AD680JTZ [ADI]

Bandgap, Low Power 2.5v Reference;
AD680JTZ
型号: AD680JTZ
厂家: ADI    ADI
描述:

Bandgap, Low Power 2.5v Reference

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Low Power, Low Cost  
2.5 V Reference  
AD680  
FEATURES  
Low quiescent current at 250 μA max  
CONNECTION DIAGRAMS  
TP*  
1
2
3
4
8
7
6
5
TP*  
TP*  
V
Laser trimmed to high accuracy  
2.5 V 5 mV max (AN, AR grades)  
Trimmed temperature coefficient  
20 ppm/°C max (AN, AR grades)  
+V  
IN  
AD680  
TEMP  
TOP VIEW  
OUT  
(Not to Scale)  
GND  
NC  
Low noise at 8 μV p-p from 0.1 Hz to 10 Hz  
250 nV/√Hz wideband  
Temperature output pin (N, R packages)  
NC = NO CONNECT  
*TP DENOTES FACTORY TEST POINT.  
NO CONNECTIONS SHOULD BE MADE  
TO THESE PINS.  
Available in three package styles  
Figure 1. 8-Lead PDIP and 8-Lead SOIC Pin Configuration  
8-lead PDIP, 8-lead SOIC, and 3-pin TO-92  
AD680  
BOTTOM VIEW  
(Not to Scale)  
GENERAL DESCRIPTION  
The AD680 is a band gap voltage reference that provides a fixed  
2.5 V output from inputs between 4.5 V and 36 V. The  
3
2
1
+V  
V
GND  
IN  
OUT  
architecture of the AD680 enables the reference to be operated  
at a very low quiescent current while still realizing excellent dc  
characteristics and noise performance. Trimming of the high  
stability thin-film resistors is performed for initial accuracy and  
temperature coefficient, resulting in low errors over temperature.  
Figure 2. Connection Diagram TO-92  
PRODUCT HIGHLIGHTS  
1. High Accuracy.  
The AD680 band gap reference operates on a very low  
quiescent current which rivals that of many 2-terminal  
references. This makes the complete, higher accuracy AD680  
ideal for use in power-sensitive applications.  
The precision dc characteristics of the AD680 make it ideal for  
use as a reference for DACs that require an external precision  
reference. The device is also ideal for ADCs and, in general, can  
offer better performance than the standard on-chip references.  
Based upon its low quiescent current, which rivals that of many  
incomplete 2-terminal references, the AD680 is recommended  
for low power applications, such as hand-held, battery-operated  
equipment.  
2. Low Errors.  
Laser trimming of both initial accuracy and temperature coef-  
ficients results in low errors over temperature without the use  
of external components. The AD680AN and AD680AR have  
a maximum variation of 6.25 mV between −40°C and +85°C.  
A temperature output pin is provided on the 8-lead package  
versions of the AD680. The temperature output pin provides an  
output voltage that varies linearly with temperature and allows  
the AD680 to be configured as a temperature transducer while  
providing a stable 2.5 V output.  
3. Low Noise.  
The AD680 noise is low, typically 8 μV p-p from 0.1 Hz to  
10 Hz. Spectral density is also low, typically 250 nV/√Hz.  
4. Temperature Transducer.  
The AD680 is available in five grades. The AD680AN is speci-  
fied for operation from −40°C to +85°C, while the AD680JN is  
specified for 0°C to 70°C operation. Both the AD680AN and  
AD680JN are available in 8-lead PDIP packages. The AD680AR  
is specified for operation from −40°C to +85°C, while the  
AD680JR is specified for 0°C to 70°C operation. Both are  
available in 8-lead SOIC packages. The AD680JT is specified for  
0°C to 70°C operation and is available in a 3-pin TO-92  
package.  
The temperature output pin on the 8-lead package versions  
enables the AD680 to be configured as a temperature  
transducer.  
5. Low Cost.  
PDIP packaging provides machine insertability, while SOIC  
packaging provides surface-mount capability. TO-92  
packaging offers a cost-effective alternative to 2-terminal  
references, offering a complete solution in the same package  
in which 2-terminal references are usually found.  
Rev. H  
Information furnished by Analog Devices is believed to be accurate and reliable.  
However, no responsibility is assumed by Analog Devices for its use, nor for any  
infringements of patents or other rights of third parties that may result from its use.  
Specifications subject to change without notice. No license is granted by implication  
or otherwise under any patent or patent rights of Analog Devices. Trademarks and  
registered trademarks are the property of their respective owners.  
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.  
Tel: 781.329.4700  
Fax: 781.461.3113  
www.analog.com  
©2005 Analog Devices, Inc. All rights reserved.  
 
