LTC6911-2_15 [Linear]
Dual Matched Amplifiers with Digitally Programmable Gain in MSOP;型号: | LTC6911-2_15 |
厂家: | Linear |
描述: | Dual Matched Amplifiers with Digitally Programmable Gain in MSOP |
文件: | 总20页 (文件大小:235K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
AGND
–1
–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 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
TJMAX = 150°C, θJA = 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
U
U
GAI SETTI GS A D PROPERTIES
Table 1 (LTC6911-1)
NOMINAL
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
0
–1
–2
–5
–10
–20
–50
–100
10
10
5
2
1
0.5
0.2
0.1
5
5
2.5
1
0.5
0.25
0.1
0.05
3
3
(Open)
10
5
2
1
1
1
1
0
0
1
0
1
0
6
1.5
0.6
0.3
0.15
0.06
0.03
0
1
1
14
20
26
34
40
1
0
0
1
0
1
1
1
0
1
1
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
0
G1
0
0
G0
0
1
Volts/Volt
0
(dB)
–120
0
10
10
5
5
3
3
(Open)
10
–1
0
1
0
–2
6
5
2.5
1.5
5
0
1
1
1
1
0
0
1
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
1.25
1.25
1.25
1
1
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
3.1 4.65
2.1 3.25
2.5 4.00
3.1 5.00
3.1 5.00
mA
mA
mA
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
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
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
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
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
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
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
mA
S
V = ±5V
S
AGND Open-Circuit Voltage
V = 5V
S
●
2.45 2.5 2.55
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
V
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
55
80
75
50
50
80
75
dB
dB
S
AGND
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
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
–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
4.50
2.43
4.50
4.50
V
V
V
S
V = 5V
V = 2.7V
●
●
●
0.27
0.50
0.50
0.27
0.50
0.50
V
V
V
S
V = 5V
S
V = ±5V
S
V = 2.7V, Pins 4, 5, 6 = 2.43V
●
●
●
1
5
1
5
µA
µA
µA
S
V = 5V, Pins 4, 5, 6 = 4.5V
S
V = ±5V, Pins 4, 5, 6 = 4.5V
10
10
S
V = 2.7V, Pins 4, 5, 6 = 0.27V
●
●
●
1
5
10
1
5
10
µA
µA
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
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
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
dB
S
L
V = 5V, Gain = 5, R = 10k
S
L
V = 5V, Gain = 10, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
dB
S
L
V = 5V, Gain = 10, R = 500Ω
S
L
V = 5V, Gain = 20, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
dB
S
L
V = 5V, Gain = 100, R = 500Ω
S
L
V = ±5V, Gain = 1, R = 10k
●
●
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
dB
S
L
V = ±5V, Gain = 5, R = 10k
S
L
V = ±5V, Gain = 10, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
dB
S
L
V = ±5V, Gain = 10, R = 500Ω
S
L
V = ±5V, Gain = 20, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
dB
S
L
V = ±5V, Gain = 100, R = 500Ω
S
L
Gain Temperature Coefficient
V = 5V, Gain = 1, R = Open
2
2
ppm/°C
ppm/°C-
ppm/°C
ppm/°C
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
1.0
0.2
1.0
0.4
3.0
3.0
1.0
1.0
0.2
1.0
0.4
3.0
3.0
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
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
dB
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
mV
Offset Voltage Magnitude Drift
Referred to INA or INB Pins (Note 8)
Gain = 1
Gain = 10
12
6.6
20
11
µV/°C
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
kΩ
kΩ
kΩ
Gain = 1
Gain = 2
Gain = 5
Gain > 5
2
2
1
1
DC Input Resistance Match
Gain = 1
Gain = 2
Gain = 5
Gain > 5
●
●
●
●
10
5
10
5
Ω
Ω
Ω
Ω
R
– R
INA
INB
2
2
1
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
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Gain = 1
Gain = 2
Gain = 5
Gain = 10
Gain = 20
Gain = 50
Gain = 100
30
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
RMS
RMS
RMS
RMS
RMS
RMS
RMS
µV
µV
µV
µV
µV
µV
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
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
Gain = 2
Gain = 5
14
14
Gain = 10
Gain = 20
Gain = 50
Gain = 100
12
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
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
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
dB
S
L
V = 5V, Gain = 4, R = 10k
S
L
V = 5V, Gain = 8, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
dB
S
L
V = 5V, Gain = 8, R = 500Ω
S
L
V = 5V, Gain = 16, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
dB
S
L
V = 5V, Gain = 64, R = 500Ω
S
L
V = ±5V, Gain = 1, R = 10k
●
●
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
–0.1 0.02 0.1
dB
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
dB
S
L
V = ±5V, Gain = 4, R = 10k
S
L
V = ±5V, Gain = 8, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
dB
S
L
V = ±5V, Gain = 8, R = 500Ω
S
L
V = ±5V, Gain = 16, R = 10k
●
●
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
–0.15 0.02 0.15
dB
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
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
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
S
L
V = 5V, Gain = 2, R = Open
