LTC2381-16
16-Bit, 250ksps, Low Power
SAR ADC with Serial Interface
FEATURES
DESCRIPTION
250ksps Throughput Rate
nn ±2LSB INL (Max)
nn Guaranteed 16-Bit No Missing Codes
nn Low Power: 3.25mW at 250ksps, 13µW at 1ksps
nn 92dB SNR (Typ) at f = 20kHz
IN
nn Extended Acquisition Time of 3.25µs Allows Use of
Lower Power Drivers
nn Guaranteed Operation to 125°C
nn 2.5V Supply
nn Fully Differential Input Range ±2.5V
nn External 2.5V Reference Input
nn No Pipeline Delay, No Cycle Latency
nn 1.8V to 5V I/O Voltages
nn SPI-Compatible Serial I/O with Daisy-Chain Mode
nn Internal Conversion Clock
nn 16-Pin MSOP and 4mm × 3mm DFN Packages
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.
nn
APPLICATIONS
Medical Imaging
High Speed Data Acquisition
nn Portable or Compact Instrumentation
nn Industrial Process Control
nn Low Power Battery-Operated Instrumentation
nn ATE
nn
nn
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 daisy-chain mode. The fast 250ksps
throughput with no cycle latency makes the LTC2381-16
ideally suited for a wide variety of high speed applications.
An internal oscillator sets the conversion time, easing external timing considerations. The LTC2381-16 automatically
powers down between conversions, leading 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.
TYPICAL APPLICATION
32k Point FFT fS = 250ksps, fIN = 20kHz
10µF
ANALOG INPUT
0V TO 2.5V
50Ω
LT6350
100Ω
IN+
100Ω
VDD
OVDD
IN–
REF
2.5V
GND
CHAIN
RDL/SDI
SDO
SCK
BUSY
CNV
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
–20
0.1µF
LTC2381-16
3300pF
50Ω
SINGLE-ENDEDTO-DIFFERENTIAL
DRIVER
0
1.8V TO 5V
–40
SAMPLE CLOCK
238116 TA01
47µF
(X5R, 0805 SIZE)
AMPLITUDE (dBFS)
2.5V
–60
–80
–100
–120
–140
–160
–180
0
25
50
75
FREQUENCY (kHz)
100
125
238116 TA02a
238116fa
For more information www.linear.com/LTC2381-16
1
LTC2381-16
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltage (VDD)................................................2.8V
Supply Voltage (OVDD).................................................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 (OVDD + 0.3V)
Digital Output Voltage
(Note 3)............................ (GND –0.3V) to (OVDD + 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
1
VDD
2
GND
3
+
4
IN–
5
GND
6
REF
7
REF
8
IN
16 GND
15 OVDD
17
GND
TOP VIEW
CHAIN
VDD
GND
IN+
IN–
GND
REF
REF
14 SDO
13 SCK
12 RDL/SDI
11 BUSY
10 GND
9 CNV
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
OVDD
SDO
SCK
RDL/SDI
BUSY
GND
CNV
MS PACKAGE
16-LEAD (4mm × 5mm) PLASTIC MSOP
DE PACKAGE
16-LEAD (4mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 110°C/W
TJMAX = 150°C, θJA = 43°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
http://www.linear.com/product/LTC2381-16#orderinfo
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2381CMS-16#PBF
LTC2381CMS-16#TRPBF
238116
16-Lead Plastic MSOP
0°C to 70°C
LTC2381IMS-16#PBF
LTC2381IMS-16#TRPBF
238116
16-Lead Plastic MSOP
–40°C to 85°C
LTC2381HMS-16#PBF
LTC2381HMS-16#TRPBF 238116
16-Lead Plastic MSOP
–40°C to 125°C
LTC2381CDE-16#PBF
LTC2381CDE-16#TRPBF
23816
16-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
LTC2381IDE-16#PBF
LTC2381IDE-16#TRPBF
23816
16-Lead (4mm × 3mm) Plastic DFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
2
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
CONDITIONS
VIN+
Absolute Input Range (IN+)
MIN
(Note 5)
l
VIN –
Absolute Input Range (IN–)
(Note 5)
l
VIN+ – VIN–
Input Differential Voltage range
VIN = VIN+ – VIN–
l
VCM
Common-Mode Input Range
l
VREF/2–
0.05
IIN
Analog Input Leakage Current
l
CIN
Analog Input Capacitance
CMRR
Input Common Mode Rejection Ratio
TYP
MAX
UNITS
VREF
V
–0.05
VREF
V
–VREF
+VREF
V
VREF/2+
0.05
V
±1
µA
–0.05
Sample Mode
Hold Mode
VREF/2
45
5
pF
pF
70
dB
CONVERTER CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL PARAMETER
CONDITIONS
MIN
MAX
UNITS
Resolution
16
Bits
No Missing Codes
l
16
Bits
l
–2
±0.9
2
LSB
l
–1
±0.5
1
LSB
l
–6
±0.25
6
Transition Noise
INL
Integral Linearity Error
DNL
Differential Linearity Error
BZE
Bipolar Zero-Scale Error
0.6
(Note 6)
(Note 7)
Bipolar Zero-Scale Error Drift
FSE
TYP
l
Bipolar Full-Scale Error
LSBRMS
3
(Note 7)
l
–14
Bipolar Full-Scale Error Drift
±3
LSB
mLSB/°C
14
±0.1
LSB
ppm/°C
DYNAMIC
ACCURACY l denotes the specifications which apply over the full operating temperature range,
The
otherwise specifications are at TA = 25°C and AIN = –1dBFS. (Notes 4, 8)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
SINAD
Signal-to-(Noise + Distortion) Ratio
fIN = 20kHz
l
88.5
92
fIN = 20kHz
l
SNR
Signal-to-Noise Ratio
THD
Total Harmonic Distortion
89
fIN = 20kHz, First 5 Harmonics
l
SFDR
Spurious Free Dynamic Range
fIN = 20kHz
MAX
dB
92
–106
UNITS
dB
–99
dB
107
dB
–3dB Input Bandwidth
30
MHz
Aperture Delay
2
ns
30
ps
250
ns
Aperture Jitter
Transient Response
Full-Scale Step
238116fa
For more information www.linear.com/LTC2381-16
3
LTC2381-16
REFERENCE
INPUT
The
l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
CONDITIONS
VREF
Reference Voltage
(Note 5)
l
MIN
IREF
Load Current
(Note 9)
l
TYP
2.4
MAX
UNITS
2.6
V
285
µA
