LTC2381-16
16-Bit, 250ksps, Low Power
SAR ADC with Serial Interface
FEATURES
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DESCRIPTION
The LTC
®
2381-16 is a low noise, low power, high speed
16-bit successive approximation register (SAR) ADC.
Operating from a 2.5V supply, the LTC2381-16 has a
±2.5V fully differential input range. The LTC2381-16
consumes only 3.25mW and achieves ±2LSB INL max,
no missing codes at 16-bits and 92dB SNR.
The LTC2381-16 has a high speed SPI-compatible serial
interface that supports 1.8V, 2.5V, 3.3V and 5V logic
while also featuring a daisychain mode. The fast 250ksps
throughput with no cycle latency makes the LTC2381-16
ideally suited for a wide variety of high speed applica-
tions. An internal oscillator sets the conversion time,
easing external timing considerations. The LTC2381-16
automatically powers down between conversions, lead-
ing to reduced power dissipation that scales with the
sampling rate.
The LTC2381-16 features a proprietary sampling
architecture that enables the ADC to begin acquiring the
next sample during the current conversion. The resulting
extended acquisition time of 3.25μs allows the use of
extremely low power ADC drivers.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
250ksps Throughput Rate
±2LSB INL (Max)
Guaranteed 16-Bit No Missing Codes
Low Power: 3.25mW at 250ksps, 13μW at 1ksps
92dB SNR (typ) at f
IN
= 20kHz
Extended Acquisition Time of 3.25μs Allows Use of
Lower Power Drivers
Guaranteed Operation to 125°C
2.5V Supply
Fully Differential Input Range ±2.5V
External 2.5V Reference Input
No Pipeline Delay, No Cycle Latency
1.8V to 5V I/O Voltages
SPI-Compatible Serial I/O with Daisy-Chain Mode
Internal Conversion Clock
16-pin MSOP and 4mm
×
3mm DFN Packages
APPLICATIONS
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Medical Imaging
High Speed Data Acquisition
Portable or Compact Instrumentation
Industrial Process Control
Low Power Battery-Operated Instrumentation
ATE
TYPICAL APPLICATION
2.5V
10μF
1.8V TO 5V
0.1μF
AMPLITUDE (dBFS)
ANALOG INPUT
0V TO 2.5V
50Ω
LT6350
50Ω
SINGLE-ENDED-
TO-DIFFERENTIAL
DRIVER
100Ω
3300pF
IN
–
100Ω
REF
2.5V
GND
IN
+
32k Point FFT f
S
= 250ksps, f
IN
= 20kHz
0
–20
–40
–60
–80
–100
–120
–140
–160
–180
0
25
50
75
FREQUENCY (kHz)
100
125
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
V
DD
LTC2381-16
OV
DD
CHAIN
RDL/SDI
SDO
SCK
BUSY
CNV
238116 TA01
SAMPLE CLOCK
47μF
(X5R, 0805 SIZE)
238116 TA02a
238116f
1
LTC2381-16
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltage (V
DD
) ...............................................2.8V
Supply Voltage (OV
DD
) ................................................6V
Reference Input (REF)..............................................2.8V
Analog Input Voltage (Note 3)
IN
+
, IN
–
......................... (GND –0.3V) to (REF + 0.3V)
Digital Input Voltage
(Note 3)........................... (GND –0.3V) to (OV
DD
+ 0.3V)
Digital Output Voltage
(Note 3)........................... (GND –0.3V) to (OV
DD
+ 0.3V)
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC2381C ................................................ 0°C to 70°C
LTC2381I .............................................–40°C to 85°C
LTC2381H .......................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
CHAIN
V
DD
GND
IN
+
IN
–
GND
REF
REF
1
2
3
4
5
6
7
