FeaTures
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LTC2378-20
20-Bit, 1Msps, Low Power
SAR ADC with 0.5ppm INL
DescripTion
The
LTC
®
2378-20
is a low noise, low power, high speed
20-bit successive approximation register (SAR) ADC.
Operating from a 2.5V supply, the LTC2378-20 has a
±V
REF
fully differential input range with V
REF
ranging from
2.5V to 5.1V. The LTC2378-20 consumes only 21mW and
achieves ±2ppm INL maximum, no missing codes at 20
bits with 104dB SNR.
The LTC2378-20 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 1Msps
throughput with no cycle latency makes the LTC2378-20
ideally suited for a wide variety of high speed applications.
An internal oscillator sets the conversion time, easing exter-
nal timing considerations. The LTC2378-20 automatically
powers down between conversions, leading to reduced
power dissipation that scales with the sampling rate.
The LTC2378-20 features a unique digital gain compres-
sion (DGC) function, which eliminates the driver amplifier’s
negative supply while preserving the full resolution of the
ADC. When enabled, the ADC performs a digital scaling
function that maps zero-scale code from 0V to
0.1 •
V
REF
and full-scale code from V
REF
to
0.9 •
V
REF
. For a typical
reference voltage of 5V, the full-scale input range is now
0.5V to 4.5V, which provides adequate headroom for
powering the driving amplifier from a single 5.5V supply.
1Msps Throughput Rate
±0.5ppm INL (Typ)
Guaranteed 20-Bit No Missing Codes
Low Power: 21mW at 1Msps, 21µW at 1ksps
104dB SNR (Typ) at f
IN
= 2kHz
–125dB
THD (Typ) at f
IN
= 2kHz
Digital Gain Compression (DGC)
Guaranteed Operation to 85°C
2.5V Supply
Fully Differential Input Range ±V
REF
V
REF
Input Range from 2.5V to 5.1V
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-Lead MSOP and 4mm
×
3mm DFN Packages
applicaTions
n
n
n
n
n
n
Medical Imaging
High Speed Data Acquisition
Portable or Compact Instrumentation
Industrial Process Control
Low Power Battery-Operated Instrumentation
ATE
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
SoftSpan is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Patents Pending. Protected by U.S. Patents, including
7705765, 7961132, 8319673.
Typical applicaTion
2.5V
10µF
V
REF
0V
V
REF
0V
6800pF
3300pF
V
DD
IN
+
LTC2378-20
IN
–
6800pF
REF
2.5V TO 5.1V
GND
OV
DD
1.8V TO 5V
0.1µF
CHAIN
RDL/SDI
SDO
SCK
BUSY
CNV
REF/DGC
237820 TA01a
Integral Nonlinearity vs Output Code
2.0
1.5
1.0
INL ERROR (ppm)
+
–
10
0.5
0
–0.5
–1.0
–1.5
–2.0
–524288
–262144
0
262144
OUTPUT CODE
524288
237820fb
10
SAMPLE CLOCK
V
REF
47µF
(X7R, 1210 SIZE)
237820 TA01b
For more information
www.linear.com/LTC2378-20
1
LTC2378-20
absoluTe MaxiMuM raTings
(Notes 1, 2)
Supply Voltage (V
DD
) ...............................................2.8V
Supply Voltage (OV
DD
) ................................................6V
Reference Input (REF).................................................6V
Analog Input Voltage (Note 3)
IN
+
, IN
–
......................... (GND –0.3V) to (REF + 0.3V)
REF/DGC Input (Note 3) .... (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
LTC2378C ................................................ 0°C to 70°C
LTC2378I .............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
pin conFiguraTion
TOP VIEW
CHAIN
V
DD
GND
IN
+
IN
–
GND
REF
REF/DGC
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/DGC
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
= 40°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
MS PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 110°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC2378CMS-20#PBF
LTC2378IMS-20#PBF
LTC2378CDE-20#PBF
LTC2378IDE-20#PBF
TAPE AND REEL
http://www.linear.com/product/LTC2378-20#orderinfo
PART MARKING*
237820
237820
23780
23780
PACKAGE DESCRIPTION
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
0°C to 70°C
–40°C to 85°C
LTC2378CMS-20#TRPBF
LTC2378IMS-20#TRPBF
LTC2378CDE-20#TRPBF
LTC2378IDE-20#TRPBF
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.
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.
