Datasheet

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LT1991

1991fh

–

∆V

M(IN)

P(IN)

–

OUT

= V

REF

∆V

SWING 40mV TO

EITHER RAIL

OUT

<0.1Ω

REF

2.5V

INPUT RANGE

–0.5V TO 5.1V

= 900kΩ

LT1991

1991 TA01

50k

150k

450k

4pF

450k

4pF

FEATURES

APPLICATIONS

DESCRIPTION

Precision, 100µA

Gain Selectable Amplifier

The LT

1991 combines a precision operational amplifier

with eight precision resistors to form a one-chip solution

for accurately amplifying voltages. Gains from –13 to 14

with a gain accuracy of 0.04% can be achieved using no

external components. The device is particularly well suited

for use as a difference amplifier, where the excellent resis-

tor matching results in a common mode rejection ratio of

greater than 75dB.

The amplifier features a 50µV maximum input offset volt-

age and a gain bandwidth product of 560kHz. The device

operates from any supply voltage from 2.7V to 36V and

draws only 100µA supply current on a 5V supply. The

output swings to within 40mV of either supply rail.

The resistors have excellent matching, 0.04% over tem-

perature for the 450k resistors. The matching temperature

coefficient is guaranteed less than 3ppm/°C. The resis-

tors are extremely linear with voltage, resulting in a gain

nonlinearity of less than 10ppm.

The LT1991 is fully specified at 5V and ±15V supplies

and from –40°C to 125°C. The device is available in space

saving 10-lead MSOP and low profile (0.8mm) 3mm ×

3mm DFN packages.

Rail-to-Rail Gain = 1 Difference Amplifier

Pin Configurable as a Difference Amplifier,

Inverting and Noninverting Amplifier

Difference Amplifier

Gain Range 1 to 13

CMRR >75dB

Noninverting Amplifier

Gain Range 0.07 to 14

Inverting Amplifier

Gain Range –0.08 to –13

Gain Error <0.04%

Gain Drift < 3ppm/°C

Wide Supply Range: Single 2.7V to Split ±18V

Micropower: 100µA Supply Current

Precision: 50µV Maximum Input Offset Voltage

560kHz Gain Bandwidth Product

Rail-to-Rail Output

Space Saving 10-Lead MSOP and DFN Packages

Handheld Instrumentation

Medical Instrumentation

Strain Gauge Amplifiers

Differential to Single-Ended Conversion

RESISTOR MATCHING (%)

PERCENTAGE OF UNITS (%)

0.04

1991 TA01b

–0.02

0.02

–0.04

450k RESISTORS

LT1991A

Distribution of Resistor Matching

L, LT, LTC and LT M are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

TYPICAL APPLICATION

Summary of content (28 pages)

