LM4132BMF-3.3/NOPB National Semiconductor, LM4132BMF-3.3/NOPB Datasheet - Page 17

• Manufacturer Part Number: LM4132BMF-3.3/NOPB
• Description: IC REF VOLT PREC LDO SOT23-5
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM4132BMF-3.3/NOPB

• Reference Type: Series
• Voltage - Output: 3.3V
• Tolerance: ±0.1%
• Temperature Coefficient: 20ppm/°C
• Voltage - Input: 3.7 ~ 5.5 V
• Number Of Channels: 1
• Current - Quiescent: 100µA
• Current - Output: 20mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Cathode: -
• Other names: *LM4132BMF-3.3/NOPB; LM4132BMF-3.3; LM4132BMF-3.3TR

Application Information
THEORY OF OPERATION
The foundation of any voltage reference is the band-gap
circuit. While the reference in the LM4132 is developed from
the gate-source voltage of transistors in the IC, principles of
the band-gap circuit are easily understood using a bipolar
example. For a detailed analysis of the bipolar band-gap
circuit, please refer to Application Note AN-56.
SUPPLY AND ENABLE VOLTAGES
To ensure proper operation, V
specified range. An acceptable range of input voltages is
The enable pin uses an internal pull-up current source (I
ULL_UP
external source. If the part is not enabled by an external
source, it may be connected to V
enable voltages is given by the enable transfer characteris-
tics. See the Electrical Characteristics section and Enable
Transfer Characteristics figure for more detail. Note, the part
will not operate correctly for V
COMPONENT SELECTION
A small ceramic (X5R or X7R) capacitor on the input must be
used to ensure stable operation. The value of C
sized according to the output capacitor value. The value of
C
capacitor is used, C
Noise on the power-supply input may affect the output noise.
Larger input capacitor values (typically 4.7µF to 22µF) may
help reduce noise on the output and significantly reduce
overshoot during startup. Use of an additional optional by-
pass capacitor between the input and ground may help
further reduce noise on the output. With an input capacitor,
the LM4132 will drive any combination of resistance and
capacitance up to V
The LM4132 is designed to operate with or without an output
capacitor and is stable with capacitive loads up to 10µF.
Connecting a capacitor between the output and ground will
significantly improve the load transient response when
switching from a light load to a heavy load. The output
capacitor should not be made arbitrarily large because it will
effect the turn-on time as well as line and load transients.
While a variety of capacitor chemistry types may be used, it
is typically advisable to use low esr ceramic capacitors. Such
capacitors provide a low impedance to high frequency sig-
nals, effectively bypassing them to ground. Bypass capaci-
tors should be mounted close to the part. Mounting bypass
capacitors close to the part will help reduce the parasitic
trace components thereby improving performance.
SHORT CIRCUITED OUTPUT
The LM4132 features indefinite short circuit protection. This
protection limits the output current to 75mA when the output
is shorted to ground.
TURN ON TIME
Turn on time is defined as the time taken for the output
voltage to rise to 90% of the preset value. The turn on time
depends on the load. The turn on time is typically 33.2µs
when driving a 1µF load and 78.8µs when driving a 10µF
load. Some users may experience an extended turn on time
(up to 10ms) under brown out conditions and low tempera-
tures (-40˚C).
IN
must satisfy the relationship C
) 2µA) that may be left floating or triggered by an
V
IN
>
V
REF
IN
REF
must have a minimum value of 0.1µF.
+ 400mV (I
/20mA and 10µF respectively.
EN
EN
IN
>
IN
and V
LOAD
. An acceptable range of
≥ C
V
IN
OUT
.
IN
≤ 10mA)
must be within a
. When no output
IN
must be
P -
17
THERMAL HYSTERESIS
Thermal hysteresis is defined as the change in output volt-
age at 25
that thermal hysteresis is the difference in output voltage
between two points in a given temperature profile. An illus-
trative temperature profile is shown in Figure 1.
This may be expressed analytically as the following:
Where
V
V
V
V
The LM4132 features a low thermal hysteresis of 75 ppm
(typical) from -40˚C to 125˚C after 8 temperature cycles.
TEMPERATURE COEFFICIENT
Temperature drift is defined as the maximum deviation in
output voltage over the operating temperature range. This
deviation over temperature may be illustrated as shown in
Figure 2.
Temperature coefficient may be expressed analytically as
the following:
HYS
REF
REF1
REF2
FIGURE 2. Illustrative V
= Nominal preset output voltage
= Thermal hysteresis expressed in ppm
= V
= V
FIGURE 1. Illustrative Temperature Profile
o
REF
REF
C after some deviation from 25
before temperature fluctuation
after temperature fluctuation.
REF
vs Temperature Profile
o
C. This is to say
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