LTC2380-24: 24-Bit, 1.5Msps/2Msps, Low Power SAR ADC with Integrated Digital Filter

34 Pages·2015·1.86 MB·English

by  Linear Technology Corporation

LTC2380-24
24-Bit, 1.5Msps/2Msps,
Low Power SAR ADC with
Integrated Digital Filter
FEATURES DESCRIPTION
n Guaranteed 24-Bits No Missing Codes The LTC®2380-24 is a low noise, low power, high speed
n ±0.5ppm INL (Typ) 24-bit successive approximation register (SAR) ADC with
n Integrated Digital Filter with Real-Time Averaging an integrated digital averaging filter. Operating from a 2.5V
n Low Power: 28mW at 2Msps supply, the LTC2380-24 has a ±V fully differential input
REF
n 100dB SNR (Typ) at 1.5Msps range with V ranging from 2.5V to 5.1V. The LTC2380-
REF
n 145dB Dynamic Range (Typ) at 30.5sps 24 consumes only 28mW and achieves ±3.5ppm INL
n –117dB THD (Typ) at f = 2kHz maximum and no missing codes at 24 bits.
IN
n 50Hz/60Hz Rejection
The LTC2380-24 has an easy to use integrated digital
n Digital Gain Compression (DGC)
averaging filter that can average 1 to 65536 conversion
n Guaranteed Operation to 85°C
results real-time, dramatically improving dynamic range
n Single 2.5V Supply
from 101dB at 1.5Msps to 145dB at 30.5sps. No separate
n Fully Differential Input Range Up to ±5V
programming interface or configuration register is required.
n 1.8V to 5V SPI-Compatible Serial I/O with Daisy-
Chain Mode The high speed SPI-compatible serial interface supports
n 16-Lead MSOP and 4mm × 3mm DFN Packages 1.8V, 2.5V, 3.3V and 5V logic while also featuring a daisy-
chain mode. The LTC2380-24 automatically powers down
APPLICATIONS between conversions, reducing power dissipation at lower
sampling rates.
n Seismology
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
n Energy Exploration SoftSpan is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents, including 7705765, 7961132, 8319673,
n Medical Imaging 8810443 and Patents pending.
n High Speed Data Acquisition
n Industrial Process Control
n ATE
TYPICAL APPLICATION
Integral Nonlinearity vs Output Code
3.0
2.5V 1.8V TO 5V
2.0
10µF 0.1µF
m) 1.0
VREF + 10Ω 6800pF IN+ VDD OVDD RCDHLA/SINDI R (pp
0V SDO RO 0
VREF – 3300pF IN– LTC2380-24 BCSUNCSKVY SAMPLE CLOCK INL ER –1.0
0V 10Ω 6800pF RREEFF GND REF/DGC VREF
–2.0
2.5V TO 5.1V 238024 TA01
47µF
–3.0
(X7R, 1210 SIZE) 0 4194304 8388608 12582912 16777216
OUTPUT CODE
3681 TA01b
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LTC2380-24
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltage (V ) ...............................................2.8V Digital Output Voltage
DD
Supply Voltage (OV ) ................................................6V (Note 3) ..........................(GND – 0.3V) to (OV + 0.3V)
DD DD
Reference Input (REF) .................................................6V Power Dissipation ..............................................500mW
Analog Input Voltage (Note 3) Operating Temperature Range
IN+, IN– .............................(GND – 0.3V) to (REF + 0.3V) LTC2380C ................................................0°C to 70°C
REF/DGC Input (Note 3) ....(GND – 0.3V) to (REF + 0.3V) LTC2380I .............................................–40°C to 85°C
Digital Input Voltage Storage Temperature Range ..................–65°C to 150°C
(Note 3) ..........................(GND – 0.3V) to (OV + 0.3V)
DD
PIN CONFIGURATION
TOP VIEW
CHAIN 1 16 GND
TOP VIEW
VDD 2 15 OVDD CHAIN 1 16 GND
GND 3 14 SDO VDD 2 15 OVDD
IINN+– 45 G1N7D 1132 SRCDKL/SDI GIINNND+– 345 111432 SSRDCDKOL/SDI
GND 6 11 BUSY GND 6 11 BUSY
REF 7 10 GND REF 7 10 GND
REF/DGC 8 9 CNV
REF/DGC 8 9 CNV
MS PACKAGE
DE PACKAGE 16-LEAD PLASTIC MSOP
16-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 150°C, θJA = 110°C/W
TJMAX = 150°C, θJA = 40°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC2380CMS-24#PBF LTC2380CMS-24#TRPBF 238024 16-Lead Plastic MSOP 0°C to 70°C
LTC2380IMS-24#PBF LTC2380IMS-24#TRPBF 238024 16-Lead Plastic MSOP –40°C to 85°C
LTC2380CDE-24#PBF LTC2380CDE-24#TRPBF 23804 16-Lead (4mm × 3mm) Plastic DFN 0°C to 70°C
LTC2380IDE-24#PBF LTC2380IDE-24#TRPBF 23804 16-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C
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.
