Datasheet

V =
HYST
V V-
PRE POST
V
NOM
´ 10 (ppm)
6
(
(
Drift=
V V-
OUTMAX OUTMIN
V
OUT
TempRange´
´ 10 (ppm)
6
(
(
1
2
3
6
5
4
R
LOAD
0.47 Fm
+5V
GND_F
ContactandTraceResistance
GND_S
ENABLE
OUT_F
OUT_S
IN
REF32xx
REF3212, REF3220
REF3225, REF3230
REF3233, REF3240
SBVS058C –JUNE 2005– REVISED AUGUST 2011 www.ti.com
THERMAL HYSTERESIS LONG-TERM STABILITY
Thermal hysteresis for the REF32xx is defined as the Long-term stability refers to the change of the output
change in output voltage after operating the device at voltage of a reference over a period of months or
+25°C, cycling the device through the specified years. This effect lessens as time progresses, as is
temperature range, and returning to +25°C. It can be shown by the long-term stability Typical Characteristic
expressed as: curves. The typical drift value for the REF32xx is
55ppm from 0 to 1000 hours. This parameter is
characterized by measuring 30 units at regular
intervals for a period of 1000 hours.
Where:
LOAD REGULATION
V
HYST
= thermal hysteresis (in units of ppm).
Load regulation is defined as the change in output
V
NOM
= the specified output voltage.
voltage as a result of changes in load current. The
V
PRE
= output voltage measured at +25°C
load regulation of the REF32xx is measured using
pretemperature cycling.
force and sense contacts, as shown in Figure 24.
V
POST
= output voltage measured after the device
has been cycled through the specified
temperature range of –40°C to +125°C and
returned to +25°C. (1)
TEMPERATURE DRIFT
The REF32xx is designed to exhibit minimal drift
error, which is defined as the change in output
voltage over varying temperature. The drift is
calculated using the box method, as described by
Equation 2:
(2)
The REF32xx features a typical drift coefficient of
4ppm/°C from 0°C to +125°C—the primary
temperature range for many applications. For the
extended industrial temperature range of –40°C to
Figure 24. Accurate Load Regulation of REF32xx
+125°C, the REF32xx family drift increases to a
typical value of 10.5ppm/°C.
The force and sense lines can be used to effectively
NOISE PERFORMANCE
eliminate the impact of contact and trace resistance,
resulting in accurate voltage at the load. By
Typical 0.1Hz to 10Hz voltage noise can be seen in
connecting the force and sense lines at the load, the
the Typical Characteristic curve, 0.1Hz to 10Hz
REF32xx compensates for the contact and trace
Voltage Noise. The noise voltage of the REF32xx
resistances because it measures and adjusts the
increases with output voltage and operating
voltage actually delivered at the load.
temperature. Additional filtering can be used to
improve output noise levels, although care should be
The GND_S pin is connected to the internal ground of
taken to ensure the output impedance does not
the device through ESD protection diodes. Because
degrade AC performance.
of that connection, the maximum differential voltage
between the GND_S and GND_F pins must be kept
below 200mV to prevent these dioes from
unintentionally turning on.
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