R1 + R2||R3

(4.1)R2||R3

(4.1)R2

R2 + R1||R3

LM20

SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015

www.ti.com

(12)

(13)

8.2.2.3 Application Curve

Figure 8. Thermostat Output Waveform

8.3 System Examples

8.3.1 Conserving Power Dissipation With Shutdown

The LM20 draws very little power; therefore, it can simply be shutdown by driving its supply pin with the output of

an logic gate as shown in Figure 9.

Figure 9. Conserving Power Dissipation With Shutdown

8.3.2 Analog-to-Digital Converter Input Stage

Most CMOS ADCs found in ASICs have a sampled data comparator input structure that is notorious for causing

grief to analog output devices such as the LM20 and many operational amplifiers. The cause of this grief is the

requirement of instantaneous charge of the input sampling capacitor in the ADC. This requirement is easily

accommodated by the addition of a capacitor. Because not all ADCsFigure 10 have identical input stages, the

charge requirements will vary necessitating a different value of compensating capacitor. This ADC is shown as

an example only. If a digital output temperature is required, refer to devices such as the LM74.

Figure 10. Suggested Connection to a Sampling Analog to Digital Converter Input Stage

14

Submit Documentation Feedback

Copyright © 1999–2015, Texas Instruments Incorporated

Product Folder Links: LM20