ADR420BRZ Analog Devices Inc, ADR420BRZ Datasheet - Page 16
![IC VREF PREC 2.048V 10MA 8SOIC](/photos/5/66/56684/505-8-soic_sml.jpg)
ADR420BRZ
Manufacturer Part Number
ADR420BRZ
Description
IC VREF PREC 2.048V 10MA 8SOIC
Manufacturer
Analog Devices Inc
Series
XFET®r
Datasheet
1.ADR425ARZ.pdf
(24 pages)
Specifications of ADR420BRZ
Temperature Coefficient
3ppm/°C
Design Resources
High Accuracy, Bipolar Voltage Output Digital-to-Analog Conversion Using AD5765 (CN0073) High Accuracy, Bipolar Voltage Output Digital-to-Analog Conversion Using AD5763 (CN0074)
Reference Type
Series
Voltage - Output
2.048V
Tolerance
±0.05%
Voltage - Input
4 ~ 18 V
Number Of Channels
1
Current - Quiescent
500µA
Current - Output
10mA
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (3.9mm Width)
Topology
Series
Input Voltage
4V To 18V
Reference Voltage
2.048V
Reference Voltage Tolerance
1mV
Voltage Reference Case Style
SOIC
No. Of Pins
8
Fixed / Adjust / Prog
Precision
Output Voltage (max)
2.048V
Reference Voltage Accuracy (max)
0.05
Line Regulation
35ppm/V
Load Regulation
70ppm/mA
Input Voltage (max)
18V
Operating Temp Range
-40C to 125C
Operating Temperature Classification
Automotive
Mounting
Surface Mount
Pin Count
8
Package Type
SOIC N
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Cathode
-
Lead Free Status / Rohs Status
Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ADR420BRZ
Manufacturer:
ADI
Quantity:
205
Part Number:
ADR420BRZ
Manufacturer:
ADI/亚德诺
Quantity:
20 000
Company:
Part Number:
ADR420BRZ-REEL7
Manufacturer:
NS
Quantity:
6 234
ADR420/ADR421/ADR423/ADR425
THEORY OF OPERATION
The ADR42x series of references uses a reference generation
technique known as XFET (eXtra implanted junction FET).
This technique yields a reference with low supply current, good
thermal hysteresis, and exceptionally low noise. The core of the
XFET reference consists of two junction field-effect transistors
(JFET), one having an extra channel implant to raise its pinch-
off voltage. By running the two JFETs at the same drain current,
the difference in pinch-off voltage can be amplified and used to
form a highly stable voltage reference.
The intrinsic reference voltage is about 0.5 V with a negative
temperature coefficient of about −120 ppm/°C. This slope is
essentially constant to the dielectric constant of silicon and can
be closely compensated by adding a correction term generated
in the same fashion as the proportional-to-temperature (PTAT)
term used to compensate band gap references. The primary
advantage over a band gap reference is that the intrinsic tem-
perature coefficient is approximately 30 times lower (therefore
requiring less correction). This results in much lower noise
because most of the noise of a band gap reference comes from
the temperature compensation circuitry.
Figure 38 shows the basic topology of the ADR42x series. The
temperature correction term is provided by a current source
with a value designed to be proportional to absolute tempera-
ture. The general equation is
where:
G is the gain of the reciprocal of the divider ratio.
ΔV
I
Each ADR42x device is created by on-chip adjustment of R2
and R3 to achieve the specified reference output.
PTAT
P
is the difference in pinch-off voltage between the two JFETs.
is the positive temperature coefficient correction current.
V
OUT
I
PTAT
= G × (ΔV
*EXTRA CHANNEL IMPLANT
V
OUT
*
I
1
= G(ΔV
Figure 38. Simplified Schematic
P
− R1 × I
P
I
– R1 × I
1
ΔV
P
PTAT
PTAT
R1
)
)
ADR420/ADR421/
ADR423/ADR425
R2
R3
GND
V
V
IN
OUT
Rev. H | Page 16 of 24
(1)
DEVICE POWER DISSIPATION CONSIDERATIONS
The ADR42x family of references is guaranteed to deliver load
currents to 10 mA with an input voltage that ranges from 4.5 V
to 18 V. When these devices are used in applications at higher
currents, the following equation should be used to account for
the temperature effects due to power dissipation increases:
where:
T
temperature, respectively.
P
θ
BASIC VOLTAGE REFERENCE CONNECTIONS
Voltage references, in general, require a bypass capacitor
connected from V
illustrates the basic configuration for the ADR42x family of
references. Other than a 0.1 μF capacitor at the output to help
improve noise suppression, a large output capacitor at the
output is not required for circuit stability.
NOISE PERFORMANCE
The noise generated by ADR42x references is typically less
than 2 μV p-p over the 0.1 Hz to 10 Hz band for the ADR420,
ADR421, and ADR423. Figure 24 shows the 0.1 Hz to 10 Hz
noise of the ADR421, which is only 1.75 μV p-p. The noise
measurement is made with a band-pass filter made of a 2-pole
high-pass filter with a corner frequency at 0.1 Hz and a 2-pole
low-pass filter with a corner frequency at 10 Hz.
TURN-ON TIME
At power-up (cold start), the time required for the output
voltage to reach its final value within a specified error band
is defined as the turn-on settling time. Two components typi-
cally associated with this are the time for the active circuits to
settle and the time for the thermal gradients on the chip to
stabilize. Figure 31 to Figure 35 show the turn-on settling time
for the ADR421.
JA
D
J
and T
is the device power dissipation.
is the device package thermal resistance.
T
J
V
= P
IN
10µF
A
are the junction temperature and the ambient
D
Figure 39. Basic Voltage Reference Configuration
× θ
+
JA
0.1µF
+ T
OUT
TP = TEST PIN (DO NOT CONNECT)
A
NIC = NO INTERNAL CONNECTION
to GND. The circuit in Figure 39
NIC
TP
1
2
3
4
(Not to Scale)
ADR420/
ADR421/
ADR423/
ADR425
TOP VIEW
8
7
6
5
TP
NIC
OUTPUT
TRIM
0.1µF
(2)