LINER LTC2314-14 14-bit, 4.5msps serial sampling adc in tsot Datasheet

LTC2314-14
14-Bit, 4.5Msps Serial
Sampling ADC in TSOT
FEATURES
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DESCRIPTION
4.5Msps Throughput Rate
Guaranteed 14-Bit No Missing Codes
Internal Reference: 2.048V/4.096V Span
Low Noise: 77.5dB SNR
Low Power: 6.2mA at 4.5Msps and 5V
Dual Supply Range: 3V/5V operation
Sleep Mode with < 1µA Typical Supply Current
Nap Mode with Quick Wake-up < 1 conversion
Separate 1.8V to 5V Digital I/O Supply
High Speed SPI-Compatible Serial I/O
Guaranteed Operation from –40°C to 125°C
8-Lead TSOT-23 Package
The LTC®2314-14 is a 14-bit, 4.5Msps, serial sampling A/D
converter that draws only 6.2mA from a wide range analog
supply adjustable from 2.7V to 5.25V. The LTC2314-14
contains an integrated bandgap and reference buffer which
provide a low cost, high performance (20ppm/°C max)
and space saving applications solution. The LTC2314-14
achieves outstanding AC performance of 77dB SINAD and
–85dB THD while sampling a 500kHz input frequency.
The extremely high sample rate-to-power ratio makes the
LTC2314-14 ideal for compact, low power, high speed
systems. The LTC2314-14 also provides both nap and
sleep modes for further optimization of the device power
within a system.
APPLICATIONS
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The LTC2314-14 has a high-speed SPI-compatible serial
interface that supports 1.8V, 2.5V, 3V and 5V logic. The
fast 4.5Msps throughput makes the LTC2314-14 ideally
suited for a wide variety of high speed applications.
Communication Systems
High Speed Data Acquisition
Handheld Terminal Interface
Medical Imaging
Uninterrupted Power Supplies
Battery Operated Systems
Automotive
Complete 14-/12-Bit Pin-Compatible SAR ADC Family
500ksps
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.
2.5Msps
4.5Msps
5Msps
14-Bit
LTC2312-14 LTC2313-14 LTC2314-14
12-Bit
LTC2312-12 LTC2313-12
LTC2315-12
Power 3V/5V 9mW/15mW 14mW/25mW 18mW/31mW 19mW/32mW
TYPICAL APPLICATION
5V Supply, Internal Reference, 4.5Msps, 14-bit Sampling ADC
0
LTC2314-14
VDD
CS
2.2µF
ANALOG INPUT
0V TO 4.096V
REF
SCK
GND
SDO
AIN
VDD = 5V
SNR = 77.5dBFS
SINAD = 76.9dBFS
THD = 84.9dB
SFDR = 88.1dB
–20
SERIAL DATA LINK TO
ASIC, PLD, MPU, DSP
OR SHIFT REGISTERS
OVDD
2.2µF
DIGITAL OUTPUT SUPPLY
1.8V TO 5V
231414 TA01
–40
AMPLITUDE (dBFS)
5V
2.2µF
32k Point FFT, fS = 4.5Msps, fIN = 500kHz
–60
–80
–100
–120
–160
–140
0
250 500 750 1000 1250 1500 1750 2000 2250
FREQUENCY (kHz)
231414 TA01a
231414fa
For more information www.linear.com/LTC2314-14
1
LTC2314-14
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2)
Supply Voltage (VDD, OVDD)........................................6V
Reference (REF) and Analog Input (AIN) Voltage
(Note 3).......................................(–0.3V) to (VDD + 0.3V)
Digital Input Voltage (Note 3)... (–0.3V) to (OVDD + 0.3V)
Digital Output Voltage.............. (–0.3V) to (OVDD + 0.3V)
