Elantec EL4450 Wideband four-quadrant multiplier Datasheet

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Wideband Four-Quadrant Multiplier
Features
General Description
• Complete four-quadrant multiplier
with output amp—requires no
extra components
• Good linearity of 0.3%
• 90 MHz bandwidth for both X and
Y inputs
• Operates on ±5V to ±15V supplies
• All inputs are differential
• 400V/µs slew rate
The EL4450C is a complete four-quadrant multiplier circuit. It offers
wide bandwidth and good linearity while including a powerful output
voltage amplifier, drawing modest supply current.
EL4450C
EL4450C
The EL4450C operates on ±5V supplies and has an analog input range
of ±2V, making it ideal for video signal processing. AC characteristics
do not vary over the ±5V to ±15V supply range.
The multiplier has an operational temperature range of -40°C to
+85°C and are packaged in plastic 14-pin P-DIP and SO.
Applications
•
•
•
•
Modulation/Demodulation
RMS computation
Real-time power computation
Nonlinearity correction/generation
Ordering Information
Part No.
Temp. Range
Package
Outline #
EL4450CN
-40°C to +85°C
14-Pin P-DIP
MDP0031
EL4450CS
-40°C to +85°C
14-Lead SO
MDP0027
Connection Diagrams
January 1996 Rev B
© 1995 Elantec, Inc.
EL4450C
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Wideband Four-Quadrant Multiplier
Absolute Maximum Ratings (T
A
V+
VS
VIN
VIN
IIN
= 25 °C)
Positive Supply Voltage
V+ to V- Supply Voltage
Voltage at any Input or Feedback
Difference between Pairs of Inputs or Feedback
Current into any Input or Feedback Pin
16.5V
33V
V+ to V6V
4 mA
IOUT
PD
TA
TS
Output Current
Maximum Power Dissipation
Operating Temperature Range
Storage Temperature Range
30 mA
See Curves
-40°C to +85°C
-60°C to +150°C
Important Note:
All parameters having Min/Max specifications are guaranteed. The Test Level column indicates the specific device testing actually performed during
production and Quality inspection. Elantec performs most electrical tests using modern high-speed automatic test equipment, specifically the LTX77
Series system. Unless otherwise noted, all tests are pulsed tests, therefor TJ = TC = TA.
Test Level
Test Procedure
I
100% production tested and QA sample tested per QA test plan QCX0002.
II
100% production tested at TA = 25°C and QA sample tested at TA = 25°C, TMAX and TMIN per QA test plan QCX0002.
III
QA sample tested per QA test plan QCX0002.
IV
Parameter is guaranteed (but not tested) by Design and Characterization Data.
V
Parameter is typical value at TA = 25°C for information purposes only.
Open-Loop DC Electrical Characteristics
Power Supplies at ±5V, TA = 25°C, VFB = VOUT.
Parameter
VDIFF
Description
Differential Input Voltage—Clipping
Min
Typ
Test Level
Units
1.8
2.0
I
V
1.0
V
V
I
V
0.2% nonlinearity
VCM
Common-Mode Range of VDIFF = 0, VS = ±5V
±2.5
±2.8
VS = ±15V
±12.5
±12.8
VOS
Input Offset Voltage
IB
Input Bias Current
IOS
Input Offset Current between XIN+ and XIN-, YIN+ and YIN-, REF and FB
Gain
Gain Factor of VOUT = Gain × XIN+ × YIN
0.45
Max
I
V
8
35
I
mV
µA
9
20
I
0.5
4
I
µA
0.5
0.55
I
V/V2
%
NLx
Nonlinearity of X Input; XIN between -1V and +1V
0.3
0.7
I
NLy
Nonlinearity of Y Input; YIN between -1V and +1V
0.2
0.35
I
%
RIN
Input resistance
230
V
kΩ
CMRR
Common-Mode Rejection Ratio, XIN and YIN
70
90
I
dB
PSRR
Power-Supply Rejection Ratio, FB
60
72
I
dB
VO
Output Voltage Swing
(VIN = 0, VREF Varied)
VS = ±5V
±2.5
±2.8
I
V
VS = ±15V
±12.5
±12.8
I
mA
I
mA
XIN+ to XIN-, YIN+ to YIN-,
REF to FB
ISC
Output Short-Circuit Current
IS
Supply Current, VS = ±15V
90
40
85
15.4
2
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Closed-Loop AC Electrical Characteristics
Power Supplies at ±12V, TA = 25°C, RL = 500¾, CL = 15pF
Test Level
Units
BW, -3 dB
-3 dB Small-Signal Bandwidth, X or Y
90
V
MHz
BW, ±0.1 dB
0.1 dB Flatness Bandwidth
10
V
MHz
Peaking
Frequency Response Peaking
1.0
V
dB
SR
Slew Rate, VOUT between -2V and +2V
400
I
V/µs
VN
Input-Referred Noise Voltage Density
100
V
nV/Hz
Parameter
Description
Min
300
Typ
Max
Test Circuit
Note: For typical performance curves, RF = 0, RG = ×, VS = ±5V, RL = 500¾, and CL = 15 pF unless otherwise noted.
