LM20

SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LM20 features make it suitable for many general temperature sensing applications. Multiple package options

expand on its, flexibility.

8.1.1 Capacitive Loads

The LM20 handles capacitive loading well. Without any precautions, the LM20 can drive any capacitive load less

than 300 pF as shown in Figure 2. Over the specified temperature range the LM20 has a maximum output

impedance of 160

Ω. In an extremely noisy environment, it may be necessary to add some filtering to minimize

noise pickup. It is recommended that 0.1

μF be added from V+ to GND to bypass the power supply voltage, as

shown in Figure 4. In a noisy environment, it may even be necessary to add a capacitor from the output to

ground with a series resistor as shown in Figure 4. A 1-

μF output capacitor with the 160-Ω maximum output

impedance and a 200-

Ω series resistor will form a 442-Hz lowpass filter. Because the thermal time constant of

the LM20 is much slower, the overall response time of the LM20 will not be significantly affected.

In situations where a transient load current is placed on the circuit output the series resistance value may be

increased to compensate for any ringing that may be observed.

Figure 2. LM20 No Decoupling Required for Capacitive Loads Less Than 300 pF

Table 2. Capacitive Loading Isolation

Minimum R (

Ω)

C (µF)

200

1

470

0.1

680

0.01

1 k

0.001

Figure 3. LM20 With Compensation for Capacitive Loading Greater Than 300 pF

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