DIGITAL INPUTS AND DIGITAL OUTPUTS
The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL PARAMETER
CONDITIONS
MIN
VIH
High Level Input Voltage
l
VIL
Low Level Input Voltage
l
IIN
Digital Input Current
TYP
MAX
UNITS
0.8 • OVDD
VIN = 0V to OVDD
l
–10
OVDD – 0.2
V
0.2 • OVDD
V
10
µA
CIN
Digital Input Capacitance
VOH
High Level Output Voltage
IO = –500 µA
l
5
pF
VOL
Low Level Output Voltage
IO = 500 µA
l
IOZ
Hi-Z Output Leakage Current
VOUT = 0V to OVDD
l
ISOURCE
Output Source Current
VOUT = 0V
–10
mA
ISINK
Output Sink Current
VOUT = OVDD
10
mA
V
–10
0.2
V
10
µA
POWER
REQUIREMENTS l denotes the specifications which apply over the full operating temperature
The
range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
CONDITIONS
VDD
Supply Voltage
OVDD
Supply Voltage
IDD
Supply Current
Power Down Mode
Power Down Mode
250ksps Sample Rate
Conversion Done
Conversion Done (H-Grade)
PD
Power Dissipation
Power Down Mode
Power Down Mode
250ksps Sample Rate
Conversion Done
Conversion Done (H-Grade)
l
MIN
TYP
MAX
UNITS
2.375
2.5
2.625
V
1.71
l
l
l
5.25
V
1.3
0.5
0.5
1.7
40
110
mA
µA
µA
3.25
1.25
1.25
4.25
100
275
mW
µW
µW
ADC
TIMING CHARACTERISTICS l denotes the specifications which apply over the full operating
The
temperature range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
CONDITIONS
fSMPL
Maximum Sampling Frequency
l
tCONV
Conversion Time
l
2
tACQ
Acquisition Time
l
3.25
tACQ = tCYC – tHOLD (Note 10)
MIN
TYP
MAX
UNITS
250
ksps
3
µs
µs
tHOLD
Maximum Time Between Acquisitions
l
tCYC
Time Between Conversions
l
4
750
ns
us
tCNVH
CNV High Time
l
20
ns
tBUSYLH
CNV ↑ to BUSY Delay
CL = 20pF (Note 11)
l
tCNVL
Minimum Low Time for CNV
(Note 11)
l
200
ns
tSCK
SCK Period
(Notes 11, 12)
l
10
ns
4
20
ns
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
ADC
TIMING CHARACTERISTICS l denotes the specifications which apply over the full operating
The
temperature range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
tSCKH
SCK High Time
CONDITIONS
l
4
ns
tSCKL
SCK Low Time
l
4
ns
tSSDISCK
SDI Setup Time From SCK ↑
(Note 11)
l
4
ns
tHSDISCK
SDI Hold Time From SCK ↑
(Note 11)
l
1
ns
tSCKCH
SCK Period in Chain Mode
tSCKCH = tSSDISCK + tDSDO (Note 11)
l
13.5
ns
tDSDO
SDO Data Valid Delay from SCK ↑
CL = 20pF (Note 11)
l
tHSDO
SDO Data Remains Valid Delay from SCK ↑
CL = 20pF (Note 10)
l
tDSDOBUSYL
SDO Data Valid Delay from BUSY ↓
CL = 20pF (Note 10)
tEN
Bus Enable Time After RDL ↓
(Note 11)
tDIS
Bus Relinquish Time After RDL ↑
(Note 11)
l
tSSCKRDL
SCK Setup Time from RDL/SDI ↓
(Note 10)
l
1
ns
tHSCKRDL
SCK Hold Time from RDL/SDI ↓
(Note 10)
l
16
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 OVDD, they will be clamped by internal diodes. This product can handle
input currents up to 100mA below ground or above REF or OVDD without
latch-up.
Note 4: VDD = 2.5V, OVDD = 2.5V, REF = 2.5V, fSMPL = 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.
MIN
TYP
MAX
UNITS
9.5
ns
l
5
ns
l
16
ns
13
ns
1
ns
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: fSMPL = 250kHz, IREF varies proportionately with sample rate.
Note 10: Guaranteed by design, not subject to test.
Note 11: Parameter tested and guaranteed at OVDD = 1.71V, OVDD = 2.5V
and OVDD = 5.25V.
Note 12: tSCK of 10ns maximum allows a shift clock frequency up to
100MHz for rising capture.
0.8*OVDD
tWIDTH
0.2*OVDD
tDELAY
tDELAY
0.8*OVDD
0.8*OVDD
0.2*OVDD
0.2*OVDD
50%
50%
238216 F01
Figure 1. Voltage Levels for Timing Specifications
238116fa
For more information www.linear.com/LTC2381-16
5
LTC2381-16
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VDD = 2.5V, OVDD = 2.5V, REF = 2.5V,
fSMPL = 250ksps, unless otherwise noted.
Integral Nonlinearity
vs Output Code
Differential Nonlinearity
vs Output Code
2.0
DC Histogram
1.0
1600000
1.5
1400000
0.5
0.5
0.0
–0.5
–1.0
1200000
1000000
COUNTS
DNL ERROR (LSB)
INL ERROR (LSB)
1.0
0.0
200000
–16384
0
16384
OUTPUT CODE
–1.0
–32768
32768
–16384
0
16384
OUTPUT CODE
238116 G01
SNR, SINAD (dBFS)
AMPLITUDE (dBFS)
–100
–120
–140
–160
100
92
SNR
91.5
SINAD
91
90
125
2
–95
90.5
50
75
FREQUENCY (kHz)
1
–90
92.5
–80
25
0
CODE
THD, Harmonics
vs Input Frequency
93
–60
0
–1
238116 G03
SNR, SINAD vs Input Frequency
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
–40
–2
238116 G02
32k Point FFT fS = 250ksps,
fIN = 20kHz
–20
0
32768
HARMONICS, THD (dBFS)
–2.0
–32768
–180
600000
400000
–0.5
–1.5
0
800000
–100
3RD
THD
–105
–110
2ND
–115
–120
–125
0
25
50
75
FREQUENCY (kHz)
–130
100
0
25
50
75
FREQUENCY (kHz)
238116 G05
100
238116 G06
238116 G04
92.50
SNR
SINAD
92.0
91.5
91.0
–40
THD, Harmonics vs Temperature
–100
HARMONICS, THD (dBFS)
SNR, SINAD (dBFS)
92.5
SNR, SINAD vs Temperature
93.00
SNR, SINAD (dBFS)
93.0
SNR, SINAD vs Input level,
fIN = 20kHz
SNR
92.00
SINAD
91.50
–30
–20
–10
INPUT LEVEL (dB)
0
238116 G07
91.00
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (ºC)
–105
–110
–115
–120
–55 –35 –15
THD
2ND
3RD
5 25 45 65 85 105 125
TEMPERATURE (°C)
238116 G08
238116 G09
6
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VDD = 2.5V, OVDD = 2.5V, REF = 2.5V,
fSMPL = 250ksps, unless otherwise noted.