Typical Performance Curves
Transfer Function of X Input for
Various Y Inputs
Transfer Function of Y Input for
Various X Inputs
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Frequency Response
for Various Feedback
Divider Ratios
X Input Frequency Response
for Various Y DC Inputs
Change in Bandwidth
and Peaking vs Temperature
Frequency Response
for Various RL, CL
VS = ±5V
Y Input Frequency Response
for Various X DC Inputs
Total Harmonic Distortion
of X Input vs Frequency
4
Frequency Response
for Various RL, CL
VS = ±15V
-3 dB Bandwidth
and Peaking
vs Supply Voltage
Total Harmonic Distortion
of Y Input vs Frequency
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Slew Rate
vs Supply Voltage
Slew Rate
vs Die Temperature
Input Voltage Noise
vs Frequency
Nonlinearity of X Input
Bias Current
vs Die Temperature
CMRR vs Frequency
Nonlinearity of Y Input
Common-Mode Input Range
vs Supply Voltage
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EL4450C
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Supply Current
vs Die Temperature
Supply Current
vs Supply Voltage
6
14-Pin Package
Power Dissipation vs
Ambient Temperature
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Applications Information
The EL4450 is a complete four-quadrant multiplier with
90 MHz bandwidth. It has three sets of inputs; a differential multiplying X-input, a differential multiplying Yinput, and another differential input which is used to
complete a feedback loop with the output. Here is a typical connection:
Figure 1.
The gain of the feedback divider is H, and H = RG/(RG +
RF). The transfer function of the part is
used to create more of a frequency-compensated divider.
The value of the capacitor should scale with the parasitic
capacitance at the FB input. It is also practical to place
small capacitors across both the feedback resistors
(whose values maintain the desired gain) to swamp out
parasitics. For instance, two 10 pF capacitors across
equal divider resistors for a maximum gain of 1 will
dominate parasitic effects and allow a higher divider
resistance.
VOUT = AO × (1/2 × ((VINX+–VINX-) × (VINY+–VINY-)) + (VREF–VFB)).
VFB is connected to VOUT through a feedback network,
so V FB = H*V OUT . A O is the open-loop gain of the
amplifier, and is about 600. The large value of AO drives
(1/2 × ((VINX+–VINX-) × (VINY+–VINY-)) + (VREF–VFB))→0.
Rearranging and substituting for VREF
VOUT = (1/2 × ((VINX+–VINX-) × (VINY+–VINY-)) +VREF)/H, or
VOUT = (XY/2 + VREF)/H
The REF pin can be used as the output’s ground reference, or for DC offsetting of the output, or it can be used
to sum in another signal.
Thus the output is equal to one-half the product of X and
Y inputs and offset by VREF, all gained up by the feedback divider ratio. The EL4450 is stable for a direct
connection between VOUT and FB, and the feedback
divider may be used for higher output gain, although
with the traditional loss of bandwidth.
Input Connections
The input transistors can be driven from resistive and
capacitive sources, but are capable of oscillation when
presented with an inductive input. It takes about 80 nH
of series inductance to make the inputs actually oscillate,
equivalent to four inches of unshielded wiring or about 6
of unterminated input transmission line. The oscillation
has a characteristic frequency of 500 MHz. Placing
one’s finger (via a metal probe) or an oscilloscope probe
on the input will kill the oscillation. Normal high-frequency construction obviates any such problems, where
the input source is reasonably close to the input. If this is
It is important to keep the feedback divider’s impedance
at the FB terminal low so that stray capacitance does not
diminish the loop’s phase margin. The pole caused by
the parallel impedance of the feedback resistors and
stray capacitance should be at least 150 MHz; typical
strays
of 3 pF thus require a feedback impedance of 360¾ or
less, Alternatively, a small capacitor across RF can be
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EL4450C
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not possible, one can insert series resistors of around to
51¾ to de-Q the inputs.
