Analog Devices AD606JR-REEL, AD606JR, AD606JN, AD606JCHIPS, AD606JR-REEL7 Datasheet

50 MHz, 80 dB Demodulating

a

Logarithmic Amplifier with Limiter Output

FEATURES
Logarithmic Amplifier Performance

–75 dBm to +5 dBm Dynamic Range

≤1.5 nV/√Hz Input Noise

Usable to >50 MHz

37.5 mV/dB Voltage Output
On-Chip Low-Pass Output Filter

Limiter Performance

ⴞ1 dB Output Flatness over 80 dB Range
ⴞ3ⴗ Phase Stability at 10.7 MHz over 80 dB Range

Adjustable Output Amplitude

Low Power

+5 V Single Supply Operation
65 mW Typical Power Consumption
CMOS-Compatible Power-Down to 325 ␮W typ
<5 ␮s Enable/Disable Time

APPLICATIONS
Ultrasound and Sonar Processing
Phase-Stable Limiting Amplifier to 100 MHz
Received Signal Strength Indicator (RSSI)
Wide Range Signal and Power Measurement

PRODUCT DESCRIPTION

The AD606 is a complete, monolithic logarithmic amplifier
using a 9-stage “successive-detection” technique. It provides
both logarithmic and limited outputs. The logarithmic output is
from a three-pole post-demodulation low-pass filter and provides

AD606

a loadable output voltage of +0.1 V dc to +4 V dc. The logarith­mic scaling is such that the output is +0.5 V for a sinusoidal
input of –75 dBm and +3.5 V at an input of +5 dBm; over this

range the logarithmic linearity is typically within ±0.4 dB. All

scaling parameters are proportional to the supply voltage.

The AD606 can operate above and below these limits, with
reduced linearity, to provide as much as 90 dB of conversion
range. A second low-pass filter automatically nulls the input
offset of the first stage down to the submicrovolt level. Adding
external capacitors to both filters allows operation at input fre­quencies as low as a few hertz.

The AD606’s limiter output provides a hard-limited signal

output as a differential current of ±1.2 mA from open-collector

outputs. In a typical application, both of these outputs are

loaded by 200 Ω resistors to provide a voltage gain of more than

90 dB from the input. Transition times are 1.5 ns, and the

phase is stable to within ±3° at 10.7 MHz for signals from

–75 dBm to +5 dBm.

The logarithmic amplifier operates from a single +5 V supply
and typically consumes 65 mW. It is enabled by a CMOS logic

level voltage input, with a response time of <5 µs. When dis-
abled, the standby power is reduced to <1 mW within 5 µs.

The AD606J is specified for the commercial temperature range

of 0°C to +70°C and is available in 16-lead plastic DIPs or

SOICs. Consult the factory for other packages and temperature
ranges.

FUNCTIONAL BLOCK DIAGRAM

REFERENCE

AND POWER-UP

30kV 30kV

1.5kV

250V

1.5kV

HIGH-END

DETECTORS

AD606

12345678

INLO COMM ISUM ILOG BFIN VLOG OPCM LMLO

12mA/dB

ONE-POLE

FILTER

2mA/dB

REV. B

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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

LMHILADJFIL2FIL1VPOSPRUPCOMMINHI

910111213141516

30pF

X1

30pF

MAIN SIGNAL PATH

9.375kV

9.375kV

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 1999

OFFSET-NULL

LOW-PASS FILTER

11.15dB/STAGE

2pF

2pF

360kV

360kV

TWO-POLE

SALLEN-KEY

FILTER

X2

FINAL

LIMITER

AD606–SPECIFICATIONS

(@ TA = +25ⴗC and supply = +5 V unless otherwise noted; dBm assumes 50 ⍀)

Model AD606J
Parameter Conditions Min Typ Max Units

SIGNAL INPUT

Log Amp f
Limiter f

MAX

MAX

AC Coupled; Sinusoidal Input 50 MHz
AC Coupled; Sinusoidal Input 100 MHz

Dynamic Range 80 dB

Input Resistance Differential Input 500 2,500 Ω

Input Capacitance Differential Input 2 pF

SIGNAL OUTPUT

Limiter Flatness –75 dBm to +5 dBm Input Signal at 10.7 MHz –1.5 +1.5 dB

With Pin 9 to V
and Pin 8 to V

Output Current At Pins 8 or 9, Proportional to V

via a 200 Ω Resistor

POS

via a 200 Ω Resistor

POS

, LADJ Grounded 1.2 mA

POS

LADJ Open Circuited 0.48 mA

Phase Variation with Input Level –75 dBm to +5 dBm Input Signal at 10.7 MHz ±3 Degrees

LOG (RSSI) OUTPUT

Nominal Slope At 10.7 MHz; (0.0075 × V

)/dB 37.5 mV/dB

POS

At 45 MHz 35 mV/dB

Slope Accuracy Untrimmed at 10.7 MHz –15 ±5 +15 %

Intercept Sinusoidal Input; Independent of V

POS

–88.33 dBm
Logarithmic Conformance –75 dBm to +5 dBm Input Signal at 10.7 MHz –1.5 0.4 +1.5 dB
Nominal Output Input Level = –75 dBm 0.5 V