INL/DNL vs Temperature
Full-Scale Error vs Temperature
0
–FS
MAX DNL
0
MIN DNL
–0.5
–0.25
OFFSET ERROR (LSB)
FULL-SCALE ERROR (LSB)
INL/DNL ERROR (LSB)
MAX INL
0.5
–0.5
Offset Error vs Temperature
0
1
–1
+FS
–1.5
–0.5
–0.75
MIN INL
–1
–55 –35 –15
–2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
Supply Current vs Temperature
Supply Current vs Sampling Rate
1.4
IVDD + IOVDD + IREF
25
POWER SUPPLY CURRENT (mA)
IVDD
POWER-DOWN CURRENT (µA)
POWER SUPPLY CURRENT (mA)
30
IREF
238116 G12
Shutdown Current vs Temperature
1.5
0.5
5 25 45 65 85 105 125
TEMPERATURE (°C)
238116 G11
238116 G10
1
–1
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
20
15
10
5
1.2
1
0.8
0.6
0.4
0.2
IOVDD
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
238116 G13
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
0
0
50
100
150
200
SAMPLING RATE (kHz)
250
238116 G14
238116 G15
238116fa
For more information www.linear.com/LTC2381-16
7
LTC2381-16
PIN FUNCTIONS
CHAIN (Pin 1): Chain Mode Selector Pin. When low, the
LTC2381-16 operates in Normal Mode and the RDL/SDI
input pin functions to enable or disable SDO. When high,
the LTC2381-16 operates in Chain Mode and the RDL/
SDI pin functions as SDI, the daisy chain serial data input.
RDL/SDI (Pin 12): When CHAIN is low, the part is in Normal Mode and the pin is treated as a bus enabling input.
When CHAIN is high, the part is in chain mode and the
pin is treated as a serial data input pin where data from
another ADC in the daisy chain is input.
VDD (Pin 2): 2.5V Digital Power Supply. The range of
VDD is 2.375V to 2.625V. Bypass VDD to GND with a 10µF
ceramic capacitor.
SCK (Pin 13): Serial Data Clock Input. When SDO is enabled,
the conversion result or daisy chain data from another ADC
is shifted out on the rising edges of this clock MSB first.
GND (Pins 3, 6, 10 and 16): Ground.
SDO (Pin 14): Serial Data Output. The conversion result or
daisy chain data is output on this pin on each rising edge
of SCK MSB first. The output data is in 2’s complement
format.
IN+, IN– (Pins 4, 5): Positive and Negative Differential
Analog Inputs.
REF (Pins 7, 8): Reference Input. The range of REF is 2.4V
to 2.6V. This pin is referred to the GND pin and should be
decoupled closely to the pin with a 47µF ceramic capacitor
(X5R, 0805 size).
OVDD (Pin 15): I/O Interface Digital Power. The range of
OVDD is 1.71V to 5.25V. This supply is nominally set to
the same supply as the host interface (1.8V, 2.5V, 3.3V,
or 5V). Bypass OVDD to GND with a 0.1µF capacitor.
CNV (Pin 9): Convert Input. A rising edge on this input
initiates a new conversion. When the conversion is done,
the part powers down as long as CNV is held high. When
CNV is returned low, the part powers up in preparation
for the next conversion.
GND (Exposed Pad Pin 17 – DFN Package Only): Ground.
Exposed pad must be soldered directly to the ground plane.
BUSY (Pin 11): BUSY indicator. Goes high at the start of
a new conversion and returns low when the conversion
has finished.
FUNCTIONAL BLOCK DIAGRAM
VDD = 2.5V
REF = 2.5V
OVDD = 1.8V to 5V
LTC2381-16
IN+
+
16-BIT SAMPLING ADC
IN–
SPI
PORT
–
CONTROL LOGIC
CHAIN
SDO
RDL/SDI
SCK
CNV
BUSY
GND
238116 BD01
8
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
TIMING DIAGRAM
Conversion Timing Using the Serial Interface
CHAIN, RDL/SDI = 0
POWER-UP
CNV
POWER-DOWN
CONVERT
BUSY
HOLD
ACQUIRE
SCK
D15 D14 D13 D2 D1 D0
SDO
238116 TD01
APPLICATIONS INFORMATION
OVERVIEW
CONVERTER OPERATION
The LTC2381-16 is a low noise, low power, high speed 16-bit
successive approximation register (SAR) ADC. Operating
from a single 2.5V supply, the LTC2381-16 supports a
large ±2.5V fully differential input range, making it ideal
for high performance applications which require a wide
dynamic range. The LTC2381-16 achieves ±2LSB INL max,
no missing codes at 16-bits and 92dB SNR.
A rising edge on the CNV pin initiates a conversion. During
the conversion phase, the 16-bit CDAC is sequenced
through a successive approximation algorithm, effectively comparing the sampled input with binary-weighted
fractions of the reference voltage (e.g. VREF/2, VREF/4 …
VREF/65536) using the differential comparator. At the end
of conversion, the CDAC output approximates the sampled
analog input. The ADC control logic then prepares the 16bit digital output code for serial transfer.
Fast 250ksps throughput with no cycle latency makes the
LTC2381-16 ideally suited for a wide variety of high speed
applications. An internal oscillator sets the conversion time,
easing external timing considerations. The LTC2381-16
dissipates only 3.25mW at 250ksps, while an auto
power-down feature is provided to further reduce power
dissipation during inactive periods.
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.
TRANSFER FUNCTION
The LTC2381-16 digitizes the full-scale voltage of 2 × REF
into 216 levels, resulting in an LSB size of 76µV with
REF = 2.5V. The ideal transfer function is shown in Figure 2.
The output data is in 2’s complement format.
ANALOG INPUT
The analog inputs of the LTC2381-16 are fully differential
in order to maximize the signal swing that can be digitized.
The analog inputs can be modeled by the equivalent circuit
238116fa
For more information www.linear.com/LTC2381-16
9
LTC2381-16
APPLICATIONS INFORMATION
shown in Figure 3. The diodes at the input provide ESD
protection. In the acquisition phase, each input sees approximately 45pF (CIN) from the sampling CDAC in series
with 40Ω (RON) from the on-resistance of the sampling
switch. Any unwanted signal that is common to both inputs will be reduced by the common mode rejection of the
ADC. The inputs draw a current spike while charging the
CIN capacitors during acquisition. When the LTC2381-16
is not acquiring the input, the analog inputs draw only a
small leakage current.
