MAX5490
100k
Ω
Precision-Matched Resistor-Divider in
SOT23
4 _______________________________________________________________________________________
Detailed Description
As shown in the Block Diagram, the MAX5490 consists
of two precision, low-ratio-drift resistors with an end-to-
end resistance of 100kΩ (R
1
+ R
2
). P3 is the set point
of the divider. The maximum working voltage of the
MAX5490 is 80V. This device offers a wide range of
resistance ratios (R
1
/R
2
) from 1:1 to 100:1 and is ideal
for precision operational amplifier gain/attenuation con-
trol. A maximum initial ratio accuracy of 0.035% and a
low 1ppm/°C ratio drift enhance system accuracy.
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, θ
J-A
,
for a 3-pin SOT23 package is 141°C/W. Calculate the
resulting temperature rise as:
∆T = 64mW x 141°C/W = 9.02°C
If the ratio temperature coefficient is 1ppm/°C (typ), the
total error introduced by self-heating is:
9.02°C x 1ppm/°C = 9.02ppm
