lm4128amfx-1.8 National Semiconductor Corporation, lm4128amfx-1.8 Datasheet - Page 13

• Manufacturer Part Number: lm4128amfx-1.8
• Description: Sot-23 Precision Micropower Series Voltage Reference
• Manufacturer: National Semiconductor Corporation

T
V
V
temperature range
V
temperature range
ΔT = Operating temperature range.
The LM4128 features a low temperature drift of 75 ppm (max)
to 100 ppm (max), depending on the grade, from -40°C to
125°C.
LONG TERM STABILITY
Long-term stability refers to the fluctuation in output voltage
over a long period of time (1000 hours). The LM4128 features
a typical long-term stability of 50 ppm over 1000 hours. The
measurements are made using 5 units of each voltage option,
at a nominal input voltage (5V), with no load, at room tem-
perature.
EXPRESSION OF ELECTRICAL CHARACTERISTICS
Electrical characteristics are typically expressed in mV, ppm,
or a percentage of the nominal value. Depending on the ap-
plication, one expression may be more useful than the other.
To convert one quantity to the other one may apply the fol-
lowing:
ppm to mV error in output voltage:
Where:
V
Bit error (1 bit) to voltage error (mV):
D
REF
REF_MIN
REF_MAX
REF
= Temperature drift
= Nominal preset output voltage
is in volts (V) and V
= Minimum output voltage over operating
= Maximum output voltage over operating
ERROR
is in milli-volts (mV).
13
V
number of bits.
mV to ppm error in output voltage:
Where:
V
Voltage error (mV) to percentage error (percent):
Where:
V
PRINTED CIRCUIT BOARD and LAYOUT
CONSIDERATIONS
References in SOT packages are generally less prone to PC
board mounting than devices in Small Outline (SOIC) pack-
ages. To minimize the mechanical stress due to PC board
mounting that can cause the output voltage to shift from its
initial value, mount the reference on a low flex area of the PC
board, such as near the edge or a corner.
The part may be isolated mechanically by cutting a U shape
slot on the PCB for mounting the device. This approach also
provides some thermal isolation from the rest of the circuit.
Bypass capacitors must be mounted close to the part. Mount-
ing bypass capacitors close to the part will reduce the para-
sitic trace components thereby improving performance.
REF
REF
REF
is in volts (V), V
is in volts (V) and V
is in volts (V) and V
ERROR
ERROR
ERROR
is in milli-volts (mV), and n is the
is in milli-volts (mV).
is in milli-volts (mV).
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