LTC6911HMS-1_技术文档

LTC6911-1/LTC6911-2

Dual Matched Amplifiers

with Digitally Programmable

Gain in MSOP

U

FEATURES

DESCRIPTIO

The LTC^®6911 is a family of low noise digitally program-

mable gain amplifiers (PGAs) that are easy to use and

occupy very little PC board space. The matched gain of

both channels is adjustable using a 3-bit parallel interface

to select voltage gains of 0, 1, 2, 5, 10, 20, 50 and 100V/

V (LTC6911-1) and 0, 1, 2, 4, 8, 16, 32 and 64V/V

(LTC6911-2). All gains are inverting.

■

3-Bit Digital Gain Control:

(Inverting Gains of 0, 1, 2, 5, 10, 20, 50

and 100V/V) -1 Option

(Inverting Gains of 0, 1, 2, 4, 8, 16, 32

and 64V/V) -2 Option

■

Two Matched Programmable Gain Amplifiers

■

Channel-to-Channel Gain Matching of 0.1dB (Max)

■

Rail-to-Rail Input Range

Rail-to-Rail Output Swing

The LTC6911 family consists of two matched inverting

amplifiers with rail-to-rail outputs. When operated with

unity gain, they will also process rail-to-rail input signals.

A half-supply reference generated internally at the AGND

pin supports single power supply applications. Operating

from single or split supplies from 2.7V to 10.5V, the

LTC6911 family is offered in a 10-lead MSOP package.

■

Single or Dual Supply: 2.7V to 10.5V Total

■

11MHz Gain Bandwidth Product

Input Noise: 10nV/√Hz

■

Total System Dynamic Range to 120dB

■

Input Offset Voltage: 2mV, Gain of 10

■

Low Profile 10-Lead MSOP Package

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

U

APPLICATIO S

■

Data Acquisition Systems

■

Dynamic Gain Changing

■

Automatic Ranging Circuits

Automatic Gain Control

■

U

TYPICAL APPLICATIO

+

V

2.7V TO 10.5V 0.1µF

Frequency Response (LTC6911-1)

50

7

9

V

= 10V, V = 5mV

IN

S

RMS

GAIN OF –100 (DIGITAL INPUT 111)

DIGITAL

40

30

INPUT

GAIN IN V/V

1

2

3

10

V

=

G2 G1 G0 LTC6911-1 LTC6911-2

OUTA

V

INA

GAIN • V

GAIN OF –50 (DIGITAL INPUT 110)

INA

INB

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

AGND

–1

≥1µF

GAIN OF –20 (DIGITAL INPUT 101)

GAIN OF –10 (DIGITAL INPUT 100)

GAIN OF –5 (DIGITAL INPUT 011)

–2

–5

–10

–20

–50

–100

–2

20

10

–4

LTC6911-X

–8

–16

–32

–64

8

V

OUTB

=

GAIN OF –2 (DIGITAL INPUT 010)

GAIN OF –1 (DIGITAL INPUT 001)

V

INB

GAIN • V

0

–10

100

691112 TA01

1k

10k

100k

1M

10M

4

5

6

G2

FREQUENCY (Hz)

691112 TA02

G0

G1

sn691112 691112fs

1

LTC6911-1/LTC6911-2

W W

U W

U

ABSOLUTE AXI U RATI GS

(Note 1)

PACKAGE/ORDER I FOR ATIO

Total Supply Voltage (V⁺to V^–) .............................. 11V

Input Current ..................................................... ±10mA

Operating Temperature Range (Note 2)

LTC6911C-1/LTC6911C-2 .................. –40°C to 85°C

LTC6911I-1/LTC6911I-2 .................... –40°C to 85°C

LTC6911H-1/LTC6911H-2 ................ –40°C to 125°C

Specified Temperature Range (Note 3)

LTC6911C-1/LTC6911C-2 .................. –40°C to 85°C

LTC6911I-1/LTC6911I-2 .................... –40°C to 85°C

LTC6911H-1/LTC6911H-2 ................ –40°C to 125°C

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

Lead Temperature (Soldering, 10 sec).................. 300°C

TOP VIEW

INA

AGND

INB

1

2

3

4

5

10 OUTA

–

9

8

7

6

V

OUTB

+

G0

V

G1

G2

MS PACKAGE

10-LEAD PLASTIC MSOP

T_JMAX= 150°C, θ_JA= 230°C/W

ORDER PART NUMBER

MS PART MARKING

LTC6911CMS-1

LTC6911IMS-1

LTC6911HMS-1

LTC6911CMS-2

LTC6911IMS-2

LTC6911HMS-2

LTAHK

LTAHM

LTBCF

LTAHH

LTAHJ

LTBCG

Consult LTC Marketing for parts specified with wider operating temperature ranges.

U

GAI SETTI GS A D PROPERTIES

Table 1 (LTC6911-1)

NOMINAL

MAXIMUM LINEAR INPUT RANGE (V

)

P-P

INPUT

IMPEDANCE

(kΩ)

DIGITAL INPUTS

VOLTAGE GAIN

Dual 5V

Supply

Single 5V

Supply

Single 3V

Supply

G2

0

G1

0

G0

0

Volts/Volt

(dB)

–120

0

–1

–2

–5

–10

–20

–50

–100

10

5

2

1

0.5

0.2

0.1

5

2.5

1

0.5

0.25

0.1

0.05

3

(Open)

10

5

2

1

0

1

0

1

0

6

1.5

0.6

0.3

0.15

0.06

0.03

0

1

14

20

26

34

40

1

0

1

0

1

0

1

Table 2 (LTC6911-2)

NOMINAL

INPUT

NOMINAL

VOLTAGE GAIN

MAXIMUM LINEAR INPUT RANGE (V

)

P-P

DIGITAL INPUTS

Dual 5V

Supply

Single 5V

Supply

Single 3V

Supply

IMPEDANCE

(kΩ)

G2

0

G1

0

G0

0

1

Volts/Volt

0

(dB)

–120

0

10

5

3

(Open)

10

–1

0

1

0

–2

6

5

2.5

1.5

5

0

1

0

1

0

1

0

–4

–8

–16

–32

–64

12

2.5

1.25

0.625

0.3125

0.156

0.078

0.75

0.375

0.188

0.094

0.047

2.5

18.1

24.1

30.1

36.1

1.25

0.625

0.3125

0.156

1.25

1

sn691112 691112fs

2

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-1/LTC6911-2

Total Supply Voltage (V )

●

2.7

10.5

2.7

10.5

V

S

Supply Current per Channel

V = 2.7V, V = V = V

AGND

●

2.1 3.15

2.5 3.75

3.1 4.65

2.1 3.25

2.5 4.00

3.1 5.00

mA

S

INA

INB

V = 5V, V = V = V

S

INA

INB

AGND

V = ±5V, V = V = 0V, Pins 4, 5, 6 = –4.5V or 5V

S

INA

INB

V = ±5V, V = V = 0V, Pin 4 = 4.5V,

S

INA

INB

Pins 5, 6 = 0.5V

Output Voltage Swing LOW (Note 4)

V = 2.7V, R = 10k Tied to Mid Supply

●

12

60

30

110

12

60

35

125

mV

S

L

V = 2.7V, R = 500Ω Tied to Mid Supply

S

L

V = 5V, R = 10k Tied to Mid Supply

●

20

40

20

45

mV

S

L

V = 5V, R = 500Ω Tied to Mid Supply

100 170

100 190

S

L

V = ±5V, R = 10k Tied to 0V

●

30

50

30

60

mV

S

L

V = ±5V, R = 500Ω Tied to 0V

190 260

190 290

S

L

Output Voltage Swing HIGH (Note 4)