PAGE 1
LT1991 Precision, 100µA Gain Selectable Amplifier FEATURES DESCRIPTION Pin Configurable as a Difference Amplifier, Inverting and Noninverting Amplifier n Difference Amplifier Gain Range 1 to 13 CMRR >75dB n Noninverting Amplifier Gain Range 0.07 to 14 n Inverting Amplifier Gain Range –0.08 to –13 n Gain Error <0.04% n Gain Drift < 3ppm/°C n Wide Supply Range: Single 2.
PAGE 2
LT1991 ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V – ) ................................40V Input Voltage (Pins P1/M1, Note 2) .........................±60V Input Voltage (Other Inputs Note 2) ...................V+ + 0.2V to V – – 0.2V Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range (Note 4) LT1991C................................................–40°C to 85°C LT1991I.................................................–40°C to 85°C LT1991H..........
PAGE 3
LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted.
PAGE 4
LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted.
PAGE 5
LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN ∆G Gain Error VS = ±15V, VOUT = ±10V; RL = 10k G=1 G = 3 or 9 l l TYP MAX UNITS ±0.08 ±0.
PAGE 6
LT1991 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration, VS = 5V, 0V or ±15V; VCM = VREF = half supply, unless otherwise noted. SYMBOL PARAMETER CONDITIONS PSRR Power Supply Rejection Ratio VS = ±1.
PAGE 7
LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Swing vs Temperature 200 TA = 25°C 125 TA = –40°C 100 75 50 60 2 4 VEE –50 6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (±V) –25 0 25 50 75 100 –300 25 TA = 85°C –400 TA = 25°C –500 –600 –700 –800 –900 1 2 3 4 5 6 7 LOAD CURRENT (mA) 8 9 SOURCING 5 0.02 250 0 –250 –0.03 4 5 6 7 8 9 10 11 12 13 GAIN (V/V) 1991 G07 –0.04 VS = 5V, 0V REPRESENTATIVE PARTS 0 –50 –100 –150 1 2 3 5 4 1991 G05 0.30 0.25 –0.
PAGE 8
LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Bandwidth vs Gain CMRR vs Frequency 120 VS = 5V, 0V TA = 25°C 100 110 100 GAIN = 1 CMRR (dB) 60 40 20 90 1 2 3 4 70 60 50 5 6 7 8 9 10 11 12 13 GAIN SETTING (V/V) 30 20 20 10 10 1k 10k FREQUENCY (Hz) VS = 5V, 0V TA = 25°C 100 100 Gain Error vs Temperature 0.030 GAIN = 1 VS = ±15V GAIN = 1 60 40 0.1 0.
PAGE 9
LT1991 TYPICAL PERFORMANCE CHARACTERISTICS Small Signal Transient Response Small Signal Transient Response Small Signal Transient Response GAIN = 9 GAIN = 3 GAIN = 1 50mV/DIV 50mV/DIV 50mV/DIV 1991 G18 5µs/DIV PIN FUNCTIONS 1991 G19 5µs/DIV 5µs/DIV 1991 G20 (Difference Amplifier Configuration) P1 (Pin 1): Noninverting Gain-of-1 input. Connects a 450k internal resistor to the op amp’s noninverting input. OUT (Pin 6): Output. VOUT = VREF + 1 • (VP1 – VM1) + 3 • (VP3 – VM3) + 9 • (VP9 – VM9).
PAGE 10
LT1991 APPLICATIONS INFORMATION Introduction The LT1991 may be the last op amp you ever have to stock. Because it provides you with several precision matched resistors, you can easily configure it into several different classical gain circuits without adding external components. The several pages of simple circuits in this data sheet demonstrate just how easy the LT1991 is to use. It can be configured into difference amplifiers, as well as into inverting and noninverting single ended amplifiers.
PAGE 11
LT1991 APPLICATIONS INFORMATION The maximum voltage allowed on the P3, M3, P9, and M9 inputs includes the positive and negative supply plus a diode drop. These pins should not be driven more than 0.2V outside of the supply rails. This is because they are connected through diodes to internal manufacturing postpackage trim circuitry, and through a substrate diode to VEE. If more than 10mA is allowed to flow through these pins, there is a risk that the LT1991 will be detrimmed or damaged.
PAGE 12