8
17
GND
16 GND
15 OV
DD
14 SDO
13 SCK
12 RDL/SDI
11 BUSY
10 GND
9 CNV
TOP VIEW
CHAIN
V
DD
GND
IN
+
IN
–
GND
REF
REF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
OV
DD
SDO
SCK
RDL/SDI
BUSY
GND
CNV
DE PACKAGE
16-LEAD (4mm 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
MS PACKAGE
16-LEAD (4mm 5mm) PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 110°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC2381CMS-16#PBF
LTC2381IMS-16#PBF
LTC2381HMS-16#PBF
LTC2381CDE-16#PBF
LTC2381IDE-16#PBF
TAPE AND REEL
LTC2381CMS-16#TRPBF
LTC2381IMS-16#TRPBF
LTC2381HMS-16#TRPBF
LTC2381CDE-16#TRPBF
LTC2381IDE-16#TRPBF
PART MARKING
238116
238116
238116
23816
23816
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead (4mm
×
3mm) Plastic DFN
16-Lead (4mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
238116f
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LTC2381-16
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
+
V
IN
–
V
IN
+ – V
IN
–
V
CM
I
IN
C
IN
CMRR
PARAMETER
Absolute Input Range (IN
+
)
Absolute Input Range (IN
–
)
Input Differential Voltage range
Common-Mode Input Range
Analog Input Leakage Current
Analog Input Capacitance
Input Common Mode Rejection Ratio
Sample Mode
Hold Mode
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
(Note 5)
(Note 5)
V
IN
= V
IN
+ – V
IN
–
l
l
l
l
l
MIN
–0.05
–0.05
–V
REF
V
REF
/2–
0.05
TYP
MAX
V
REF
V
REF
+V
REF
UNITS
V
V
V
V
μA
pF
pF
dB
V
REF
/2
V
REF
/2+
0.05
±1
45
5
70
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
SYMBOL PARAMETER
Resolution
No Missing Codes
Transition Noise
INL
DNL
BZE
FSE
Integral Linearity Error
Differential Linearity Error
Bipolar Zero-Scale Error
Bipolar Zero-Scale Error Drift
Bipolar Full-Scale Error
Bipolar Full-Scale Error Drift
(Note 7)
l
CONVERTER CHARACTERISTICS
CONDITIONS
l
l
l
l
l
MIN
16
16
TYP
MAX
UNITS
Bits
Bits
0.6
(Note 6)
(Note 7)
–2
–1
–6
–14
±0.9
±0.5
±0.25
3
±3
±0.1
14
2
1
6
LSB
RMS
LSB
LSB
LSB
mLSB/°C
LSB
ppm/°C
DYNAMIC ACCURACY
SYMBOL PARAMETER
SINAD
SNR
THD
SFDR
The
l
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C and A
IN
= –1dBFS. (Notes 4, 8)
CONDITIONS
f
IN
= 20kHz
f
IN
= 20kHz
f
IN
= 20kHz, First 5 Harmonics
f
IN
= 20kHz
l
l
l
MIN
88.5
89
TYP
92
92
–106
107
30
2
30
MAX
UNITS
dB
dB
Signal-to-(Noise + Distortion) Ratio
Signal-to-Noise Ratio
Total Harmonic Distortion
Spurious Free Dynamic Range
–3dB Input Bandwidth
Aperture Delay
Aperture Jitter
Transient Response
–99
dB
dB
MHz
ns
ps
ns
Full-Scale Step
250
238116f
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LTC2381-16
REFERENCE INPUT
SYMBOL
V
REF
I
REF
PARAMETER
Reference Voltage
Load Current
The
l
denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
(Note 5)
(Note 9)
l
l
MIN
2.4
TYP
MAX
2.6
285
UNITS
V
μA
DIGITAL INPUTS AND DIGITAL OUTPUTS
SYMBOL PARAMETER
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
I
SOURCE
I
SINK
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
Digital Input Capacitance
High Level Output Voltage
Low Level Output Voltage
Hi-Z Output Leakage Current
Output Source Current
Output Sink Current
I
O
= –500 μA
I
O
= 500 μA
V
OUT
= 0V to OV
DD
V
OUT
= 0V
V
OUT
= OV
DD
V
IN
= 0V to OV
DD
CONDITIONS
The
l
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
MIN
l
l
l
l
l
l
TYP
MAX
0.2 • OV
DD
UNITS
V
V
μA
pF
V
0.8 • OV
DD
–10
5
OV
DD
– 0.2
0.2
–10
–10
10
10
10