• RPAR is the parallel of all resistors loading the output
For instance, the EL4450C draws a maximum of 18 mA.
With light loading, RPAR→× and the dissipation with
±5V supplies is 180 mW. The maximum supply voltage
that the device can run on for a given PD and the other
parameters is
Signal Amplitudes
Signal input common-mode voltage must be between
(V-) + 2.5V and (V+) -2.5V to ensure linearity. Additionally, the differential voltage on any input stage must
be limited to ± 6V to prevent damage. The differential
signal range is ± 2V in the EL4450C. The input range is
substantially constant with temperature.
VS,max = (PD + VO2/RPAR)/(2IS + VO/RPAR)
The maximum dissipation a package can offer is
PD,max = (TJ,max–TA,max)/θJA
Where TJ,max is the maximum junction temperature,
150°C for reliability, less to retain optimum electrical
performance
The Ground Pin
The ground pin draws only 6 µA maximum DC current,
and may be biased anywhere between (V-) +2.5V and
(V+) -3.5V. The ground pin is connected to the IC’s substrate and frequency compensation components. It
serves as a shield within the IC and enhances input stage
CMRR over frequency, and if connected to a potential
other than ground, it must be bypassed.
TA,max is the ambient temperature, 70°C for commercial and 85°C for industrial range
θJA is the thermal resistance of the mounted package,
obtained from data sheet dissipation curves
The more difficult case is the SO-14 package. With a
maximum junction temperature of 150°C and a maxim u m a m b i e n t t e m pe r a t u r e o f 8 5° C , t he 6 5° C
temperature rise and package thermal resistance of
120°/W gives a dissipation of 542 mW at 85°C. This
allows the full maximum operating supply voltage
unloaded, but reduced if loaded significantly.
Power Supplies
The EL4450C works well on supplies from ± 3V to ±
15V. The supplies may be of different voltages as long
as the requirements of the GND pin are observed (see
the Ground Pin section for a discussion). The supplies
should be bypassed close to the device with short leads.
4.7 µF tantalum capacitors are very good, and no smaller
bypasses need be placed in parallel. Capacitors as low as
0.01 µF can be used if small load currents flow.
Output Loading
The output stage is very powerful. It typically can source
85 mA and sink 120 mA. Of course, this is too much
current to sustain and the part will eventually be
destroyed by excessive dissipation or by metal traces on
the die opening. The metal traces are completely reliable
while delivering the 30 mA continuous output given in
the Absolute Maximum Ratings table in this data sheet,
or higher purely transient currents.
Single-polarity supplies, such as +12V with +5V can be
used, where the ground pin is connected to +5V and Vto ground. The inputs and outputs will have to have their
levels shifted above ground to accommodate the lack of
negative supply.
The power dissipation of the EL4450C increases with
power supply voltage, and this must be compatible with
the package chosen. This is a close estimate for the dissipation of a circuit:
Gain accuracy degrades only 0.2% from no load to 100¾
load. Heavy resistive loading will degrade frequency
response and video distortion for loads < 100¾.
Capacitive loads will cause peaking in the frequency
response. If a capacitive load must be driven, a smallvalued series resistor can be used to isolate it. 12¾ to
51¾ should suffice. A 22¾ series resistor will limit
peaking to 2.5 dB with even a 220 pF load.
PD =2*IS,max*VS + (VS–VO)*VO/RPAR
where
•
•
•
IS,max is the maximum supply current
VS is the ± supply voltage (assumed equal)
VO is the output voltage
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about 37 dB worst-case. Better suppression can be
obtained by nulling the offset of the X input. Similarly,
nulling the offset of the Y input will improve signal-port
suppression. Driving an input differentially will also
maximize feedthrough suppression at frequencies
beyond 10 MHz.