AD680* PRODUCT PAGE QUICK LINKS  
Last Content Update: 02/23/2017  
COMPARABLE PARTS  
View a parametric search of comparable parts.  
DESIGN RESOURCES  
AD680 Material Declaration  
PCN-PDN Information  
Quality And Reliability  
Symbols and Footprints  
DOCUMENTATION  
Application Notes  
AN-713: The Effect of Long-Term Drift on Voltage  
References  
DISCUSSIONS  
View all AD680 EngineerZone Discussions.  
Data Sheet  
AD680: Bandgap, Low Power 2.5 V Reference Data Sheet  
SAMPLE AND BUY  
Visit the product page to see pricing options.  
TOOLS AND SIMULATIONS  
AD680 SPICE Macro-Model  
AD680A SPICE Macro-Model  
AD680J SPICE Macro-Model  
AD680JT SPICE Macro-Model  
TECHNICAL SUPPORT  
Submit a technical question or find your regional support  
number.  
DOCUMENT FEEDBACK  
Submit feedback for this data sheet.  
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trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.  
AD680  
TABLE OF CONTENTS  
Specifications..................................................................................... 3  
Load Regulation ............................................................................8  
Temperature Performance............................................................8  
Temperature Output Pin ..............................................................9  
Differential Temperature Transducer.........................................9  
Low Power, Low Voltage Reference for Data Converters ........9  
4.5 V Reference from a 5 V Supply .......................................... 10  
Voltage Regulator for Portable Equipment............................. 10  
Outline Dimensions....................................................................... 11  
Ordering Guide .......................................................................... 12  
Absolute Maximum Ratings............................................................ 4  
Output Protection ........................................................................ 4  
ESD Caution.................................................................................. 4  
Pin Configuration and Connection Diagram............................... 5  
Theory of Operation ........................................................................ 6  
Applying the AD680 .................................................................... 6  
Noise Performance ....................................................................... 6  
Turn-on Time................................................................................ 7  
Dynamic Performance................................................................. 7  
REVISION HISTORY  
8/05—Rev. G to Rev. H  
Changes to Ordering Guide ..........................................................11  
12/04—Rev. F to Rev. G  
Updated Format ................................................................. Universal  
Changes to Ordering Guide ..........................................................11  
5/04—Rev. E to Rev. F  
Changes to ORDERING GUIDE ...................................................3  
5/03—Rev. D to Rev. E  
Changes to ORDERING GUIDE ...................................................3  
Added ESD Caution ..........................................................................3  
Changes to Figure 20.........................................................................7  
Updated OUTLINE DIMENSIONS ...............................................8  
7/01—Rev. C to Rev. D  
Changes to SPECIFICATIONS........................................................2  
Changes to ORDERING GUIDE ....................................................3  
Table I added ......................................................................................6  
Rev. H | Page 2 of 12  
AD680  
SPECIFICATIONS  
TA = 25°C, VIN = 5 V, unless otherwise noted. Specifications in boldface are tested on all production units at final electrical test. Results  
from these tests are used to calculate outgoing quality levels. All minimum and maximum specifications are guaranteed.  
Table 1.  
AD680AN/AD680AR  
Min Typ Max  
AD680JN/AD680JR  
Min Typ Max  
AD680JT  
Typ  
Parameter  
Min  
Max  
Unit  
OUTPUT VOLTAGE  
Output Voltage, VO  
Initial Accuracy, VOERR  
2.495 2.500 2.505  
2.490 2.500 2.510  
−10 +10  
2.490 2.500 2.510  
V
mV  
%
−5  
+5  
−10  
+10  
−0.20  
+0.20 −0.40  
+0.40 −0.40  
+0.40  
OUTPUT VOLTAGE DRIFT1  
0°C to 70°C  
−40°C to +85°C  
10  
10  
25  
25  
10  
25  
30  
ppm/°C  
ppm/°C  
20  
LINE REGULATION  
4.5 V ≤ +VIN ≤ 15 V  
40  
40  
40  
40  
40  
40  
40  
40  
40  
40  
40  
40  
μV/V  
μV/V  
μV/V  
μV/V  
(@ TMIN to TMAX  
15 V ≤ +VIN ≤ 36 V  
(@ TMIN to TMAX  
)
)
LOAD REGULATION  
0 < IOUT < 10 mA  
80  
80  
100  
100  
250  
280  
1.25  
80  
80  
100  
100  
250  
280  
1.25  
80  
80  
100  
100  
250  
280  
1.25  
μV/mA  
μV/mA  
μA  
(@ TMIN to TMAX  
QUIESCENT CURRENT  
(@ TMIN to TMAX  
)
195  
195  
195  
)
μA  
POWER DISSIPATION  
OUTPUT NOISE  
1
1
1
mW  
0.1 Hz to 10 Hz  
Spectral Density, 100 Hz  
CAPACITIVE LOAD  
8
250  
10  
50  
50  
8
250  
10  
8
250  
10  
50  
50  
μV p-p  
nV/√Hz  
nF  
50  
LONG-TERM STABILITY  
SHORT-CIRCUIT CURRENT TO GROUND  
TEMPERATURE PIN  
25  
25  
25  
25  
25  
25  
ppm/1,000 hr  
mA  
50  
Voltage Output @ 25°C  
Temperature Sensitivity  
Output Current  
540  
−5  
596  
2
660  
+5  
540  
−5  
596  
2
660  
+5  
mV  
mV/°C  
μA  
Output Resistance  
12  
12  
kΩ  
TEMPERATURE RANGE  
Specified Performance  
Operating Performance2  
−40  
−40  
+85  
+85  
0
−40  
70  
+85  
0
−40  
70  
+85  
°C  
°C  
1 Maximum output voltage drift is guaranteed for all packages.  
2 The operating temperature range is defined as the temperature extremes at which the device will still function. Parts may deviate from their specified performance  
outside their specified temperature range.  
Rev. H | Page 3 of 12  
 
