Analog Devices AD22050R-REEL, AD22050R, AD22050N Datasheet

a		Single-Supply Sensor
		Interface Amplifier
		AD22050

FEATURES

Gain of 320. Alterable from 31 to 3160

Input CMR from Below Ground to 63 (VS – 1 V)

Output Span 20 mV to (VS – 0.2) V

1-, 2-, 3-Pole Low-Pass Filtering Available Accurate Midscale Offset Capability Differential Input Resistance 400 kV Drives 1 kV Load to +4 V Using VS = +5 V

Supply Voltage: +3.0 V to +36 V

Transient Spike Protection and RFI Filters Included Peak Input Voltage (40 ms): 60 V

Reversed Supply Protection: –34 V

Operating Temperature Range: –408C to +1258C

FUNCTIONAL BLOCK DIAGRAM

+VS	OFS	A1	A2
AD22050
IN+
A1			A2	OUT
IN–
				GND

APPLICATIONS

Current Sensing

Motor Control

Interface for Pressure Transducers, Position Indicators, Strain Gages, and Other Low Level Signal Sources

GENERAL DESCRIPTION

The AD22050 is a single-supply difference amplifier for amplifying and low-pass filtering small differential voltages (typically 100 mV FS at a gain of 40) from sources having a large commonmode voltage.

Supply voltages from +3.0 V to +36 V can be used. The input common-mode range extends from below ground to +24 V using

a +5 V supply with excellent rejection of this common-mode voltage. This is achieved by the use of a special resistive attenuator at the input, laser trimmed to a very high differential balance.

Provisions are included for optional low-pass filtering and gain adjustment. An accurate midscale offset feature allows bipolar signals to be amplified.

+VS (CAR BATTERY)		+5V
SOLENOID
LOAD		ANALOG OUTPUT
		4V PER AMP
100mV	AD22050	200kV
		CORNER FREQUENCY
CMOS DRIVER		= 0.796Hz-mF
	C
POWER		ANALOG GROUND
DARLINGTON

CHASSIS	SINGLE-POLE LOW-PASS FILTERING, GAIN: 40

Figure 1. Typical Application Circuit for a Current Sensor Interface

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AD22050–SPECIFICATIONS (TA = +258C, VS = +5 V, and VCM = 0, RL = 10 kV unless otherwise noted)

Parameter		Test Conditions	Min	Typ	Max	Units
INPUTS (Pins 1 and 8)
+CMR	Positive Common-Mode Range	TA = TMIN to TMAX			+24	V
–CMR	Negative Common-Mode Range	TA = TMIN to +85°C	–1.0			V
CMRRLF	Common-Mode Rejection Ratio	f ≤ 10 Hz	80	90		dB
CMRRHF	Common-Mode Rejection Ratio	f = 10 kHz	60	75		dB
RINCM	Common-Mode Input Resistances	Pin 1 or Pin 8 to Pin 2	180	240	300	kΩ
RMATCH	Matching of Resistances			± 0.5		%
RINDIFF	Differential Input Resistance	Pin 1 to Pin 8	280	400		kΩ
PREAMPLIFIER	Closed-Loop Gain1
GCL			9.7	10.0	10.3
VO	Output Voltage Range (Pin 3)		+0.01		+4.8	V
RO	Output Resistance2		97	100	103	kΩ
OUTPUT BUFFER	Closed-Loop Gain1	RLOAD ≥ 10 kΩ	1.94		2.06
GCL				2.0
VO	Output Voltage Range3	TA = TMIN to TMAX	+0.02		+4.8	V
RO	Output Resistance (Pin 5)	VO ≥ 0.1 V dc, IO < 1 mA		2.0		Ω
OVERALL SYSTEM	Gain1	VO ≥ 0.1 V dc	19.9		20.1
G				20.0
	Over Temperature	TA = TMIN to TMAX	19.8		20.2
VOS	Input Offset Voltage4		–1	0.03	1	mV
	Over Temperature	TA = TMIN to TMAX	–3		3	mV
OFS	Midscale Offset (Pin 7) Scaling		0.49	0.50	0.51	V/V
	Input Resistance	Pin 7 to Pin 2	2.5	3.0		kΩ
IOSC	Short-Circuit Output Current	TA = TMIN to TMAX	7	11	25	mA
BW–3 dB	–3 dB Bandwidth	VO = +1 V dc		30		kHz
SR	Slew Rate			0.2		V/µs
NSD	Noise Spectral Density3	f = 100 Hz to 10 kHz		0.2		µV/√Hz
POWER SUPPLY
VS	Operating Range	TA = TMIN to TMAX	3.0	5	36	V
IS	Quiescent Supply Current5	TA = +25°C, VS = +5 V		200	500	µA
TEMPERATURE RANGE						°C
TOP	Operating Temperature Range		–40		+125

NOTES

1Specified for default mode, i.e., with no external components. The overall gain is trimmed to 0.5%, while the individual gains of A1 and A2 may be subject to a maximum ±3% tolerance. Note that the actual gain in a particular application can be modified by the use of external resistor networks.