V = 2.7V, R = 10k Tied to Mid Supply

●

10

50

20

80

10

50

25

90

mV

S

L

V = 2.7V, R = 500Ω Tied to Mid Supply

S

L

V = 5V, R = 10k Tied to Mid Supply

●

10

90

30

160

10

90

35

175

mV

S

L

V = 5V, R = 500Ω Tied to Mid Supply

S

L

V = ±5V, R = 10k Tied to 0V

●

20

40

20

45

mV

S

L

V = ±5V, R = 500Ω Tied to 0V

180 250

180 270

S

L

Output Short-Circuit Current (Note 5) V = 2.7V

●

±27

±35

±27

±35

mA

S

V = ±5V

S

AGND Open-Circuit Voltage

V = 5V

S

●

2.45 2.5 2.55

V

AGND (Common Mode)

Input Voltage Range

V = 2.7V

S

V = ±5V

S

●

0.55

0.75

–4.30

1.60

3.65

0.55

0.75

1.60

3.65

3.20

V

S

V = 5V

3.20 –4.30

AGND Rejection (i.e., Common

Mode Rejection or CMRR)

V = 2.7V, V

S

= 1.1V to 1.6V

= –2.5V to 2.5V

●

55

80

75

50

80

75

dB

S

AGND

V = ±5V, V

Power Supply Rejection Ratio (PSRR) V = 2.7V to ±5V

●

60

80

57

80

dB

S

Slew Rate

V = 5V, V

S

= V

OUTA

= 1.1V to 3.9V

12

16

12

16

V/µs

S

OUTA

OUTB

V = ±5V, V

= V

= ±1.4V

OUTB

Signal Attenuation at Gain = 0 Setting Gain = 0 (Digital Inputs 000), f = 20kHz

●

–120

dB

Digital Input “High” Voltage

Digital Input “Low” Voltage

Digital Input “High” Current

Digital Input “Low” Current

V = 2.7V

S

V = ±5V

S

●

2.43

4.50

2.43

4.50

V

S

V = 5V

V = 2.7V

●

0.27

0.50

0.27

0.50

V

S

V = 5V

S

V = ±5V

S

V = 2.7V, Pins 4, 5, 6 = 2.43V

●

1

5

1

5

µA

S

V = 5V, Pins 4, 5, 6 = 4.5V

S

V = ±5V, Pins 4, 5, 6 = 4.5V

10

S

V = 2.7V, Pins 4, 5, 6 = 0.27V

●

1

5

10

1

5

10

µA

S

V = 5V, Pins 4, 5, 6 = 0.5V

S

V = ±5V, Pins 4, 5, 6 = 0.5V

S

sn691112 691112fs

3

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-1 Only

Voltage Gain (Note 6)

V = 2.7V, Gain = 1, R = 10k

●

–0.07

0

0.07

–0.08

0

0.07

dB

S

L

V = 2.7V, Gain = 1, R = 500Ω

–0.11 –0.02 0.07

–0.13 –0.02 0.07

S

L

V = 2.7V, Gain = 2, R = 10k

●

5.94 6.01 6.08

5.93 6.01 6.08

dB

S

L

V = 2.7V, Gain = 5, R = 10k

13.85 13.95 14.05 13.8 13.95 14.05

S

L

V = 2.7V, Gain = 10, R = 10k

●

19.7 19.93 20.1

19.6 19.85 20.1

19.65 19.93 20.1

19.45 19.85 20.1

dB

S

L

V = 2.7V, Gain = 10, R = 500Ω

S

L

V = 2.7V, Gain = 20, R = 10k

●

25.75 25.94 26.1

33.5 33.8 34.1

25.65 25.94 26.1

33.4 33.8 34.1

dB

S

L

V = 2.7V, Gain = 50, R = 10k

S

L

V = 2.7V, Gain = 100, R = 10k

●

39.0 39.6 40.1

37.4 38.9 40.1

38.8 39.6 40.1

36.5 38.9 40.1

dB

S

L

V = 2.7V, Gain = 100, R = 500Ω

S

L

V = 5V, Gain = 1, R = 10k

●

–0.08 0.01 0.08

–0.11 –0.01 0.07

–0.09 0.01 0.08

–0.13 –0.01 0.07

dB

S

L

V = 5V, Gain = 1, R = 500Ω

S

L

V = 5V, Gain = 2, R = 10k

●

5.95 6.02 6.09

13.8 13.96 14.1

5.94 6.02 6.09

13.78 13.96 14.1

dB

S

L

V = 5V, Gain = 5, R = 10k

S

L

V = 5V, Gain = 10, R = 10k

●

19.8 19.94 20.1

19.6 19.87 20.1

19.75 19.94 20.1

19.45 19.87 20.1

dB

S

L

V = 5V, Gain = 10, R = 500Ω

S

L

V = 5V, Gain = 20, R = 10k

●

25.8 25.94 26.1

33.5 33.84 34.1

25.75 25.94 26.1

33.4 33.84 34.1

dB

S

L

V = 5V, Gain = 50, R = 10k

S

L

V = 5V, Gain = 100, R = 10k

●

39.3 39.7 40.1

38.0 39.2 40.1

39.1 39.7 40.1

37.0 39.2 40.1

dB

S

L

V = 5V, Gain = 100, R = 500Ω

S

L

V = ±5V, Gain = 1, R = 10k

●

–0.06 0.01 0.08

–0.10 0.00 0.08

–0.07 0.01 0.08

–0.11 0.00 0.08

dB

S

L

V = ±5V, Gain = 1, R = 500Ω

S

L

V = ±5V, Gain = 2, R = 10k

●

5.95 6.02 6.09

13.8 13.96 14.1

5.94 6.02 6.09

13.79 13.96 14.1

dB

S

L

V = ±5V, Gain = 5, R = 10k

S

L

V = ±5V, Gain = 10, R = 10k

●

19.8 19.94 20.1

19.7 19.91 20.1

19.75 19.94 20.1

19.60 19.91 20.1

dB

S

L

V = ±5V, Gain = 10, R = 500Ω

S

L

V = ±5V, Gain = 20, R = 10k

●

25.8 25.95 26.1

33.7 33.87 34.1

25.75 25.95 26.1

33.60 33.87 34.1

dB

S

L

V = ±5V, Gain = 50, R = 10k

S

L

V = ±5V, Gain = 100, R = 10k

●

39.4 39.8 40.2

38.8 39.5 40.1

39.25 39.8 40.2

38.00 39.5 40.1

dB

S

L

V = ±5V, Gain = 100, R = 500Ω

S

L

Channel-to-Channel Voltage

Gain Match

V = 2.7V, Gain = 1, R = 10k

●

–0.1 0.02 0.1

dB

S

L

V = 2.7V, Gain = 1, R = 500Ω

S

L

V = 2.7V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 5, R = 10k

S

L

V = 2.7V, Gain = 10, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 10, R = 500Ω

S

L

V = 2.7V, Gain = 20, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 50, R = 10k

S

L

V = 2.7V, Gain = 100, R = 10k

●

–0.20 0.02 0.20

–1.00 0.02 1.00

–0.20 0.02 0.20

–1.50 0.02 1.50

dB

S

L

V = 2.7V, Gain = 100, R = 500Ω

S

L

sn691112 691112fs

4

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-1 Only

Channel-to-Channel Voltage

Gain Match

V = 5V, Gain = 1, R = 10k

●

–0.1 0.02 0.1

dB

S

L

V = 5V, Gain = 1, R = 500Ω

S

L

V = 5V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 5, R = 10k

S

L

V = 5V, Gain = 10, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 10, R = 500Ω