AD680  
ABSOLUTE MAXIMUM RATINGS  
Table 2.  
Parameter  
Stresses above those listed under Absolute Maximum Ratings  
may cause permanent damage to the device. This is a stress  
rating only; functional operation of the device at these or any  
other conditions above those indicated in the operational  
section of this specification is not implied. Exposure to absolute  
maximum rating conditions for extended periods may affect  
device reliability.  
Rating  
VIN to Ground  
36 V  
Power Dissipation (25°C)  
Storage Temperature  
Lead Temperature (Soldering, 10 sec)  
500 mW  
−65°C to +125°C  
300°C  
Package Thermal Resistance θJA (All Packages) 120°C/W  
OUTPUT PROTECTION  
Output safe for indefinite short to GND and momentary short  
to −VIN.  
ESD CAUTION  
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on  
the human body and test equipment and can discharge without detection. Although this product features  
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy  
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance  
degradation or loss of functionality.  
Rev. H | Page 4 of 12  
 
AD680  
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS  
TP*  
1
2
3
4
8
7
6
5
TP*  
TP*  
V
+V  
IN  
AD680  
TEMP  
TOP VIEW  
OUT  
(Not to Scale)  
GND  
NC  
NC = NO CONNECT  
*TP DENOTES FACTORY TEST POINT.  
NO CONNECTIONS SHOULD BE MADE  
TO THESE PINS.  
Figure 3. 8-Lead PDIP and 8-Lead SOIC Pin Configuration  
AD680  
BOTTOM VIEW  
(Not to Scale)  
3
2
1
+V  
V
GND  
IN  
OUT  
Figure 4. Connection Diagram  
Table 3. Pin Function Descriptions  
Pin No.  
Mnemonic  
Descriptions  
1, 7, 8  
TP  
Test Point. A factory test point. No connections are made to these pins.  
2
3
4
5
6
+VIN  
Input Voltage.  
Temperature Output.  
Ground.  
No Connect.  
Output Voltage.  
TEMP  
GND  
NC  
VOUT  
Rev. H | Page 5 of 12  
 