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LTC2380-24
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V + Absolute Input Range (IN+) (Note 5) l −0.1 V + 0.1 V
IN REF
V – Absolute Input Range (IN–) (Note 5) l −0.1 V + 0.1 V
IN REF
V + – V – Input Differential Voltage Range V = V + – V – l −V V V
IN IN IN IN IN REF REF
V Common Mode Input Range l −V /2 – 0.1 V /2 V /2 + 0.1 V
CM REF REF REF
I Analog Input Leakage Current 0.01 μA
IN
C Analog Input Capacitance Sample Mode 45 pF
IN
Hold Mode 5 pF
CMRR Input Common Mode Rejection Ratio f = 1MHz 86 dB
IN
CONVERTER CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Resolution l 24 Bits
No Missing Codes l 24 Bits
N Number of Averages l 1 65536
Transition Noise N = 1, f = 1.5Msps l 55.7 LSB
SMPL RMS
N = 16, f = 2Msps l 13.6 LSB
SMPL RMS
N = 1024, f = 2Msps l 1.75 LSB
SMPL RMS
N = 16384, f = 2Msps l 0.55 LSB
SMPL RMS
INL Integral Linearity Error N = 1, f = 1.5Msps (Note 6) l –3.5 ±0.5 3.5 ppm
SMPL
N = 1, f = 1.5Msps REF/DGC = GND (Note 6) l –3.5 ±0.5 3.5 ppm
SMPL
N = 4, f = 2Msps (Note 6) l –3.5 ±0.5 3.5 ppm
SMPL
DNL Differential Linearity Error (Note 7) l –0.5 ±0.2 0.5 LSB
ZSE Zero-Scale Error (Note 8) l −10 0 10 ppm
Zero-Scale Error Drift ±7 ppb/°C
FSE Full-Scale Error (Note 8) l −100 ±10 100 ppm
Full-Scale Error Drift ±0.05 ppm/°C
DYNAMIC ACCURACY
The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T = 25°C and A = –1dBFS. (Notes 4, 9)
A IN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DR Dynamic Range IN+ = IN– = V , V = 5V, N = 1, f = 1.5Msps 101 dB
CM REF SMPL
IN+ = IN– = V , V = 5V, N = 16, f = 2Msps 113 dB
CM REF SMPL
IN+ = IN– = V , V = 5V, N = 1024, f = 2Msps 131 dB
CM REF SMPL
IN+ = IN– = V , V = 5V, N = 16384, f = 2Msps 141 dB
CM REF SMPL
IN+ = IN– = V , V = 5V, N = 65536, f = 2Msps 145 dB
CM REF SMPL
SINAD Signal-to-(Noise + Distortion) Ratio f = 2kHz, V = 5V l 97.5 100 dB
IN REF
SNR Signal-to-Noise Ratio f = 2kHz, V = 5V, N = 1, f = 1.5Msps l 97.5 100 dB
IN REF SMPL
f = 2kHz, V = 5V, REF/DGC = GND, N = 1, f = 1.5Msps l 95.5 98 dB
IN REF SMPL
f = 2kHz, V = 2.5V, N = 1, f = 1.5Msps l 92.5 95 dB
IN REF SMPL
f = 2kHz, V = 5V, N = 16, A = –20dBFS, f = 2Msps 112 dB
IN REF IN SMPL
f = 100Hz, V = 5V, N = 1024, A = –20dBFS, f = 2Msps 130 dB
IN REF IN SMPL
THD Total Harmonic Distortion f = 2kHz, V = 5V, N = 1, f = 1.5Msps l –117 –114 dB
IN REF SMPL
f = 2kHz, V = 5V, REF/DGC = GND, N = 1, f = 1.5Msps l –119 –114 dB
IN REF SMPL
f = 2kHz, V = 2.5V, N = 1, f = 1.5Msps l –117 –113 dB
IN REF SMPL
f = 2kHz, V = 5V, N = 16, A = –20dBFS, f = 2Msps –140 dB
IN REF IN SMPL
f = 100Hz, V = 5V, N = 1024, A = –20dBFS, f = 2Msps –140 dB
IN REF IN SMPL
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LTC2380-24
DYNAMIC ACCURACY
The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T = 25°C and A = –1dBFS. (Notes 4, 9)
A IN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
SFDR Spurious Free Dynamic Range f = 2kHz, V = 5V l 114 120 dB
IN REF
–3dB Input Linear Bandwidth 34 MHz
Aperture Delay 500 ps
Aperture Jitter 4 ps
RMS
Transient Response Full–Scale Step 115 ns
REFERENCE INPUT
The l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Reference Voltage (Note 5) l 2.5 5.1 V
REF
