REF5025-HT
SBOS502D –SEPTEMBER 2009–REVISED APRIL 2012
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TEMPERATURE DRIFT
+V
The REF5025 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:
REF5025
DNC
VIN
DNC
VTEMP
OPA(1)
NC
VOUTMAX * VOUTMIN
2.6mV/°C
6
VOUT
TEMP
Drift + ǒ
Ǔ
10 (ppm)
VOUT Temp Range
GND TRIM/NR
(1)
TEMPERATURE MONITORING
NOTE: (1) Low drift op amp
The temperature output terminal (TEMP, pin 3)
provides a temperature-dependent voltage output
with approximately 60-kΩ source impedance. As
seen in Figure 10, the output voltage follows the
nominal relationship:
Figure 28. Buffering the TEMP Pin Output
POWER DISSIPATION
VTEMP PIN = 509 mV + 2.64 × T(°C)
(2)
(2)
The REF5025 is specified to deliver current loads of
±10 mA over the specified input voltage range. The
temperature of the device increases according to the
equation:
(For –55°C to 125°C only. Refer to Figure 10 of the
TYPICAL CHARACTERISTICS for 125°C to 210°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 79-mV change in voltage at the TEMP
pin.
TJ = TA + PD × θJA
(3)
(3)
Where:
TJ = Junction temperature (°C)
TA = Ambient temperature (°C)
PD = Power dissipated (W)
θJA
= Junction-to-ambient thermal resistance
(°C/W)
The TEMP pin has high output impedance (see
Figure 24). Loading this pin with a low-impedance
circuit induces a measurement error; however, it does
not have any effect on VOUT accuracy. To avoid
errors caused by low-impedance loading, buffer the
TEMP pin output with a suitable low-temperature drift
op amp as shown in Figure 28.
The REF5025 junction temperature must not exceed
the absolute maximum rating of 210°C.
NOISE PERFORMANCE
Typical 0.1-Hz to 10-Hz voltage noise for each
member of the REF5025 is specified in the Electrical
Characterisitics 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.
10
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