P1

P2

P3

IN

OUT

Figure 2. Noninverting Amplifier Configuration

A

V

V

R

R

OUT

IN

2

A

V

V

R

R

OUT

IN

==

+

1

1

2

A

V

V

R

RR

OUT

IN

==

+

2

12

A

V

V

R

RR

OUT

IN

==

+

2

12

Typical Applications