AD680  
THEORY OF OPERATION  
Band gap references are the high performance solution for low  
supply voltage operation. A typical precision band gap consists  
of a reference core and buffer amplifier. Based on a new, pat-  
ented band gap reference design (Figure 5), the AD680 merges  
the amplifier and the core band gap function to produce a  
compact, complete precision reference.  
Reference outputs are frequently required to handle fast  
transients caused by input switching networks, commonly  
found in ADCs and measurement instrumentation equipment.  
Many of the dynamic problems associated with this situation  
can be minimized with a few simple techniques. Using a series  
resistor between the reference output and the load tends to  
“decouple” the reference output from the transient source, or a  
relatively large capacitor connected from the reference output to  
ground can serve as a charge storage element to absorb and  
deliver charge as required by the dynamic load. A 50 nF capaci-  
tor is recommended for the AD680 in this case; this is large  
enough to store the required charge, but small enough not to  
disrupt the stability of the reference.  
Central to the device is a high gain amplifier with an intentionally  
large proportional to absolute temperature (PTAT) input offset.  
This offset is controlled by the area ratio of the amplifier input  
pair, Q1 and Q2, and is developed across Resistor R1. Transistor  
Q12s base emitter voltage has a complementary to absolute  
temperature (CTAT) characteristic. Resistor R2 and the parallel  
combination of Resistor R3 and Resistor R4 “multiply” the PTAT  
voltage across the R1 resistor. Trimming the R3 and R4 resistors  
to the proper ratio produces a temperature invariant of 2.5 V at  
the output. The result is an accurate, stable output voltage  
accomplished with a minimum number of components.  
The 8-lead PDIP and 8-lead SOIC packaged versions of the  
AD680 also provide a temperature output pin. The voltage on  
this pin is nominally 596 mV at 25°C. This pin provides an  
output linearly proportional to temperature with a  
characteristic of 2 mV/°C.  
+V  
IN  
NOISE PERFORMANCE  
Q9  
Q8  
The noise generated by the AD680 is typically less than 8 μV p-p  
over the 0.1 Hz to 10 Hz band. Figure 6 shows the 0.1 Hz to 10 Hz  
noise of a typical AD680. The noise measurement is made with a  
band-pass filter made of a 1-pole high-pass filter, with a corner  
frequency at 0.1 Hz, and a 2-pole low-pass filter, with a corner  
frequency at 12.6 Hz, to create a filter with a 9.922 Hz bandwidth.  
Q11  
Q3  
Q2  
Q4  
V
OUT  
Q5  
Q1  
1
×
R1  
R2  
R3  
R4  
8
×
C1  
1s  
Q10  
R5  
Q12  
100  
90  
R6  
R7  
Q6  
Q7  
TEMP  
GND  
5μV  
Figure 5. Schematic Diagram  
APPLYING THE AD680  
The AD680 is simple to use in virtually all precision reference  
applications. When power is applied to +VIN and the GND pin  
is tied to ground, VOUT provides a 2.5 V output. The AD680  
typically requires less than 250 μA of current when operating  
from a supply of 4.5 V to 36 V.  
10  
0%  
Figure 6. 0.1 Hz to 10 Hz Noise  
To operate the AD680, the +VIN pin must be bypassed to the  
GND pin with a 0.1 μF capacitor tied as close to the AD680 as  
possible. Although the ground current for the AD680 is small,  
typically 195 μA, a direct connection should be made between  
the AD680 GND pin and the system ground plane.  
Noise in a 300 kHz bandwidth is approximately 800 μV p-p.  
Figure 7 shows the broadband noise of a typical AD680.  
Rev. H | Page 6 of 12  
 
 
 
