SM74601 Datasheet, PDF (11/14 Pages) Texas Instruments – SOT-23 Precision Micropower Series Voltage Reference

SM74601
www.ti.com
SNOSBA5A – SEPTEMBER 2011 – REVISED APRIL 2013
LONG TERM STABILITY
Long-term stability refers to the fluctuation in output voltage over a long period of time (1000 hours). The
SM74601 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 temperature.
EXPRESSION OF ELECTRICAL CHARACTERISTICS
Electrical characteristics are typically expressed in mV, ppm, or a percentage of the nominal value. Depending
on the application, one expression may be more useful than the other. To convert one quantity to the other one
may apply the following:
ppm to mV error in output voltage:
V_REF x ppm_ERROR
10³
= V_ERROR
where
• V_REF is in volts (V)
• V_ERROR is in milli-volts (mV).
(4)
Bit error (1 bit) to voltage error (mV):
V_REF
2ⁿ
x 10³
= V_ERROR
• V_REF is in volts (V)
• V_ERROR is in milli-volts (mV)
• n is the number of bits
(5)
mV to ppm error in output voltage:
V_ERROR
V_REF
x 10³ _{= ppmERROR}
where
• V_REF is in volts (V)
• V_ERROR is in milli-volts (mV)
(6)
Voltage error (mV) to percentage error (percent):
V_{ERROR x 0.1 = Percent_Error}
V_REF
where
• V_REF is in volts (V)
• V_ERROR is in milli-volts (mV)
(7)
PRINTED CIRCUIT BOARD and LAYOUT CONSIDERATIONS
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. Mounting bypass capacitors close to the part will reduce
the parasitic trace components thereby improving performance.
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