6

SCD5035 Rev J 10/22/2014

Aeroflex Plainview

Another application for the Aeroflex PCS5035 device is to provide precision excitation sources and

threshold detection for five temperature sensors. The temperature sensors are typically thermistors, but can

also be RTDs or silicon diodes. Since these devices have negative temperature coefficients, the device

resistance is inversely related to the temperature. A typical application is shown below. The PCS5035

contains five independent current sources, internally trimmed to 80 uA (+ 2µA) each. The PCS5035 also

contains an internal precision bandgap voltage reference, set to 2.000 Volts (+ 0.010Volts). Five complete

temperature monitor circuits can be obtained by connecting external thermistors as shown below. The

threshold is reached when the temperature of the thermistor produces a resistance of exactly 25K



(2.00V/80uA). If the temperature is low, the sensor voltage is greater than 2.000 Volts and the comparator

output is high; when the temperature is high, the comparator output goes low. The comparator output

configurations are open-collector, with internal 10K

 pullup resistors. This allows the comparator outputs to

be wire-ORed.

To set the thresholds at other temperatures, several options are available: Other thermistor types may be

selected; shunt resistors may be used to adjust the sensor response; an external reference voltage may be

used.

I = 80µA

+5V

10K



10K



+

-

+

-

Sensor

1

1

5

Sensor

5

t°

t°

Internal

Precision

Bandgap

Reference

Temperature Threshold Monitor with Internal Bandgap Reference Voltage