Datasheet AD584 (Analog Devices) - 9

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Data Sheet AD584
The AD584 can also use an NPN or NPN Darlington transistor to The temperature characteristics and long-term stability of the boost its output current. Simply connect the 10 V output terminal device is essentially the same as that of a unit used in standard of the AD584 to the base of the NPN booster and take the 3-terminal mode. output from the booster emitter, as shown in Figure 13. The
ANALOG
5.0V pin or the 2.5V pin must connect to the actual output in
GND V+ 8
this configuration. Variable or adjustable outputs (as shown in
VOUT 1µF 1
Figure 3 and Figure 4) can be combined with a 5.0 V connection to
2
obtain outputs above 5.0 V.
AD584 5.0V TAP RAW SUPPLY (≈5V > VOUT) 4 COMMON VREF DARLINGTON –5V R NPN 2N6057 S 2.4kΩ 5%
016
–15V V+
00527-
8
Figure 15. 2-Terminal, −5 V Reference
10.0V 1 V 5.0V OUT 2 (5V, 12A
The AD584 can also be used in 2-terminal mode to develop a
AD584 AS SHOWN) 2.5V
positive reference. VIN and VOUT are tied together and to the
3
positive supply through an appropriate supply resistor. The
1kΩ 4
014
COMMON
performance characteristics are similar to those of a negative 00527- 2-terminal connection. The only advantage of this connection Figure 13. NPN Output Current Booster over the standard 3-terminal connection is that a lower primary
THE AD584 AS A CURRENT LIMITER
supply can be used, as low as 0.5 V above the desired output The AD584 represents an alternative to current limiter diodes voltage. This type of operation requires considerable attention that require factory selection to achieve a desired current. Use of to load and to the primary supply regulation to ensure that the current limiting diodes often results in temperature coefficients AD584 always remains within its regulating range of 1 mA to of 1%/°C. Use of the AD584 in this mode is not limited to a set 5 mA (2 mA to 5 mA for operation beyond 85°C). current limit; it can be programmed from 0.75 mA to 5 mA
10 V REFERENCE WITH MULTIPLYING CMOS DACs
with the insertion of a single external resistor (see Figure 14).
OR ADCs
The minimum voltage required to drive the connection is 5 V. The AD584 is ideal for application with the AD7533 10-bit
V+
multiplying CMOS DAC, especially for low power applications.
8 VOUT = 2.5V
It is equally suitable for the AD7574 8-bit ADC. In the standard
1
hook-up, as shown in Figure 16, the standard output voltages are
AD584 3 2.5V 2.5V = i + 0.75mA
inverted by the amplifier/DAC configuration to produce converted
R TAP
voltage ranges. For example, a +10 V reference produces a 0 V to
R 4 LOAD
−10 V range. If an OP1177 amplifier is used, total quiescent
COMMON
015 supply current is typical y 2 mA. 00527-
+15V
Figure 14. A Two-Component Precision Current Limiter
NEGATIVE REFERENCE VOLTAGES FROM AN AD584 V+ 8
The AD584 can also be used in a 2-terminal Zener mode to
10.0V AD584 1
provide a precision −10 V, −7.5 V, or −5.0 V reference. As shown in
4
Figure 15, the VIN and VOUT terminals are connected together to
COMMON
the positive supply (in this case, ground). The AD584 COMMON
VREF 15 14
pin is connected through a resistor to the negative supply. The
BIT 1 (MSB) RFB 4 16
output is now taken from the COMMON pin instead of V
DIGITAL
OUT. With
INPUT +15V 5
1 mA flowing through the AD584 in this mode, a typical unit
IOUT1 AD7533 1
shows a 2 mV increase in the output level over that produced in
VOUT IOUT2 0V TO –10V
3-terminal mode. Also, note that the effective output impedance in
13 2 BIT 10 (LSB) 3 –15V
017 this connection increases from 0.2 Ω typical to 2 Ω. It is essential
COMMON
00527- to arrange the output load and the supply resistor, R S, so that Figure 16. Low Power 10-Bit CMOS DAC Application the net current through the AD584 is always between 1 mA and 5 mA (between 2 mA and 5 mA for operation beyond 85°C). Rev. C | Page 9 of 12 Document Outline Features General Description Pin Configurations Product Highlights Table of Contents Revision History Specifications Absolute Maximum Ratings ESD Caution Theory of Operation Applying the AD584 Performance over Temperature Output Current Characteristics Dynamic Performance Noise Filtering Using the Strobe Terminal Percision High Current Supply The AD584 as a Current Limiter Negative Reference Voltages from an AD584 10 V Reference with Multiplying CMOS DACs or ADCs Precision DAC Reference Outline Dimensions Ordering Guide