S
L
V = 5V, Gain = 4, R = Open
–7
–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
0
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
ppm/°C
S
L
V = 5V, Gain = 2, R = Open
–0.5
0.5
0.5
1.0
4.0
4.0
–0.5
0.5
0.5
1.0
4.0
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
110
93
110
110
93
dB
dB
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
mV
Offset Voltage Magnitude Drift
Referred to INA or INB Pins (Note 8)
Gain = 1
Gain = 8
12
6.8
20
11
µV/°C
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
kΩ
kΩ
kΩ
Gain = 1
Gain = 2
Gain = 4
Gain > 4
5
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 TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 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
Ω
Ω
Ω
R
– R
INB
2
2
1
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
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Gain = 1
Gain = 2
Gain = 4
Gain = 8
Gain = 16
Gain = 32
Gain = 64
30
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
µV
µV
µV
µV
µV
µV
µV
RMS
RMS
RMS
RMS
RMS
RMS
RMS
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
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
Total Harmonic Distortion
Gain-Bandwidth Product
Gain = 8, f = 10kHz, V
= 1V
RMS
–90
–90
dB
%
IN
OUT
0.003
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
VOUTA
VOUTB
IsolationA = 20 •log10 OUTB , IsolationB = 20 •log10
VOUTA
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
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
V
= 5V
OUT
S
A
S
S
GAIN = 1
= 1V
RMS
INPUT REFERRED
GAIN = 1
GAIN = 1
+SUPPLY
–SUPPLY
GAIN = 10
GAIN = 10
GAIN = 100
GAIN = 100
90
85
1k
10k
100k
1k
10k
100k
1M
10M
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
6911 G05
6911 G06
6911 G04
LTC6911-1 Distortion vs Frequency
with Light Loading (RL = 10k)
LTC6911-1 Distortion vs Frequency
LTC6911-1 THD + Noise
vs Input Voltage
with Heavy Loading (RL = 500Ω)
–30
–40
–50
–30
–40
–50
–20
–30
V
V
= ±2.5V
V
V
= ±2.5V
S
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
–80
–80
–90
f
= 1kHz
IN
S
GAIN = 1
150k
–90
–90
–100
–110
V
= ±5V
GAIN = 1
BW = 100Hz TO 22kHz
–100
–100
50k
100k
200k
50k
100k
FREQUENCY (Hz)
200k
0
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
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
V
= 5V
OUT
S
S
A
S
GAIN = 1
= 1V
RMS
INPUT REFERRED
GAIN = 1
GAIN = 8
+SUPPLY
–SUPPLY
GAIN = 1
GAIN = 8
GAIN = 64
GAIN = 64
90
85
1k
10k
100k
1M
10M
100k
1M
1k
10k
FREQUENCY (Hz)
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
6911 G14
6911 G15
6911 G13
LTC6911-2 Distortion vs Frequency
with Light Loading (RL = 10k)
LTC6911-2 Distortion vs Frequency
LTC6911-2 THD + Noise
vs Input Voltage
with Heavy Loading (RL = 500Ω)
–30
–40
–50
–20
–30
–30
–40
–50
V
V
= ±2.5V
V
V
= ±2.5V
S
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
–80
–80
–90
GAIN = 1
f
= 1kHz
IN
S
–90
–90
–100
–110
V
= ±5V
GAIN = 1
BW = 100Hz TO 22kHz
–100
–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
U
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
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
U
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
V
0.1µF
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
V
V
0.1µF
0.1µF
0.1µF
10
9
8
7
6
10
9
8
7
6
LTC6911-X
LTC6911-X
1
2
3
4
5
1
2
3
4
5
+
–
+
V
+ V
V
REFERENCE
REFERENCE
2
ANALOG
GROUND
PLANE
ANALOG
GROUND
PLANE
2
≥1µF
≥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
U
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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, VOS(IN), are referred to the input pin
(INA or INB). These offsets are directly related to the
internal amplifier input voltage offset, VOS(OA), by the
magnitude of programmed gain, G:
G
1+ G
VOS(OA) = VOS(IN)
The input referred offset, VOS(IN), for any gain setting can
be inferred from VOS(OA) and the gain magnitude, G. For
example, an internal offset VOS(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
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APPLICATIO S I FOR ATIO
of 1, or 1.5mV at a gain setting of 2. At high gains, VOS(IN)
approaches VOS(OA). (Offset voltage is random and can
have either polarity centered on 0V.) The MOS input
circuitryoftheinternalopampinFigure1drawsnegligible
inputcurrents(unlikesomeopamps), soonlyVOS(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 9.9VP-P
,
or 3.5VRMS (maximum input), to the 3.8µVRMS (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
499Ω
1
2
3
10
V
INA
V
AGND
270pF
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
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
0.1µF
0.1µF
+
–
V
V
OUT
OUT
G0 G1 G2
DIGITAL GAIN CONTROL
High CMRR (Differential Input)
–5V
+
–
V
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
OUT
IN
–
V
LTC6911-1
OR
LTC6911-2
5V
–5V
8
5V
7
6
0.1µF
0.1µF
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
相关型号:
LTC6911HMS-1#TR
LTC6911 - Dual Matched Amplifiers with Digitally Programmable Gain in MSOP; Package: MSOP; Pins: 10; Temperature Range: -40°C to 125°C
Linear
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