Power Dissipation................................................100mW
Operating Temperature Range
LTC2314C................................................. 0°C to 70°C
LTC2314I..............................................–40°C to 85°C
LTC2314H........................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature Range (Soldering, 10 sec)......... 300°C
TOP VIEW
VDD
REF
GND
AIN
1
2
3
4
8
7
6
5
CS
SCK
SDO
OVDD
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 195°C/W
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2314CTS8-14#TRMPBF
LTC2314CTS8-14#TRPBF
LTFZF
8-Lead Plastic TSOT-23
0°C to 70°C
LTC2314ITS8-14#TRMPBF
LTC2314ITS8-14#TRPBF
LTFZF
8-Lead Plastic TSOT-23
LTC2314HTS8-14#TRMPBF
LTC2314HTS8-14#TRPBF
LTFZF
8-Lead Plastic TSOT-23
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on 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/
–40˚C to 85˚C
–40˚C to 125˚C
231414fa
2
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LTC2314-14
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
VAIN
Absolute Input Range
VIN
Input Voltage Range
IIN
Analog Input DC Leakage Current
CIN
Analog Input Capacitance
CONDITIONS
MIN
l
(Note 11)
TYP
UNITS
–0.05
VDD + 0.05
V
0
VREF
V
1
µA
–1
l
MAX
Sample Mode
Hold Mode
13
3
pF
pF
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
Resolution
No Missing Codes
MIN
l
14
l
14
TYP
MAX
UNITS
Bits
Bits
Transition Noise
(Note 6)
0.7
LSBRMS
INL
Integral Linearity Error
VDD = 5V (Note 5)
VDD = 3V (Note 5)
l
l
–3.75
–4.25
±1
±1.5
3.75
4.25
LSB
LSB
DNL
Differential Linearity Error
VDD = 5V
VDD = 3V
l
l
–0.99
–0.99
±0.3
±0.4
0.99
0.99
LSB
LSB
Offset Error
VDD = 5V
VDD = 3V
l
l
–9
–22
±2
±4
9
22
LSB
LSB
Full-Scale Error
VDD = 5V
VDD = 3V
l
l
–18
–26
±5
±7
18
26
LSB
LSB
Total Unadjusted Error
VDD = 5V
VDD = 3V
l
l
–22
–30
±6
±8
22
30
LSB
LSB
DYNAMIC ACCURACY
The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at TA = 25°C and AIN = –1dBFS. (Note 4)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
SINAD
Signal-to-(Noise + Distortion) Ratio
fIN = 500kHz, VDD = 5V
fIN = 500kHz, VDD = 3V
SNR
Signal-to-Noise Ratio
THD
l
l
72
69
77
72.6
dB
dB
fIN = 500kHz, VDD = 5V
fIN = 500kHz, VDD = 3V
l
l
73
69.5
77.5
73
dB
dB
Total Harmonic Distortion
First 5 Harmonics
fIN = 500kHz, VDD = 5V
fIN = 500kHz, VDD = 3V
l
l
–85
–85
–75
–74
dB
dB
SFDR
Spurious Free Dynamic Range
fIN = 500kHz, VDD = 5V
fIN = 500kHz, VDD = 3V
l
l
–87
–87
–77
–75
dB
dB
IMD
Intermodulation Distortion
2nd Order Terms
3rd Order Terms
fIN1 = 461kHz, fIN2 = 541kHz
AIN1, AIN2 = –7dBFS
Full Power Bandwidth
At 3dB
At 0.1dB
–3dB Input Linear Bandwidth
SINAD ≥ 74dB
MAX
UNITS
–79.4
–90.8
dBc
dBc
130
20
MHz
MHz
5
MHz
tAP
Aperture Delay
1
ns
tJITTER
Aperture Jitter
10
psRMS
231414fa
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3
LTC2314-14
REFERENCE INPUT/OUTPUT
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL PARAMETER
VREF
CONDITIONS
VREF Output Voltage