I Reference Input Current (Note 10) l 1.9 2.1 mA
REF
V High Level Input Voltage REF/DGC Pin l 0.8V V
IHDGC REF
V Low Level Input Voltage REF/DGC Pin l 0.2V V
ILDGC REF
DIGITAL INPUTS AND DIGITAL OUTPUTS
The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V High Level Input Voltage l 0.8 • OV V
IH DD
V Low Level Input Voltage l 0.2 • OV V
IL DD
I Digital Input Current V = 0V to OV l –10 10 μA
IN IN DD
C Digital Input Capacitance 5 pF
IN
V High Level Output Voltage I = –500µA l OV – 0.2 V
OH O DD
V Low Level Output Voltage I = 500µA l 0.2 V
OL O
I Hi-Z Output Leakage Current V = 0V to OV l –10 10 µA
OZ OUT DD
I Output Source Current V = 0V –10 mA
SOURCE OUT
I Output Sink Current V = OV 10 mA
SINK OUT DD
POWER REQUIREMENTS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Supply Voltage l 2.375 2.5 2.625 V
DD
OV Supply Voltage l 1.71 5.25 V
DD
I Supply Current N = 4, f = 2Msps l 11.2 13 mA
VDD SMPL
I Supply Current N = 4, f = 2Msps (C = 20pF) 0.4 mA
OVDD SMPL L
I Power Down Mode Conversion Done (I + I + I ) l 1 90 μA
PD VDD OVDD REF
P Power Dissipation N = 4, f = 2Msps 28 32.5 mW
D SMPL
Power Down Mode Conversion Done (I + I + I ) 2.5 225 μW
VDD OVDD REF
ADC TIMING CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
f Maximum Sampling Frequency N ≥ 4 l 2 Msps
SMPL
f Output Data Rate l 1.5 Msps
ODR
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LTC2380-24
ADC TIMING CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. (Note 4)
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t Conversion Time l 343 392 ns
CONV
t Acquisition Time t = t – t – t (Note 7) l 115 ns
ACQ ACQ CYC CONV BUSYLH
t Time Between Conversions l 500 ns
CYC
t CNV High Time l 20 ns
CNVH
t Minimum Low Time for CNV (Note 11) l 20 ns
CNVL
tBUSYLH CNV↑ to BUSY↑ Delay CL = 20pF l 13 ns
tQUIET SCK Quiet Time from CNV↑ (Note 7) l 10 ns
t SCK Period (Notes 11, 12) l 10 ns
SCK
t SCK High Time l 4 ns
SCKH
t SCK Low Time l 4 ns
SCKL
tSSDISCK SDI Setup Time From SCK↑ (Note 11) l 4 ns
tHSDISCK SDI Hold Time From SCK↑ (Note 11) l 1 ns
t SCK Period in Chain Mode t = t + t (Note 11) l 13.5 ns
SCKCH SCKCH SSDISCK DSDO
tDSDO SDO Data Valid Delay from SCK↑ CL = 20pF, OVDD = 5.25V l 7.5 ns
CL = 20pF, OVDD = 2.5V l 8 ns
C = 20pF, OV = 1.71V l 9.5 ns
L DD
tHSDO SDO Data Remains Valid Delay from SCK↑ CL = 20pF (Note 7) l 1 ns
tDSDOBUSYL SDO Data Valid Delay from BUSY↓ CL = 20pF (Note 7) l 5 ns
tEN Bus Enable Time After RDL↓ (Note 11) l 16 ns
tDIS Bus Relinquish Time After RDL↑ (Note 11) l 13 ns
Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 7: Guaranteed by design, not subject to test.
may cause permanent damage to the device. Exposure to any Absolute Note 8: Bipolar zero-scale error is the offset voltage measured from –0.5LSB
Maximum Rating condition for extended periods may affect device when the output code flickers between 0000 0000 0000 0000 0000 0000
reliability and lifetime. and 1111 1111 1111 1111 1111 1111. Full-scale bipolar error is the
Note 2: All voltage values are with respect to ground. worst-case of –FS or +FS untrimmed deviation from ideal first and last code
Note 3: When these pin voltages are taken below ground or above REF or transitions and includes the effect of offset error.
