Rainbow Electronics LM19 - Manual (Page 4)

Electrical Characteristics
(Continued)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: When the input voltage (V I ) at any pin exceeds power supplies (V I
< GND or V I
> V + ), the current at that pin should be limited to 5 mA.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 k Ω resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin.
Note 4: The junction to ambient thermal resistance ( θ
JA
) is specified without a heat sink in still air.
Note 5: Typicals are at T
J
= T
A
= 25˚C and represent most likely parametric norm.
Note 6: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 7: Accuracy is defined as the error between the measured and calculated output voltage at the specified conditions of voltage, current, and temperature
(expressed in˚C).
Note 8: Non-Linearity is defined as the deviation of the calculated output-voltage-versus-temperature curve from the best-fit straight line, over the temperature
range specified.
Note 9: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating effects can be
computed by multiplying the internal dissipation by the thermal resistance.
Note 10: Negative currents are flowing into the LM19. Positive currents are flowing out of the LM19. Using this convention the LM19 can at most sink −1 µA and
source +16 µA.
Note 11: Load regulation or output impedance specifications apply over the supply voltage range of +2.4V to +5.5V.
Note 12: Line regulation is calculated by subtracting the output voltage at the highest supply input voltage from the output voltage at the lowest supply input voltage.
Typical Performance Characteristics
Temperature Error vs. Temperature Thermal Response in Still Air
20004034
20004035
1.0 LM19 Transfer Function
The LM19’s transfer function can be described in different
ways with varying levels of precision. A simple linear transfer
function, with good accuracy near 25˚C, is
V
O
= −11.69 mV/˚C x T + 1.8663 V
Over the full operating temperature range of −55˚C to
+130˚C, best accuracy can be obtained by using the para-
bolic transfer function
V
O
= (−3.88x10 −6 xT 2 ) + (−1.15x10 −2 xT) + 1.8639
solving for T:
A linear transfer function can be used over a limited tempera-
ture range by calculating a slope and offset that give best
results over that range. A linear transfer function can be
calculated from the parabolic transfer function of the LM19.
The slope of the linear transfer function can be calculated
using the following equation:
m = −7.76 x 10 −6 x T − 0.0115,
where T is the middle of the temperature range of interest
and m is in V/˚C. For example for the temperature range of
T
min
=−30 to T
max
=+100˚C:
T=35˚C
and
m = −11.77 mV/˚C
The offset of the linear transfer function can be calculated
using the following equation:
b = (V
OP
(T
max
) + V
OP
(T) + m x (T
max
+T))/2
,
where:
• V
OP
(T
max
) is the calculated output voltage at T
max
using
the parabolic transfer function for V
O
• V
OP
(T) is the calculated output voltage at T using the
parabolic transfer function for V
O
.
Using this procedure the best fit linear transfer function for
many popular temperature ranges was calculated in Figure
2. As shown in Figure 2 the error that is introduced by the
linear transfer function increases with wider temperature
ranges.
LM19
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