Datasheet AD584 (Analog Devices) - 8

link to page 8 link to page 8 link to page 8 link to page 8 link to page 8
AD584 Data Sheet NOISE FILTERING USING THE STROBE TERMINAL
The bandwidth of the output amplifier in the AD584 can be The AD584 has a strobe input that can be used to zero the output. reduced to filter output noise. A capacitor ranging between 0.01 µF This unique feature permits a variety of new applications in and 0.1 µF connected between the CAP and VBG terminals further signal and power conditioning circuits. reduces the wideband and feedthrough noise in the output of Figure 11 il ustrates the strobe connection. A simple NPN switch the AD584, as shown in Figure 9 and Figure 10. However, this can be used to translate a TTL logic signal into a strobe of the tends to increase the turn-on settling time of the device; therefore, output. The AD584 operates normally when there is no current allow for ample warm-up time. drawn from Pin 5. Bringing this terminal low, to less than 200 mV,
SUPPLY
allows the output voltage to go to zero. In this mode, the AD584
V+
is not required to source or sink current (unless a 0.7 V residual
8 CAP
output is permissible). If the AD584 is required to sink a transient
7 1 10.0V 0.01µF*
current while strobe is off, limit the strobe terminal input current
TO AD584 0.1µF V
by a 100 Ω resistor, as shown in Figure 11.
BG 6 4 V+ 8 STROBE 10.0V COMMON 5 1
010
100Ω *INCREASES TURN-ON TIME 2
00527-
AD584
Figure 9. Additional Noise Filtering with an External Capacitor
3 HI = OFF 20kΩ 1000 LOGIC 4 2N2222 NOISE SPECTRAL DENSITY (nV/ Hz) INPUT LO = ON 10kΩ
012
COMMON 100pF
00527-
NO CAP
Figure 11. Use of the Strobe Terminal
1000pF 100
The strobe terminal tolerates up to 5 µA leakage, and its driver
0.01µF
should be capable of sinking 500 µA continuous. A low leakage, open collector gate can be used to drive the strobe terminal directly,
NO CAP
provided the gate can withstand the AD584 output voltage plus 1 V.
TOTAL NOISE (µV rms) UP TO 10 SPECIFIED FREQUENCY PERCISION HIGH CURRENT SUPPLY
The AD584 can be easily connected to a power PNP or power PNP Darlington device to provide much greater output current
1
capability. The circuit shown in Figure 12 delivers a precision 1 1
10 100 1k 10k 100k 1M
0 10 V output with up to 4 A supplied to the load. If the load has a
FREQUENCY (Hz)
00527- significant capacitive component, the 0.1 µF capacitor is required. Figure 10. Spectral Noise Density and Total RMS Noise vs. Frequency If the load is purely resistive, improved high frequency, supply rejection results from removing the capacitor.
VIN ≥ 15V 470Ω 2N6040 0.1µF V+ 8 10.0V AD584 V 1 OUT 10V @ 4A 4
013
COMMON
00527- Figure 12. High Current Precision Supply Rev. C | Page 8 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