OUTPUT CODE (TWO’S COMPLEMENT)
ANALOG INPUT
0V TO 2.5V
011...111
BIPOLAR
ZERO
011...110
LT6350
000...001
000...000
SINGLE-ENDEDTO-DIFFERENTIAL
DRIVER
111...111
111...110
100...001
FSR = +FS – –FS
1LSB = FSR/65536
100...000
–1 0V 1
FSR/2 – 1LSB
LSB
LSB
INPUT VOLTAGE (V)
–FSR/2
238116 F02
Figure 2. LTC2381-16 Transfer Function
REF
RON
IN+
CIN
BIAS
VOLTAGE
REF
IN–
RON
CIN
238116 F03
Figure 3. The Equivalent Circuit for the
Differential Analog Input of the LTC2381-16
For best performance, a buffer amplifier should be used
to drive the analog inputs of the LTC2381-16. The amplifier provides low output impedance which produces fast
settling of the analog signal during the acquisition phase.
It also provides isolation between the signal source and
the current spike the ADC inputs draw.
2.5V
Input Filtering
0.1µF
The noise and distortion of the buffer amplifier and signal
VDD
OVDD
CHAIN
source must be considered
since
they
add to the ADC noise
IN+
RDL/SDI
SDO
and distortion.
Noisy
input
signals
should
be filtered prior
LTC2383-16
3300pF
SCK
–
BUSYappropriate
to the buffer amplifier
input with an
filter
IN
SAMPLE
CLOCKto
15Ω
CNV
REF
GND
minimize noise. The simple
1-pole
RC
lowpass
filter
(LPF1)
2.5V
20µF
shown in Figure 4 is sufficient
for many applications.
23816 TA01
Another filter network consisting of LPF2 and the 100Ω
series input resistors should be used between the buffer
and ADC inputs to both minimize the noise contribution
of the buffer and to help minimize disturbances reflected
into the buffer from sampling transients. Long RC time
constants at the analog inputs will slow down the settling
of the analog inputs. Therefore, LPF2 requires a wider
bandwidth than LPF1. A buffer amplifier with a low noise
density must be selected to minimize degradation of the
SNR. With the 482kHz lowpass filter shown in Figure 4,
the LT6350 provides the full data sheet performance of
the LTC2381-16.
High quality capacitors and resistors should be used in the
RC filters since these components can add distortion. NPO
and silver mica type dielectric capacitors have excellent
linearity. Carbon surface mount resistors can generate
distortion from self heating and from damage that may
occur during soldering. Metal film surface mount resistors
are much less susceptible to both problems.
500Ω
A low impedance source can directly drive the high impedance inputs of the LTC2381-16 without gain error. A
high impedance source should be buffered to minimize
settling time during acquisition and to optimize the distortion performance of the ADC. Minimizing settling time
1.8V TO 5V
10µF
LPF2
50Ω
SINGLE-ENDEDINPUT SIGNAL LPF1
INPUT DRIVE CIRCUITS
10
is important even for DC inputs, because the ADC inputs
draw a current spike when entering acquisition.
6600pF
LT6350
100Ω
IN+
3300pF
50Ω
LTC2381-16
100Ω
SINGLE-ENDED- BW = 482kHz
BW = 48kHz TO-DIFFERENTIAL
DRIVER
IN–
238116 F04
Figure 4. Input Signal Chain
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
APPLICATIONS INFORMATION
For single-ended input signals, a single-ended to differential
conversion circuit must be used to produce a differential
signal at the inputs of the LTC2381-16. The LT6350 ADC
driver is recommended for performing single-ended-to-differential conversions. The LT6350 is flexible and may be
configured to convert single-ended signals of various
amplitudes to the ±2.5V differential input range of the
LTC2381-16. The LT6350 is also available in H-grade to
complement the extended temperature operation of the
LTC2381-16 up to 125°C.
Figure 5 shows the LT6350 being used to convert a 0V
to 2.5V single-ended input signal. In this case, the first
amplifier is configured as a unity gain buffer and the single-ended input signal directly drives the high-impedance
input of the amplifier. As shown in the FFT of Figure 5a,
the LT6350 drives the LTC2381-16 to full data sheet performance without degrading the SNR or THD .
The LT6350 can also be used to buffer and convert
single-ended signals larger than the input range of the
LTC2381-16 in order to maximize the signal swing that
can be digitized. Figure 6 shows the LT6350 converting a
0V-5V single-ended input signal to the ±2.5V differential
input range of the LTC2381-16. In this case, the first amplifier in the LT6350 is configured as an inverting amplifier
stage, which acts to attenuate the input signal down to the
0V-2.5V input range of the LTC2381-16. In the inverting
amplifier configuration, the single-ended input signal
source no longer directly drives a high impedance input
of the first amplifier. The input impedance is instead set
by resistor RIN. RIN must be chosen carefully based on
the source impedance of the signal source. Higher values
of RIN tend to degrade both the noise and distortion of
the LT6350 and LTC2381-16 as a system. R1, R2 and R3
must be selected in relation to RIN to achieve the desired
attenuation and to maintain a balanced input impedance
in the first amplifier. Table 1 shows the resulting SNR
and THD for several values of RIN , R1, R2 and R3 in this
configuration. Figure 6a shows the resulting FFT when
using the LT6350 as shown in Figure 6.
The LT6350 can also be used to buffer and convert large,
true bipolar signals which swing below ground to the
±2.5V differential input range of the LTC2381-16. Figure
7 shows the LT6350 being used to convert a ±10V true
bipolar signal for use by the LTC2381-16. The input impedance is again set by resistor RIN. Table 2 shows the
resulting SNR and THD for several values of RIN. Figure
LT6350
+
–
8
1
0V to 2.5V
RINT
4
OUT1
0V to
2.5V
5
OUT2
2.5V to
0V
RINT
2
+
–
–
+
VCM = VREF/2
238116 F05
Figure 5. LT6350 Converting a 0V-2.5V Single-Ended Signal
to a ±2.5V Differential Input Signal
0
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
–20
–40
AMPLITUDE (dBFS)
Single-Ended-to-Differential Conversion
–60
–80
–100
–120
–140
–160
–180
0
25
50
75
FREQUENCY (kHz)
100
125
238116 F05a
Figure 5a. 32k Point FFT Plot for Circuit Shown in Figure 5
238116fa
For more information www.linear.com/LTC2381-16
11
LTC2381-16
APPLICATIONS INFORMATION
VCM
VREF
R2 = 1.24k
200pF
R2 = 1k
150pF
10µF
LT6350
+
–
8
R4 = 680Ω
R3 = 2k
4
RINT
1
RIN = 2k
RINT
2
R1 = 1k
75pF
0V to 5V
OUT1
+
–
–
+
5
OUT2
2.5V to
0V
RIN = 10k
–120
5
OUT2
0V to
2.5V
VCM = VREF/2
238116 F07
SNR = 91.8dB
THD = –95.5dB
SINAD = 91.4dB
SFDR = 96.9dB
–80
–120
–140
–160
–180
125
0
25
50
75
FREQUENCY (kHz)
238116 F06a
100
125
238116 F07a
Figure 6a. 32k Point FFT Plot for Circuit Shown in Figure 6
7a shows the resulting FFT when using the LT6350 as
shown in Figure 7.
