MAX5491 Maxim, MAX5491 Datasheet - Page 4

• Manufacturer Part Number: MAX5491
• Description: Precision-Matched Resistor-Divider in SOT23
• Manufacturer: Maxim

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:
Figure 1. Inverting Amplifier Configuration
Figure 3. Buffered Attenuator
4
IN
_______________________________________________________________________________________
IN
P
DISS
P2
Precision-Matched Resistor-Divider in SOT23
=
Applications Information
(
V
MAX
R
R
2
)
2
P3
=
Self-Heating and Error
R
1
(
MAX5491
50
30
P1
P2
V
k
R
R
1
2
Ω
A
)
MAX5491
2
=
A
=
V
OUT
V
IN
=
P1
83 3
V
OUT
V
.
=
IN
mW
P3
R
1
= −
OUT
R
+
OUT
2
R
R
R
2
1
2
The thermal resistance from junction to ambient, θ
for a 3-pin SOT23 package is 141°C/W. Calculate the
resulting temperature rise as:
If the ratio temperature coefficient is 2ppm/°C (typ), the
total error introduced by self-heating is:
Figure 2. Noninverting Amplifier Configuration
Figure 4. Attenuator with Buffer
IN
P2
∆T = 83.3mW x 141°C/W = 11.7°C
P1
P2
11.7°C x 2ppm/°C = 23.4ppm
R
R
2
1
MAX5491
IN
R
2
Typical Applications
P3
P3
R
1
MAX5491
A
=
V
OUT
V
A
IN
=
=
V
P1
V
OUT
IN
R
1
R
+
2
=
R
1
OUT
2
OUT
+
R
R
J-A
1
2
,