S

L

V = 5V, Gain = 20, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 50, R = 10k

S

L

V = 5V, Gain = 100, R = 10k

●

–0.2 0.02 0.2

–0.8 0.02 0.8

–0.2 0.02 0.2

–1.2 0.02 1.2

dB

S

L

V = 5V, Gain = 100, R = 500Ω

S

L

V = ±5V, Gain = 1, R = 10k

●

–0.1 0.02 0.1

dB

S

L

V = ±5V, Gain = 1, R = 500Ω

S

L

V = ±5V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 5, R = 10k

S

L

V = ±5V, Gain = 10, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 10, R = 500Ω

S

L

V = ±5V, Gain = 20, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 50, R = 10k

S

L

V = ±5V, Gain = 100, R = 10k

●

–0.2 0.02 0.2

–0.6 0.02 0.6

–0.2 0.02 0.2

–0.9 0.02 0.9

dB

S

L

V = ±5V, Gain = 100, R = 500Ω

S

L

Gain Temperature Coefficient

V = 5V, Gain = 1, R = Open

2

ppm/°C

ppm/°C-

ppm/°C

S

L

V = 5V, Gain = 2, R = Open

–1.5

–11

–30

–38

–70

–140

–1.5

–11

–30

–38

–70

–140

S

L

V = 5V, Gain = 5, R = Open

S

L

V = 5V, Gain = 10, R = Open

S

L

V = 5V, Gain = 20, R = Open

S

L

V = 5V, Gain = 50, R = Open

S

L

V = 5V, Gain = 100, R = Open

S

L

Channel-to-Channel Gain Temperature V = 5V, Gain = 1, R = Open

1.0

0.2

1.0

0.4

3.0

1.0

0.2

1.0

0.4

3.0

ppm/°C

S

L

Coefficient Match

V = 5V, Gain = 2, R = Open

S L

V = 5V, Gain = 5, R = Open

S

L

V = 5V, Gain = 10, R = Open

S

L

V = 5V, Gain = 20, R = Open

S

L

V = 5V, Gain = 50, R = Open

S

L

V = 5V, Gain = 100, R = Open

S

L

Channel-to-Channel Isolation (Note 7) f = 200kHz

V = 5V, Gain = 1, R = 10k

108

107

93

108

107

93

dB

S

L

V = 5V, Gain = 10, R = 10k

S

L

V = 5V, Gain = 100, R = 10k

S

L

Offset Voltage Magnitude Referred

to INA or INB Pins (Note 8)

Gain = 1

Gain = 10

●

2.0

1.1

22

12

2.0

1.1

22

14

mV

Offset Voltage Magnitude Drift

Referred to INA or INB Pins (Note 8)

Gain = 1

Gain = 10

12

6.6

20

11

µV/°C

sn691112 691112fs

5

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-1 Only

DC Input Resistance at

INA or INB Pins (Note 9)

DC V or V = 0V

INA INB

Gain = 0

●

>100

10

5

>100

10

5

MΩ

kΩ

Gain = 1

Gain = 2

Gain = 5

Gain > 5

2

1

DC Input Resistance Match

Gain = 1

Gain = 2

Gain = 5

Gain > 5

●

10

5

10

5

Ω

R

– R

INA

INB

2

1

DC Small-Signal Output Resistance

at OUTA or OUTB Pins

DC V or V = 0V

INA INB

Gain = 0

0.4

0.7

1.0

1.9

3.4

6.4

15

0.4

0.7

1.0

1.9

3.4

6.4

15

Ω

Gain = 1

Gain = 2

Gain = 5

Gain = 10

Gain = 20

Gain = 50

Gain = 100

30

Gain-Bandwidth Product

Gain = 100, f = 200kHz

●

7

11

18

6

11

18

MHz

IN

Wideband Noise (Referred to Input)

f = 1kHz to 200kHz

Gain = 0 (Output Noise Only)

Gain = 1

7.5

12.3

8.5

6.1

5.2

5.0

4.5

3.8

7.5

12.3

8.5

6.1

5.2

5.0

4.5

3.8

µV

RMS

µV

Gain = 2

Gain = 5

Gain = 10

Gain = 20

Gain = 50

Gain = 100

Voltage Noise Density

(Referred to Input)

f = 50kHz

Gain = 1

28

19

28

19

nV/√Hz

Gain = 2

Gain = 5

14

Gain = 10

Gain = 20

Gain = 50

Gain = 100

12

11.5

10.8

9.9

11.5

10.8

9.9

Total Harmonic Distortion

Gain = 10, f = 10kHz, V

= 1V

RMS

–90

0.003

–90

0.003

dB

%

IN

OUT

Gain = 10, f = 100kHz, V

= 1V

RMS

–82

0.008

–82

0.008

dB

%

IN

OUT

sn691112 691112fs

6

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-2 Only

Voltage Gain (Note 6)