Table 1. SNR, THD vs RIN for 0-5V Single-Ended Input Signal
RIN
(Ω)
R1
(Ω)
R2
(Ω)
R3
(Ω)
R4
(Ω)
SNR
(dB)
THD
(dB)
2k
1k
1k
2k
680
92
–100
10k
1.24k
1.24k
10k
1.1k
92
–96
50k
6.19k
6.19k
50k
5.49k
91
–96
100k
12.4k
12.4k
100k
11k
91
–97
ADC REFERENCE
The LTC2381-16 requires an external reference to define its
input range. A low noise, low temperature drift reference
12
–
+
–100
–160
100
2.5V to
0V
–60
–140
50
75
FREQUENCY (kHz)
OUT1
220pF
–40
–80
25
+
–
–20
–100
0
2
R1 = 1.24k
4
RINT
0
–60
–180
RINT
Figure 7. LT6350 Converting a ±10V Single-Ended Signal to
a ±2.5V Differential Input Signal
AMPLITUDE (dBFS)
–40
+
–
±10V
SNR = 91.7dB
THD = –100dB
SINAD = 91.2dB
SFDR = 103.5dB
–20
8
1
VCM = VREF/2
Figure 6. LT6350 Converting a 0V-5V Single-Ended Signal
to a ±2.5V Differential Input Signal
AMPLITUDE (dBFS)
10µF R4 = 1.1k
R3 = 10k
0V to
2.5V
238116 F06
0
LT6350
Figure 7a. 32k Point FFT Plot for Circuit Shown in Figure 7
10k
5k
5k
10k
3.3k
91
–100
50k
25k
25k
50k
16k
91
–97
Table 2. SNR, THD vs RIN for ±10V Single-Ended Input Signal
RIN
(Ω)
R1
(Ω)
R2
(Ω)
R3
(Ω)
R4
(Ω)
SNR
(dB)
THD
(dB)
is critical to achieving the full data sheet performance
of the ADC. Linear Technology offers a portfolio of high
performance references designed to meet the needs of
many applications. With its small size, low power and high
accuracy, the LTC6652-2.5 is particularly well suited for
use with the LTC2381-16. The LTC6652-2.5 offers 0.05%
(max) initial accuracy and 5ppm/°C (max) temperature coefficient for high precision applications. The LTC6652-2.5
is fully specified over the H-grade temperature range and
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
APPLICATIONS INFORMATION
The REF pin of the LTC2381-16 draws charge (QCONV)
from the 47µF bypass capacitor during each conversion
cycle. The reference replenishes this charge with a DC
current, IREF = QCONV/tCYC. The DC current draw of the
REF pin, IREF , depends on the sampling rate and output
code. If the LTC2381-16 is used to continuously sample
a signal at a constant rate, the LTC6652-2.5 will keep the
deviation of the reference voltage over the entire code
span to less than 0.5LSBs.
When idling, the REF pin on the LTC2381-16 draws only a
small leakage current(< 1µA). In applications where a burst
of samples is taken after idling for long periods as shown
in Figure 8, IREF quickly goes from approximately 0µA to
a maximum of 285µA at 250ksps. This step in DC current
draw triggers a transient response in the reference that
must be considered since any deviation in the reference
output voltage will affect the accuracy of the output code.
In applications where the transient response of the reference is important, the fast settling LTC6655-2.5 reference
is recommended. Inserting a 1Ω resistor between the
47µF bypass capacitor and reference output as shown in
Figure 9 helps to improve the transient settling time and
minimize the reference voltage deviation.
DYNAMIC PERFORMANCE
Fast Fourier Transform (FFT) techniques are used to test
the ADC’s frequency response, distortion and noise at the
rated throughput. By applying a low distortion sine wave
VOUT_S
LTC6655-2.5
VOUT_F
1Ω
REF
47µF
LTC2381-16
238116 F09
Figure 9. LTC6655-2.5 Driving REF of LTC2381-16
0
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
–20
–40
AMPLITUDE (dBFS)
complements the extended temperature operation of the
LTC2381-16 up to 125°C. We recommend bypassing the
LTC6652-2.5 with a 47µF ceramic capacitor (X5R, 0805
size) close to the REF pin. All performance curves shown
in this data sheet were obtained using the LTC6652-2.5.
–60
–80
–100
–120
–140
–160
–180
0
25
50
75
FREQUENCY (kHz)
100
125
238116 F10
Figure 10. 32k Point FFT of the LTC2381-16
and analyzing the digital output using an FFT algorithm,
the ADC’s spectral content can be examined for frequencies outside the fundamental. The LTC2381-16 provides
guaranteed tested limits for both AC distortion and noise
measurements.
Signal-to-Noise and Distortion Ratio (SINAD)
The signal-to-noise and distortion ratio (SINAD) is the
ratio between the RMS amplitude of the fundamental input
CNV
IDLE
PERIOD
IDLE
PERIOD
238116 F08
Figure 8. CNV Waveform Showing Burst Sampling
238116fa
For more information www.linear.com/LTC2381-16
13
LTC2381-16
APPLICATIONS INFORMATION
frequency and the RMS amplitude of all other frequency
components at the A/D output. The output is band-limited
to frequencies from above DC and below half the sampling
frequency. Figure 10 shows that the LTC2381-16 achieves
a typical SINAD of 92dB at a 250kHz sampling rate with
a 20kHz input.
supply voltage drops below 1V. Once the supply voltage
reenters the nominal supply voltage range, the POR will
reinitialize the ADC. No conversions should be initiated
until 20µs after a POR event to ensure the reinitialization
period has ended. Any conversions initiated before this
time will produce invalid results.
Signal-to-Noise Ratio (SNR)
TIMING AND CONTROL
The signal-to-noise ratio (SNR) is the ratio between the
RMS amplitude of the fundamental input frequency and
the RMS amplitude of all other frequency components
except the first five harmonics and DC. Figure 10 shows
that the LTC2381-16 achieves a typical SNR of 92dB at a
250kHz sampling rate with a 20kHz input.