237820fb
2
For more information
www.linear.com/LTC2378-20
LTC2378-20
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
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
f
IN
= 500kHz
CONDITIONS
(Note 5)
(Note 5)
V
IN
= V
IN
+ – V
IN
–
l
l
l
l
elecTrical characTerisTics
MIN
–0.1
–0.1
–V
REF
V
REF
/2–
0.1
TYP
MAX
V
REF
+ 0.1
V
REF
+ 0.1
+V
REF
UNITS
V
V
V
V
µA
pF
pF
dB
V
REF
/2
0.01
45
5
86
V
REF
/2+
0.1
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
MIN
20
20
TYP
MAX
UNITS
Bits
Bits
2.3
(Note 6)
REF/DGC = GND, (Note 6)
(Note 10)
(Note 7)
l
l
l
l
ppm
RMS
2
2
0.5
13
100
ppm
ppm
ppm
ppm
ppb/°C
ppm
ppm/°C
–2
–2
–0.5
–13
–100
±0.5
±0.5
±0.2
0
±7
±10
±0.05
DynaMic accuracy
SYMBOL PARAMETER
SINAD
SNR
Signal-to-Noise Ratio
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
= 2kHz, V
REF
= 5V
f
IN
= 2kHz, V
REF
= 5V
f
IN
= 2kHz, V
REF
= 5V, REF/DGC = GND
f
IN
= 2kHz, V
REF
= 2.5V
f
IN
= 2kHz, V
REF
= 5V
f
IN
= 2kHz, V
REF
= 5V, REF/DGC = GND
f
IN
= 2kHz, V
REF
= 2.5V
f
IN
= 2kHz, V
REF
= 5V
l
l
l
l
l
l
l
l
MIN
101
101
99
95.4
TYP
104
104
102
98
–125
–125
–123
MAX
UNITS
dB
dB
dB
dB
Signal-to-(Noise + Distortion) Ratio
THD
Total Harmonic Distortion
–114
–114
–113
dB
dB
dB
dB
MHz
ps
ps
ns
SFDR
Spurious Free Dynamic Range
–3dB Input Bandwidth
Aperture Delay
Aperture Jitter
Transient Response
115
128
34
500
4
Full-Scale Step
312
237820fb
For more information
www.linear.com/LTC2378-20
3
LTC2378-20
reFerence inpuT
SYMBOL
V
REF
I
REF
V
IHDGC
V
ILDGC
PARAMETER
Reference Voltage
Reference Input Current
High Level Input Voltage REF/DGC Pin
Low Level Input Voltage REF/DGC Pin
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
l
l
MIN
2.5
TYP
0.94
MAX
5.1
1.1
0.2V
REF
UNITS
V
mA
V
V
0.8V
REF
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
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
= –500µA
I
O
= 500µA
V
OUT
= 0V to OV
DD
V
OUT
= 0V
V
OUT
= OV
DD
l
l
l
DigiTal inpuTs anD DigiTal ouTpuTs
CONDITIONS
MIN
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
IN
= 0V to OV
DD
l
V
µA
mA
mA
power requireMenTs
SYMBOL
V
DD
OV
DD
I
VDD
I
OVDD
I
PD
P
D
PARAMETER
Supply Voltage
Supply Voltage
Supply Current
Supply Current
Power Down Mode
Power Dissipation
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
MIN
2.375
1.71
TYP
2.5
8.4
0.2
1
21
2.5
MAX
2.625
5.25
10
90
25
225
UNITS
V
V
mA
mA
µA
mW
µW
1Msps Sample Rate
1Msps Sample Rate (C
L
= 20pF)
Conversion Done (I
VDD
+ I
OVDD
+ I
REF
)
1Msps Sample Rate
Conversion Done (I
VDD
+ I
OVDD
+ I
REF
)
l
l
aDc TiMing characTerisTics
SYMBOL
f
SMPL
t
CONV
t
ACQ
t
CYC
t
CNVH
t
BUSYLH
t
CNVL
t
QUIET
t
SCK
PARAMETER
Maximum Sampling Frequency
Conversion Time
Acquisition Time
Time Between Conversions
CNV High Time
CNV↑ to BUSY Delay
Minimum Low Time for CNV
SCK Quiet Time from 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
615
312
1
20
TYP
MAX
1
675
UNITS
Msps
ns
ns
µs
ns
t
ACQ
= t
CYC
– t
CONV
– t
BUSYLH
(Note 10)
l
l
l
C
L
= 20pF
(Note 11)
(Note 10)
(Notes 11, 12)
l
l
l
l
13
20
20
10
ns
ns
ns
ns
237820fb
4
For more information
www.linear.com/LTC2378-20
LTC2378-20
aDc TiMing characTerisTics
SYMBOL
t
SCKH
t
SCKL
t
SSDISCK
t
HSDISCK
t
SCKCH
t
DSDO
t
HSDO
t
DSDOBUSYL
t
EN
t
DIS
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↑
(Note 11)
(Note 11)
t
SCKCH
= t
SSDISCK
+ t
DSDO
(Note 11)
C
L
= 20pF, OV
DD
= 5.25V
C
L
= 20pF, OV
DD
= 2.5V
C
L
= 20pF, OV
DD
= 1.71V
C
L
= 20pF (Note 10)
C
L
= 20pF (Note 10)
(Note 11)
(Note 11)
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
7.5
8
9.5
1
5
16
13
ns
ns
ns
ns
ns
ns
ns
SDO Data Remains Valid Delay from SCK↑
SDO Data Valid Delay from BUSY↓
Bus Enable Time After RDL↓
Bus Relinquish Time After RDL↑
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 effect 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 = 5V, V
CM
= 2.5V, f
SMPL
= 1MHz,
REF/DGC = V
REF
.
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 0000
and 1111 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 ±5V input with a
5V reference voltage.
Note 9:
f
SMPL
= 1MHz, 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%
237820 F01
Figure 1. Voltage Levels for Timing Specifications
237820fb
For more information
www.linear.com/LTC2378-20
5
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