OV , they will be clamped by internal diodes. This product can handle Note 9: All specifications in dB are referred to a full-scale ±5V input with a
DD
input currents up to 100mA below ground or above REF or OV without 5V reference voltage.
DD
latchup. Note 10: f = 2MHz, I varies proportionally with sample rate.
SMPL REF
Note 4: VDD = 2.5V, OVDD = 2.5V, REF = 5V, VCM = 2.5V, fSMPL = 1.5MHz, Note 11: Parameter tested and guaranteed at OVDD = 1.71V, OVDD = 2.5V
REF/DGC = VREF, N = 1. and OVDD = 5.25V.
Note 5: Recommended operating conditions. Note 12: t of 10ns maximum allows a shift clock frequency up to
SCK
Note 6: Integral nonlinearity is defined as the deviation of a code from a 100MHz for rising edge capture.
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
0.8 (cid:127) OVDD tWIDTH
0.2 (cid:127) OVDD
tDELAY tDELAY 50% 50%
0.8 (cid:127) OVDD 0.8 (cid:127) OVDD 238024 F01
0.2 (cid:127) OVDD 0.2 (cid:127) OVDD
Figure 1. Voltage Levels for Timing Specifications
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LTC2380-24
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, V = 2.5V, OV = 2.5V, V = 2.5V,
A DD DD CM
REF = 5V, f = 1.5Msps, N = 1, unless otherwise noted.
SMPL
Integral Nonlinearity vs Output Differential Nonlinearity vs
Code Output Code DC Histogram, N = 1
3.0 1.0 10000
σ = 55.7
0.8
2.0
0.6 8000
0.4
m) 1.0 B)
INL ERROR (pp –1.00 DNL ERROR (LS –––0000....4202 COUNTS 46000000
–0.6 2000
–2.0
–0.8
–3.0 –1.0 0
0 4194304 8388608 12582912 16777216 0 4194304 8388608 12582912 16777216 –300 –200 –100 0 100 200 300
OUTPUT CODE OUTPUT CODE CODE
238024 G01 238024 G02 238024 G03
DC Histogram, N = 16, DC Histogram, N = 1024, DC Histogram, N = 16384,
f = 2Msps f = 2Msps f = 2Msps
SMPL SMPL SMPL
10000 10000 10000
σ = 13.6 σ = 1.75 σ = 0.55
8000 8000 8000
6000 6000 6000
S S S
T T T
N N N
U U U
O O O
C 4000 C 4000 C 4000
2000 2000 2000
0 0 0
–300 –200 –100 0 100 200 300 –8 –6 –4 –2 0 2 4 6 8 –8 –6 –4 –2 0 2 4 6 8
CODE CODE CODE
238024 G04 238024 G05 238024 G06
DC Histogram, N = 65536, 128k Point FFT f = 1.5Msps, 128k Point FFT f = 2Msps,
SMPL SMPL
f = 2Msps f = 2kHz f = 2kHz, N = 16
SMPL IN IN
10000 0 0
σ = 0.33 SNR = 100.3dB SNR = 112.4dB
–20 THD = –117.3dB –20
SINAD = 100.2dB
8000 –40 SFDR = 117.4dB –40
S) –60 S) –60
F F
COUNTS 46000000 LITUDE (dB–1–0800 LITUDE (dB –1–0800
P P
M–120 M –120
A A
2000 –140 –140
–160 –160
0 –180 –180
–8 –6 –4 –2 0 2 4 6 8 0 150 300 450 600 750 0 12.5 25 37.5 50 62.5
CODE FREQUENCY (kHz) FREQUENCY (kHz)
238024 G07 238024 G08 238024 G09
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LTC2380-24
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, V = 2.5V, OV = 2.5V, V = 2.5V,
A DD DD CM
REF = 5V, f = 1.5Msps, N = 1, unless otherwise noted.