Total Harmonic Distortion (THD)
Total Harmonic Distortion (THD) is the ratio of the RMS
sum of all harmonics of the input signal to the fundamental
itself. The out-of-band harmonics alias into the frequency
band between DC and half the sampling frequency (fSMPL/2). THD is expressed as:
THD = 20 log
V 22 + V 32 + V 42 + …+ VN2
V1
where V1 is the RMS amplitude of the fundamental fre
quency and V2 through VN are the amplitudes of the second
through Nth harmonics.
POWER CONSIDERATIONS
The LTC2381-16 provides two power supply pins: the 2.5V
power supply (VDD), and the digital input/output interface
power supply (OVDD). The flexible OVDD supply allows the
LTC2381-16 to communicate with any digital logic operating
between 1.8V and 5V, including 2.5V and 3.3V systems.
Power Supply Sequencing
The LTC2381-16 does not have any specific power supply
sequencing requirements. Care should be taken to adhere
to the maximum voltage relationships described in the
Absolute Maximum Ratings section. The LTC2381-16
has a power-on-reset (POR) circuit that will reset the
LTC2381-16 at initial power-up or whenever the power
14
The LTC2381-16 conversion is controlled by CNV. A rising
edge on CNV will start a conversion. Once a conversion
has been initiated, it cannot be restarted until the conversion is complete. For optimum performance, CNV should
be driven by a clean low jitter signal. Converter status is
indicated by the BUSY output which remains high while
the conversion is in progress. To ensure that no errors
occur in the digitized results, any additional transitions
on CNV should occur within 40ns from the start of the
conversion or after the conversion has been completed.
1.4
POWER SUPPLY CURRENT (mA)
CNV Timing
1.2
1
0.8
0.6
0.4
0.2
0
0
50
100
150
200
SAMPLING RATE (kHz)
250
238116 F11
Figure 11. Power Supply Current of the LTC2381-16
Versus Sampling Rate
ACQUISITION
A proprietary sampling architecture allows the LTC2381-16
to begin acquiring the input signal for the next conversion
750ns after the start of the current conversion. This extends
For more information www.linear.com/LTC2381-16
238116fa
LTC2381-16
APPLICATIONS INFORMATION
the acquisition time to 3.25µs, easing settling requirements
and allowing the use of extremely low power ADC drivers.
(Refer to the Timing Diagram.)
Internal Conversion Clock
The LTC2381-16 has an internal clock that is trimmed to
achieve a maximum conversion time of 2.5µs.
Auto Power-Down
The LTC2381-16 automatically powers down after a conversion has been completed as long as CNV remains high.
During power-down, the data from the last conversion
can be clocked out. To minimize power dissipation during
power-down, disable SDO and turn off SCK. To power up
the part, bring CNV low at least 200ns (tCONVL) before the
initiation of the next conversion. The auto power-down
feature will reduce the power dissipation of the LTC238116 as the sampling frequency is reduced. Since the time
required to power up the part does not change at lower
sample rates, the LTC2381-16 can remain powered-down
for a larger fraction of the conversion cycle (tCYC), thereby reducing the average power dissipation which scales
linearly with sampling rate as shown in Figure 11.
DIGITAL INTERFACE
The LTC2381-16 has a serial digital interface. The flexible
OVDD supply allows the LTC2381-16 to communicate with
any digital logic operating between 1.8V and 5V, including
2.5V and 3.3V systems.
The serial output data is clocked out on the SDO pin when
an external clock is applied to the SCK pin if SDO is enabled.
Clocking out the data after the conversion will yield the
best performance. With a shift clock frequency of at least
15MHz, a 250ksps throughput is still achieved. The serial
output data changes state on the rising edge of SCK and
can be captured on the falling edge or next rising edge of
SCK. D15 remains valid till the first rising edge of SCK.
The serial interface on the LTC2381-16 is simple and
straightforward to use. The following sections describe the
operation of the LTC2381-16. Several modes are provided
depending on whether a single or multiple ADCs share the
SPI bus or are daisy-chained.
238116fa
For more information www.linear.com/LTC2381-16
15
LTC2381-16
APPLICATIONS INFORMATION
Normal Mode, Single Device
Figure 12 shows a single LTC2381-16 operated in Normal
Mode with CHAIN and RDL/SDI tied to ground. With RDL/
SDI grounded, SDO is enabled and the MSB(D15) of the
new conversion data is available at the falling edge of
BUSY. This is the simplest way to operate the LTC2381-16.
When CHAIN = 0, the LTC2381-16 operates in Normal
mode. In Normal mode, RDL/SDI enables or disables the
serial data output pin SDO. If RDL/SDI is high, SDO is in
high-impedance. If RDL/SDI is low, SDO is driven.
CONVERT
DIGITAL HOST
CNV
CHAIN
LTC2381-16
RDL/SDI
BUSY
IRQ
SDO
DATA IN
SCK
CLK
238116 F10
CONVERT
POWER-DOWN
POWER-UP
ACQUIRE
CONVERT
ACQUIRE
CHAIN = 0
tCYC
tCNVH
tCNVL
CNV
tHOLD
BUSY
tACQ
tACQ = tCYC – tHOLD
tCONV
tSCK
tBUSYLH
SCK
tSCKH
1
2
3
SDO
15
16
tSCKL
tHSDO
tDSDOBUSYL
14
tDSDO
D15
D14
D13
D1
D0
238116 F10a
(RDL/SDI = 0)
Figure 12. Using a Single LTC2381-16 in Normal Mode
16
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
APPLICATIONS INFORMATION
Normal Mode, Multiple Devices
time in order to avoid bus conflicts. As shown in Figure 13,
the RDL/SDI inputs idle high and are individually brought
low to read data out of each device between conversions.
When RDL/SDI is brought low, the MSB of the selected
device is output onto SDO. To ensure the MSB is properly
output and captured, SCK must be held low at least 1ns
before and 16ns after bringing RDL/SDI low.
Figure 13 shows multiple LTC2381-16 devices operating
in Normal Mode(CHAIN = 0) sharing CNV, SCK and SDO.
By sharing CNV, SCK and SDO, the number of required
signals to operate multiple ADCs in parallel is reduced.