2.7V ≤ VDD ≤ 3.6V
4.75 ≤ VDD ≤ 5.25V
VREF Temperature Coefficient
l
l
MIN
TYP
MAX
UNITS
2.040
4.080
2.048
4.096
2.056
4.112
V
V
7
20
l
ppm/°C
VREF Output Resistance
Normal Operation
Overdrive Condition
(VREFIN ≥ VREFOUT + 50mV)
2
52
Ω
kΩ
VREF Line Regulation
2.7V ≤ VDD ≤ 3.6V
4.75 ≤ VDD ≤ 5.25V
0.4
0.2
mV/V
mV/V
4.15
V
VREF 2.048V/4.096V Supply Threshold
VREF 2.048V/4.096V Supply Threshold Hysteresis
VREF Input Voltage Range
(External Reference Input)
150
2.7V ≤ VDD ≤ 3.6V
4.75 ≤ VDD ≤ 5.25V
l
l
VREF + 50mV
VREF + 50mV
mV
V
V
VDD
4.3
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
l
–10
OVDD–0.2
CIN
Digital Input Capacitance
High Level Output Voltage
IO = –500µA (Source)
l
MAX
UNITS
0.8 • OVDD
VIN = 0V to OVDD
VOH
TYP
V
0.2 • OVDD
V
10
μA
5
VOL
Low Level Output Voltage
IO = 500µA (Sink)
l
IOZ
High-Z Output Leakage Current
VOUT = 0V to OVDD, CS = High
l
COZ
High-Z Output Capacitance
CS = High
ISOURCE
Output Source Current
ISINK
Output Sink Current
pF
V
–10
0.2
V
10
µA
4
pF
VOUT = 0V, OVDD = 1.8V
–20
mA
VOUT = OVDD = 1.8V
20
mA
POWER REQUIREMENTS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 4)
SYMBOL
PARAMETER
VDD
Supply Voltage
3V Operational Range
5V Operational Range
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
2.7
4.75
3
5
3.6
5.25
V
V
l
1.71
OVDD
Digital Output Supply Voltage
ITOTAL =
IVDD + IOVDD
Supply Current, Static Mode
Operational Mode
Nap Mode
Sleep Mode
CS = 0V, SCK = 0V
l
l
PD
Power Dissipation, Static Mode
Operational Mode
Nap Mode
Sleep Mode
CS = 0V, SCK = 0V
l
l
l
l
5.25
V
3.2
6.2
1.8
0.8
4
7.2
mA
mA
mA
µA
16
31
9
4
20
36
5
25
mW
mW
mW
µW
231414fa
4
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LTC2314-14
ADC TIMING 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
fSAMPLE(MAX) Maximum Sampling Frequency
fSCK
Shift Clock Frequency
tSCK
Shift Clock Period
MIN
TYP
MAX
UNITS
(Notes 7, 8)
l
4.5
MHz
(Notes 7, 8)
l
87.5
MHz
l
tTHROUGHPUT Minimum Throughput Time, tACQ + tCONV
11.4
ns
222
l
ns
Conversion Time
l
182
ns
tACQ
Acquisition Time
l
40
ns
t1
Minimum CS Pulse Width
(Note 7)
l
10
ns
t2
SCK Setup Time After CS↓
(Note 7)
l
5
t3
SDO Enable Time After CS↓
(Notes 7, 8)
l
10
ns
t4
SDO Data Valid Access Time after SCK↓
(Notes 7, 8, 9)
l
9.1
ns
↔
tCONV
ns
t5
SCLK Low Time
l
4.5
ns
t6
SCLK High Time
l
4.5
ns
t7
SDO Data Valid Hold Time After SCK↓
(Notes 7, 8, 9)
l
1
ns
t8
SDO into Hi-Z State Time After 16th SCK↓
(Notes 7, 8, 10)
l
3
10
ns
t9
SDO into Hi-Z State Time After CS↑
(Notes 7, 8, 10)
l
3
10
ns
t10
CS↑ Setup Time After 14th SCK↓
(Note 7)
l
5
Latency
l
ns
1 Cycle Latency
tWAKE_NAP
Power-Up Time from Nap Mode
See Nap Mode Section
50
ns
tWAKE_SLEEP
Power-Up Time from Sleep Mode
See Sleep Mode Section
1.1
ms
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 VDD
(AIN, REF) or OVDD (SCK, CS, SDO) they will be clamped by internal
diodes. This product can handle input currents up to 100mA below ground
or above VDD or OVDD without latch-up.
