Datasheet

R5
60kW
REF50xx
TEMP
V
OUT
GND
TRIM/NR
V
IN
aT
aT
(10 Am
at+25 C)°
R2 R1
R3
R4
10kW
1kW
1.2V
DNC
TEMP
V
OUT
V
IN
GND
DNC
NC
TRIM/NR
REF50xx
+V
SUPPLY
10kW
1kW
470kW
DNC
TEMP
V
OUT
V
IN
GND
DNC
NC
TRIM/NR
REF50xx
C
BYPASS
1 Fto10 Fm m
C
L
1 Fto50 Fm m
+V
SUPPLY
V
OUT
REF5020-EP, REF5025-EP
REF5040-EP, REF5050-EP
SBOS471A –APRIL 2010–REVISED JUNE 2010 www.ti.com
APPLICATION INFORMATION
The REF50xx is family of low-noise, precision
SUPPLY VOLTAGE
bandgap voltage references that are specifically
designed for excellent initial voltage accuracy and
The REF50xx family of voltage references features
drift. Figure 22 shows a simplified block diagram of
extremely low dropout voltage. With the exception of
the REF50xx.
the REF5020, which has a minimum supply
requirement of 2.7 V, these references can be
operated with a supply of 200 mV above the output
voltage in an unloaded condition. For loaded
conditions, a typical dropout voltage versus load plot
is shown in Figure 6 of the Typical Characteristics.
OUTPUT ADJUSTMENT USING THE TRIM/NR
PIN
The REF50xx provides a very accurate,
factory-trimmed voltage output. However, V
OUT
can
be adjusted using the trim and noise reduction pin
(TRIM/NR, pin 5). Figure 24 shows a typical circuit
that allows an output adjustment of ±15 mV
Figure 22. REF50xx Simplified Block Diagram
BASIC CONNECTIONS
Figure 23 shows the typical connections for the
REF50xx. A supply bypass capacitor ranging
between 1 mF to 10 mF is recommended. A 1-mF to
50-mF output capacitor (C
L
) must be connected from
V
OUT
to GND. The ESR value of C
L
must be less than
or equal to 1.5 Ω to ensure output stability. To
Figure 24. V
OUT
Adjustment Using the TRIM/NR
minimize noise, the recommended ESR of C
L
is
Pin
between 1 Ω and 1.5 Ω.
The REF50xx allows access to the bandgap through
the TRIM/NR pin. Placing a capacitor from the
TRIM/NR pin to GND (see Figure 25) in combination
with the internal R
3
and R
4
resistors creates a
low-pass filter. A capacitance of 1 mF creates a
low-pass filter with the corner frequency between 10
Hz and 20 Hz. Such a filter decreases the overall
noise measured on the V
OUT
pin by half. Higher
capacitance results in a lower filter cutoff frequency,
further reducing output noise. Note that use of this
capacitor increases startup time.
Figure 23. Basic Connections
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Product Folder Link(s): REF5020-EP REF5025-EP REF5040-EP REF5050-EP