V = 2.7V, Gain = 1, R = 10k

●

–0.07

0

0.07

–0.08

0

0.07

dB

S

L

V = 2.7V, Gain = 1, R = 500Ω

–0.11 –0.02 0.07

–0.13 –0.02 0.07

S

L

V = 2.7V, Gain = 2, R = 10k

●

5.94 6.01 6.08

5.93 6.01 6.08

dB

S

L

V = 2.7V, Gain = 4, R = 10k

11.9 12.02 12.12 11.88 12.02 12.12

S

L

V = 2.7V, Gain = 8, R = 10k

●

17.80 18.00 18.15 17.75 18.00 18.15

17.65 17.94 18.15 17.55 17.94 18.15

dB

S

L

V = 2.7V, Gain = 8, R = 500Ω

S

L

V = 2.7V, Gain = 16, R = 10k

●

23.8 24.01 24.25 23.75 24.01 24.25

dB

S

L

V = 2.7V, Gain = 32, R = 10k

29.7 30 30.2

29.65 30 30.2

S

L

V = 2.7V, Gain = 64, R = 10k

●

35.3 35.8 36.2

34.2 35.3 36.2

35.15 35.8 36.2

33.65 35.3 36.2

dB

S

L

V = 2.7V, Gain = 64, R = 500Ω

S

L

V = 5V, Gain = 1, R = 10k

●

–0.08 0.00 0.08

–0.10 –0.01 0.08

–0.09 0.00 0.08

–0.12 –0.01 0.08

dB

S

L

V = 5V, Gain = 1, R = 500Ω

S

L

V = 5V, Gain = 2, R = 10k

●

5.96 6.02 6.1

5.95 6.02 6.1

dB

S

L

V = 5V, Gain = 4, R = 10k

11.85 12.02 12.15 11.83 12.02 12.15

S

L

V = 5V, Gain = 8, R = 10k

●

17.85 18.01 18.15 17.83 18.01 18.15

17.65 17.96 18.15 17.50 17.96 18.15

dB

S

L

V = 5V, Gain = 8, R = 500Ω

S

L

V = 5V, Gain = 16, R = 10k

●

23.85 24.02 24.15 23.80 24.02 24.15

dB

S

L

V = 5V, Gain = 32, R = 10k

29.70 30.02 30.2

29.65 30.02 30.2

S

L

V = 5V, Gain = 64, R = 10k

●

35.5 35.9 36.3

34.7 35.6 36.1

35.40 35.9 36.3

34.20 35.6 36.1

dB

S

L

V = 5V, Gain = 64, R = 500Ω

S

L

V = ±5V, Gain = 1, R = 10k

●

–0.06 0.01 0.08

–0.10 0.00 0.08

–0.07 0.01 0.08

–0.11 0.00 0.08

dB

S

L

V = ±5V, Gain = 1, R = 500Ω

S

L

V = ±5V, Gain = 2, R = 10k

●

5.96 6.02 6.1

5.95 6.02 6.1

dB

S

L

V = ±5V, Gain = 4, R = 10k

11.9 12.03 12.15 11.88 12.03 12.15

S

L

V = ±5V, Gain = 8, R = 10k

●

17.85 18.02 18.15 17.83 18.02 18.15

17.80 17.99 18.15 17.73 17.99 18.15

dB

S

L

V = ±5V, Gain = 8, R = 500Ω

S

L

V = ±5V, Gain = 16, R = 10k

●

23.85 24.03 24.15 23.82 24.03 24.15

dB

S

L

V = ±5V, Gain = 32, R = 10k

29.85 30 30.2

29.8 30 30.2

S

L

V = ±5V, Gain = 64, R = 10k

●

35.65 36.0 36.20 35.55 36.0 36.20

35.20 35.8 36.20 34.80 35.8 36.20

dB

S

L

V = ±5V, Gain = 64, R = 500Ω

S

L

Channel-to-Channel

Voltage Gain Match

V = 2.7V, Gain = 1, R = 10k

●

–0.1 0.02 0.1

dB

S

L

V = 2.7V, Gain = 1, R = 500Ω

S

L

V = 2.7V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 4, R = 10k

S

L

V = 2.7V, Gain = 8, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 8, R = 500Ω

S

L

V = 2.7V, Gain = 16, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 2.7V, Gain = 32, R = 10k

S

L

V = 2.7V, Gain = 64, R = 10k

●

–0.2 0.02 0.2

–0.7 0.02 0.7

–0.2 0.02 0.2

–1.0 0.02 1.0

dB

S

L

V = 2.7V, Gain = 64, R = 500Ω

S

L

sn691112 691112fs

7

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

V = 5V, Gain = 1, R = 10k

LTC6911-2 Only

●

–0.1 0.02 0.1

dB

S

L

V = 5V, Gain = 1, R = 500Ω

S

L

V = 5V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 4, R = 10k

S

L

V = 5V, Gain = 8, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 8, R = 500Ω

S

L

V = 5V, Gain = 16, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = 5V, Gain = 32, R = 10k

S

L

V = 5V, Gain = 64, R = 10k

●

–0.15 0.02 0.15

–0.60 0.02 0.60

–0.15 0.02 0.15

–0.80 0.02 0.80

dB

S

L

V = 5V, Gain = 64, R = 500Ω

S

L

V = ±5V, Gain = 1, R = 10k

●

–0.1 0.02 0.1

dB

S

L

V = ±5V, Gain = 1, R = 500Ω

S

L

V = ±5V, Gain = 2, R = 10k

●

–0.1 0.02 0.1

–0.15 0.02 0.15

–0.1 0.02 0.1

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 4, R = 10k

S

L

V = ±5V, Gain = 8, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 8, R = 500Ω

S

L

V = ±5V, Gain = 16, R = 10k

●

–0.15 0.02 0.15

dB

S

L

V = ±5V, Gain = 32, R = 10k

S

L

V = ±5V, Gain = 64, R = 10k

●

–0.15 0.02 0.15

–0.40 0.02 0.40

–0.15 0.02 0.15

–0.60 0.02 0.60

dB

S

L

V = ±5V, Gain = 64, R = 500Ω

S

L

Gain Temperature Coefficient

V = 5V, Gain = 1, R = Open

2

–1

2

–1

ppm/°C

S

L

V = 5V, Gain = 2, R = Open

S

L

V = 5V, Gain = 4, R = Open

–7

S

L

V = 5V, Gain = 8, R = Open

–21

–28

–40

–115

–21

–28

–40

–115

S

L

V = 5V, Gain = 16, R = Open

S

L

V = 5V, Gain = 32, R = Open

S

L

V = 5V, Gain = 64, R = Open

S

L

Channel-to-Channel Gain

Temperature Coefficient Match

V = 5V, Gain = 1, R = Open

0

ppm/°C

S

L

V = 5V, Gain = 2, R = Open

–0.5

0.5

1.0

4.0

–0.5

0.5

1.0

4.0

S

L

V = 5V, Gain = 4, R = Open

S

L

V = 5V, Gain = 8, R = Open

S

L

V = 5V, Gain = 16, R = Open

S

L

V = 5V, Gain = 32, R = Open

S

L

V = 5V, Gain = 64, R = Open

S

L

Channel-to-Channel Isolation (Note 7) f = 200kHz

V = 5V, Gain = 1, R = 10k

110

93

110

93

dB

S

L

V = 5V, Gain = 8, R = 10k

S

L

V = 5V, Gain = 64, R = 10k

S

L

Offset Voltage Magnitude

Referred to INA or INB Pins (Note 8)

Gain = 1

Gain = 8

●

2.0

1.1

22

12

2.0

1.1

22

14

mV

Offset Voltage Magnitude Drift

Referred to INA or INB Pins (Note 8)

Gain = 1

Gain = 8

12

6.8

20

11

µV/°C

DC Input Resistance at

INA or INB Pins (Note 9)

DC V or V = 0V

INA INB

Gain = 0

●

>100

10

>100

10

MΩ

kΩ

Gain = 1

Gain = 2

Gain = 4

Gain > 4

5

2.5

1.25

2.5

1.25

sn691112 691112fs

8

LTC6911-1/LTC6911-2

ELECTRICAL CHARACTERISTICS

to midsupply point, unless otherwise noted.

The ● denotes the specifications that apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_S= 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), R_L= 10k

C/I GRADES

MIN TYP MAX

H GRADE

MIN TYP MAX UNITS

PARAMETER

CONDITIONS

LTC6911-2 Only

DC Input Resistance Match

INA

Gain = 1

Gain = 2

Gain = 4

Gain > 4

●

10

5

10

5

Ω

R

– R

INB

2

1

DC Small-Signal Output Resistance

at OUTA or OUTB Pins

DC V or V = 0V

INA INB

Gain = 0

0.4

0.7

1.0

1.9

3.4

6.4

15

0.4

0.7

1.0

1.9

3.4

6.4

15

Ω

Gain = 1

Gain = 2

Gain = 4

Gain = 8

Gain = 16

Gain = 32

Gain = 64

30

Wideband Noise (Referred to Input)

f = 1kHz to 200kHz

Gain = 0 (Output Noise Only)

Gain = 1

7.4

12.4

8.5

6.5

5.5

5.2

4.9

4.3

7.4

12.4

8.5

6.5

5.5

5.2

4.9

4.3

µV

RMS

Gain = 2

Gain = 4

Gain = 8

Gain = 16

Gain = 32

Gain = 64

Voltage Noise Density

(Referred to Input)

f = 50kHz

Gain = 1

Gain = 2

Gain = 4

Gain = 8

Gain = 16

Gain = 32

Gain = 64

28.0

19.0

14.8

12.7

11.8

11.5

10.9

28.0

19.0

14.8

12.7

11.8

11.5

10.9

nV/√Hz

Total Harmonic Distortion

Gain-Bandwidth Product

Gain = 8, f = 10kHz, V

= 1V

RMS

–90

dB

%

IN

OUT

0.003

Gain = 8, f = 100kHz, V

= 1V

RMS

–82

0.008

–82

0.008

dB

%

IN

OUT

Gain = 64, f = 200kHz

●

6

11

17

6

11

17

MHz

IN

Note 1: Absolute Maximum Ratings are those values beyond which the life

of the device may be impaired.

