Datasheet REF01, REF02, REF03 (Analog Devices) - 16

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REF01/REF02/REF03 Data Sheet APPLICATIONS INFORMATION BASIC REFERENCE APPLICATION PRECISION CURRENT SOURCE WITH ADJUSTABLE
Figure 38 shows the basic configuration for any
OUTPUT
REF01/REF02/REF03 device. Input and output capacitance A higher-precision current source can be implemented with the values can be tailored for performance, provided they fol ow the circuit shown in Figure 40. guidelines described
U1
in the Input and Output Capacitors section.
REF02 U1 0V TO (5V + VL) +12V VIN VOUT REF01/ B REF02/ AD5201 W TEMP TRIM REF03 GND 100kΩA VIN VIN VOUT VO +12V R C1 C2 SET 1kΩ 0.1µF TEMP TRIM 0.1µF U2 GND
038
V+ OP1177
00375-
–5V TO V V– V
Figure 38. Basic Reference Application
L L R
041
LOW COST CURRENT SOURCE L 1kΩ –12V IL
00375- Unlike most references, the quiescent current of the Figure 40. Programmable 0 mA to 5 mA Current Source REF01/REF02/REF03 series remains constant with respect to By adding a mechanical or digital potentiometer, this circuit the load current (refer to Figure 22). As a result, a simple, low becomes an adjustable current source. If a digital potentiometer cost current source can be constructed by configuring the is used, the load current is simply the voltage across terminal B reference as shown in Figure 39. to terminal W of the digital potentiometer divided by the value
VIN
of the resistor RSET.
IIN
V × D
REF01/
REF I = [ L A]
REF02/ VOUT
RSET
REF03 R
where D is the decimal equivalent of the digital potentiometer
SET ISET = (VOUT – VL)/RSET
input code.
GND
A dual-supply op amp should be used since the ground
VL I
potential of REF02 can swing from −5.0 V to VL while the
Q ≈ 0.6mA
potentiometer is swung from zero-scale to ful -scale.
R I L L = ISET + IQ
040
PRECISION BOOSTED OUTPUT REGULATOR
00375- The output current sourcing capability of the Figure 39. Simple Current Source REF01/REF02/REF03 series can be boosted by using an In this configuration, the current through the resistor RSET (ISET) external op amp and MOSFET, as shown in Figure 41. is equal to (VOUT − VL)/RSET. IL is simply the sum of ISET and IQ.
N1
However, since IQ typical y varies from 0.55 mA to 0.65 mA,
V
this circuit should be limited to low precision, general-purpose
IN VO U1 RL CL 2N7002
applications.
200Ω 1µF REF01/ 15V REF02/ REF03 R1 R2 100Ω 100Ω VIN VOUT V+ OP1177 TEMP TRIM V– GND U2 C1
042
1000pF
00375- Figure 41. Precision Boosted Output Regulator In this circuit, U2 forces VO to VREF by regulating the current through N1, thereby sourcing the load current directly from the input voltage source connected at V IN. Using the components shown, this circuit can source up to 50 mA with an input volt- age of 15.0 V. The circuit’s current sourcing capability can be further increased by replacing N1 with a higher-power MOSFET. Rev. M | Page 16 of 20 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION PIN CONFIGURATIONS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS REF01 SPECIFICATIONS REF02 SPECIFICATIONS REF03 SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION INPUT AND OUTPUT CAPACITORS OUTPUT ADJUSTMENT TEMPERATURE MONITORING LONG-TERM STABILITY BURN-IN POWER DISSIPATION APPLICATIONS INFORMATION BASIC REFERENCE APPLICATION LOW COST CURRENT SOURCE PRECISION CURRENT SOURCE WITH ADJUSTABLE OUTPUT PRECISION BOOSTED OUTPUT REGULATOR BIPOLAR VOLTAGE REFERENCE ADJUSTABLE REFERENCE WITH POSITIVE AND NEGATIVE SWING OUTLINE DIMENSIONS REF01 ORDERING GUIDE REF02 ORDERING GUIDE REF03 ORDERING GUIDE