6

TEMP

6

1.8015

V

T

1525.04

2.4182

10

3.479

10-

-

= -

+

´

+

´

6

2

2

O

V = (

3.47 10

(T

30) ) + (1.082 10

(T

30)) + 1.8015 V

-

-

-

´

´

-

´

´

-

VTEMP

GND

HYST

REF

TEMP

SENSOR

+

-

V+

V

+

LM26__D

US

HYST

LM26

SNIS115S – MAY 2001 – REVISED SEPTEMBER 2015

www.ti.com

Functional Block Diagrams (continued)

Figure 5. LM26-_ _D Output Pin Block Diagram

8.3 Feature Description

8.3.1 Hysteresis

The HYST pin level sets the comparator hysteresis. Setting the HYST pin to GND selects 10°C hysteresis, while

setting it to V+ selects 2°C. A series resistor can be used for protection purposes. The input leakage current of

the pin is less than 10 µA. The value of the resistor will depend on the value of V+ as well as the leakage current.

For example with V+ = 3.3 V the input threshold level for VIH = 0.8 × 3.3 V = 2.64 V, thus the voltage drop across

the resistor should be less than 0.66 V. The 10-µA input leakage current requires the resistor value to be less

than 66 k

Ω.

8.3.2 VTEMP Output

The VTEMP output provides an output voltage that can be used to determine the temperature reading of the LM26.

The temperature reading of the LM26 can be calculated using the equation:

(1)

or

(2)

The VTEMP output has very weak drive capability (1-µA source, 40-µA sink). So care should be taken when

attaching circuitry to this pin. Capacitive loading may cause the VTEMP output to oscillate. Simply adding a resistor

in series as shown in Figure 6 and Figure 7 will prevent oscillations from occurring. To determine the value of the

resistor follow the guidelines given in Table 1. The same value resistor will work for either placement of the

resistor. If an additional capacitive load is placed directly on the LM26 output, rather than across CLOAD, it should

be at least a factor of 10 smaller than CLOAD.

Table 1. Resistive Compensation for Capacitive Loading of VTEMP

CLOAD

R (

Ω)

≤100pF

0

1nF

8200

10nF

3000

100nF

1000

≥1µF

430

8

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