Datasheet
Data Sheet ADR01/ADR02/ADR03/ADR06
Rev. R | Page 15 of 20
APPLICATIONS INFORMATION
OVERVIEW
The ADR01/ADR02/ADR03/ADR06 are high precision, low
drift 10.0 V, 5.0 V, 2.5 V, and 3.0 V voltage references available
in an ultracompact footprint. The 8-lead SOIC versions of the
devices are drop-in replacements of the REF01/REF02/REF03
sockets with improved cost and performance.
These devices are standard band gap references (see Figure 34).
The band gap cell contains two NPN transistors (Q18 and Q19)
that differ in emitter area by 2×. The difference in their V
BE
produces a proportional-to-absolute temperature current (PTAT)
in R14, and, when combined with the V
BE
of Q19, produces a
band gap voltage, V
BG
, that is almost constant in temperature.
With an internal op amp and the feedback network of R5 and
R6, V
O
is set precisely at 10.0 V, 5.0 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
Input and Output Capacitors
Although the ADR01/ADR02/ADR03/ADR06 are designed to
function stably without any external components, connecting a
0.1 μF ceramic capacitor to the output is highly recommended
to improve stability and filter out low level voltage noise. An
additional 1 μF to 10 μF electrolytic, tantalum, or ceramic
capacitor can be added in parallel to improve transient per-
formance in response to sudden changes in load current;
however, the designer should keep in mind that doing so
increases the turn-on time of the device.
A 1 μF to 10 μF electrolytic, tantalum or ceramic capacitor can
also be connected to the input to improve transient response in
applications where the supply voltage may fluctuate. An addi-
tional 0.1 μF ceramic capacitor should be connected in parallel
to reduce supply noise. Mount both input and output capacitors
as close to the device pins as possible.
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 10.0 V/5.0 V/2.5 V/3.0 V. For
finer adjustment, add a series resistor of 470 kΩ. With the con-
figuration shown in Figure 35, 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 performance
of the device, provided the temperature coefficients of the resis-
tors are relatively low.
U1
ADR01/
ADR02/
ADR03/
ADR06
V
O
C2
0.1µF
C1
0.1µF
V
IN
V
IN
V
OUT
TEMP
TRIM
GND
02747-035
Figure 33. Basic Configuration
R1
R2 R3
R4
V
IN
Q23
Q1
Q2
Q7
Q8
Q9
Q3
Q10
D1
D2
Q4
V
O
D3
C1
R13
Q12
Q13
R5
I1
R12
Q14
Q15
2×
1×
V
BG
R20
TRIM
Q18
TEMP
R27
Q19
Q16
Q17
Q20
R6
R42
R41
R24
R32
R11
R17
R14
GND
02747-034
Figure 34. Simplified Schematic Diagram
U1
ADR01/
ADR02/
ADR03/
ADR06
V
IN
V
OUT
TEMP
TRIM
GND
V
IN
V
O
POT
10kΩ
R2
1kΩ
R1
470kΩ
02747-036
Figure 35. Optional Trim Adjustment
Temperature Monitoring
As described at the end of the Overview section, the ADR01/
ADR02/ADR03/ADR06 provide a TEMP output (Pin 1 in Figure 1
and Pin 3 in Figure 2) that varies linearly with temperature.
This output can be used to monitor the temperature change in the
system. The voltage at V
TEMP
is approximately 550 mV at 25°C,
and the temperature coefficient is approximately 1.96 mV/°C
(see Figure 36). A voltage change of 39.2 mV at the TEMP pin
corresponds to a 20°C change in temperature.