V
μA
mA
mA
POWER REQUIREMENTS
SYMBOL
V
DD
OV
DD
I
DD
PARAMETER
Supply Voltage
Supply Voltage
Supply Current
Power Down Mode
Power Down Mode
Power Dissipation
Power Down Mode
Power Down Mode
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
l
l
l
l
MIN
2.375
1.71
TYP
2.5
1.3
0.5
0.5
3.25
1.25
1.25
MAX
2.625
5.25
1.7
40
110
4.25
100
275
UNITS
V
V
mA
μA
μA
mW
μW
μW
250ksps Sample Rate
Conversion Done
Conversion Done (H-Grade)
250ksps Sample Rate
Conversion Done
Conversion Done (H-Grade)
P
D
ADC TIMING CHARACTERISTICS
SYMBOL
f
SMPL
t
CONV
t
ACQ
t
HOLD
t
CYC
t
CNVH
t
BUSYLH
t
CNVL
t
SCK
PARAMETER
Maximum Sampling Frequency
Conversion Time
Acquisition Time
Maximum Time Between Acquisitions
Time Between Conversions
CNV High Time
CNV
↑
to BUSY Delay
Minimum Low Time for CNV
SCK Period
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
l
l
MIN
2
3.25
TYP
MAX
250
3
750
UNITS
ksps
μs
μs
ns
us
ns
t
ACQ
= t
CYC
– t
HOLD
(Note 10)
l
l
l
l
l
l
l
4
20
20
200
10
C
L
= 20pF (Note 11)
(Note 11)
(Notes 11, 12)
ns
ns
ns
238116f
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LTC2381-16
ADC TIMING CHARACTERISTICS
SYMBOL
t
SCKH
t
SCKL
t
SSDISCK
t
HSDISCK
t
SCKCH
t
DSDO
t
HSDO
t
DSDOBUSYL
t
EN
t
DIS
t
SSCKRDL
t
HSCKRDL
PARAMETER
SCK High Time
SCK Low Time
SDI Setup Time From SCK
↑
SDI Hold Time From SCK
↑
SCK Period in Chain Mode
SDO Data Valid Delay from SCK
↑
SDO Data Remains Valid Delay from SCK
↑
SDO Data Valid Delay from BUSY
↓
Bus Enable Time After RDL
↓
Bus Relinquish Time After RDL
↑
SCK Setup Time from RDL/SDI
↓
SCK Hold Time from RDL/SDI
↓
(Note 11)
(Note 11)
t
SCKCH
= t
SSDISCK
+ t
DSDO
(Note 11)
C
L
= 20pF (Note 11)
C
L
= 20pF (Note 10)
C
L
= 20pF (Note 10)
(Note 11)
(Note 11)
(Note 10)
(Note 10)
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
l
l
l
l
l
l
l
l
l
l
l
l
MIN
4
4
4
1
13.5
TYP
MAX
UNITS
ns
ns
ns
ns
ns
9.5
1
5
16
13
1
16
ns
ns
ns
ns
ns
ns
ns
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All voltage values are with respect to ground.
Note 3:
When these pin voltages are taken below ground or above REF
or OV
DD
, they will be clamped by internal diodes. This product can handle
input currents up to 100mA below ground or above REF or OV
DD
without
latch-up.
Note 4:
V
DD
= 2.5V, OV
DD
= 2.5V, REF = 2.5V, f
SMPL
= 250kHz.
Note 5:
Recommended operating conditions.
Note 6:
Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 7:
Bipolar zero-scale error is the offset voltage measured from
–0.5LSB when the output code flickers between 0000 0000 0000 0000
and 1111 1111 1111 1111. Full-scale bipolar error is the worst-case of
–FS or +FS untrimmed deviation from ideal first and last code transitions
and includes the effect of offset error.
Note 8:
All specifications in dB are referred to a full-scale ±2.5V input with
a 2.5V reference voltage.
Note 9:
f
SMPL
= 250kHz, I
REF
varies proportionately with sample rate.
Note 10:
Guaranteed by design, not subject to test.
Note 11:
Parameter tested and guaranteed at OV
DD
= 1.71V, OV
DD
= 2.5V
and OV
DD
= 5.25V.
Note 12:
t
SCK
of 10ns maximum allows a shift clock frequency up to
100MHz for rising capture.
0.8*OV
DD
0.2*OV
DD
t
DELAY
0.8*OV
DD
0.2*OV
DD
t
DELAY
0.8*OV
DD
0.2*OV
DD
50%
t
WIDTH
50%
238216 F01
Figure 1. Voltage Levels for Timing Specifications
238116f
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