LM76 datasheet(6/15 Pages) NSC

6 / 15 page

Logic Electrical Characteristics (Continued)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating

the device beyond its rated operating conditions.

Note 2: When the input voltage (VI) at any pin exceeds the power supplies (VI < GND or VI > +VS) the current at that pin should be limited to 5 mA. The 20 mA

maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.

Note 3: See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in a current National Semicon-

ductor Linear Data Book for other methods of soldering surface mount devices.

Note 4: Human body model, 100 pF discharged through a 1.5 k

Ω resistor. Machine model, 200 pF discharged directly into each pin.

Note 5: LM76

θJA (thermal resistance, junction-to-ambient) when attached to a printed circuit board with 2 oz. foil is 200˚C/W.

Note 6: While the LM76 has a full-scale-range in excess of 128˚C, prolonged operation at temperatures above 125˚C is not recommended.

Note 7: The LM76 will operate properly over the +VS supply voltage range of 3V to 5.5V for the LM76CNM-3 and the LM76CHM-5. The LM76CNM-3 is tested and

specified for rated accuracy at the nominal supply voltage of 3.3V. Accuracy of the LM76CNM-3 will degrade 0.2˚C for a ±1% variation in +VS from the nominal value.

The LM76CHM-5 is tested and specified for a rated accuracy at the nominal supply voltage of 5.0V. Accuracy of the LM76CHM-5 will degrade 0.08˚C for a ±1%

variation in +VS from the nominal value.

Note 8: Typicals are at TA = 25˚C and represent most likely parametric norm.

Note 9: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 10: 12 bits + sign, two’s complement

Note 11: This specification is provided only to indicate how often temperature data is updated. The LM76 can be read at any time without regard to conversion state

(and will yield last conversion result). If a conversion is in process it will be interrupted and restarted after the end of the read.

Note 12: For best accuracy, minimize output loading. Higher sink currents can affect sensor accuracy with internal heating. This can cause an error of 0.64˚C at full

rated sink current and saturation voltage based on junction-to-ambient thermal resistance.

Note 13: Hysteresis value adds to the TLOW setpoint value (e.g.: if TLOW setpoint = 10˚C, and hysteresis = 2˚C, then actual hysteresis point is 10+2 = 12˚C); and

subtracts from the THIGH and T_CRIT setpoints (e.g.: if THIGH setpoint = 64˚C, and hysteresis = 2˚C, then actual hysteresis point is 64−2 = 62˚C). For a detailed

discussion of the function of hysteresis refer to

Section 1.1, TEMPERATURE COMPARISON, and Figure 3.

Note 14: Default values set at power up.

Electrical Characteristics

Continued

1.0 Functional Description

The LM76 temperature sensor incorporates a band-gap type

temperature sensor, 13-bit ADC, and a digital comparator

with user-programmable upper and lower limit values. The

comparator activates either the INT line for temperatures

outside the T

LOW and THIGH window, or the T_CRIT_A line

for temperatures which exceed T_CRIT. The lines are pro-

grammable for mode and polarity.

1.1 TEMPERATURE COMPARISON

LM76 provides a window comparison against a lower (T

LOW)

and upper (T

HIGH)

trip point. A second upper trip point

(T_CRIT) functions as a critical alarm shutdown.

Figure 3

depicts the comparison function as well as the modes of op-

eration.

1.1.1 STATUS BITS

The internal Status bits operate as follows:

DS101015-5

FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)

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