Note 6: Gain is measured with a DC large-signal test using an output

excursion between approximately 30% and 70% of the total supply

voltage.

Note 2: The LTC6911C and LTC6911I are guaranteed functional over the

operating temperature range of –40°C to 85°C. The LTC6911H is

guaranteed functional over the operating temperature range of –40°C to

125°C.

Note 3: The LTC6911C is guaranteed to meet specified performance from

0°C to 70°C. The LTC6911C is designed, characterized and expected to

meet specified performance from –40°C to 85°C but is not tested or QA

sampled at these temperatures. LTC6911I is guaranteed to meet specified

performance from –40°C to 85°C. The LTC6911H is guaranteed to meet

specified performance from –40°C to 125°C.

Note 4: Output voltage swings are measured as differences between the

output and the respective supply rail.

Note 5: Extended operation with output shorted may cause junction

temperature to exceed the 150°C limit and is not recommended.

Note 7: Channel-to-channel isolation is measured by applying a 200kHz

input signal to one channel so that its output varies 1V

and measuring

RMS

the output voltage RMS of the other channel relative to AGND with its

input tied to AGND. Isolation is calculated:

V

V_OUTA

V_OUTB

Isolation_A= 20 •log₁₀^OUTB, Isolation_B= 20 •log₁₀

V_OUTA

Note 8: Offset voltage referred to the INA or INB input is (1 + 1/G) times

the offset voltage of the internal op amp, where G is the nominal gain

magnitude. See Applications Information.

Note 9: Input resistance can vary by approximately ±30% part-to-part at a

given gain setting (input resistance match remains as specified).

sn691112 691112fs

9

LTC6911-1/LTC6911-2

U W

TYPICAL PERFOR A CE CHARACTERISTICS ^(LTC6911-1)

LTC6911-1 Gain Shift

LTC6911-1 –3dB Bandwidth

vs Gain Setting

LTC6911-1 Frequency Response

vs Temperature

50

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0.100

0.075

0.050

0.025

0

V

= 10V, V = 5mV

IN

V

•

= 5mV

RMS

V

S

= 5V

S

RMS

IN

V

•

= 2.7V

OUTPUT UNLOADED

S

GAIN OF 100 (DIGITAL INPUT 111)

= ±5V

40

30

S

GAIN = 100

GAIN = 10

GAIN OF 50 (DIGITAL INPUT 110)

GAIN OF 20 (DIGITAL INPUT 101)

GAIN OF 10 (DIGITAL INPUT 100)

GAIN OF 5 (DIGITAL INPUT 011)

•

20

10

GAIN = 1

–0.025

–0.050

–0.075

–0.100

•

GAIN OF 2 (DIGITAL INPUT 010)

GAIN OF 1 (DIGITAL INPUT 001)

0

•

–10

•

100

1k

10k

100k

1M

10M

–25

0

50

1

10

100

–50

75

100

25

FREQUENCY (Hz)

GAIN

TEMPERATURE (°C)

6911 G02

6911 G01

6911 G03

LTC6911-1 Channel Isolation

vs Frequency

LTC6911-1 Power Supply

Rejection vs Frequency

LTC6911-1 Noise Density

vs Frequency

100

10

1

90

80

70

60

50

40

30

20

10

0

120

115

110

105

100

95

V

T

= ±2.5V

= 25°C

V

= ±2.5V

V

= 5V

OUT

S

A

S

GAIN = 1

= 1V

RMS

INPUT REFERRED

GAIN = 1

+SUPPLY

–SUPPLY

GAIN = 10

GAIN = 100

90

85

1k

10k

100k

1k

10k

100k

1M

10M

100k

1M

FREQUENCY (Hz)

6911 G05

6911 G06

6911 G04

LTC6911-1 Distortion vs Frequency

with Light Loading (R_L= 10k)

LTC6911-1 Distortion vs Frequency

LTC6911-1 THD + Noise

vs Input Voltage

with Heavy Loading (R_L= 500Ω)

–30

–40

–50

–30

–40

–50

–20

–30

V

= ±2.5V

V

= ±2.5V

S

= 1V

(2.83V

)

= 1V

(2.83V

)

OUT

RMS

P-P

OUT

RMS

P-P

GAIN = 100

GAIN = 10

GAIN = 100

GAIN = 10

GAIN = 1

–40

–50

GAIN = 100

GAIN = 10

–60

–70

–60

–70

–60

–70

–80

–90

f

= 1kHz

IN

S

GAIN = 1

150k

–90

–100

–110

V

= ±5V

GAIN = 1

BW = 100Hz TO 22kHz

–100

50k

100k

200k

50k

100k

FREQUENCY (Hz)

200k

0

150k

1m

10n

0.1

1

10

INPUT VOLTAGE (V

)

P-P

FREQUENCY (Hz)

6911 G09

6911 G07

6911 G08

sn691112 691112fs

10

LTC6911-1/LTC6911-2

U W

TYPICAL PERFOR A CE CHARACTERISTICS ^(LTC6911-2)

LTC6911-2 Gain Shift

LTC6911-2 –3dB Bandwidth

vs Gain Setting

LTC6911-2 Frequency Response

vs Temperature

50

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0.100

0.075

0.050

0.025

0

V

= ±5V

IN

V

IN

V

•

V

•

= 10mV

RMS

V

S

= 5V

S

•

= 10mV

= 2.7V

OUTPUT UNLOADED

RMS

S

= ±5V

40

30

S

GAIN OF 64

GAIN OF 32

GAIN OF 16

GAIN OF 8

GAIN OF 4

GAIN OF 2

GAIN = 64

•

GAIN = 8

GAIN = 1

20

10

–0.025

–0.050

–0.075

–0.100

•

GAIN OF 1

•

0

•

–10

100

1k

10k

100k

1M

10M

–25

0

50

1

10

GAIN

100

–50

75

100

25

FREQUENCY (Hz)

TEMPERATURE (°C)

6911 G11

6911 G010

6911 G12

LTC6911-2 Channel Isolation

vs Frequency

LTC6911-2 Power Supply

Rejection vs Frequency

LTC6911-2 Noise Density

vs Frequency

90

80

70

60

50

40

30

20

10

0

100

10

1

120

115

110

105

100

95

V

= ±2.5V

V

T

= ±2.5V

= 25°C

V

= 5V

OUT

S

A

S

GAIN = 1

= 1V

RMS

INPUT REFERRED

GAIN = 1

GAIN = 8

+SUPPLY

–SUPPLY

GAIN = 1

GAIN = 8

GAIN = 64

90

85

1k

10k

100k

1M

10M

100k

1M

1k

10k

FREQUENCY (Hz)

100k

FREQUENCY (Hz)

6911 G14

6911 G15

6911 G13

LTC6911-2 Distortion vs Frequency

with Light Loading (R_L= 10k)

LTC6911-2 Distortion vs Frequency

LTC6911-2 THD + Noise

vs Input Voltage

with Heavy Loading (R_L= 500Ω)

–30

–40

–50

–20

–30

–40

–50

V

= ±2.5V

V

= ±2.5V

S

= 1V

(2.83V

)

= 1V

(2.83V

)

P-P

OUT

RMS

P-P

OUT

RMS

GAIN = 64

GAIN = 8

–40

GAIN = 64

–50

GAIN = 8

–60

–70

–60

–70

GAIN = 1

–60

GAIN = 64

GAIN = 8

–70

–80

–90

GAIN = 1

f

= 1kHz

IN

S

–90

–100

–110

V

= ±5V

GAIN = 1

BW = 100Hz TO 22kHz

–100

50k

100k

FREQUENCY (Hz)