Since SDO is shared, the RDL/SDI input of each ADC must
be used to allow only one LTC2381-16 to drive SDO at a
RDL2
RDL1
CONVERT
CNV
CHAIN
CNV
CHAIN
LTC2381-16
SDO
B
BUSY
LTC2381-16
A
IRQ
DIGITAL HOST
SDO
RDL/SDI
RDL/SDI
SCK
SCK
DATA IN
CLK
238116 F11
POWER-DOWN
CONVERT
ACQUIRE
CONVERT
POWER-UP
ACQUIRE
CHAIN = 0
CNV
BUSY
tCNVL
tHOLD
tCONV
tBUSYLH
RDL/SDIA
RDL/SDIB
tSCK
tHSCKRDL
1
SCK
2
tSSCKRDL
SDO
Hi-Z
tSCKH
3
14
15
tHSDO
D15A
D14A
D13A
17
D1A
D0A
18
19
30
31
32
tSCKL
tDIS
tDSDO
tEN
16
Hi-Z
D15B
D14B
D13B
D1B
D0B
Hi-Z
238116 F11a
Figure 13. Normal Mode with Multiple Devices Sharing CNV, SCK and SDO
238116fa
For more information www.linear.com/LTC2381-16
17
LTC2381-16
APPLICATIONS INFORMATION
When CHAIN = OVDD, the LTC2381-16 operates in Chain
Mode. In Chain Mode, SDO is always enabled and RDL/
SDI serves as the serial data input pin (SDI) where daisy
chain data output from another ADC can be input.
This is useful for applications where hardware constraints
may limit the number of lines needed to interface to a large
number of converters. Figure 14 shows an example with
two daisy chained devices. The MSB of converter A will
appear at SDO of converter B after 16 SCK cycles. The
MSB of converter A is clocked in at the SDI/RDL pin of
converter B on the rising edge of the first SCK.
CONVERT
OVDD
OVDD
CNV
CHAIN
RDL/SDI
CNV
CHAIN
LTC2381-16
RDL/SDI
SDO
A
DIGITAL HOST
LTC2381-16
IRQ
BUSY
B
DATA IN
SDO
SCK
SCK
CLK
238116 F12
POWER-DOWN
CONVERT
POWER-UP
CONVERT
ACQUIRE
ACQUIRE
CHAIN = OVDD
RDL/SDIA = 0
tCYC
tCNVL
CNV
tHOLD
BUSY
tCONV
tBUSYLH
tSCKCH
SCK
1
2
3
14
tSCKH
15
tSSDISCK
16
18
30
31
32
tSCKL
tHSDO
tHSDISCK
SDOA = RDL/SDIB
17
tDSDO
D15A
D14A
D13A
D1A
D0A
D15B
D14B
D13B
D1B
D0B
tDSDOBUSYL
SDOB
D15A
D14A
D1A
D0A
238116 F14
Figure 14. Chain Mode Timing Diagram
18
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
BOARD LAYOUT
To obtain the best performance from the LTC2381-16
a printed circuit board is recommended. Layout for the
printed circuit board (PCB) should ensure the digital and
analog signal lines are separated as much as possible. In
particular, care should be taken not to run any digital clocks
or signals alongside analog signals or underneath the ADC.
Recommended Layout
The following is an example of a recommended PCB layout.
A single solid ground plane is used. Bypass capacitors to
the supplies are placed as close as possible to the supply
pins. Low impedance common returns for these bypass
capacitors are essential to the low noise operation of the
ADC. The analog input traces are screened by ground.
For more details and information refer to DC1571A, the
evaluation kit for the LTC2381-16.
Partial Top Silkscreen
238116 F13
238116fa
For more information www.linear.com/LTC2381-16
19
LTC2381-16
BOARD LAYOUT
Partial Layer 1 Component Side
238116 BL01
Partial Layer 2 Ground Plane
238116 BL02
20
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
BOARD LAYOUT
Partial Layer 3 PWR Plane
238116 BL03
Partial Layer 4 Bottom Layer
238116 BL04
238116fa
For more information www.linear.com/LTC2381-16
21
AIN –
E7
VREF/2
EXT
R39
ØΩ
JP5
HD1X3-100
EXT_CM
AIN+
R14
Ø
COUPLING
AC
DC
C46
1µF
3
2
1
C8
1µF
+2.5V
R15
1k
HD1X3-100
JP2
CM
C18
OPT
C17
10µF
JP1
HD1X3-100
COUPLING
AC
DC
1
C47
OPT C48
10µF
6.3V
4
2
5
4
+3.3V
C2
0.1µF
R3
CLK
33Ω
TO CPLD
R41
OPT
R40
1k
R18
1k
R9
1k
C49
OPT
C63
10µF
6.3V
3
V+
C43
1µF
C55
1µF
6
C45 V –
10µF
2 +IN2
8 +IN1
V–
C62
10µF
R37
1k
R34
ØΩ
C61
10µF
6.3V
C42
15pF
R32
ØΩ
V+
C44
1µF
C57
0.1µF
V+
C59
1µF
OUT2 5
–IN1
OUT1 4
U15
7 LT6350CMS8
SHDN
U2
R6 3 U8
3
NC7SZ04P5X NC7SVU04P5X
1k
2
R5
49.9Ω
1206
2
5
+3.3V
C1
0.1µF
R2
1k
+3.3V
3
CLKIN
1
C60
1µF
C58
OPT
R35
OPT
R36
49.9Ω
R45
ØΩ
R32
49.9Ω
R31
OPT
SDO
C10
OPT
1
3
5
7
9
11
13
9V TO
10V
R1
100Ω
IN–
IN+
C10
0.1µF
C6
10µF
6.3V
C39
OPT R1
NPO 100Ω
C9
10µF
6.3V
C19
3300pF
1206 NPO
+2.5V
+3.3V
U10
LTC6652AHMS8-2.5
1
8
DNC GND
2
7
VIN
GND
3
6
V
SHDN OUT
4
5
GND GND
R38
OPT
C11
0.1µF
9V TO 10V
C7
0.1µF
C12
1µF
1
2
3
E6
EXT_REF
J3
DC590
2
4
6
8
10
12
14
CNV
SCK
SDO
BUSY
R1
ØΩ
R7
1k
3
2
1
C56
0.1µF
JP6
FS
EXT
6652
3
3
R17 R13
2k
1k
U9
NC7SZ04P5X
2
4
VSS
6
5
7
3
2
1
C15
0.1µF
U7
C14
0.1µF 8 24LC025-I/ST
VCC
SCL
SCK
SDA
WP
CNV
ARRAY
A2
EEPROM
A1
A0
4
5
+3.3V
R10
4.99k
R11
4.99k
CLKOUT
C16 1
0.1µF
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
DB8
DB9
DB10
DB11
DB12
DB13
DB14
DB15
DB16
DB17
3
5
2 CNVST_33
FROM CPLD
U4
NC7SVU04P5X
+3.3V
C4
0.1µF
R12
4.99k
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
J2
CON-EDGE 40-100
R4
7 33Ω 4
8
+3.3V
C3
0.1µF
R8
33Ω
DC590 DETECT
TO CPLD
PR\
Q
CLR\
Q\
5
2
D
VCC
1
CP
GND
+3.3V
C13
0.8VREF
0.1µF
VREF
6
U3
NL17SZ74
+3.3V
4
HD1X3-100
U6
OPT NC7SZ66P5X 5
CNV
VCC
9
2 B
A 1
13 SCK
OE
4
14 SDO
GND
11 BUSY
3
12 RD
C20
47µF
6.3V
0805
RDL/SDI
LTC2381-16
JP4
REF
HD1X3-100
VDD 2
OVDD 15
7
8
C5
0.1µF
2
+
–
For more information www.linear.com/LTC2381-16
3
REF
REF1
GND
GND
GND
GND
–
+
22
3
6
10
16
1
R1
33Ω
LTC2381-16
BOARD LAYOUT
Partial Schematic of Demoboard
238116fa
LTC2381-16
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTC2381-16#packaging for the most recent package drawings.