Input Level = –35 dBm 2 V
Input Level = +5 dBm 3.5 V

Accuracy over Temperature After Calibration at –35 dBm at 10.7 MHz –3 +3 dB

to T

T

MIN

MAX

Video Response Time From Onset of Input Signal Until Output Reaches 400 ns

95% of Final Value

POWER-DOWN INTERFACE

Power-Up Response Time Time Delay Following HI Transition Until 3.5 µs

Device Meets Full Specifications
AC Coupled with 100 pF Coupling Capacitors

Input Bias Current Logical HI Input (See Figure 12) 1 nA

Logical LO Input 4 µA

POWER SUPPLY

Operating Range 4.5 5.5 V
Powered-Up Current Zero Signal Input 13 mA

T

Powered-Down Current T

Specifications subject to change without notice.

MIN

MIN

to T
to T

MAX

MAX

13 20 mA

65 200 µA

–2–

REV. B

AD606

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS

Supply Voltage V
Internal Power Dissipation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . +9 V

POS

2

. . . . . . . . . . . . . . . . . . . 600 mW

1

Operating Temperature Range . . . . . . . . . . . . . 0°C to +70°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C

Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300°C

NOTES

1

Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent 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.

2

Specification is for device in free air:

16-Lead Plastic DIP Package: θJA = 85°C/W
16-Lead SOIC Package: θJA = 100°C/W

ORDERING GUIDE

Temperature Package Package

Model Range Description Option

AD606JN 0°C to +70°C 16-Lead Plastic DIP N-16
AD606JR 0°C to +70°C 16-Lead Narrow-Body R-16A

SOIC

AD606JR-REEL 0°C to +70°C 13" Tape and Reel R-16A
AD606JR-REEL7 0°C to +70°C 7" Tape and Reel R-16A

AD606-EB Evaluation Board

AD606JCHIPS 0°C to +70°C Die

PIN DESCRIPTION

Plastic DIP (N)

and

Small Outline (R)

Packages

1

INLO INHI

COMM COMM

2

ISUM PRUP

3

ILOG VPOS

4

AD606

BFIN FIL1

VLOG FIL2

OPCM LADJ

LMLO LMHI

TOP VIEW

5

(Not to Scale)

6

7

8

16

15

14

13

12

11

10

9

PIN FUNCTION DESCRIPTIONS

Pin Mnemonic Function

1 INLO DIFFERENTIAL RF INPUT

–75 dBm to +5 dBm, Inverting, AC Coupled.

2 COMM POWER SUPPLY COMMON

Connect to Ground.

3 ISUM LOG DETECTOR SUMMING NODE

4 ILOG LOG CURRENT OUTPUT

Normally No Connection; 2 µA/dB Output

Current.

5 BFIN BUFFER INPUT

Optionally Used to Realize Low Frequency
Post-Demodulation Filters.

6 VLOG BUFFERED LOG OUTPUT

37.5 mV/dB (100 mV to 4.5 V).

7 OPCM OUTPUT COMMON

Connect to Ground.

8 LMLO DIFFERENTIAL LIMITER OUTPUT

1.2 mA Full-Scale Output Current. Open
Collector Output Must Be “Pulled” Up to

VPOS with R ≤ 400 Ω.

9 LMHI DIFFERENTIAL LIMITER OUTPUT

1.2 mA Full-Scale Output Current. Open
Collector Output Must Be “Pulled” Up to

VPOS with R ≤ 400 Ω.

10 LADJ LIMITER LEVEL ADJUSTMENT

Optionally Used to Adjust Limiter Output
Current.

11 FIL1 OFFSET LOOP LOW-PASS FILTER

Normally No Connection; a Capacitor Between
FIL1 and FIL2 May Be Added to Lower the
Filter Cutoff Frequency.

12 FIL2 OFFSET LOOP LOW-PASS FILTER

Normally No Connection; See Above.

13 VPOS POSITIVE SUPPLY

Connect to +5 V at 13 mA.

14 PRUP POWER UP

CMOS (5 V) Logical High = Device On

(≈ 65 mW).

CMOS (0 V) Logical Low = Device Off

(≈ 325 µW).

15 COMM POWER SUPPLY COMMON

Connect to Ground.

16 INHI DIFFERENTIAL RF INPUT

–75 dBm to +5 dBm, Noninverting, AC-Coupled.

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 the AD606 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. B

–3–

AD606

INPUT LEVEL CONVENTIONS

RF logarithmic amplifiers usually have their input specified in
“dBm,” meaning “decibels with respect to 1 mW.” Unfortu­nately, this is not precise for several reasons.

1. Log amps respond not to power but to voltage. In this re­spect, it would be less ambiguous to use “dBV” (decibels
referred to 1 V) as the input metric. Also, power is dependent
on the rms (root mean-square) value of the signal, while log
amps are not inherently rms responding.

2. The response of a demodulating log amp depends on the
waveform. Convention assumes that the input is sinusoidal.
However, the AD606 is capable of accurately handling any
input waveform, including ac voltages, pulses and square
waves, Gaussian noise, and so on. See the AD640 data sheet,
which covers the effect of waveform on logarithmic intercept,
for more information.