AD680  
In some applications, a varying load may be both resistive and  
capacitive in nature, or the load may be connected to the  
AD680 by a long capacitive cable.  
500μV  
50μs  
100  
90  
+V  
IN  
500μV  
V
OUT  
0.1μF  
V
AD680  
OUT  
249Ω  
10  
V
OUT  
0V  
V
L
0%  
Figure 9. Transient Load Test Circuit  
Figure 7. Broadband Noise at 300 kHz  
TURN-ON TIME  
2V  
50mV  
5μs  
100  
90  
Upon application of power (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  
normally associated with this are the time for the active circuits  
to settle, and the time for the thermal gradients on the chip to  
stabilize. The turn-on settling time of the AD680 is about 20 μs  
to within 0.025% of its final value, as shown in Figure 8.  
V
L
V
OUT  
10  
5V  
1mV  
10μs  
0%  
100  
90  
V
IN  
Figure 10. Large Scale Transient Response  
V
OUT  
2V  
5mV  
5μs  
10  
100  
90  
V
IN  
0%  
V
Figure 8. Turn-On Settling Time  
OUT  
The AD680 thermal settling characteristic benefits from its  
compact design. Once initial turn-on is achieved, the output  
linearly approaches its final value; the output is typically within  
0.01% of its final value after 25 ms.  
10  
0%  
DYNAMIC PERFORMANCE  
The output stage of the amplifier is designed to provide the  
AD680 with static and dynamic load regulation superior to  
less complete references. Figure 9 to Figure 11 display the char-  
acteristics of the AD680 output amplifier driving a 0 mA to  
10 mA load. Longer settling times result if the reference is  
forced to sink any transient current.  
Figure 11. Fine Scale Settling for Transient Load  
Rev. H | Page 7 of 12  
 
 
 
 
 
AD680  
+V  
IN  
TEMPERATURE PERFORMANCE  
The AD680 is designed for reference applications where tem-  
perature performance is important. Extensive temperature  
testing and characterization ensure that the devices performance  
is maintained over the specified temperature range.  
V
OUT  
0.1μF  
V
AD680  
OUT  
C
L
1000pF  
249Ω  
V
OUT  
0V  
V
L
Some confusion exists in the area of defining and specifying  
reference voltage error over temperature. Historically, references  
have been characterized using a maximum deviation per degree  
centigrade, that is, ppm/°C. However, because of nonlinearities  
in temperature characteristics that originated in standard Zener  
references (such as “S” type characteristics), most manufac-  
turers now use a maximum limit error band approach to specify  
devices. This technique involves measuring the output at three  
or more different temperatures to specify an output voltage  
error band.  
Figure 12. Capacitive Load Transient Response Test Circuit  
Figure 13 displays the output amplifier characteristics driving a  
1,000 pF, 0 mA to 10 mA load.  
2V  
5mV  
5μs  
100  
90  
V
L
2.501  
2.500  
2.499  
2.498  
SLOPE = TC  
V
– V  
MIN  
MAX  
– T  
=
=
V
–6  
× 10  
OUT  
(T  
) ×  
2.5V  
2.501 – 2.498  
(85°C – (–40°C)) 2.5V  
MAX  
MIN  
–6  
× 10  
×
= 9.6ppm/°C  
10  
0%  
Figure 13. Output Response with Capacitive Load  
–50 –30 –10 0  
20  
40  
60 80  
100  
TEMPERATURE (°C)  
LOAD REGULATION  
Figure 15. Typical AD680AN/AD680AR Temperature Drift  
Figure 14 depicts the load regulation characteristics of  
the AD680.  
Figure 15 shows a typical output voltage drift for the AD680AN/  
AD680AR and illustrates the test methodology. The box in  
Figure 15 is bounded on the left and right sides by the operat-  
ing temperature extremes, and on the top and bottom by the  
maximum and minimum output voltages measured over the  
operating temperature range.  
1V  
1mV  
100μs  
100  
90  
V
L
The maximum height of the box for the appropriate temperature  
range and device grade is shown in Table 4. Duplication of these  
results requires a combination of high accuracy and stable tem-  
perature control in a test system. Evaluation of the AD680 will  
produce a curve similar to that in Figure 15, but output readings  
could vary depending upon the test equipment used.  
V
OUT  
10  
0%  
Table 4. Maximum Output Change in mV  
Figure 14. Typical Load Regulation Characteristics  
Maximum Output Change (mV)  
Device Grade  
AD680JN/AD680JR  
AD680JT  
0°C to 70°C  
4.375  
5.250  
−40°C to +85°C  
Not applicable  
Not applicable  
6.250  
AD680AN  
Not applicable  
Rev. H | Page 8 of 12  
 