2The actual output resistance of A1 is only a few ohms, but access to this output, via Pin 3, is always through the resistor R12 (see Figure 16) which is 100 kΩ, trimmed to ± 3%.

3For VCM ≤ 20 V. For VCM > 20 V, VOL 1 mV/V × VCM. 4Referred to the input (Pins 1 and 8).

5With VDM = 0 V. Differential mode signals are referred to as VDM, while VCM refers to common-mode voltages—see the section Product Description and Figure 3.

All min and max specifications are guaranteed, although only those marked in boldface are tested on all production units at final test. Specifications subject to change without notice.

ORDERING GUIDE

Model	Temperature Range	Package Descriptions	Package Options
AD22050N	–40°C to +125°C	Plastic DIP	N-8
AD22050R	–40°C to +125°C	Plastic SOIC	SO-8
AD22050R-Reel	–40°C to +125°C	Tape and Reel	SO-8*

*Quantities must be in increments of 2,500 pieces each.

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AD22050

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . +3.0 V to +36 V Peak Input Voltage (40 ms) . . . . . . . . . . . . . . . . . . . . . . +60 V

VOFS (Pin 7 to Pin 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . +20 V Reversed Supply Voltage Protection . . . . . . . . . . . . . . . –34 V

Operating Temperature . . . . . . . . . . . . . . . . –40°C to +125°C Storage Temperature . . . . . . . . . . . . . . . . . . –65°C to +150°C Output Short Circuit Duration . . . . . . . . . . . . . . . . Indefinite 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; the functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

				PIN CONFIGURATIONS
Plastic Mini-DIP Package							Plastic SOIC Package
		(N-8)							(SO-8)
						+IN
–IN
	1				8		–IN	1		8	+IN
GND		AD22050				OFFSET	GND		AD22050
	2				7			2		7	OFFSET
A1		TOP VIEW				+VS	A1		TOP VIEW		+VS
	3	(Not to Scale)			6			3	(Not to Scale)	6
A2						OUT	A2				OUT
	4				5			4		5

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 AD22050 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

PRODUCT DESCRIPTION

The AD22050 is a single-supply difference amplifier consisting of a precision balanced attenuator, a very low drift preamplifier and an output buffer amplifier (A1 and A2, respectively, in Figure 2). It has been designed so that small differential signals (VDM in Figure 3) can be accurately amplified and filtered in the presence of large common-mode voltages (VCM) without the use of any other active components.

+VS	OFS	A1	A2
AD22050
IN+			A2
A1				OUT
IN–
				GND

Figure 2. Simplified Schematic

The resistive attenuator network is situated at the input to the AD22050 (Pins 1 and 8), allowing the common-mode voltage at Pins 1 and 8 to be six times greater than that which can be tolerated by the actual input to A1. As a result, the input commonmode range extends to 6× (VS – 1 V).

Two small filter capacitors (not shown in Figure 2) have been included at the inputs of A1 to minimize the effects of any spurious RF signals present in the signal.

Internal feedback around A1 sets the closed-loop gain of the preamplifier to ×10 from the input pins; the output of A1 is connected to Pin 3 via a 100 kΩ resistor, which is trimmed to

± 3% (R12 in Figure 2) to facilitate the low-pass filtering of the signal of interest (see Low-Pass Filtering section). The inclusion of an additional resistive network allows the output of A1 to be offset to an optional voltage of one half of that supplied to Pin 7; in many cases this offset would be +VS/2 by tying Pin 7 to +VS

(Pin 6), permitting the conditioning and processing of bipolar signals (see Strain Gage Interface section).

The output buffer A2 has a gain of ×2, setting the precalibrated, overall gain of the AD22050, with no external components, to ×20. (This gain is easily user-configurable—see Altering the Gain section for details.)

The dynamic properties of the AD22050 are optimized for interfacing to transducers; in particular, current sensing shunt resistors. Its rejection of large, high frequency, common-mode signals makes it superior to that of many alternative approaches. This is due to the very careful design of the input attenuator and the close integration of this highly balanced, high impedance system with the preamplifier.

APPLICATIONS

The AD22050 can be used wherever a high gain, single-supply differencing amplifier is required, and where a finite input resistance (240 kΩ to ground, 400 kΩ between differential inputs) can be tolerated. In particular, the ability to handle a commonmode input considerably larger than the supply voltage is frequently of value.

Also, the output can run down to within 20 mV of ground, provided it is not called on to sink any load current. Finally, the output can be offset to half of a full-scale reference voltage (with a tolerance of ± 2%) to allow a bipolar input signal.

ALTERING THE GAIN

The gain of the preamplifier, from the attenuator input (Pins 1 and 8) to its output at Pin 3, is ×10 and that of the output buffer, from Pin 4 to Pin 5, is ×2, thus making the overall default gain ×20. The overall gain is accurately trimmed (to within

± 0.5%). In some cases, it may be desirable to provide for some variation in the gain; for example, in absorbing the scaling error of a transducer.

Figure 3 shows a general method for trimming the gain, either upward or downward, by an amount dependent on the resistor, R. The gain range, expressed as a percentage of the overall gain,

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