LTC6915
Zero Drift, Precision
Instrumentation Amplifier with
Digitally Programmable Gain
FEATURES
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
14 Levels of Programmable Gain
125dB CMRR Independent of Gain
Gain Accuracy 0.1% (Typ)
Maximum Offset Voltage of 10µV
Maximum Offset Voltage Drift: 50nV/°C
Rail-to-Rail Input and Output
Parallel or Serial (SPI) Interface for Gain Setting
Supply Operation: 2.7V to
±5.5V
Typical Noise: 2.5µV
P-P
(0.01Hz to 10Hz)
16-Lead SSOP and 12-Lead DFN Packages
The LTC
®
6915 is a precision programmable gain instru-
mentation amplifier. The gain can be programmed to 0, 1,
2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096
through a parallel or serial interface. The CMRR is typically
125dB with a dual 5V supply with any programmed gain.
The offset is below 10µV with a temperature drift of less
than 50nV/°C.
The LTC6915 uses charge balanced sampled data tech-
niques to convert a differential input voltage into a single
ended signal that is in turn amplified by a zero-drift
operational amplifier.
The differential inputs operate from rail-to-rail and the
single-ended output swings from rail-to-rail. The LTC6915
can be used in single power supply applications as low as
2.7V, or with dual
±5V
supplies. The LTC6915 is available
in a 16-lead SSOP package and a 12-lead DFN surface
mount package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
Thermocouple Amplifiers
Electronic Scales
Medical Instrumentation
Strain Gauge Amplifier
High Resolution Data Acquisition
TYPICAL APPLICATIO
Differential Bridge Amplifier with Gain Programmed through the Serial Interface
LTC6915 SSOP PACKAGE
3 IN
+
3V
2 IN
R < 10k
RESISTOR
ARRAY
REF 13
11 PARALLEL_SERIAL
4-BIT
LATCH
HOLD_THRU 5
V
+
16
3V
0.1µF
Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7
8-BIT
SHIFT-REGISTER
SHDN
DGND
V
–
6915 TA01
+
OUT 15
C
S
C
H
_
–
C
F
MUX
6 CS(D0)
7 D
IN
(D1)
8 CLK(D2)
9 D
OUT
(D3)
µP
TO OTHER
DEVICES
U
SENSE 14
1
10
4
6915f
U
U
1
LTC6915
ABSOLUTE
AXI U RATI GS
Total Supply Voltage (V
+
to V
–
) ............................... 11V
Input Current ......................................................
±10mA
|V
IN+
– V
REF
| ....................................................... 5.5V
|V
IN–
– V
REF
| ....................................................... 5.5V
|V
+
– V
DGND
| ....................................................... 5.5V
|V
DGND
– V
–
| ....................................................... 5.5V
Digital Input Voltage ......................................... V
–
to V
+
Operating Temperature Range
LTC6915C .............................................–0°C to 70°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
IN
–
IN
+
V
–
ORDER PART
NUMBER
12 V
+
11 OUT
10 REF
9
8
7
PARALLEL_SERIAL
DGND
D
OUT
(D3)
1
2
3
4
5
6
LTC6915CDE
LTC6915IDE
DFN PART
MARKING
6915
6915I
CS(D0)
D
IN
(D1)
CLK(D2)
DE12 PACKAGE
12-LEAD (4mm
×
3mm) PLASTIC DFN
UNDERSIDE METAL CONNECTED TO V–
T
JMAX
= 125°C,
θ
JA
= 160°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL
PARAMETER
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Nonlinearity
V
OS
Input Offset Voltage (Note 3)
Average Input Offset Drift (Note 3)
I
B
I
OS
Average Input Bias Current (Note 4)
Average Input Offset Current (Note 4)
CONDITIONS
A
V
= 1 (R
L
=10k)
A
V
= 2 to 32 (R
L
= 10k)
A
V
= 64 to 1024 (R
L
= 10k)
A
V
= 2048, 4096 (R
L
= 10k)
A
V
= 1
V
CM
= 200mV
T
A
= –40°C to 85°C
T
A
= 85°C to 125°C
V
CM
= 1.2V
V
CM
= 1.2V
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
V
+
= 3V, V
–
= 0V, V
REF
= 200 mV
–0.075
–0.5
–0.6
–1
0
0
–0.1
–0.2
3
–3
0.075
0.5
0.6
1.0
