REF5010, REF5020
REF5025, REF5030
REF5040, REF5045, REF5050
www.ti.com
SBOS410E –JUNE 2007–REVISED JUNE 2010
TEMPERATURE DRIFT
To avoid errors caused by low-impedance loading,
buffer the TEMP pin output with
a
suitable
The REF50xx is designed for minimal drift error,
which is defined as the change in output voltage over
temperature. The drift is calculated using the box
method, as described by the following equation:
low-temperature drift op amp, such as the OPA333,
OPA335, or OPA376, as shown in Figure 32.
+V
VOUTMAX * VOUTMIN
6
Drift + ǒ
Ǔ
10 (ppm)
VOUT Temp Range
(1)
REF50xx
DNC
VIN
DNC
The REF50xx features a maximum drift coefficient of
3ppm/°C for the high-grade version, and 8ppm/°C for
the standard-grade.
VTEMP
OPA(1)
NC
2.6mV/°C
VOUT
TEMP
GND TRIM/NR
space
NOTE: (1) Low drift op amp, such as the OPA333, OPA335, or OPA376.
THERMAL HYSTERESIS
Thermal hysteresis for the REF50xx is defined as the
change in output voltage after operating the device at
+25°C, cycling the device through the specified
temperature range, and returning to +25°C. It can be
expressed as Equation 2:
Figure 32. Buffering the TEMP Pin Output
POWER DISSIPATION
The REF50xx family is specified to deliver current
loads of ±10mA over the specified input voltage
range. The temperature of the device increases
according to the equation:
· 106(ppm)
|VPRE - VPOST
|
VHYST
=
(
VNOM
(2)
TJ = TA + PD × qJA
(3)
Where:
Where:
VHYST = thermal hysteresis (in units of ppm).
VNOM = the specified output voltage.
TJ = Junction temperature (°C)
TA = Ambient temperature (°C)
PD = Power dissipated (W)
VPRE
= output voltage measured at +25°C
pretemperature cycling.
qJA
(°C/W)
= Junction-to-ambient thermal resistance
VPOST = output voltage measured after the device
has been cycled from +25°C through the
specified temperature range of –40°C to +125°C
and returned to +25°C.
The REF50xx junction temperature must not exceed
the absolute maximum rating of +150°C.
TEMPERATURE MONITORING
NOISE PERFORMANCE
The temperature output terminal (TEMP, pin 3)
provides a temperature-dependent voltage output
with approximately 60kΩ source impedance. As seen
in Figure 8, the output voltage follows the nominal
relationship:
Typical 0.1Hz to 10Hz voltage noise for each member
of the REF50xx family is specified in the Electrical
Characteristics: Per Device table. The noise voltage
increases with output voltage and operating
temperature. Additional filtering can be used to
improve output noise levels, although care should be
taken to ensure the output impedance does not
degrade performance.
VTEMP PIN = 509mV + 2.64 × T(°C)
This pin indicates general chip temperature, accurate
to approximately ±15°C. Although it is not generally
suitable for accurate temperature measurements, it
can be used to indicate temperature changes or for
temperature compensation of analog circuitry. A
temperature change of 30°C corresponds to an
approximate 79mV change in voltage at the TEMP
pin.
For additional information about how to minimize
noise and maximize performance in mixed-signal
applications such as data converters, refer to the
series of Analog Applications Journal articles entitled,
How a Voltage Reference Affects ADC Performance.
This three-part series is available for download from
the TI website under three literature numbers:
SLYT331, SLYT339, and SLYT355 for Part I, Part II,
and Part III, respectively.
The TEMP pin has high output impedance (see
Figure 28). Loading this pin with a low-impedance
circuit induces a measurement error; however, it does
not have any effect on VOUT accuracy.
Copyright © 2007–2010, Texas Instruments Incorporated
Submit Documentation Feedback
11
Product Folder Link(s): REF5010 REF5020 REF5025 REF5030 REF5040 REF5045 REF5050