LM26CIM5-RPA datasheet(9/24 Pages) TI

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TEMP

1.8015

1525.04

2.4182

3.479

10-

= -

V = (

3.47 10

30) ) + (1.082 10

30)) + 1.8015 V

LM26

V+

VTEMP

GND

HYST

OS/OS/US/

CLOAD

0.12f

Heavy Capacitive

Load, Cable/Wiring

LM26

V+

VTEMP

GND

HYST

OS/OS/US/

CLOAD

0.12f

Heavy Capacitive

Load, Cable/Wiring

LM26

www.ti.com

SNIS115S – MAY 2001 – REVISED SEPTEMBER 2015

Figure 6. Resistor Placement for Capacitive-

Figure 7. Resistor Placement for Capacitive-

Loading Compensation of VTEMP With R in Series

With Capacitor

With Signal Path

8.4 Device Functional Modes

The LM26 after factory programming has two functional modes one with 2°C Hysteresis and the other with 10°C

hysteresis as programmed by the level of the HYST pin. Selection of the level will depend on the system noise

and the temperature transition rate.

8.4.1 After Assembly PCB Testing

The LM26's VTEMP output allows after-assembly PCB testing by following a simple test procedure. Simply

measuring the VTEMP output voltage will verify that the LM26 has been assembled properly and that its

temperature sensing circuitry is functional. The VTEMP output has very weak drive capability that can be

overdriven by 1.5mA. Therefore, one can simply force the VTEMP voltage to cause the digital output to change

state, thereby verifying that the comparator and output circuitry function after assembly. Here is a sample test

procedure that can be used to test the LM26CIM5-TPA which has an 85°C trip point.

1. Turn on V+ and measure VTEMP. Then calculate the temperature reading of the LM26 using the equation:

(3)

(4)

2. Verify that the temperature measured in step one is within (±3°C + error of reference temperature sensor) of

the ambient/board temperature. The ambient/board temperature (reference temperature) should be

measured using an extremely accurate calibrated temperature sensor.

(a) Observe that OS is high.

(b) Drive VTEMP to ground.

(d) Release the VTEMP pin.

(e) Observe that OS is now high.

(a) Observe that OS is high.

(b) Drive VTEMP voltage down gradually.

(d) VTEMPTrig = VTEMP at OS trigger (HIGH->LOW)

(e) Calculate Trig using Equation 2.

(a) Gradually raise VTEMP until OS goes HIGH. Note VTEMP.

(b) Calculate THYST using Equation 2.

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