LT1991 APPLICATIONS INFORMATION with VMORE = 0, the op amp output is at VREF. From the max VEXT (the high cm limit), as VMORE goes positive, the op amp output will go more negative from VREF by the amount VMORE • RF/RG, so: representation of the circuit on the top. The LT1991 is shown on the bottom configured in a precision gain of 5.5. One of the benefits of the noninverting op amp configuration is that the input impedance is extremely high. The LT1991 maintains this benefit.
PAGE 13
LT1991 APPLICATIONS INFORMATION Table 1. Configuring the M Pins for Simple Noninverting Gains. The P Inputs are driven as shown in the examples on the next page M9, M3, M1 Connection Gain M9 M3 M1 1 Output Output Output 1.077 Output Output Ground 1.1 Output Float Ground 1.25 Float Output Ground 1.273 Output Ground Output 1.3 Output Ground Float 1.4 Output Ground Ground 2 Float Float Ground 2.5 Float Ground Output 2.8 Ground Output Output 3.
PAGE 14
LT1991 APPLICATIONS INFORMATION VS+ 8 M9 9 M3 10 M1 VIN 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 VS+ 8 M9 9 M3 10 M1 6 VOUT 1 P1 2 P3 3 P9 VIN 4 VS– 7 VCC LT1991 VEE VOUT VIN 4 LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS– 7 VCC LT1991 VEE OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VIN 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 VS+ 8 M9 9 M3 10 M1 6 VOUT 1 P1 2 P3 3 P9 VIN 4 VS– 6 VOUT 4 VS+ 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4 LT1991 OUT REF 5 6 GAIN = 5.
PAGE 15
LT1991 APPLICATIONS INFORMATION Attenuation Using the P Input Resistors Attenuation happens as a matter of fact in difference amplifier configurations, but it is also used for reducing peak signal level or improving input common mode range even in single ended systems. When signal conditioning indicates a need for attenuation, the LT1991 resistors are ready at hand. The four precision resistors can provide several attenuation levels, and these are tabulated in Table 2 as a design reference.
PAGE 16
LT1991 APPLICATIONS INFORMATION Inverting Configuration Table 3. Configuring the M Pins for Simple Inverting Gains The inverting amplifier, shown in Figure 8, is another classical op amp configuration. The circuit is actually identical to the noninverting amplifier of Figure 4, except that VIN and GND have been swapped. The list of available gains is shown in Table 3, and some of the circuits are shown in Figure 9. Noise gain is 1+|Gain|, as is the usual case for inverting amplifiers.
PAGE 17
LT1991 APPLICATIONS INFORMATION VS+ 8 M9 9 M3 10 M1 VIN 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VIN VOUT VS+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 4 VS– LT1991 VEE 1 P1 2 P3 3 P9 LT1991 VEE OUT REF 5 6 VIN VOUT 1 P1 2 P3 3 P9 4 VIN 7 VCC LT1991 VEE VIN 7 VCC LT1991 VEE OUT REF 5 6 VOUT OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 VS– VIN VIN 7 VCC LT1991 OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 4 1 P1 2 P3 3 P9 LT1991 VEE OUT REF 5 4 6 VOUT VS+ 7 VCC LT1991 VEE OUT REF 5 6 VOUT 4
PAGE 18
LT1991 APPLICATIONS INFORMATION Difference Amplifiers RF The resistors in the LT1991 allow it to easily make difference amplifiers also. Figure 10 shows the basic 4-resistor difference amplifier and the LT1991. A difference gain of 3 is shown, but notice the effect of the additional dashed connections. By connecting the 450k resistors in parallel, the gain is reduced by a factor of 2. Of course, with so many resistors, there are many possible gains.
PAGE 19
LT1991 APPLICATIONS INFORMATION VIN VIN VS+ 8 M9 9 M3 10 M1 – 1 P1 2 P3 3 P9 + 7 VCC LT1991 VEE OUT REF 5 6 – VIN VOUT VS+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 + VIN 4 VS– LT1991 VEE VIN+ 1 P1 2 P3 3 P9 7 VCC LT1991 VEE OUT REF 5 6 VIN– 8 M9 9 M3 10 M1 VIN+ 1 P1 2 P3 3 P9 VOUT 4 VIN+ 1 P1 2 P3 3 P9 VIN+ 1 P1 2 P3 3 P9 7 VCC LT1991 OUT REF 5 6 VOUT 1 P1 2 P3 3 P9 VIN+ 4 – VIN 7 VCC LT1991 VEE OUT REF 5 6 VOUT VIN+ 4 VS– VIN– 1 P1 2 P3 3 P9 VIN– 7 VCC LT1991 OUT