 
 
 
 
AD680  
LOW POWER, LOW VOLTAGE REFERENCE FOR  
DATA CONVERTERS  
TEMPERATURE OUTPUT PIN  
The 8-lead package versions of the AD680 provide a tempera-  
ture output pin on Pin 3 of each device. The output of Pin 3  
(TEMP) is a voltage that varies linearly with temperature. VTEMP  
at 25°C is 596 mV, and the temperature coefficient is 2 mV/°C.  
Figure 16 shows the output of this pin over temperature.  
The AD680 has a number of features that make it ideally suited  
for use with ADCs and DACs. The low supply voltage required  
makes it possible to use the AD680 with todays converters that  
run on 5 V supplies without having to add a higher supply  
voltage for the reference. The low quiescent current (195 μA),  
combined with the completeness and accuracy of the AD680,  
make it ideal for low power applications, such as hand-held,  
battery-operated meters.  
The temperature pin has an output resistance of 12 kΩ and is  
capable of sinking or sourcing currents of up to 5 μA without  
disturbing the reference output. This enables the TEMP pin to  
be buffered by many inexpensive operational amplifiers that  
have bias currents below this value.  
The AD7701 is an ADC that is well-suited for the AD680.  
Figure 18 shows the AD680 used as the reference for this  
converter. The AD7701 is a 16-bit ADC with on-chip digital  
filtering intended for the measurement of wide dynamic range  
and low frequency signals, such as those representing chemical,  
physical, or biological processes. It contains a charge balancing  
(Σ–Δ) ADC, a calibration microcontroller with on-chip static  
RAM, a clock oscillator, and a serial communications port.  
760  
720  
680  
640  
600  
560  
520  
480  
440  
This entire circuit runs on 5 V supplies. The power dissipation  
of the AD7701 is typically 25 mW and, when combined with  
the power dissipation of the AD680 (1 mW), the entire circuit  
consumes just 26 mW of power.  
+5V  
ANALOG  
SUPPLY  
–50 –40 –30 –20 –10  
0
10 20 30 40 50 60 70 80 90  
0.1μF  
10μF  
TEMPERATURE (°C)  
AD7701  
AV  
V
DD  
Figure 16. TEMP Pin Transfer Characteristics  
DV  
DD  
V
IN  
0.1μF  
SLEEP  
MODE  
DIFFERENTIAL TEMPERATURE TRANSDUCER  
V
OUT  
REF  
0.1μF  
Figure 17 shows a differential temperature transducer that can  
be used to measure temperature changes in the environment of  
the AD680. This circuit operates from a 5 V supply. The  
temperature-dependent voltage from the TEMP pin of the  
AD680 is amplified by a factor of 5 to provide wider full-scale  
range and more current sourcing capability. An exact gain of 5  
can be achieved by adjusting the trim potentiometer until the  
output varies by 10 mV/°C. To minimize resistance changes  
with temperature, use resistors with low temperature  
coefficients, such as metal film resistors.  
AD680  
DATA READY  
DRDY  
CS  
GND  
READ (TRANSMIT)  
SERIAL CLOCK  
SERIAL DATA  
SCLK  
RANGE  
SELECT  
SDATA  
BP/UP  
CAL  
CLKIN  
CALIBRATE  
ANALOG  
INPUT  
CLKOUT  
SC1  
A
IN  
ANALOG  
GND  
AGND  
SC2  
0.1μF  
DGND  
0.1μF  
DV  
SS  
AV  
SS  
5V  
–5V  
ANALOG  
SUPPLY  
2
5V  
0.1μF  
10μF  
V
IN  
7
3
TEMP  
3
2
+
0.1μF  
Δ
V
Δ
OUT  
T
= 10mV/°C  
6
Figure 18. Low Power, Low Voltage Supply Reference  
for the AD7701 16-Bit ADC  
OP90  
AD680  
4
GND  
4
R
B
R
F
1.69kΩ  
1%  
6.98kΩ  
1%  
R
BP  
100Ω  
Figure 17. Differential Temperature Transducer  
Rev. H | Page 9 of 12  
 