200k

1m

10n

0.1

1

10

0

150k

50k

100k

200k

0

150k

INPUT VOLTAGE (V

)

P-P

FREQUENCY (Hz)

6911 G18

6911 G17

6911 G16

sn691112 691112fs

11

LTC6911-1/LTC6911-2

U

PI FU CTIO S

INA(Pin1):AnalogInput.TheinputsignaltotheAchannel

amplifier of the LTC6911-X is the voltage difference be-

tween the INA and AGND pin. The INA pin connects

internally to a digitally controlled resistance whose other

endisacurrentsummingpointatthesamepotentialasthe

AGND pin (Figure 1). At unity gain (digital input 001), the

value of this input resistance is approximately 10kΩ and

the INA pin voltage range is rail-to-rail (V⁺to V^–). At gain

settings above unity, the input resistance falls. The linear

input range at INA also falls inversely proportional to the

programmed gain. Tables 1 and 2 summarize this behav-

ior. The higher gains are designed to boost lower level

signals with good noise performance. In the “zero” gain

state (digital input 000), analog switches disconnect the

INA pin internally and this pin presents a very high input

resistance. Theinputmayvaryfromrailtorailinthe“zero”

gain setting, but the output is insensitive to it and is forced

to the AGND potential.

CircuitrydrivingtheINApinmustconsidertheLTC6911-X’s

inputresistance, itslot-to-lotvariance, andthevariationof

this resistance from gain setting to gain setting. Signal

sources with significant output resistance may introduce

a gain error as the source’s output resistance and the

LTC6911-X’s input resistance form a voltage divider. This

is especially true at higher gain settings where the input

resistance is the lowest.

In single supply voltage applications, it is important to

remember that the LTC6911-X’s DC ground reference for

both input and output is AGND, not V^–. With increasing

gains,theLTC6911-X’sinputvoltagerangeforanunclipped

output is no longer rail-to-rail but diminishes inversely to

gain, centered about the AGND potential.

G2

6

G1

5

G0

4

CMOS LOGIC

INA

AGND

INB

1

2

3

INPUT R ARRAY

FEEDBACK R ARRAY

–

MOS-INPUT

+

–

10 OUTA

–

V

OP AMP

+

10k

9

8

7

V

+

–

10k

MOS-INPUT

OP AMP

OUTB

+

V

691112 F01

INPUT R ARRAY

FEEDBACK R ARRAY

Figure 1. Block Diagram

sn691112 691112fs

12

LTC6911-1/LTC6911-2

U

PI FU CTIO S

AGND (Pin 2): Analog Ground. The AGND pin is at the

midpoint of an internal resistive voltage divider, develop-

ing a potential halfway between the V⁺and V^–pins, with an

equivalent series resistance to the pin of nominally 5kΩ

(Figure 1). AGND is also the noninverting input to both the

internal channel A and channel B amplifiers. This makes

AGNDthegroundreferencevoltagefortheINA,INB,OUTA

and OUTB pins. Recommended analog ground plane con-

nectiondependsonhowpowerisappliedtotheLTC6911-X

(see Figures 2, 3 and 4). Single power supply applications

typically use V^–for the system signal ground. The analog

ground plane in single supply applications should there-

foretietoV^–, andtheAGNDpinshouldbebypassedtothis

ground plane by a high quality capacitor of at least 1µF

(Figure 2). The AGND pin provides an internal analog

referencevoltageathalftheV⁺supplyvoltage.Dualsupply

applications with symmetrical supplies (such as ±5V)

have a natural system ground plane potential of zero volts,

whichcanbetieddirectlytotheAGNDpin,makingthezero

volt ground plane the input and output reference voltage

for the LTC6911-X (Figure 3). Finally, if dual asymmetrical

power supplies are used, the supply ground is still the

natural ground plane voltage. To maximize signal swing

capability with an asymmetrical supply, however, it is

often desirable to refer the LTC6911-X’s analog input and

outputtoavoltageequidistantfromthetwosupplyrailsV⁺

and V^–. The AGND pin will provide such a potential when

open-circuited and bypassed with a capacitor (Figure 4).

–

+

V

0.1µF

10

9

8

7

6

5

LTC6911-X

1

2

3

4

ANALOG

GROUND

PLANE

SINGLE-POINT

SYSTEM GROUND

DIGITAL GROUND PLANE

(IF ANY)

691112 F03

Figure 3. Dual Supply Ground Plane Connection

+

–

+

V

0.1µF

10

9

8

7

6

10

9

8

7

6

LTC6911-X

1

2

3

4

5

1

2

3

4

5

+

–

+

V

+ V

V

REFERENCE

2

ANALOG

GROUND

PLANE

ANALOG

GROUND

PLANE

2

≥1µF

SINGLE-POINT

SYSTEM GROUND

SINGLE-POINT

SYSTEM GROUND

DIGITAL GROUND PLANE

(IF ANY)

DIGITAL GROUND PLANE

(IF ANY)

691112 F02

691112 F04

Figure 4. Asymmetrical Dual Supply Ground Plane Connection

Figure 2. Single Supply Ground Plane Connection

sn691112 691112fs

13

LTC6911-1/LTC6911-2

U

PI FU CTIO S

In noise sensitive applications where AGND does not

directly tie to a ground plane, as in Figures 2 and 4, it is

important to AC-bypass the AGND pin. Otherwise, chan-

nel-to-channel isolation is degraded and wideband noise

will enter the signal path from the thermal noise of the

internal voltage divider resistors that present a Thévenin

equivalent resistance of approximately 5kΩ. This noise

can reduce SNR by at least 3dB at high gain settings. An

external capacitor from AGND to the ground plane, whose

impedance is well below 5kΩ at frequencies of interest,

will filter and suppress this noise. A 1µF high quality

capacitor is effective for frequencies down to 1kHz. Larger

capacitors extend this suppression to lower frequencies.

This issue does not arise in dual supply applications

because the AGND pin ties directly to ground.

have small pull-down current sources (<10µA) which will

force both channels into the “zero” gain state (digital input

000) if the logic inputs are externally floated. No speed

limitation is associated with the digital logic because it is

memoryless and much faster than the analog signal path.

V^–, V⁺(Pins 7, 9): Power Supply Pins. The V⁺and V^–pins

should be bypassed with 0.1µF capacitors to an adequate

analog ground plane using the shortest possible wiring.

Electrically clean supplies and a low impedance ground

are important for the high dynamic range available from

the LTC6911-X (see further details under the AGND pin

description). Low noise linear power supplies are recom-

mended. Switching power supplies require special care to

prevent switching noise coupling into the signal path,

reducing dynamic range.

Inapplicationsrequiringananaloggroundreferenceother

than half the total supply voltage, the user can override the

built-in analog ground reference by tying the AGND pin to

a reference voltage within the AGND voltage range speci-

fied in the Electrical Characteristics table. The AGND pin

will load the external reference with approximately 5kΩ

returned to the half-supply potential. AGND should still be

capacitively bypassed to a ground plane as noted above.

Do not connect the AGND pin to the V^–pin.