15
±10
±50
±100
5
1.5
10
3
%
%
%
%
ppm
µV
nV/°C
nV/°C
nA
nA
2
U
U
W
W W
U
W
(Note 1)
LTC6915I .............................................–40°C to 85°C
LTC6915H .........................................–40°C to 125°C
Junction Temperature
(GN Package) ................................................... 150°C
(DFN Package).................................................. 125°C
Storage Temperature
(GN Package) ....................................–65°C to 150°C
(DFN Package)...................................–65°C to 125°C
Lead Temperature (Soldering 10 sec)................... 300°C
TOP VIEW
SHDN 1
IN
–
2
IN
+
3
V
–
4
HOLD_THRU 5
CS(D0) 6
D
IN
(D1) 7
CLK(D2) 8
16 V
+
15 OUT
14 SENSE
13 REF
12 NC
11 PARALLEL_SERIAL
10 DGND
9
D
OUT
(D3)
ORDER PART
NUMBER
LTC6915CGN
LTC6915IGN
LTC6915HGN
GN PART
MARKING
6915
6915I
6915H
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 135°C/W
MIN
TYP
MAX
UNITS
6915f
LTC6915
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL
CMRR
PARAMETER
Common Mode Rejection Ratio
CONDITIONS
A
V
= 1024, V
CM
= 0V to 3V, LTC6915C
A
V
= 1024, V
CM
= 0.1V to 2.9V, LTC6915I
A
V
= 1024, V
CM
= 0V to 3V, LTC6915I
A
V
= 1024, V
CM
= 0.1V to 2.9V, LTC6915H
A
V
= 1024, V
CM
= 0V to 2.97V, LTC6915H
V
S
= 2.7V to 6V
Sourcing 200µA
Sourcing 2mA
Sinking 200µA
Sinking 2mA
No Load at OUT, V
CM
= 200mV
No Load at OUT, Capacitive Load at
D
OUT
(C
L
) = 15pF, Continuous CLK
Frequency = 4MHz, CS= LOW,
Gain Control Code = 0001
V
SHDN
= 2.7V (Hardware Shutdown)
V
SHDN
= 1V, Gain Control Code = 0000
(Software Shutdown )
q
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
V
+
= 3V, V
–
= 0V, V
REF
= 200 mV
MIN
100
100
95
100
85
110
2.95
2.75
TYP
119
119
119
MAX
UNITS
dB
dB
dB
dB
dB
dB
V
V
PSRR
Power Supply Rejection Ratio (Note 5)
Output Voltage Swing High
(Referenced to V
–
)
Output Voltage Swing Low
(Referenced to V
–
)
Supply Current, Parallel Mode
Supply Current, Serial Mode (Note 6)
116
2.98
2.87
18
130
0.88
1.1
50
300
1.3
1.65
mV
mV
mA
mA
Supply Current Shutdown
q
q
q
q
q
1
125
2.7
4
180
µA
µA
V
SHDN Input High
SHDN Input Low
SHDN and HOLD_THRU Input Current (Note 2)
Internal Op Amp Gain Bandwidth
Slew Rate
Internal Sampling Frequency
V
+
= 5V, V
–
= 0V, V
REF
= 200mV
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Nonlinearity
V
OS
Input Offset Voltage (Note 3)
Average Input Offset Drift (Note 3)
Average Input Bias Current (Note 4)
I
OS
CMRR
Average Input Offset Current (Note 4)
Common Mode Rejection Ratio
A
V
= 1 (R
L
= 10k)
A
V
= 2 to 32 (R
L
= 10k)
A
V
= 64 to 1024 (R
L
= 10k)
A
V
= 2048, 4096 (R
L
= 10k)
A
V
= 1
V
CM
= 200mV
T
A
= –40°C to 85°C
T
A
= 85°C to 125°C
V
CM
= 1.2V
V
CM
= 1.2V
A
V
= 1024, V
CM
= 0V to 5V, LTC6915C
A
V
= 1024, V
CM
= 0.1V to 4.9V, LTC6915I
A
V
= 1024, V
CM
= 0V to 5V, LTC6915I
A
V
= 1024, V
CM
= 0.1V to 4.9V, LTC6915H
A
V
= 1024, V
CM
= 0V to 4.97V, LTC6915H
V
S
= 2.7V to 6V
Sourcing 200µA
Sourcing 2mA
Sinking 200µA
Sinking 2mA
1
5
200
0.2
–0.5
3
0
0
–0.1
–0.2
3
–3
0.075
0.5
0.6
1
15
±10
±50
±100
5
1.5
105
105
95
100
85
110
4.95
4.80
125
125
125
10
3
V
µA
kHz
V/µs
kHz
%
%
%
%
ppm
µV
nV/°C
nV/°C
nA
nA
dB
dB
dB
dB
dB
dB
V
V
q
q
q
q
q
–0.075
–0.5
–0.6
–1
q
q
q
q
q
q
q
q
q
q
q
q
q
PSRR
Power Supply Rejection Ratio (Note 5)
Output Voltage Swing High
Output Voltage Swing Low
116
4.99
4.93
17
120
50
300
mV
mV
6915f
3
LTC6915
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Supply Current, Parallel Mode
Supply Current, Serial Mode (Note 6)
V
+
= 5V, V
–
= 0V, V
REF
= 200mV
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
No Load at OUT, V
CM
= 200mV
No Load at OUT, Capacitive Load at
