Analog Devices AD641AP, AD641AN, AD641-EB, 5962-9559801MRA Datasheet

a	250 MHz Demodulating
	Logarithmic Amplifier

FEATURES

Logarithmic Amplifier Performance

Usable to 250 MHz

44 dB Dynamic Range

62.0 dB Log Conformance

37.5 mV/dB Voltage Output

Stable Slope and Intercepts

2.0 nV/√Hz Input Noise Voltage

50 mV Input Offset Voltage

Low Power

65 V Supply Operation

9 mA (+VS), 35 mA (–VS) Quiescent Current

Onboard Resistors

Onboard 103 Attenuator

Dual Polarity Current Outputs

Direct Coupled Differential Signal Path

APPLICATIONS

IF/RF Signal Processing

Received Signal Strength Indicator (RSSI)

High Speed Signal Compression

High Speed Spectrum Analyzer

ECM/Radar

PRODUCT DESCRIPTION

The AD641 is a 250 MHz, demodulating logarithmic amplifier with an accuracy of ±2.0 dB and 44 dB dynamic range. The AD641 uses a successive detection architecture to provide an output current that is logarithmically proportional to its input voltage. The output current can be converted to a voltage using one of several on-chip resistors to select the slope. A single AD641 provides up to 44 dB of dynamic range at speeds up to 250 MHz, and two cascaded AD641s together can provide 58 dB of dynamic range at speeds up to 250 MHz. The AD641 is fully stable and well characterized over either the industrial or military temperature ranges.

The AD641 is not a logarithmic building block, but rather a complete logarithmic solution for compressing and measuring wide dynamic range signals. The AD641 is comprised of five stages and each stage has a full wave rectifier, whose current depends on the absolute value of its input voltage. The output of these stages are summed together to provide the demodulated output current scaled at 1 mA per decade (50 µA/dB).

Without utilizing the 10× input attenuator, log conformance of 2.0 dB is maintained over the input range –44 dBm to 0 dBm. The attenuator offers the most flexibility without significantly impacting performance.

REV. C

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.

AD641

PIN CONFIGURATIONS

20-Lead Plastic DIP (N)

20-Lead Cerdip (Q)

	–INPUT						+INPUT
		1				20
	ATN LO						ATN OUT
		2				19
	ATN COM						CKT COM
		3				18
	ATN COM						RG1
		4				17
	ATN IN		AD641				RG0
		5				16
	BL1		TOP VIEW				RG2
		6				15
			(Not to Scale)
	–V						LOG OUT
		7				14
	S
	ITC						LOG COM
		8				13
	BL2						+VS
		9				12
							+OUTPUT
	–OUTPUT	10				11

20-Lead PLCC (P)

			ATN COM		ATN LO		–INPUT		+INPUT		ATN OUT
	3			2			1	20			19
ATN COM
	4							PIN 1					18	CKT COM
								IDENTIFIER
ATN IN	5				AD641								17	RG1
BL1	6												16	RG0
					TOP VIEW
–V	7			(Not to Scale)									15	RG2
S
ITC	8												14	LOG OUT
			9		10		11		12		13
			BL2		–OUTSIG		+OUTSIG		+V		LOGCOM
									S

The 250 MHz bandwidth and temperature stability make this product ideal for high speed signal power measurement in RF/ IF systems. ECM/Radar and Communication applications are routinely in the 100 MHz–180 MHz range for power measurement. The bandwidth and accuracy, as well as dynamic range, make this part ideal for high speed, wide dynamic range signals.

The AD641 is offered in industrial (–40°C to +85°C) and military (–55°C to +125°C) package temperature ranges. Industrial versions are available in plastic DIP and PLCC; MIL versions are packaged in cerdip.

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

AD641–SPECIFICATIONS

ELECTRICAL CHARACTERISTICS (VS = 65 V; TA = +258C, unless otherwise noted)

