SNOS641F – OCTOBER 1999 – REVISED JULY 2013
Functional Block Diagram
*LM4041-N ADJ only
**LM4041-N 1.2 only
APPLICATIONS INFORMATION
The LM4041-N is a precision micro-power curvature-corrected bandgap shunt voltage reference. For space
critical applications, the LM4041-N is available in the sub-miniature SOT-23 and SC70 surface-mount package.
The LM4041-N 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 LM4041-N remains stable.
Design effort is further reduced with the choice of either a fixed 1.2V or an adjustable reverse breakdown
voltage. The minimum operating current is 60
μA
for the LM4041-N 1.2 and the LM4041-N ADJ. Both versions
have a maximum operating current of 12 mA.
LM4041-Ns using the SOT-23 package have pin 3 connected as the (-) output through the package's die attach
interface. Therefore, the LM4041-N 1.2's pin 3 must be left floating or connected to pin 2 and the LM4041-N
ADJ's pin 3 is the (-) output.
LM4041-Ns using the SC70 package have pin 2 connected as the (−) output through the packages' die attach
interface. Therefore, the LM4041-N 1.2's pin 2 must be left floating or connected to pin 1, and the LM4041-N
ADJ's pin 2 is the (−) output.
The typical thermal hysteresis specification is defined as the change in +25°C voltage measured after thermal
cycling. The device is thermal cycled to temperature -40°C and then measured at 25°C. Next the device is
thermal cycled to temperature +125°C and again measured at 25°C. The resulting V
OUT
delta shift between the
25°C measurements is thermal hysteresis. Thermal hysteresis is common in precision references and is induced
by thermal-mechanical package stress. Changes in environmental storage temperature, operating temperature
and board mounting temperature are all factors that can contribute to thermal hysteresis.
In a conventional shunt regulator application
an external series resistor (R
S
) is connected between
the supply voltage and the LM4041-N. R
S
determines the current that flows through the load (I
L
) and the
LM4041-N (I
Q
). Since load current and supply voltage may vary, R
S
should be small enough to supply at least
the minimum acceptable I
Q
to the LM4041-N 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
L
is at its minimum, R
S
should
be large enough so that the current flowing through the LM4041-N is less than 12 mA.
R
S
should be selected based on the supply voltage, (V
S
), the desired load and operating current, (I
L
and I
Q
), and
the LM4041-N's reverse breakdown voltage, V
R
.
The LM4041-N ADJ's output voltage can be adjusted to any value in the range of 1.24V through 10V. It is a
function of the internal reference voltage (V
REF
) and the ratio of the external feedback resistors as shown in
. The output voltage is found using the equation
V
O
= V
REF
[(R2/R1) + 1]
where
12
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