SMPL
128k Point FFT f = 2Msps, 32k Point FFT f = 2Msps, 8k Point FFT f = 2Msps,
SMPL SMPL SMPL
f = 100Hz, N = 1024 f = 10Hz, N = 16384 IN+ = IN– = V , N = 65536
IN IN CM
0 0 0
SNR = 130.2dB SNR = 138.3dB DR = 145dB
–20 –20 –20
–40 –40 –40
S) –60 S) –60 S) –60
F F F
dB –80 dB –80 dB –80
E ( E ( E (
D –100 D–100 D –100
U U U
T T T
LI –120 LI–120 LI –120
P P P
M M M
A –140 A–140 A –140
–160 –160 –160
–180 –180 –180
–200 –200 –200
0 244 488 732 976 0 15.3 30.5 45.8 61 0 3 6 9 12 15
FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (Hz)
238024 G10 238024 G11 238024 G12
Dynamic Range, Transition Noise THD, Harmonics vs Input
vs Number of Averages (N) SNR, SINAD vs Input Frequency Frequency
150 100 101 –90
TRANSITION NOISE 100
DYNAMIC RANGE (dB)111112340000 110 TRANSITION NOISE (LSB) SNR, SINAD (dBFS) 999999456789 SNR SINAD THD, HARMONICS (dBFS) ––––111132100000 THD 23NRDD
93
DYNAMIC RANGE
100 0.1 92 –140
1 10 100 1k 10k 70k 0 25 50 75 100 125 150 175 200 0 25 50 75 100 125 150 175 200
NUMBER OF AVERAGES (N) FREQUENCY (kHz) FREQUENCY (kHz)
238024 G13 238024 G14 238024 G15
SNR, SINAD vs Input level, SNR, SINAD vs Reference THD, Harmonics vs Reference
f = 2kHz Voltage, f = 2kHz Voltage, f = 2kHz
IN IN IN
101.5 101 –115.0
THD
100 SNR –120.0
101.0
SNR, SINAD (dBFS) 110000..05 SINADSNR SNR, SINAD (dBFS) 99997889 SINAD HD, HARMONICS (dBFS) –––111332505...000 2ND 3RD
T
99.5
–140.0
96
99.0 95 –145.0
–40 –30 –20 –10 0 2.5 3 3.5 4 4.5 5 2.5 3 3.5 4 4.5 5
INPUT LEVEL (dB) REFERENCE VOLTAGE (V) REFERENCE VOLTAGE (V)
238024 G16 238024 G17 238024 G18
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LTC2380-24
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, V = 2.5V, OV = 2.5V, V = 2.5V,
A DD DD CM
REF = 5V, f = 1.5Msps, N = 1, unless otherwise noted.
SMPL
SNR, SINAD vs Temperature, THD, Harmonics vs Temperature,
f = 2kHz f = 2kHz INL vs Temperature
IN IN
101.0 –110 4.0
3.0
SNR –115 THD
100.5
S) 2.0 MAX INL
SNR, SINAD (dBFS) 19090..50 SINAD D, HARMONICS (dBF –––111322050 3RD INL ERROR (PPM) –11..000
99.0 TH 2ND –2.0 MIN INL
–135
–3.0
98.5 –140 –4.0
–40 –15 10 35 60 85 –40 –15 10 35 60 85 –40 –15 10 35 60 85
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)
238024 G19 238024 G20 238024 G21
Full-Scale Error vs Temperature Zero-Scale Error vs Temperature Supply Current vs Temperature
10 5 12
4
10
ULL–SCALE ERROR (ppm) –505 +–FFSS ERO–SCALE ERROR (ppm) ––210123 SUPPLY CURRENT (mA) 468 IIIIIIVVOORRDDVVEEFFDDDD DD –––––– ffffffSSSSSSMMMMMMPPPPPPLLLLLL ====== 212121M.M.M.555MsMMsspppsssssspp,p,, s s s , , , NNNNNN ====== 414141
F Z –3
2
–4
–10 –5 0
–40 –15 10 35 60 85 –40 –15 10 35 60 85 –40 –15 10 35 60 85
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)
238024 G22 238024 G23 238024 G24
Power-Down Current vs Reference Current vs Reference
Temperature CMRR vs Input Frequency Voltage
10 100 2.0
IVDD+IOVDD+IREF
µA) 8 95 A)
DOWN CURRENT ( 46 CMRR (dB) 8950 NCE CURRENT (m 1.5 fSMPL = 2Msps
R– 80 RE 1.0
OWE 2 REFE fSMPL = 1.5Msps
P 75
0 70 0.5
–40 –15 10 35 60 85 0.001 0.01 0.1 1 10 2.5 3 3.5 4 4.5 5
TEMPERATURE (°C) FREQUENCY (MHz) REFERENCE VOLTAGE (V)
238024 G25 238024 G26 238024 G27
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LTC2380-24
PIN FUNCTIONS
CHAIN (Pin 1): Chain Mode Selector Pin. When low, the BUSY (Pin 11): BUSY Indicator. Goes high at the start of
LTC2380-24 operates in normal mode and the RDL/SDI a new conversion and returns low when the conversion
input pin functions to enable or disable SDO. When high, has finished. Logic levels are determined by OV .