			AD641A			AD641S
Parameter	Conditions		Min	Typ	Max	Min	Typ	Max	Units
TRANSFER FUNCTION1		(IOUT = IY LOG |VIN/VX|for VIN = 0.75 mV to ±200 mV dc)
LOG AMPLIFIER PERFORMANCE
3 dB Bandwidth				250			250		MHz
Voltage Compliance Range			–0.3		+VS – 1	–0.3		+VS – 1	V
Slope Current, IY			0.98	1.00	1.02	0.98	1.00	1.02	mA
Accuracy vs. Temperature				0.002			0.002		%/°C
Over Temperature	TMIN to TMAX					0.98		1.02	mA
Intercept dBm	250 MHz		–40.84	–40.43	–39.96	–40.84	–40.43	–39.96	dBm
Over Temperature	TMIN to TMAX, 250 MHz					–40.59		–39.47	dBm
Zero Signal Output Current2				–0.2			–0.2		mA
ITC Disabled	Pin 8 to COM			–0.27			–0.27		mA
Maximum Output Current					2.3			2.3	mA
DYNAMIC RANGE
Single Configuration				44			44		dB
Over Temperature	TMIN to TMAX			40			38		dB
Dual Configuration				58			58		dB
Over Temperature	TMIN to TMAX			52			52		dB
LOG CONFORMANCE	f = 250 MHz			± 0.5	± 2.0		± 0.5	± 2.0
Single Configuration	–44 dBm to 0 dBm								dB
Over Temperature	–42 dBm to –4 dBm; TMIN to TMAX			±1.0	±2.5		±1.0	±2.5	dB
	–42 dBm to –2 dBm, TMIN to TMAX						± 0.5	± 2.0
Dual Configuration	S: –60 dBm to –2 dBm;			± 0.5	± 2.0				dB
Over Temperature	A: –56 dBm to –4 dBm, TMIN to TMAX			±1.0	±2.5		±1.0	±2.5	dB
LIMITER CHARACTERISTICS				± 1.6			± 1.6
Flatness	–44 dBm to 0 dBm @ 10.7 MHz								dB
Phase Variation	–44 dBm to 0 dBm @ 10.7 MHz			± 2.0			± 2.0		Degrees
INPUT CHARACTERISTICS									kΩ
Input Resistance	Differential			500			500
Input Offset Voltage	Differential			50	200		50	200	µV
vs. Temperature				0.8			0.8		µV/°C
Over Temperature	TMIN to TMAX							300	µV
vs. Supply				2			2		µV/V
Input Bias Current				7	25		7	25	µA
Input Bias Offset				1			1		µA
Common Mode Input Range			–2		+0.3	–2		+0.3	V
SIGNAL INPUT (Pins 1, 20)
Input Capacitance	Either Pin to COM			2			2		pF
Noise Spectral Density	1 kHz to 10 MHz			2			2		nV/√Hz
Tangential Sensitivity	BW = 100 MHz			–72			–72		dBm
INPUT ATTENUATOR
(Pins 2, 3, 4, 5 & 19)
Attenuation3	Pins 5 to Pin 19			20			20		dB
Input Resistance	Pins 5 to 3/4			300			300		Ω
APPLICATION RESISTORS									kΩ
(Pins 15, 16, 17)			0.995	1.000	1.005	0.995	1.000	1.005
OUTPUT CHARACTERISTICS
(Pins 10, 11)				± 180			± 180
Peak Differential Output4									mV
Output Resistance	Either Pin to COM			75			75		Ω
Quiescent Output Voltage	Either Pin to COM			–90			–90		mV
POWER SUPPLY			± 4.5		± 7.5	± 4.5		± 7.5
Voltage Supply Range									V
Quiescent Current
+VS (Pin 12)	TMIN to TMAX			9	15		9	15	mA
–VS (Pin 7)	TMIN to TMAX			35	60		35	60	mA

NOTES

1Logarithms to base 10 are used throughout. The response is independent of the sign of VIN.

2The zero-signal current is a function of temperature unless internal temperature compensation (ITC) pin is grounded. 3Attenuation ratio trimmed to calibrate intercept to 10 mV when in use. It has a temperature coefficient of +0.3%/°C. 4The fully limited signal output will appear to be a square wave; its amplitude is proportional to absolute temperature.

Specifications subject to change without notice.

–2–

REV. C

AD641

ORDERING GUIDE

		Temperature		Package			Package
Model		Range		Description			Option
AD641AN		–40°C to	+85°C	Plastic DIP			N-20
AD641AP		–40°C to	+85°C	PLCC			P-20A
5962-9559801MRA		–55°C to	+125°C	Cerdip			Q-20
AD641-EB				Evaluation Board
	THERMAL CHARACTERISTICS
					uJC		uJA
					(8C/W)		(8C/W)
20-Lead Plastic DIP Package (N)					24		61
20-Lead Cerdip Package (Q)					25		85
20-Lead Plastic Leadless Chip Carrier (P)					28		75

ABSOLUTE MAXIMUM RATINGS*	±7.5 V
Supply Voltages . . . . . . . . . . . . . . . . . . . . . . .
Input Voltage (Pin 1 or Pin 20 to COM) . . .	–3 V to +300 mV
Attenuator Input Voltage (Pin 5 to Pin 3/4) . .	. . . . . . . . . ±4 V
Storage Temperature Range, Q . . . . . . . . . .	–65°C to +150°C
Storage Temperature Range, N, P . . . . . . . .	–65°C to +125°C
Ambient Temperature Range, Rated Performance
Industrial, AD641A . . . . . . . . . . . . . . . . . .	–40°C to +85°C
Military, AD641S . . . . . . . . . . . . . . . . . .	–55°C to +125°C
Lead Temperature Range (Soldering 60 sec) .	. . . . . . . +300°C

*Stresses above those listed under Absolute Maximum Ratings may cause permanent 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 adversely affect device reliability.

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 AD641 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.

WARNING!