Mixer Applications
Because of its lower distortion levels, the Y input is the
better choice for a mixer’s signal port. The X input
would receive oscillator amplitudes of about 1V RMS
maximum. Carrier suppression is initially limited by the
offset voltage of the Y input, 20 mV maximum, and is
AC Level Detectors
Square-law converters are commonly used to convert
AC signals to DC voltages corresponding to the original
amplitude in subsystems like automatic gain controls
(AGC’s) and amplitude-stabilized oscillators. Due to the
controlled AC amplitudes, the inputs of the multiplier
will see a relatively constant signal level. Best performance will be obtained for inputs between 200 mVRMS
and 1 VRMS. The traditional use of the EL4450C as an
AGC detector and control loop would be:
Figure 2. Traditional AGC Detector/DC Feedback Circuit
The EL4450C simply provides an output equal to the
square of the input signal and an integrator filters out the
AC component, while comparing the DC component to
an amplitude reference. The integrator output is the DC
control voltage to the variable-gain sections of the AGC
(not shown). If a negative polarity of reference is
required, one of the multiplier input terminal pairs is
reversed, inverting the multiplier output. In-
put bias current will cause input voltage offsets due to
source impedances; putting a compensating resistor in
series with the grounded inputs of the EL4450C will
reduce this offset greatly.
This control system will attempt to force
VIN,RMS2/4=VREF.
The extra op-amp can be eliminated by using this circuit:
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EL4450C
EL4450C
Wideband Four-Quadrant Multiplier
EL4450C
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EL4450C
Wideband Four-Quadrant Multiplier
Figure 3. Simplified AGC Detector/DC Feedback Circuit
Here the internal op-amp of the EL4450C replaces the
external amplifier. The feedback capacitor CF does not
provide a perfect integration action; a zero occurs at a
frequency of 1/2¼RCF. This is canceled by including
another RCF pair at the AGC control output. If the reference voltage must be negative, the resistor at pin 11 is
connected to ground rather than the reference and pin 10
connected to the reference.
eliminate it. The reference is connected to pin 10 and the
resistor R connected to pin 11 reconnected to ground,
and one of the multiplier input connections are reversed.
Square-law detectors have a restricted input range, about
10:1, because the output rapidly disappears into the DC
errors as signal amplitudes reduce. This circuit gives a
multiplier output that is the absolute value of the input,
thus increasing range to 100:1:
The amplitude reference will have to support some AC
currents flowing through R. If this is a problem, several
changes can be made to
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Figure 4. Absolute-Value Input Circuitry
An ECL comparator produces an output corresponding
to the sign of the input, which when multiplied by the
input produces an effective
absolute-value function. The RC product connected to
the X inputs simply emulates the time delay of the compa rator to m aintain c ircuit ac curac y at higher
frequencies.
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Wideband Four-Quadrant Multiplier
EL4450C
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Wideband Four-Quadrant Multiplier
Nonlinear Function Generation
The REF pin of the EL4450C can be used to sum in various quantities of polynomial function generators. For
instance, this sum of REF allows a linear signal path
which can have various amounts of squared signal
added:
Figure 5. Polynomial Function Generator
The diode and I pulldown assure that the output will
always produce the positive square-root of the input signal. Ipulldown should be large enough to assure that the
diode be forward-biased for any load current. In this
configuration, the bandwidth of the circuit will reduce
for smaller input signals.
The polarity of the squared signal can be reversed by
swapping one of the X or Y input pairs.
The REF and FB pins also simplify feedback schemes
that allow square-rooting:
Figure 6. Square-Rooter
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The REF and FB terminals can also be used to implement division:
The output frequency response reduces for smaller values of VX, but is not affected by VREF.
Figure 7. Divider Connection
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General Disclaimer
Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes in the circuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any circuits described
herein and makes no representations that they are free from patent infringement.
January 1996 Rev B
WARNING - Life Support Policy
Elantec, Inc. products are not authorized for and should not be used
within Life Support Systems without the specific written consent of
Elantec, Inc. Life Support systems are equipment intended to support or sustain life and whose failure to perform when properly used
in accordance with instructions provided can be reasonably
expected to result in significant personal injury or death. Users contemplating application of Elantec, Inc. Products in Life Support
Systems are requested to contact Elantec, Inc. factory headquarters
to establish suitable terms & conditions for these applications. Elantec, Inc.’s warranty is limited to replacement of defective
components and does not cover injury to persons or property or
other consequential damages.
Elantec, Inc.
1996 Tarob Court
Milpitas, CA 95035
Telephone: (408) 945-1323
(800) 333-6314
Fax:
(408) 945-9305
European Office: 44-71-482-4596
14
Printed in U.S.A.
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