 
 
 
AD680  
4.5 V REFERENCE FROM A 5 V SUPPLY  
VOLTAGE REGULATOR FOR PORTABLE  
EQUIPMENT  
The AD680 can be used to provide a low power, 4.5 V reference,  
as shown in Figure 19. In addition to the AD680, the circuit  
uses a low power op amp and a transistor in a feedback con-  
figuration that provides a regulated 4.5 V output for a power  
supply voltage as low as 4.7 V. The high quality tantalum 10 μF  
capacitor (C1) in parallel with the ceramic 0.1 μF capacitor (C2)  
and the 3.9 Ω resistor (R5) ensure a low output impedance up to  
approximately 50 MHz (see Figure 19).  
The AD680 is ideal for providing a stable, low cost, low power  
reference voltage in portable equipment power supplies.  
Figure 20 shows how the AD680 can be used in a voltage  
regulator that not only has low output noise (as compared to a  
switch mode design) and low power, but it also has a very fast  
recovery after current surges. Some caution should be taken in  
the selection of the output capacitors. Too high an ESR (effective  
series resistance) could endanger the stability of the circuit. A solid  
tantalum capacitor, 16 V or higher, and an aluminum electro-  
lytic capacitor, 10 V or higher, are recommended for C1 and C2,  
respectively. Also, the path from the ground side of C1 and C2  
to the ground side of R1 should be kept as short as possible.  
4.7V TO 15V  
R3  
1kΩ  
CC  
3.3μF  
2N2907A  
V
IN  
+IN  
–IN  
V+  
6
7
V
3
2
OUT  
0.1μF  
OUT  
OP90  
AD680  
+
C1  
10μF  
C2  
0.1μF  
R4  
3.57kΩ  
4
GND  
CHARGER  
INPUT  
V–  
CF  
0.1μF  
R5  
3.9Ω  
0.1μF  
R3  
510kΩ  
2
R2  
6V  
LEAD-ACID  
BATTERY  
+
R1  
V
IN  
2.5kΩ  
2kΩ  
V
6
3
2
3
7
OUT  
1%  
1%  
6
AD680  
TEMP  
GND  
4
IRF9530  
OP777  
Figure 19. 4.5 V Reference Running from a Single 5 V Supply  
4
+
R2  
402kΩ 1%  
C1  
+
C2  
1000μF  
ELECT  
R1  
402kΩ 1%  
+
68μF  
TANT  
Figure 20. Voltage Regulator for Portable Equipment  
Rev. H | Page 10 of 12  
 
 
 