DE Package
16-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1732 Rev Ø)
0.70 ±0.05
3.30 ±0.05
3.60 ±0.05
2.20 ±0.05
1.70 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.45 BSC
3.15 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 ±0.10
(2 SIDES)
R = 0.05
TYP
9
R = 0.115
TYP
0.40 ±0.10
16
3.30 ±0.10
3.00 ±0.10
(2 SIDES)
1.70 ±0.10
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
(DE16) DFN 0806 REV Ø
8
0.200 REF
1
0.23 ±0.05
0.45 BSC
0.75 ±0.05
3.15 REF
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
238116fa
For more information www.linear.com/LTC2381-16
23
LTC2381-16
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTC2381-16#packaging for the most recent package drawings.
MS Package
16-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1669 Rev A)
0.889 ±0.127
(.035 ±.005)
5.10
(.201)
MIN
3.20 – 3.45
(.126 – .136)
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
0.50
(.0197)
BSC
0.305 ±0.038
(.0120 ±.0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
DETAIL “A”
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
0° – 6° TYP
0.280 ±0.076
(.011 ±.003)
REF
16151413121110 9
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
0.18
(.007)
SEATING
PLANE
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
1234567 8
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
24
0.86
(.034)
REF
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS16) 0213 REV A
238116fa
For more information www.linear.com/LTC2381-16
LTC2381-16
REVISION HISTORY
REV
DATE
DESCRIPTION
A
07/16
Updated graphs G01, G02 and G03
PAGE NUMBER
6
238116fa
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 representation
that the interconnection
of its information
circuits as described
herein will not infringe on existing patent rights.
For more
www.linear.com/LTC2381-16
25
LTC2381-16
TYPICAL APPLICATION
ADC Driver: Single-Ended Input to Differential Output with Filter
0
SNR = 91.8dB
THD = –106dB
SINAD = 91.6dB
SFDR = 107dB
–20
LPF1
500Ω
6600pF
LT6350
8
1
+
–
4
RINT
RINT
+
–
2
BW = 48kHz
LPF2
50Ω
+
–
100Ω
–40
IN+
3300pF
5
LTC2381-16
50Ω
100Ω
BW = 482kHz
IN–
238116 TA03
AMPLITUDE (dBFS)
SINGLE-ENDED
INPUT SIGNAL
–60
–80
–100
–120
–140
VCM = VREF/2
–160
–180
0
25
50
75
FREQUENCY (kHz)
100
125
238116 TA04
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
ADCs
LTC2383-16/LTC2382-16 16-Bit, 1Msps/500ksps Serial ADC
2.5V Supply, Differential Input, 92dB SNR, ±2.5V Input Range,16-Pin MSOP
and 4mmx3mm16-Pin DFN Packages,Pin Compatible with the LTC2382-16
LTC2393-16
16-Bit, 1Msps Parallel/Serial ADC
5V Supply, Differential Input, 94dB SNR, 4.096V Input Range, 48-Pin LQFP
Package, Pin Compatible with the LTC2392-16, LTC2391-16
LTC2392-16
16-Bit, 500ksps Parallel/Serial ADC
5V Supply, Differential Input, 94dB SNR, 4.096V Input Range, 48-Pin LQFP
Package, Pin Compatible with the LTC2393-16, LTC2391-16
LTC2391-16
16-Bit, 250ksps Parallel/Serial ADC
5V Supply, Differential Input, 94dB SNR, 4.096V Input Range, 48-Pin LQFP
Package, Pin Compatible with the LTC2393-16, LTC2392-16
LTC1864/LTC1864L
16-Bit, 250ksps/150ksps 1-Channel µPower, ADC
5V/3V Supply, 1-Channel, 4.3mW/1.3mW, MSOP-8 Package
LTC1865/LTC1865L
16-Bit, 250ksps 2-Channel µPower ADC
5V/3V Supply, 1-Channel, 4.3mW/1.3mW, MSOP-8 Package
LTC2302/LTC2306
12-Bit, 500ksps, 1-/2-Channel, Low Noise, ADC
5V Supply, 14mW at 500ksps, 10-Pin DFN Package
LTC2355-14/LTC2356-14 14-Bit, 3.5Msps Serial ADC
3.3V Supply, 1-Channel, Unipolar/Bipolar, 18mW, MSOP-10 Package
DACs
LTC2641
16-Bit Single Serial VOUT DACs
±1LSB INL, ±1LSB DNL, MSOP-8 Package, 0V to 5V Output
LTC2630
12-/10-/8-Bit Single VOUT DACs
SC70 6-Pin Package, Internal Reference, ±1LSB INL (12 Bits)
REFERENCES
LTC6652
Precision Low Drift Low Noise Buffered Reference 2.5V, 5ppm/°C Max Tempco, 2.1ppm Peak-to-Peak Noise, MSOP-8
Package
LTC6655
Precision Low Drift Low Noise Buffered Reference 2.5V, 5ppm/°C Max Tempco, 0.25ppm Peak-to-Peak Noise, MSOP-8 Package
AMPLIFIERS
LT6350
Low Noise Single-Ended-To-Differential ADC Driver Rai-to-Rail Input and Outputs, 240ns 0.01% Settling Time, DFN-8 or
MSOP-8 Packages
LT6200/LT6200-5/
LT6200-10
165MHz/800MHz/1.6GHz Op Amp with Unity
Gain/AV = 5/AV = 10
Low Noise Voltage: 0.95nV/√Hz (100kHz), Low Distortion: –80dB at 1MHz,
TSOT23-6 Package
LT6202/LT6203
Single/Dual 100MHz Rail-to-Rail Input/Output
Noise Low Power Amplifiers
1.9nV√Hz, 3mA Maximum, 100MHz Gain Bandwidth
LTC1992
Low Power, Fully Differential Input/Output
Amplifier/Driver Family
1mA Supply Current
26 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC2381-16
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC2381-16
238116fa
LT 0716 REV A • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2010
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湘ICP备2023018690号