ESD SENSITIVE DEVICE

REV. C

–3–

AD641–Typical DC Performance Characteristics

	1.015
	1.010
mA	1.005
–
CURRENT	1
	0.995
SLOPE	0.990
	0.985
	0.980	0	20	40	60	80 100 120 140
	–60 –40 –20
	TEMPERATURE –8C

Figure 1. Slope Current, IY, vs. Temperature

	1.015
– mV	1.010
	1.005
VOLTAGE
	1.000
INTERCEPT
	0.990
	0.995
	0.985
			5.0		5.5		6.0		6.5		7.0		7.5
	4.5

POWER SUPPLY VOLTAGES –6 Volts

Figure 4. Intercept Voltage, VX, vs. Supply Voltages

	2.4				2
					1
	2.2
					0
	2.0
– mA
	1.8
	1.6
OUTPUT CURRENT	1.4
	1.2				ERROR – dB
	1.0
	0.8
	0.6
	0.4
	0.2
	0
	–0.2
	–0.4
	0.1	1.0	10.0	100.0	1000.0

INPUT VOLTAGE – mV (EITHER SIGN)

Figure 7. DC Logarithmic Transfer Function and Error Curve for Single AD641

	1.20
	1.15
– mV	1.10
	1.05
INTERCEPT
	1.00
	0.95
	0.90
	0.85
	–60	–40 –20	0	20	40	60	80 100 120 140
		TEMPERATURE –8C

Figure 2. Intercept Voltage, VX, vs. Temperature

	14
	13
– mV	12
	11
INTERCEPT
	10
	9
	8
	7
	–60 –40 –20	0	20	40	60	80 100 120 140
	TEMPERATURE –8C

Figure 5. Intercept Voltage (Using Attenuator) vs. Temperature

	2.5
– dB	2.0
ERROR	1.5
ABSOLUTE	1.0
	0.5
	0	0	20	40	60	80 100 120 140
	–60 –40 –20
	TEMPERATURE –8C

Figure 8. Absolute Error vs. Temperature, VIN = ±1 mV to ±100 mV

	1.006
– mV	1.004
	1.002
CURRENT	1.000
SLOPE	0.998
	0.996
	0.994
			5.0		5.5		6.0		6.5		7.0		7.5
	4.5

POWER SUPPLY VOLTAGES –6 Volts

Figure 3. Slope Current, IY, vs. Supply Voltages

mV	+0.4
–
VOLTAGE	+0.3
	+0.2	INPUT OFFSET VOLTAGE
		DEVIATION WILL BE WITHIN
OFFSET		SHADED AREA.
	+0.1
INPUT	0
	–0.1
OF
DEVIATION	–0.2
	–0.3		0	20	40	60	80 100 120 140
	–60 –40 –20
		TEMPERATURE –8C

Figure 6. Input Offset Voltage Deviation vs. Temperature

	2.5
– dB	2.0
ERROR	1.5
ABSOLUTE	1.0
	0.5
	0	0	20	40	60	80 100 120 140
	–60 –40 –20
	TEMPERATURE –8C

Figure 9. Absolute Error vs. Temperature, Using Attenuator. VIN = ±10 mV to ±1 V, Pin 8 Grounded to Disable ITC Bias

–4–

REV. C

Typical AC Performance Characteristics–AD641

	–2.25
	–2.00	50MHz
	–1.75	150MHz
		190MHz
mA		210MHz
	–1.50	250MHz
–	–1.25
CURRENT
	–1.00
	–0.75
OUTPUT
	–0.50
	–0.25
	0.00
	0.25	0
	–52–48 –44–40 –36 –32 –28 –24 –20 –16 –12–4–8 2

INPUT LEVEL – dBm

Figure 10. AC Response at 50 MHz, 150 MHz, 190 MHz, 210 MHz at 250 MHz, vs. dBm Input (Sinusoidal Input)

	87.5
	85.0
dBm	82.5
–
LEVEL	80.0
INTERCEPT	77.5
	75.0
	72.5
	70.0
	50	100	150	170	190	210	230	250
			INPUT FREQUENCY – MHz

Figure 11. Intercept Level (dBm) vs. Frequency (Cascaded AD641s—Sinusoidal Input)

	–2.00			5
	–1.75		+1258C	4
	–1.50	+1258C	+258C	3
OUTPUT– mA	–1.25	+258C	–558C	2	INERROR– dB
	–1.00	ERROR		1
	–0.75	–558C		0
	–0.50		+1258C	–1
			+258C

	–0.25	+1258C		–558C	–2
			OUTPUT
	–0.00				–3
	0.25	+258C			–4
	0.50	–558C			–5
						0
	–52–48 –44–40 –36 –32 –28 –24 –20 –16 –12–4–8 2
			INPUT LEVEL – dBm
Figure 13. Logarithmic Response and Linearity at
200 MHz, TA for TA = –55°C, +25°C, +125°C
	1.0
– mA	0.95
CURRENT	0.90
	0.85
SLOPE
	0.80
	0.75
	50	150	190	210	250

INPUT FREQUENCY – MHz

Figure 14. Slope Current, IY, vs. Input Frequency

5µs	5µs
100
90
10
0%
20mV	20mV

Figure 12. Baseband Pulse Response of Single AD641,	Figure 15. Baseband Pulse Response of Cascaded AD641s
Inputs of 1 mV, 10 mV and 100 mV	at Inputs of 0.2 mV, 2 mV, 20 mV and 200 mV

REV. C

–5–