PAGE 20
LT1991 APPLICATIONS INFORMATION 8 M9 50k VIN– VIN+ RG RG 4pF 9 M3 150k VIN– RF 450k 10 M1 450k CROSSCOUPLING – VOUT + VIN+ VOUT = GAIN • (VIN+ – VIN–) GAIN = RF/RG RF 1 P1 450k 2 P3 150k 3 P9 50k – 6 VOUT + 4pF 450k 5 LT1991 CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED WITH LT1991. RF = 450k, RG = 150k, GAIN = 3. GAIN CAN BE ADJUSTED BY "CROSS COUPLING." MAKING THE DASHED CONNECTIONS REDUCE THE GAIN FROM 3 T0 2. WHEN CROSS COUPLING, SEE WHAT IS CONNECTED TO THE VIN+ VOLTAGE.
PAGE 21
LT1991 APPLICATIONS INFORMATION High Voltage CM Difference Amplifiers This class of difference amplifier remains to be discussed. Figure 14 shows the basic circuit on the top. The effective input voltage range of the circuit is extended by the fact that resistors RT attenuate the common mode voltage seen by the op amp inputs.
PAGE 22
LT1991 APPLICATIONS INFORMATION 3V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ 3V 7 VCC 6 VOUT OUT REF 5 1.25V LT1991 VEE 4 VIN– VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VCM = 0.8V TO 2.35V VIN– 1 P1 2 P3 3 P9 VIN+ 7 VCC 6 VOUT OUT REF 5 1.25V LT1991 VEE 4 LT1991 VEE OUT REF 5 6 VIN– VOUT 4 VIN– VIN+ 1 P1 2 P3 3 P9 LT1991 VEE 4 VEE 4 3V 7 VCC 6 VOUT OUT REF 5 1.25V OUT REF 5 6 VOUT 3V VCM = –1V TO 0.6V VDM <–40mV 3V 8 M9 9 M3 10 M1 7 VCC LT1991 1 P1 2 P3 3 P9 VIN+ VCM = 2V TO 3.
PAGE 23
LT1991 APPLICATIONS INFORMATION 5V 8 M9 9 M3 10 M1 VIN– 1 P1 2 P3 3 P9 VIN+ 5V 7 VCC LT1991 OUT REF 5 2.5V VEE 4 6 VOUT VIN– VIN+ 8 M9 9 M3 10 M1 1 P1 2 P3 3 P9 VCM = –0.5V TO 5.1V VIN– 1 P1 2 P3 3 P9 VIN+ 7 VCC LT1991 OUT REF 5 2.5V VEE 4 LT1991 VEE OUT REF 5 6 VIN– VOUT 4 6 VOUT VIN– VIN+ 1 P1 2 P3 3 P9 VEE 4 VEE 4 5V 7 VCC LT1991 6 OUT REF 5 VOUT 3V VCM = –3V TO 2.6V VDM <–40mV 5V 8 M9 9 M3 10 M1 7 VCC LT1991 1 P1 2 P3 3 P9 VIN+ VCM = 2V TO 7.
PAGE 24
LT1991 APPLICATIONS INFORMATION 5V VIN– VIN+ 8 M9 9 M3 10 M1 5V 7 VCC LT1991 1 P1 2 P3 3 P9 OUT REF 5 VEE 6 VOUT VIN– 8 M9 9 M3 10 M1 4 –5V VIN– VIN+ 5V 1 P1 2 P3 3 P9 7 VCC LT1991 OUT REF 5 VEE 6 VOUT VIN– –5V VIN+ 1 P1 2 P3 3 P9 7 VCC VEE 6 VOUT VIN– 4 –5V –5V VIN– VIN+ 1 P1 2 P3 3 P9 7 VCC VEE OUT REF 5 VCM = –56V TO 53.
PAGE 25
LT1991 TYPICAL APPLICATIONS Micropower AV = 10 Instrumentation Amplifier VM 10 + 9 8 7 VOUT 6 1/2 LT6011 – 4pF – VP + + LT1991 1/2 LT6011 – 4pF 1 2 3 4 5 1991 TA02 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) R = 0.125 TYP 6 0.40 ± 0.10 10 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 0.25 ± 0.
PAGE 26
LT1991 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev E) 0.889 ±0.127 (.035 ±.005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 3.00 ±0.102 (.118 ±.004) (NOTE 3) 0.50 0.305 ±0.038 (.0197) (.0120 ±.0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 10 9 8 7 6 3.00 ±0.102 (.118 ±.004) (NOTE 4) 4.90 ±0.152 (.193 ±.006) DETAIL “A” 0.497 ±0.076 (.0196 ±.
PAGE 27
LT1991 REVISION HISTORY (Revision history begins at Rev H) REV DATE DESCRIPTION H 5/12 Corrected specified temperature range for C-grade parts in the Order Information table. PAGE NUMBER 2 Corrected VCM = –20V to 19V and VCM = –5V to 34V configurations in Figure 17. 24 Updated Related Parts Table 28 1991fh Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 28
LT1991 TYPICAL APPLICATION Bidirectional Current Source VIN+ VS+ 8 M9 9 M3 10 M1 VIN– R2* 10k 1 P1 2 P3 3 P9 Single Supply AC Coupled Amplifier 7 8 M9 9 M3 10 M1 1µF 6 LT1991 R1 10k 5 VCC 0.1µF VIN 4 ILOAD = VS– 1 P1 2 P3 3 P9 VIN+ – VIN– 10kΩ 1 P1 2 P3 3 P9 VOUT 5 4 Analog Level Adaptor 5V 8 M9 9 M3 10 M1 5V VIN = 14V to 53V 6 LT1991 1991 TA03 Ultra-Stable Precision Attenuator 7 6 LT1991 7 GAIN = 12 BW = 7Hz TO 32kHz *SHORT R2 FOR LOWEST OUTPUT OFFSET CURRENT.