D
OUT
(C
L
) = 15pF, Continuous CLK
Frequency = 4MHz, CS = LOW,
Gain Control Code = 0001
V
SHDN
= 4.5V (Hardware Shutdown)
V
SHDN
= 1V, Gain Control Code = 0000
(Software Shutdown)
q
q
MIN
TYP
0.95
1.4
MAX
1.48
2
UNITS
mA
mA
Supply Current, Shutdown
q
q
q
q
q
2
135
4.5
10
200
µA
µA
V
SHDN Input High
SHDN Input Low
SHDN and HOLD_THRU Input Current (Note 2)
Internal Op Amp Gain Bandwidth
Slew Rate
Internal Sampling Frequency
V
+
= 5V, V
–
= –5V, V
REF
= 0V
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Error (Note 2)
Gain Nonlinearity
V
OS
Input Offset Voltage (Note 3)
Average Input Offset Drift (Note 3)
I
OS
CMRR
Average Input Bias Current (Note 4)
Average Input Offset Current (Note 4)
Common Mode Rejection Ratio
A
V
= 1 (R
L
= 10k)
A
V
= 2 to 32 (R
L
= 10k)
A
V
= 64 to 1024 (R
L
= 10k)
A
V
= 2048, 4096 (R
L
= 10k)
A
V
= 1
V
CM
= 0mV
T
A
= –40°C to 85°C
T
A
= 85°C to 125°C
V
CM
= 1V
V
CM
= 1V
A
V
= 1024, V
CM
= –5V to 5V, LTC6915C
A
V
= 1024, V
CM
= –4.9V to 4.9V, LTC6915I
A
V
= 1024, V
CM
= –5V to 5V, LTC6915I
A
V
= 1024, V
CM
= –4.9V to 4.9V, LTC6915H
A
V
= 1024, V
CM
= –5V to 4.97V, LTC6915H
V
S
= 2.7V to 11V
Sourcing 200µA
Sourcing 2mA
Sinking 200µA
Sinking 2mA
No Load, V
CM
= 200mV
No Load at OUT, Capacitive Load at
D
OUT
(C
L
) = 15pF, Continuous CLK
Frequency = 4MHz, CS = LOW,
Gain Control Code = 0001
V
SHDN
= 4V (Hardware Shutdown)
V
SHDN
= 1V, Gain Control Code = 0000
(Software Shutdown )
1
5
200
0.2
3
V
µA
kHz
V/µs
kHz
q
q
q
q
q
–0.075
–0.5
–0.6
–1
0
0
–0.1
–0.2
3
5
0.075
0.5
0.6
1
15
±20
±50
±100
%
%
%
%
ppm
nV
nV/°C
nV/°C
nA
nA
dB
dB
dB
dB
dB
dB
V
V
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
4
1.5
105
105
100
100
90
110
4.97
4.90
123
123
123
10
3
PSRR
Power Supply Rejection Ratio (Note 5)
Output Voltage Swing High
Output Voltage Swing Low
Supply Current, Parallel Mode
Supply Current, Serial Mode (Note 6)
116
4.99
4.96
–4.98
–4.90
1.1
1.73
–4.92
–4.70
1.6
2.48
mV
mV
mA
mA
Supply Current, Shutdown
q
q
q
q
160
4
25
240
µA
µA
V
SHDN Input High
SHDN Input Low
1
V
6915f
4
LTC6915
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL
V
+
= 5V, V
–
PARAMETER
= –5V, V
REF
= 0V
SHDN and HOLD_THRU Input Current (Note 2)
Internal Op Amp Gain Bandwidth
Slew Rate
Internal Sampling Frequency
Digital I/O, All Digital I/O Voltage Referenced to DGND
V
IH
V
IL
V
OH
V
OL
Digital Input High Voltage
Digital Input Low Voltage
Digital Output High Voltage
Digital Output Low Voltage
Digital Input Leakage
Timing, V
+
= 2.7V to 4.5V, V
–
= 0V (Note 7)
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
D
IN
Valid to CLK Setup
D
IN
Valid to CLK Hold
CLK Low
CLK High
CS/LD Pulse Width
LSB CLK to CS/LD
CS/LD Low to CLK
D
OUT
Output Delay
CLK Low to CS/LD Low
D
IN
Valid to CLK Setup
D
IN
Valid to CLK Hold
CLK Low
CLK High
CS/LD Pulse Width
LSB CLK to CS/LD
CS/LD Low to CLK
D
OUT
Output Delay
CLK Low to CS/LD Low
D
IN
Valid to CLK Setup
D
IN
Valid to CLK Hold
CLK High
CLK Low
CS/LD Pulse Width
LSB CLK to CS/LD
CS/LD Low to CLK
D
OUT
Output Delay
CLK Low to CS/LD Low
C
L
= 15pF
C
L
= 15pF
C
L
= 15pF
q
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
MAX
5
UNITS
µA
kHz
V/µs
kHz
V
200
0.2
3
2.0
0.8
0.3
±2
60
0
100
100
60
60
30
125
0
30
0
50
50
40
40
20
85
0
30
0
50
50
40
40
20
85
0
V
V
V
µA
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
6915f
Sourcing 500µA
Sinking 500µA
V
+
= 5V, V
–
= –5V, V
IN
= 0V to 5V
q
V
+
– 0.3
q
q
Timing, V
+
= 4.5V to 5.5V, V
–
= 0V (Note 7)
q
q
q
q
q
q
q
q
q
Timing, Dual
±4.5V
to
±5.5V
Supplies (Note 7)
q
q
q
q
q
q
q
q
q
5
PCB Design
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