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SBOS410 – JUNE 2007
APPLICATION INFORMATION
The REF50xx is family of low-noise, precision
bandgap voltage references that are specifically
designed for excellent initial voltage accuracy and
drift.
shows a simplified block diagram of
the REF50xx.
+V
SUPPLY
V
IN
REF50xx
SUPPLY VOLTAGE
The REF50xx family of voltage references features
extremely low dropout voltage. With the exception of
the REF5020, which has a minimum supply
requirement of 2.7V, these references can be
operated with a supply of 200mV above the output
voltage in an unloaded condition. For loaded
conditions, a typical dropout voltage versus load plot
is shown in
of the Typical Characteristics.
OUTPUT ADJUSTMENT (TRIM Pin)
µT
(10
m
A
at 25
°
C)
V
OUT
TEMP
µT
Bandgap
1.2V
TRIM
60kW
The REF50xx provides a very accurate voltage
output. However, V
OUT
can be adjusted from the
nominal value for the purpose of trimming system
errors by configuring the TRIM pin (pin 5). The TRIM
pin provides for adjustment of the voltage at V
OUT
over a ±15mV range.
shows a typical circuit
using the TRIM pin to adjust V
OUT
. When using this
technique, the temperature coefficients of the
resistors can degrade the temperature drift at the
output.
+V
SUPPLY
REF50xx
DNC
V
IN
DNC
NC
V
OUT
TRIM
470W
1kW
10kW
GND
Figure 21. REF50xx Simplified Block Diagram
BASIC CONNECTIONS
shows the typical connections for the
REF50xx. A supply bypass capacitor ranging
between 1μF to 10μF is recommended. A 1μF to
50μF, low-ESR output capacitor (C
L
) must be
connected to V
OUT
.
+V
SUPPLY
REF50xx
DNC
C
BYPASS
1
m
F to 10
m
F
V
IN
TEMP
GND
DNC
NC
V
OUT
TRIM
V
OUT
C
L
1
m
F to 50
m
F
TEMP
GND
Figure 23. V
OUT
Adjustment Using the TRIM Pin
TEMPERATURE DRIFT
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:
Drift
+
V
OUTMAX
*
V
OUTMIN
V
OUT
Temp Range
10
6
(ppm)
(1)
Figure 22. Basic Connections
The REF50xx features a maximum drift coefficient of
3ppm/°C for the high-grade version, and 8ppm/°C for
the standard-grade.
Copyright © 2007, Texas Instruments Incorporated
9
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