DD
the LTC2380-24 operates in chain mode and the RDL/SDI
RDL/SDI (Pin 12): Bus Enabling Input/Serial Data Input
pin functions as SDI, the daisy-chain serial data input.
Pin. This pin serves two functions depending on whether
Logic levels are determined by OV .
DD the part is operating in normal mode (CHAIN pin low) or
V (Pin 2): 2.5V Power Supply. The range of V is chain mode(CHAIN pin high). In normal mode, RDL/SDI
DD DD
2.375V to 2.625V. Bypass V to GND with a 10µF ce- is a bus enabling input for the serial data I/O bus. When
DD
ramic capacitor. RDL/SDI is low in normal mode, data is read out of the
ADC on the SDO pin. When RDL/SDI is high in normal
GND (Pins 3, 6, 10 and 16): Ground.
mode, SDO becomes Hi-Z and SCK is disabled. In chain
IN+, IN– (Pins 4, 5): Positive and Negative Differential mode, RDL/SDI acts as a serial data input pin where data
Analog Inputs. from another ADC in the daisy chain is input. Logic levels
are determined by OV .
REF (Pin 7): Reference Input. The range of REF is 2.5V DD
to 5.1V. This pin is referred to the GND pin and should be SCK (Pin 13): Serial Data Clock Input. When SDO is enabled,
decoupled closely to the pin with a 47µF ceramic capacitor the conversion result or daisy-chain data from another
(X7R, 1210 size, 10V rating). ADC is shifted out on the rising edges of this clock MSB
first. Logic levels are determined by OV .
REF/DGC (Pin 8): When tied to REF, digital gain compres- DD
sion is disabled and the LTC2380-24 defines full-scale ac- SDO (Pin 14): Serial Data Output. The conversion result or
cording to the ±VREF analog input range. When tied to GND, daisy-chain data is output on this pin on each rising edge
digital gain compression is enabled and the LTC2380-24 of SCK MSB first. The output data is in 2’s complement
defines full-scale with inputs that swing between 10% and format. Logic levels are determined by OV .
DD
90% of the ±V analog input range.
REF
OV (Pin 15): I/O Interface Digital Power. The range of
DD
CNV (Pin 9): Convert Input. A rising edge on this input OV is 1.71V to 5.25V. This supply is nominally set to
DD
powers up the part and initiates a new conversion. Logic the same supply as the host interface (1.8V, 2.5V, 3.3V,
levels are determined by OVDD. or 5V). Bypass OVDD to GND with a 0.1µF capacitor.
GND (Exposed Pad Pin 17 – DFN Package Only): Ground.
Exposed pad must be soldered directly to the ground plane.
238024f
9
For more information www.linear.com/LTC2380-24
LTC2380-24
FUNCTIONAL BLOCK DIAGRAM
VDD = 2.5V
REF = 5V OVDD = 1.8V to 5V
CHAIN
IN+ +
SDO
24-BIT DIGITAL SPI
RDL/SDI
SAMPLING ADC FILTER PORT
IN– – SCK
CNV
BUSY
CONTROL LOGIC
REF/DGC
GND
238024 BD
TIMING DIAGRAM
Conversion Timing Using the Serial Interface
CHAIN, RDL/SDI = 0
CNV
BUSY POWER-DOWN AND ACQUIRE
CONVERT
SCK
SDO D23D22D21D20D19D18D17D16D15D14D13D12D11D10D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 C15C14C13C12C11C10 C9 C8 C7 C6 C5 C4 C3 C2 C1 C0
238024 TD01
DATA FROM CONVERSION NUMBER OF SAMPLES
AVERAGED FOR DATA
238024f
10
For more information www.linear.com/LTC2380-24