Rainbow Electronics LM76 - Manual (Page 6)

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 (V
I
) at any pin exceeds the power supplies (V
I
< GND or V
I
> +V
S
) 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
Semiconductor 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 θ
JA (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 +V
S
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 +V
S
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 +V
S
from the nominal value.
Note 8: Typicals are at T
A
= 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 T
LOW
setpoint value (e.g.: if T
LOW
setpoint = 10˚C, and hysteresis = 2˚C, then actual hysteresis point is 10+2 = 12˚C); and
subtracts from the T
HIGH
and T_CRIT setpoints (e.g.: if T
HIGH
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 T
HIGH
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
operation.
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)
LM76
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