OUTB (Pin 8): Analog Output. This is the output of the B

channel internal operational amplifier and can swing rail-

to-rail (V⁺to V^–) as specified in the Electrical Characteris-

tics table. The internal op amp remains active at all times,

including the zero gain setting (digital input 000). For best

performance, loading the output as lightly as possible will

minimize signal distortion and gain error. The Electrical

Characteristics table shows performance at output cur-

rentsupto10mA, andthecurrentlimitswhichoccurwhen

the output is shorted to mid-supply at 2.7V and ±5V

supplies. Signal outputs above 10mA are possible but

current-limiting circuitry will begin to affect amplifier

performance at approximately 20mA. Long-term opera-

tion above 20mA output is not recommended. Do not

exceed a maximum junction temperature of 150°C. The

outputwilldrivecapacitiveloadsupto50pF. Capacitances

higher than 50pF should be isolated by a series resistor to

preserve AC stability.

INB (Pin 3): Analog Input. Refer to INA pin description.

G0, G1, G2 (Pins 4, 5, 6): CMOS-Level Digital Gain

ControlInputs.G2isthemostsignificantbit(MSB)andG0

is the least significant bit (LSB). These pins control the

voltage gain settings for both channels (see Tables 1

and 2). Each channel’s gain cannot be set independent of

theotherchannel.Thelogicinputpins(Gpins)areallowed

to swing from V^–to 10.5V above V^–, regardless of V⁺so

long as the logic levels meet the minimum requirements

specified in the Electrical Characteristics table. The G0, G1

and G2 pins are high impedance CMOS logic inputs, but

OUTA (Pin 10): Analog Output. Refer to OUTB pin

description.

sn691112 691112fs

14

LTC6911-1/LTC6911-2

W U U

APPLICATIO S I FOR ATIO

U

Functional Description

Timing Constraints

The LTC6911-1/LTC6911-2 are small outline, wideband

inverting 2-channel amplifiers whose voltage gain is digi-

tally programmable. Each delivers a choice of eight volt-

age gains, controlled by the 3-bit digital parallel interface

(G pins), which accept CMOS logic levels. The gain code

is always monotonic; an increase in the 3-bit binary

number (G2 G1 G0) causes an increase in the gain. Tables

1 and 2 list the nominal voltage gains for LTC6911-1 and

LTC6911-2 respectively. Gain control within each ampli-

fier occurs by switching resistors from a matched array in

or out of a closed-loop op amp circuit using MOS analog

switches (Figure 1). Bandwidth depends on gain setting.

Curves in the Typical Performance Characteristics section

show measured frequency responses.

Settling time in the CMOS gain-control logic is typically

several nanoseconds and is faster than the analog signal

path. When amplifier gain changes, the limiting timing is

analog, not digital, because the effects of digital input

changes are observed only through the analog output

(Figure 1). The LTC6911-X’s logic is static (not latched)

and therefore lacks bus timing requirements. However, as

with any programmable-gain amplifier, each gain change

causesanoutputtransientastheamplifier’soutputmoves,

with finite speed, toward a differently scaled version of the

input signal. Varying the gain faster than the output can

settle produces a garbled output signal. The LTC6911-X

analog path settles with a characteristic time constant or

time scale, τ, that is roughly the standard value for a first

order band limited response:

Digital Control

τ = 0.35/(2 π f_–3dB

)

Logic levels for the LTC6911-X digital gain control inputs

(Pins 4, 5, 6) are nominally rail-to-rail CMOS, but can

swing above V⁺so long as the positive swing does not

exceed 10.5V with respect to V^–. Each logic input has a

small pull-down current source which can sink up to 10µA

and is used to force the part into a gain of “zero” if the logic

inputs are left unconnected. A logic 1 is nominally V⁺. A

logic 0 is nominally V^–or alternatively, 0V when using ±5V

supplies. The parts are tested with the values listed in the

Electrical Characteristics table. Digital Input “High” and

“Low” voltages are 10% and 90% of the nominal full

excursion on the inputs. That is, the tested logic levels are

0.27V and 2.43V with a 2.7V supply, 0.5V and 4.5V with a

5V supply, and 0.5V and 4.5V with ±5V supplies. Do not

attempttodrivethedigitalinputswithTTLlogiclevels.TTL

logic sources should be adapted with suitable pull-up

resistors to V⁺keeping in mind the internal pull-down

current sources so that for a logic 1 they will swing to the

positive rail.

See the –3dB BW vs Gain Setting graph in the Typical

Performance Characteristics.

Offset Voltage vs Gain Setting

The Electrical Characteristics table lists DC gain depen-

dent voltage offset error in two gain configurations. The

voltage offsets listed, V_OS(IN), are referred to the input pin

(INA or INB). These offsets are directly related to the

internal amplifier input voltage offset, V_OS(OA), by the

magnitude of programmed gain, G:

G

1+ G

V_OS(OA)= V_OS(IN)

The input referred offset, V_OS(IN), for any gain setting can

be inferred from V_OS(OA)and the gain magnitude, G. For

example, an internal offset V_OS(OA)of 1mV will appear

referred to the INA and INB pins as 2mV at a gain setting

sn691112 691112fs

15

LTC6911-1/LTC6911-2

W U U

U

APPLICATIO S I FOR ATIO

of 1, or 1.5mV at a gain setting of 2. At high gains, V_OS(IN)

approaches V_OS(OA). (Offset voltage is random and can

have either polarity centered on 0V.) The MOS input

circuitryoftheinternalopampinFigure1drawsnegligible

inputcurrents(unlikesomeopamps), soonlyV_OS(OA)and

G affect the overall amplifier’s offset.

duetosmalljunctionleakagecurrents). Topreventdriving

the INA or INB pin outside the supply limit and potentially

damaging the chip, avoid AC input signals in the zero gain

state with an AC-coupled capacitor. Also, switching later

to a nonzero gain value will cause a transient pulse at the

output of the LTC6911-1 (with a time constant set by the

capacitor value and the new LTC6911-1 input resistance

value). This occurs because the INA and INB pins return to

the AGND potential forcing transient current sourced by

theamplifieroutputtochargetheAC-couplingcapacitorto

its proper DC blocking value.

AC-Coupled Operation

Adding capacitors in series with the INA and INB pins

convert the LTC6911-X into a dual AC-coupled inverting

amplifier,suppressingtheinputsignal’sDClevel(andalso

adding the additional benefit of reducing the offset voltage

from the LTC6911-X’s amplifier itself). No further compo-

nents are required because the input of the LTC6911-X

biases itself correctly when a series capacitor is added.

The INA and INB analog input pins connect internally to a

resistor whose nominal value varies between 10k and 1k

depending on the version of LTC6911 used (see the

rightmost column of Tables 1 and 2). Therefore, the low

frequency cutoff will vary with capacitor and gain setting.

For example, if a low frequency corner of 1kHz or lower on

the LTC6911-1 is desired, use a series capacitor of 0.16µF

or larger. A 0.16µF capacitor has a reactance of 1kΩ at

1kHz,givinga1kHzlower–3dBfrequencyforgainsettings

of 10V/V through 100V/V. If the LTC6911-1 is operated at

lower gain settings with an 0.16µF capacitor, the higher

input resistance will reduce the lower corner frequency

downto100Hzatagainsettingof1V/V.Thesefrequencies

scale inversely with the value of the input capacitor used.

SNR and Dynamic Range

The term “dynamic range” is much used (and abused)

with signal paths. Signal-to-noise ratio (SNR) is an unam-

biguous comparison of signal and noise levels, measured

in the same way and under the same operating conditions.