AD680  
OUTLINE DIMENSIONS  
0.400 (10.16)  
0.365 (9.27)  
0.355 (9.02)  
8
5
4
0.280 (7.11)  
0.250 (6.35)  
0.240 (6.10)  
1
5.00 (0.1968)  
4.80 (0.1890)  
0.325 (8.26)  
0.310 (7.87)  
0.300 (7.62)  
PIN 1  
0.100 (2.54)  
BSC  
8
1
5
4
0.060 (1.52)  
MAX  
0.195 (4.95)  
0.130 (3.30)  
0.115 (2.92)  
6.20 (0.2440)  
5.80 (0.2284)  
4.00 (0.1574)  
3.80 (0.1497)  
0.210  
(5.33)  
MAX  
0.015  
(0.38)  
MIN  
0.150 (3.81)  
0.130 (3.30)  
0.115 (2.92)  
0.015 (0.38)  
GAUGE  
0.014 (0.36)  
0.010 (0.25)  
0.008 (0.20)  
PLANE  
1.27 (0.0500)  
BSC  
0.50 (0.0196)  
0.25 (0.0099)  
SEATING  
PLANE  
× 45°  
1.75 (0.0688)  
1.35 (0.0532)  
0.25 (0.0098)  
0.10 (0.0040)  
0.022 (0.56)  
0.018 (0.46)  
0.014 (0.36)  
0.430 (10.92)  
MAX  
0.005 (0.13)  
MIN  
8°  
0.51 (0.0201)  
0.31 (0.0122)  
0° 1.27 (0.0500)  
COPLANARITY  
0.10  
0.25 (0.0098)  
0.17 (0.0067)  
SEATING  
PLANE  
0.070 (1.78)  
0.060 (1.52)  
0.045 (1.14)  
0.40 (0.0157)  
COMPLIANT TO JEDEC STANDARDS MS-012AA  
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS  
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR  
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN  
COMPLIANT TO JEDEC STANDARDS MS-001-BA  
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS  
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR  
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.  
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.  
Figure 21. 8-Lead Standard Small Outline Package [SOIC]  
Narrow Body  
(R-8)  
Figure 22. 8-Lead Plastic Dual In-Line Package [PDIP]  
Dimensions show in millimeters and (inches)  
Narrow Body  
(N-8)  
Dimensions shown in inches and (millimeters)  
0.210 (5.33)  
0.165 (4.19)  
0.125 (3.18)  
0.170 (4.32)  
0.050 (1.27)  
MAX  
0.205 (5.21)  
0.175 (4.45)  
0.019 (0.482)  
0.016 (0.407)  
0.055 (1.40)  
0.045 (1.15)  
SQ  
3
2
1
0.105 (2.66)  
0.095 (2.42)  
0.135 (3.43)  
MIN  
0.500 (12.70) MIN  
0.115 (2.92)  
0.080 (2.03)  
0.115 (2.92)  
0.080 (2.03)  
SEATING  
PLANE  
BOTTOM VIEW  
COMPLIANT TO JEDEC STANDARDS TO-226AA  
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS  
(IN PARENTHESES) ARE ROUNDED-OFF EQUIVALENTS FOR  
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN  
Figure 23. 3-Pin Plastic Header-Style Package [TO-92]  
(T-3)  
Dimensions shown in inches and (millimeters)  
Rev. H | Page 11 of 12  
 
AD680  
ORDERING GUIDE  
Initial  
Accuracy  
Output  
Voltage  
VO (V)  
Temperature  
Coefficient  
(ppm/°C)  
Package  
Description Package Option  
Parts per Temperature Range  
Model  
Reel  
(°C)  
(mV) (%)  
AD680AR  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
2.5  
5
5
5
5
0.20 20  
0.20 20  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
PDIP  
PDIP  
PDIP  
PDIP  
TO-92  
TO-92  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
N-8  
N-8  
N-8  
N-8  
T-3  
T-3  
−40 to +85  
−40 to +85  
−40 to +85  
−40 to +85  
−40 to +85  
0 to 70  
0 to 70  
0 to 70  
0 to 70  
−40 to +85  
−40 to +85  
0 to 70  
0 to 70  
0 to 70  
AD680AR-REEL  
AD680AR-REEL7  
AD680ARZ1  
AD680ARZ-REEL71  
AD680JR  
AD680JR-REEL7  
AD680JRZ1  
AD680JRZ-REEL71  
AD680AN  
AD680ANZ1  
AD680JN  
AD680JNZ1  
AD680JT  
AD680JTZ1  
2,500  
1,000  
0.20 20  
0.20 20  
0.20 20  
0.40 25  
0.40 25  
0.40 25  
0.40 25  
0.20 20  
0.20 20  
0.40 25  
0.40 25  
0.40 30  
0.40 30  
5
1,000  
1,000  
1,000  
10  
10  
10  
10  
5
5
10  
10  
10  
10  
0 to 70  
1 Z = Pb-free part.  
©2005 Analog Devices, Inc. All rights reserved. Trademarks  
and registered trademarks are the property of their respective owners.  
C00813–0–8/05(H)  
Rev. H | Page 12 of 12  
 
 
 

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