Detailed Description
The LM4041 shunt references use the bandgap princi-
ple to produce a stable, accurate voltage. The device
behaves similarly to an ideal zener diode; a fixed volt-
age of +1.225V is maintained across its output termi-
nals when biased with 60µA to 12mA of reverse
current. The LM4041 behaves similarly to a silicon
diode when biased with forward currents up 10mA.
Figure 3 shows a typical operating circuit. The LM4041
is ideal for providing a stable reference from a high-
voltage power supply.
Applications Information
The LM4041’s internal pass transistor is used to main-
tain a constant output voltage (V
SHUNT
) by sinking the
necessary amount of current across a source resistor.
The source resistance (R
S
) is determined from the load
current (I
LOAD
) range, supply voltage (V
S
) variations,
V
SHUNT
, and desired quiescent current.
Choose the value of R
S
when V
S
is at a minimum and
I
LOAD
is at a maximum. Maintain a minimum I
SHUNT
of
60µA at all times. The R
S
value should be large enough
to keep I
SHUNT
less than 12mA for proper regulation
when V
S
is maximum and I
LOAD
is at a minimum. To
prevent damage to the device, I
SHUNT
should never
exceed 20mA.
Therefore, the value of R
S
is bounded by the following
equation:
[V
S(MIN)
- V
R
] / [60µA + I
LOAD(MAX)
] > R
S
>
[V
S(MAX)
- V
R
] / [20mA + I
LOAD(MIN)
]
Choosing a larger resistance minimizes the total power
dissipation in the circuit by reducing the shunt current
(P
D(TOTAL)
= V
S
✕
I
SHUNT
). Provide a safety margin to
incorporate the worst-case tolerance of the resistor
used. Ensure that the resistor’s power rating is ade-
quate, using the following general power equation:
P
R
= I
SHUNT
✕
(V
S(MAX)
- V
R
)
Output Capacitance
The LM4041 does not require an external capacitor for
frequency stability and is stable for any output capaci-
tance.
Temperature Performance
The LM4041 typically exhibits an output voltage tem-
perature coefficient within ±15ppm/°C. The polarity of
the temperature coefficient may be different from one
device to another; some may have positive coefficients,
and others may have negative coefficients.
LM4041
Improved Precision Micropower
Shunt Voltage Reference
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Pin Description