In a variable gain amplifier, however, further characteriza-

tion is useful because both noise and maximum signal

level in the amplifier will vary with the gain setting, in

general. In the LTC6911-X, maximum output signal is

independent of gain (and is near the full power supply

voltage, as detailed in the Swing sections of the Electrical

Characteristics table). The maximum input level falls with

increasing gain, and the input-referred noise falls as well

(asalsolistedinthetable). Tosummarizetheusefulsignal

rangeinsuchanamplifier, wedefineDynamicRange(DR)

as the ratio of maximum input (at unity gain) to minimum

input-referred noise (at maximum gain). This DR has a

physical interpretation as the range of signal levels that

will experience an SNR above unity V/V or 0dB. At a 10V

total power supply, DR in the LTC6911-X (gains 0V/V to

Note that operating the LTC6911 family in “zero” gain

mode (digital inputs 000) open circuits the INA and INB

pinsandthisdemandssomecareifemployedwithaseries

AC-coupledinputcapacitor. Whenthechip enters the zero

gain mode, the opened INA or INB pin tends to sample and

freeze the voltage across the capacitor to the value it held

just before the zero gain state. This can place the INA or

INB pin at or near the DC potential of a supply rail (the INA

or INB pin may also drift to a supply potential in this state

100V/V) is typically 120dB (the ratio of a nominal 9.9V_P-P

,

or 3.5V_RMS(maximum input), to the 3.8µV_RMS(high gain

input noise). The SNR of an amplifier is the ratio of input

level to input-referred noise, and can be 110dB with the

LTC6911 family at unity gain.

sn691112 691112fs

16

LTC6911-1/LTC6911-2

W U U

APPLICATIO S I FOR ATIO

U

Construction and Instrumentation Cautions

substantial capacitance (>10µF) near the chip, can create

a high-Q LC resonance in the hundreds of kHz in the chip’s

supplies or ground reference. This may impair circuit

performance at those frequencies. A compact, carefully

laid out printed circuit board with a good ground plane

makesasignificantdifferenceinminimizingdistortionand

maximizing channel isolation. Finally, equipment to mea-

sure amplifier performance can itself add to distortion or

noise floors. Checking for these limits with wired shorts

from INA to OUTA and INB to OUTB in place of the chip is

a prudent routine procedure.

Electrically clean construction is important in applications

seeking the full dynamic range of the LTC6911 family of

dualamplifiers. ItisabsolutelycriticaltohaveAGNDeither

AC bypassed or wired directly, using the shortest possible

wiring,toalowimpedancegroundreturnforbestchannel-

to-channel isolation. Short, direct wiring will minimize

parasitic capacitance and inductance. High quality supply

bypass capacitors of 0.1µF near the chip provide good

decoupling from a clean, low inductance power source.

But several cm of wire (i.e., a few microhenrys of induc-

tance) from the power supplies, unless decoupled by

sn691112 691112fs

17

LTC6911-1/LTC6911-2

U

TYPICAL APPLICATIO

Expanding an ADC’s Dynamic Range

maximum sampling rate of 250ksps. An LTC6911-1, for

example, expands the ADC’s input amplitude range by

40dB while operating from the same single 5V supply. The

499Ω resistor and 270pF capacitor couple cleanly be-

tweentheLTC6911-X’soutputandtheswitched-capacitor

inputs of the LTC1865.

Figure 5 shows a compact 2-channel data acquisition

systemforwideranginginputlevels.Thisfigurecombines

an LTC6911-X programmable amplifier (10-lead MSOP)

with an LTC1865 analog-to-digital converter (ADC) in an

8-lead MSOP. This ADC has 16-bit resolution and a

+

V

0.1µF

7

9

+

V

0.1µF

499Ω

1

2

3

10

V

INA

V

AGND

270pF

CONV

SCK

CC

≥1µF

CH0

CH1

LTC1865

GND

LTC6911-X

SDO

SDI

691112 F05

8

V

INB

ADC INTERFACE

691112 F05

4

5

6

GAIN CONTROL

Figure 5. Expanding a Dual Channel ADC’s Dynamic Range

sn691112 691112fs

18

LTC6911-1/LTC6911-2

U

PACKAGE DESCRIPTIO

MS Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1661)

0.889 ± 0.127

(.035 ± .005)

5.23

(.206)

MIN

3.20 – 3.45

(.126 – .136)

3.00 ± 0.102

(.118 ± .004)

(NOTE 3)

0.497 ± 0.076

(.0196 ± .003)

0.50

0.305 ± 0.038

(.0120 ± .0015)

TYP

(.0197)

10 9

8

7 6

BSC

REF

RECOMMENDED SOLDER PAD LAYOUT

3.00 ± 0.102

(.118 ± .004)

(NOTE 4)

4.90 ± 0.152

(.193 ± .006)

DETAIL “A”

0.254

(.010)

0° – 6° TYP

GAUGE PLANE

1

2

3

4 5

0.53 ± 0.152

(.021 ± .006)

0.86

(.034)

REF

1.10

(.043)

MAX

DETAIL “A”

0.18

(.007)

SEATING

PLANE

0.17 – 0.27

(.007 – .011)

TYP

0.127 ± 0.076

(.005 ± .003)

MSOP (MS) 0603

0.50

(.0197)

BSC

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

sn691112 691112fs

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

19

LTC6911-1/LTC6911-2

U

TYPICAL APPLICATIO

Fully Differential Amplifier with Digitally Programmable Gain

High Dynamic Range (PGA Input)

–5V

0.1µF

1

2

3

4

5

10

9

1

2

3

4

8

7

6

5

+

–

V

LTC1992-1

OR

LTC1992-2

OR

LTC1992-5

OR

LTC1992-10

IN

LTC6911-1

OR

LTC6911-2

5V

–5V

8

IN

7

6

0.1µF

+

–

V

OUT

G0 G1 G2

DIGITAL GAIN CONTROL

High CMRR (Differential Input)

–5V

+

–

V

IN

0.1µF

1

2

3

4

5

10

9

1

2

3

4

8

7

6

5

+

V

LTC1992-1

OR

LTC1992-2

OR

LTC1992-5

OR

LTC1992-10

OUT

IN

–

V

LTC6911-1

OR

LTC6911-2

5V

–5V

8

5V

7

6

0.1µF

691112 TA03

G0 G1 G2

DIGITAL GAIN CONTROL

RELATED PARTS

PART NUMBER

LT^®1228

DESCRIPTION

COMMENTS

100MHz Gain Controlled Transconductance Amplifier

40MHz Video Fader and Gain Controlled Amplifier

10kHz to 150kHz Digitally Controlled Filter and PGA

Differential Input, Continuous Analog Gain Control

LT1251/LT1256

LTC1564

Two Input, One Output, Continuous Analog Gain Control

Continuous Time, Low Noise 8th Order Filter and 4-Bit PGA

LTC6910

Digitally Controlled Programmable Gain Amplifier in SOT-23 Single Channel Version of the LTC6911

LTC6915

Digitally Controlled Programmable Instrumentation

Amplifier with SPI Interface

14 Bits of Gain Control

sn691112 691112fs

LT/TP 0104 1K • PRINTED IN USA

20 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com

LINEAR TECHNOLOGY CORPORATION 2004


型号：	LTC6911HMS-1
厂家：	Linear
描述：	Dual Matched Amplifiers with Digitally Programmable Gain in MSOP 双匹配放大器，具有数字可编程增益，采用MSOP 模拟IC 信号电路放大器光电二极管
文件：	总20页 (文件大小：225K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC6911HMS-1 [Linear]

相关型号：

LTC6911HMS-1#TR

LTC6911HMS-2

LTC6911HMS-2#TR

LTC6911HMS-2#TRPBF

LTC6911IMS-1

LTC6911IMS-2

LTC6911IMS-2#TR

LTC6912

LTC6912CDE-1

LTC6912CDE-2

LTC6912CDE-2#TR

LTC6912CGN-1