Note 4. VDD = 5V, OVDD = 2.5V, fSMPL = 4.5MHz, fSCK = 87.5MHz, AIN =
–1dBFS and internal reference unless otherwise noted.
Note 5. 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 6. Typical RMS noise at code transitions.
Note 7. Parameter tested and guaranteed at OVDD = 2.5V. All input signals
are specified with tr = tf = 1nS (10% to 90% of OVDD) and timed from a
voltage level of OVDD/2.
Note 8. All timing specifications given are with a 10pF capacitance load.
Load capacitances greater than this will require a digital buffer.
Note 9. The time required for the output to cross the VIH or VIL voltage.
Note 10. Guaranteed by design, not subject to test.
Note 11. Recommended operating conditions.
231414fa
For more information www.linear.com/LTC2314-14
5
LTC2314-14
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VDD = 5V, OVDD = 2.5V, fSMPL = 4.5Msps,
unless otherwise noted.
Differential Nonlinearity
vs Output Code
DC Histogram Near Mid-Scale
(Code 8192)
2.0
1.00
7000
1.5
0.75
6000
1.0
0.50
0.5
0.25
0.0
–0.5
0.00
–0.25
–1.0
–0.50
–1.5
–0.75
0
4096
8192
12288
OUTPUT CODE
16384
–1.00
1000
0
4096
8192
12288
OUTPUT CODE
–80
–100
–75
77
SINAD
VDD = 5V
76
75
74
72
0
250 500 750 1000 1250 1500 1750 2000 2250
INPUT FREQUENCY (kHz)
79
250 500 750 1000 1250 1500 1750 2000 2250
INPUT FREQUENCY (kHz)
77
THD
3RD
2ND
–95
250 500 750 1000 1250 1500 1750 2000 2250
INPUT FREQUENCY (kHz)
231414 G06a
3RD
–95
–105
0
250 500 750 1000 1250 1500 1750 2000 2250
INPUT FREQUENCY (kHz)
231414 G06
74
71
–55 –35 –15
THD, Harmonics vs Temperature,
fIN = 500kHz
VDD = 3V
–80
SINAD
SNR
SINAD
–75
VDD = 5V
75
72
0
SNR
76
73
–100
2ND
–90
–100
SNR, SINAD vs Temperature,
fIN = 500kHz
78
SNR, SINAD (dBFS)
THD, HARMONICS (dB)
RIN/CIN = 50Ω/47pF
fS = 4.5Msps
–80 VDD = 5V
–90
SINAD
0
THD
–85
231414 G05
–75
–85
VDD = 3V
231414 G04
THD, Harmonics vs Input
Frequency (100kHz to 2.2MHz)
–105
SNR
73
–160
RIN/CIN = 50Ω/47pF
fS = 4.5Msps
–80 VDD = 3V
SNR
–120
–140
8194 8195 8196 8197 8198 8199 8200
CODE
231414 G03
THD, Harmonics vs Input
Frequency (100kHz to 2.2MHz)
THD, HARMONICS (dB)
–60
78
SNR, SINAD (dBFS)
AMPLITUDE (dBFS)
SNR, SINAD vs Input Frequency
(100kHz to 2.2MHz)
VDD = 5V
SNR = 77.5dBFS
SINAD = 76.9dBFS
THD = 84.9dB
SFDR = 88.1dB
–40
0
16384
231414 G02
32k Point FFT, fS = 4.5Msps
fIN = 500kHz
–20
3000
2000
231414 G01
0
4000
VDD = 3V
5 25 45 65 85 105 125
TEMPERATURE (°C)
231414 G07
THD, HARMONICS (dB)
–2.0
σ = 0.7
5000
COUNTS
DNL (LSB)
INL (LSB)
Integral Nonlinearity
vs Output Code
–85
THD
2ND
–90
3RD
–95
–100
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
231414 G08
231414fa
6
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LTC2314-14
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VDD = 5V, OVDD = 2.5V, fSMPL = 4.5Msps,
unless otherwise noted.
