LM4040AIZ-5.0 National Semiconductor, LM4040AIZ-5.0 Datasheet - Page 19

• Manufacturer Part Number: LM4040AIZ-5.0
• Description: Precision Micropower Shunt Voltage Reference
• Manufacturer: National Semiconductor

Applications Information
The LM4040 is a precision micro-power curvature-corrected
bandgap shunt voltage reference. For space critical applica-
tions, the LM4040 is available in the sub-miniature SOT-23
surface-mount package. The LM4040 has been designed for
stable operation without the need of an external capacitor
connected between the “+” pin and the “−” pin. If, however, a
bypass capacitor is used, the LM4040 remains stable. Re-
ducing design effort is the availability of several fixed reverse
breakdown voltages: 2.500V, 4.096V, 5.000V, 6.000, 8.192V,
and 10.000V. The minimum operating current increases from
60 µAfor the LM4040-2.5 to 100 µA for the LM4040-10.0. All
versions have a maximum operating current of 15 mA.
LM4040s in the SOT-23 packages have a parasitic Schottky
diode between pin 2 (−) and pin 3 (Die attach interface con-
tact). Therefore, pin 3 of the SOT-23 package must be left
floating or connected to pin 2.
The 4.096V version allows single +5V 12-bit ADCs or DACs
to operate with an LSB equal to 1 mV. For 12-bit ADCs or
DACs that operate on supplies of 10V or greater, the 8.192V
version gives 2 mV per LSB.
In a conventional shunt regulator application ( Figure 1 ) , an
external series resistor (R
ply voltage and the LM4040. R
flows through the load (I
current and supply voltage may vary, R
enough to supply at least the minimum acceptable I
L
) and the LM4040 (I
S
) is connected between the sup-
S
determines the current that
S
should be small
Q
). Since load
Q
to the
19
LM4040 even when the supply voltage is at its minimum and
the load current is at its maximum value. When the supply
voltage is at its maximum and I
be large enough so that the current flowing through the
LM4040 is less than 15 mA.
R
operating current, (I
breakdown voltage, V
Typical Applications
S
is determined by the supply voltage, (V
FIGURE 1. Shunt Regulator
L
R
and I
.
Q
), and the LM4040’s reverse
L
is at its minimum, R
DS011323-15
S
), the load and
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S
should