3. The impedance in which the specified power is measured is
not always stated. In the log amp context it is invariably

assumed to be 50 Ω. Thus, 0 dBm means “1 mW rms in 50 Ω,”

and corresponds to an rms voltage of
224 mV.

(1 mW × 50 Ω),

or

Popular convention requires the use of dBm to simplify the
comparison of log amp specifications. Unless otherwise stated,

sinusoidal inputs expressed as dBm in 50 Ω are used to specify

the performance of the AD606 throughout this data sheet. We
will also show the corresponding rms voltages where it helps to
clarify the specification. Noise levels will likewise be given in
dBm; the response to Gaussian noise is 0.5 dB higher than for a
sinusoidal input of the same rms value.

Note that dynamic range, being a simple ratio, is always speci­fied simply as “dB”, and the slope of the logarithmic transfer
function is correctly specified as “mV/dB,” NOT as “mV/dBm.”

LOGARITHMIC SLOPE AND INTERCEPT

A generalized logarithmic amplifier having an input voltage V
and output voltage V

must satisfy a transfer function of the

LOG

IN

form

VV VV

= log ( / )

LOG Y IN X

10

where, in the case of the AD606, the voltage VIN is the differ­ence between the voltages on pins INHI and INLO, and the
voltage V
V

are fixed voltages that determine the slope and intercept of

X

is that measured at the output pin VLOG. VY and

LOG

the logarithmic amplifier, respectively. These parameters are
inherent in the design of a particular logarithmic amplifier,
although may be adjustable, as in the AD606. When V
the logarithmic argument is one, hence the logarithm is zero. V

= VX,

IN

X

is, therefore, called the logarithmic intercept voltage because the
output voltage V
age V

is can also be interpreted as the “volts per decade” when

Y

crosses zero for this input. The slope volt-

LOG

using base-10 logarithms as shown here.

Note carefully that V

and VLOG in the above paragraph

LOG

(and elsewhere in this data sheet) are different. The first is a
voltage; the second is a pin designation.

This equation suggests that the input V

is positive, that VIN must likewise be positive, since the

if V

X

is a dc quantity, and,

IN

logarithm of a negative number has no simple meaning. In fact,
in the AD606, the response is independent of the sign of V

IN

because of the particular way in which the circuit is built. This
is part of the demodulating nature of the amplifier, which

–4–

results in an alternating input voltage being transformed into a
quasi-dc (rectified and filtered) output voltage.

The single supply nature of the AD606 results in common-mode
level of the inputs INHI and INLO being at about +2.5 V (us­ing the recommended +5 V supply). In normal ac operation,
this bias level is developed internally and the input signal is
coupled in through dc blocking capacitors. Any residual dc
offset voltage in the first stage limits the logarithmic accuracy for
small inputs. In ac operation, this offset is automatically and
continuously nulled via a feedback path from the last stage, pro­vided that the pins INHI and INLO are not shorted together, as
would be the case if transformer coupling were used for the signal.

While any logarithmic amplifier must eventually conform to the
basic equation shown above, which, with appropriate elabora­tion, can also fully account for the effect of the signal waveform
on the effective intercept,

1

it is more convenient in RF applica­tions to use a simpler expression. This simplification results
from first, assuming that the input is always sinusoidal, and
second, using a decibel representation for the input level. The
standard representation of RF levels is (incorrectly, in a log amp
context) in terms of power, specifically, decibels above 1 milli-

watt (dBm) with a presumed impedance level of 50 Ω. That

being the case, we can rewrite the transfer function as

= ( –)

VVPP

LOG Y IN X

where it must be understood that PIN means the sinusoidal input

power level in a 50 Ω system, expressed in dBm, and P

intercept, also expressed in dBm. In this case, P
simple, dimensionless numbers. (P

is sometimes called the

X

IN

is the

X

and PX are

“logarithmic offset,” for reasons which are obvious from the
above equation.) V

is still defined as the logarithmic slope,

Y

usually specified as so many millivolts per decibel, or mV/dB.

In the case of the AD606, the slope voltage, V
750 mV when operating at V

= 5 V. This can also be ex-

POS

, is nominally

Y

pressed as 37.5 mV/dB or 750 mV/decade; thus, the 80 dB
range equates to 3 V. Figure 1 shows the transfer function of the
AD606. The slope is closely proportional to V
generally be stated as V

= 0.15 × V

Y

Thus, in those applica-

POS.

, and can more

POS

tions where the scaling must be independent of supply voltage,
this must be stabilized to the required accuracy. In applications
where the output is applied to an A/D converter, the reference

4

3.5

3

2.5

2

1.5

VLOG – Volts DC

1

0.5

0

SLOPE = 37.5mV/dB

INTERCEPT
AT –88.33dBm

–80–100

INPUT SIGNAL – dBm

+20

0–20–40–60

Figure 1. Nominal Transfer Function

1

See, for example, the AD640 data sheet, which is published in Section 3 of
the Special Linear Reference Manual or Section 9.3 of the 1992 Amplifier

Applications Guide.

REV. B