ADR02 AD [Analog Devices], ADR02 Datasheet - Page 15

• Manufacturer Part Number: ADR02
• Description: Ultracompact Precision10 V/5 V/2.5 V/3.0 V Voltage References
• Manufacturer: AD [Analog Devices]

APPLICATIONS
The ADR01/ADR02/ADR03/ADR06 are high precision, low
drift 10 V, 5 V, 2.5 V, and 3.0 V voltage references available in an
ultracompact footprint. The SOIC-8 version of the devices is a
drop-in replacement of the REF01/REF02/ REF03 sockets with
improved cost and performance.
These devices are standard band gap references. The band gap
cell contains two NPN transistors (Q18 and Q19) that differ in
emitter area by 2×. The difference in their V
proportional-to-absolute temperature current (PTAT) in R14,
and, when combined with the V
voltage, V
internal op amp and the feedback network of R5 and R6, V
precisely at 10 V, 5 V, 2.5 V, and 3.0 V for the ADR01, ADR02,
ADR06, and ADR03, respectively. Precision laser trimming of
the resistors and other proprietary circuit techniques are used to
further enhance the initial accuracy, temperature curvature, and
drift performance of the ADR01/ADR02/ADR03/ADR06.
The PTAT voltage is made available at the TEMP pin of the
ADR01/ADR02/ADR03/ADR06. It has a stable 1.96 mV/°C
temperature coefficient, such that users can estimate the
temperature change of the device by knowing the voltage
change at the TEMP pin.
APPLYING THE ADR01/ADR02/ADR03/ADR06
The devices can be used without any external components to
achieve the specified performance. Because of the internal op
amp amplifying the band gap cell to 10 V/5 V/2.5 V/3.0 V,
power supply decoupling helps the transient response of the
ADR01/ADR02/ADR03/ADR06. As a result, a 0.1 µF ceramic
type decoupling capacitor should be applied as close as possible
TEMP
R12
2X
Q18
R17
R14
R27
BG,
R32
R13
R11
D3
that is almost constant in temperature. With an
Figure 34. Simplified Schematic Diagram
1X
Q19
R1
Q1
R24
Q14 Q15
Q12
Q16
R2
Q3
Q13
Q2
R3
C1
Q7
Q4
BE
D1
D2
of Q19, produces a band gap
R41
Q8
Q20
Q17
I1
R42
BE
Q23
produces a
V
BG
Q9
R5
R6
R4
Q10
R20
GND
O
V
V
TRIM
IN
O
is set
Rev. F | Page 15 of 20
to the input and output pins of the device. An optional 1 µF to
10 µF bypass capacitor can also be applied at the V
maintain the input under transient disturbance.
Output Adjustment
The ADR01/ADR02/ADR03/ADR06 trim terminal can be used
to adjust the output voltage over a nominal voltage. This feature
allows a system designer to trim system errors by setting the
reference to a voltage other than 10 V/5 V/2.5 V/3.0 V. For finer
adjustment, a series resistor of 470 kΩ can be added. With the
configuration shown in Figure 36, the ADR01 can be adjusted
from 9.70 V to 10.05 V, the ADR02 can be adjusted from 4.95 V
to 5.02 V, the ADR06 can be adjusted from 2.8 V to 3.3 V, and
the ADR03 can be adjusted from 2.3 V to 2.8 V. Adjustment of
the output does not significantly affect the temperature per-
formance of the device, provided the temperature coefficients of
the resistors are relatively low.
Temperature Monitoring
As described previously, the ADR01/ADR02/ADR03/ADR06
provide a TEMP output (Pin 3) that varies linearly with tem-
perature. This output can be used to monitor the temperature
change in the system. The voltage at VTEMP is approximately
550 mV at 25°C, and the temperature coefficient is approximately
1.96 mV/°C (see Figure 37). A voltage change of 39.2 mV at the
TEMP pin corresponds to a 20°C change in temperature.
V
IN
V
0.1µF
IN
ADR01/ADR02/ADR03/ADR06
C1
Figure 36. Optional Trim Adjustment
Figure 35. Basic Configuration
V
TEMP TRIM
ADR01/
ADR02/
ADR03/
ADR06
IN
GND
U1
V
TEMP TRIM
V
ADR01/
ADR02/
ADR03/
ADR06
IN
OUT
GND
U1
V
OUT
470kΩ
R1
C2
0.1µF
R2
1kΩ
pot
10kΩ
V
O
V
O
IN
node to