79
VDD = 5V
SNR, SINAD (dBFS)
THD
–85
3RD
–90
2ND
–95
77
SNR
SINAD
VDD = 5V
76
SINAD
75
VDD = 3.6V
74
72
5 25 45 65 85 105 125
TEMPERATURE (°C)
600
OPERATION
NOT ALLOWED
2
2.5
3
3.5
4
REFERENCE VOLTAGE (V)
fS = 5Msps
VDD = 3.6V
300
Full-Scale Error vs Temperature
fS = 3Msps
OPERATION
NOT ALLOWED
100
0
2
2.5
3
3.5
4
REFERENCE VOLTAGE (V)
Offset Error vs Temperature
Supply Current vs Temperature
6.5
3
6.25
0
–1
–2
0.5
SUPPLY CURRENT (mA)
OFFSET ERROR (LSB)
1
4.5
231414 G11
1
2
fS = 3Msps
200
231414 G10
4
VDD = 5V
400
4.5
231414 G08a
0
–0.5
VDD = 5V
6
5.75
VDD = 3V
5.5
5.25
–3
–4
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
–1
–55 –35 –15
SUPPLY CURRENT (mA)
6
0.75
0.5
VDD = 3V
VDD = 3V
OVDD = 1.8V
5
ITOT
4
IVDD
3
2
1
VDD = 5V
0
–55 –35 –15
231414 G14
Supply Current vs SCK Frequency
7
IVDD + IOVDD
0.25
5 25 45 65 85 105 125
TEMPERATURE (°C)
231414 G13
Shutdown Current vs Temperature
1
5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
231414 G12
SHUTDOWN CURRENT (µA)
FULL-SCALE ERROR (LSB)
fS = 5Msps
500
73
–100
–55 –35 –15
Reference Current
vs Reference Voltage
SNR
78
–80
THD, HARMONICS (dB)
SNR, SINAD vs Reference Voltage
fIN = 500kHz
REFERENCE CURRENT (µA)
–75
THD, Harmonics vs Temperature,
fIN = 500kHz
0
5 25 45 65 85 105 125
TEMPERATURE (°C)
10
IOVDD
20
231414 G15
30 40 50 60 70
SCK FREQUENCY (MHz)
80
90
231414 G16
231414fa
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7
LTC2314-14
TYPICAL PERFORMANCE CHARACTERISTICS
unless otherwise noted.
6.25
SUPPLY CURRENT (mA)
2.5
6.00 5Msps
fSCK = 87.5MHz
5.75
OPERATION
NOT ALLOWED
5.50
3Msps
5.25
5.00
Output Supply Current (IOVDD)
vs Output Supply Voltage (OVDD)
5Msps
3Msps
fSCK = 52.5MHz
4.75
4.50
2.6 2.9 3.2 3.5 3.8 4.1 4.4 4.7 5.0 5.3
SUPPLY VOLTAGE (V)
OUTPUT SUPPLY CURRENT (mA)
6.50
Supply Current (IVDD)
vs Supply Voltage (VDD)
TA = 25°C, VDD = 5V, OVDD = 2.5V, fSMPL = 4.5Msps,
2.0
5Msps
fSCK = 87.5MHz
1.5
1.0
3Msps
fSCK = 52.5MHz
0.5
0
1.7
2.3
2.9
3.5
4.1
4.7
OUTPUT SUPPLY VOLTAGE (V)
5.3
231414 G18
231414 G17
PIN FUNCTIONS
VDD (Pin 1): Power Supply. The ranges of VDD are 2.7V
to 3.6V and 4.75V to 5.25V. Bypass VDD to GND with a
2.2µF ceramic chip capacitor.
