ADR525BKS-REEL7 Analog Devices Inc, ADR525BKS-REEL7 Datasheet - Page 11

• Manufacturer Part Number: ADR525BKS-REEL7
• Description: IC REF VOLT SHUNT 2.5V SC-70-3
• Manufacturer: Analog Devices Inc

Specifications of ADR525BKS-REEL7

• Rohs Status: RoHS non-compliant
• Reference Type: Shunt
• Voltage - Output: 2.5V
• Tolerance: ±0.2%
• Temperature Coefficient: 40ppm/°C
• Number Of Channels: 1
• Current - Cathode: 50µA
• Current - Output: 15mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SC-70-3, SOT-323-3
• Voltage - Input: -
• Current - Quiescent: -

THEORY OF OPERATION
The ADR520/ADR525/ADR530/ADR540/ADR550 use the
band gap concept to produce a stable, low temperature coefficient
voltage reference suitable for high accuracy data acquisition
components and systems. The devices use the physical nature of a
silicon transistor base-emitter voltage (V
operating region. All such transistors have approximately a
−2 mV/°C temperature coefficient (TC), making them unsuitable
for direct use as low temperature coefficient references. Extra-
polation of the temperature characteristics of any one of these
devices to absolute zero (with the collector current proportional
to the absolute temperature), however, reveals that its V
approaches approximately the silicon band gap voltage. Thus,
if a voltage develops with an opposing temperature coefficient
to sum the V
The ADR520/ADR525/ADR530/ADR540/ADR550 circuit
shown in Figure 18 provides such a compensating voltage (V1)
by driving two transistors at different current densities and
amplifying the resultant V
positive temperature coefficient). The sum of V
provides a stable voltage reference over temperature.
APPLICATIONS
The ADR520/ADR525/ADR530/ADR540/ADR550 are a
series of precision shunt voltage references. They are designed
to operate without an external capacitor between the positive
and negative terminals. If a bypass capacitor is used to filter the
supply, the references remain stable.
All shunt voltage references require an external bias resistor (R
between the supply voltage and the reference (see Figure 19).
R
reference (I
R
•
•
BIAS
BIAS
R
current to the ADR520/ADR525/ADR530/ADR540/
ADR550, even when the supply voltage is at its minimum
value and the load current is at its maximum value.
R
15 mA when the supply voltage is at its maximum value
and the load current is at its minimum value.
needs to be chosen based on the following considerations:
sets the current that flows through the load (I
BIAS
BIAS
V
BE
+
–
must be small enough to supply the minimum I
must be large enough so that I
Δ
IN
V
BE
V1
). Because the load and the supply voltage can vary,
BE
+
–
, a zero temperature coefficient reference results.
+
–
Figure 18. Circuit Schematic
BE
difference (ΔV
BE
IN
) in the forward-biased
does not exceed
BE
, which has a
BE
and V1
L
) and the
V+
V–
BE
IN
BIAS
Rev. E | Page 11 of 16
)
ADR520/ADR525/ADR530/ADR540/ADR550
Given these conditions, R
voltage (V
the ADR520/ADR525/ADR530/ADR540/ADR550, and the
output voltage (V
ADR540/ADR550.
Precision Negative Voltage Reference
The ADR520/ADR525/ADR530/ADR540/ADR550 are suit-
able for applications where a precise negative voltage is desired.
Figure 20 shows the ADR525 configured to provide a negative
output.
Output Voltage Trim
The trim terminal of the ADR520/ADR525/ADR530/ADR540/
ADR550 can be used to adjust the output voltage over a range
of ±0.5%. This allows systems designers to trim system errors
by setting the reference to a voltage other than the preset output
voltage. An external mechanical or electrical potentiometer can
be used for this adjustment. Figure 21 illustrates how the output
voltage can be trimmed using the AD5273, an Analog Devices,
Inc., 10 kΩ potentiometer.
R
BIAS
Figure 20. Negative Precision Reference Configuration
S
), the load and operating currents (I
=
ADR530
V
I
S
L
−
+
OUT
V
I
Figure 21. Output Voltage Trim
OUT
I
IN
IN
) of the ADR520/ADR525/ADR530/
R
Figure 19. Shunt Reference
V
S
R
V
ADR525
S
BIAS
470kΩ
I
R1
IN
is determined by the supply
ADR550
+ I
I
L
L
R
V
S
–2.5V
POTENTIOMETER
10kΩ
AD5273
V
V
OUT
OUT
L
and I
IN
) of
(3)