REF (Pin 2): Reference Input/Output. The REF pin voltage defines the input span of the ADC, 0V to VREF. By
default, REF is an output pin and produces a reference
voltage VREF of either 2.048V or 4.096V depending on
VDD (see Table 2). Bypass to GND with a 2.2µF, low ESR,
high quality ceramic chip capacitor. The REF pin may be
overdriven with a voltage at least 50mV higher than the
internal reference voltage output.
GND (Pin 3): Ground. The GND pin must be tied directly
to a solid ground plane.
AIN (Pin 4): Analog Input. AIN is a single-ended input with
respect to GND with a range from 0V to VREF.
SDO (Pin 6): Serial Data Output. The A/D conversion result
is shifted out on SDO as a serial data stream with the MSB
first through the LSB last. There is 1 cycle of conversion
latency. Logic levels are determined by OVDD.
SCK (Pin 7): Serial Data Clock Input. The SCK serial clock
falling edge advances the conversion process and outputs
a bit of the serialized conversion result, MSB first to LSB
last. SDO data transitions on the falling edge of SCK. A
continuous or burst clock may be used. Logic levels are
determined by OVDD.
CS (Pin 8): Chip Select Input. This active low signal starts
a conversion on the falling edge and frames the serial data
transfer. Bringing CS high places the sample-and-hold
into sample mode and also forces the SDO pin into high
impedance. Logic levels are determined by OVDD.
OVDD (Pin 5): I/O Interface Digital Power. The OVDD range
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 to GND with a 2.2µF ceramic chip capacitor.
231414fa
8
For more information www.linear.com/LTC2314-14
LTC2314-14
BLOCK DIAGRAM
2.2µF
2.2µF
ANALOG SUPPLY
RANGE 2.7V TO 5.25V
DIGITAL SUPPLY
RANGE 1.71V TO 5.25V
1
5
VDD
OVDD
2.5V LDO
ANALOG
INPUT RANGE
0V TO VREF
AIN
+
4
14-BIT SAR ADC
S/H
–
THREE-STATE
SERIAL
OUTPUT
PORT
SDO
6
REF
SCK
2
2.2µF
GND
3
2×/4×
7
TIMING
LOGIC
1.024V
BANDGAP
CS
8
TS8 PACKAGE
231414 BD
ALL CAPACITORS UNLESS
NOTED ARE HIGH QUALITY,
CERAMIC CHIP TYPE
TIMING DIAGRAMS
SCK
16TH EDGE
t8
CS
OVDD/2
Hi-Z
SDO
t9
OVDD/2
Hi-Z
SDO
Figure 1. SDO Into Hi-Z after 16TH SCK↓
Figure 2. SDO Into Hi-Z after CS↑
231414 TD01
SCK
t7
231414 TD02
SCK
OVDD/2
V
SDO OH
VOL
SDO
Figure 3. SDO Data Valid Hold after SCK↓
t4
OVDD/2
VOH
VOL
Figure 4. SDO Data Valid Access after SCK↓
231414 TD03
231414 TD04
231414fa
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9
LTC2314-14
APPLICATIONS INFORMATION
Overview
The LTC2314-14 is a low noise, high speed, 14-bit successive approximation register (SAR) ADC. The LTC2314-14
operates over a wide supply range (2.7V to 5.25V) and
provides a low drift (20ppm/°C maximum), internal reference and reference buffer. The internal reference buffer is
automatically configured to a 2.048V span in low supply
range (2.7V to 3.6V) and to a 4.096V span in the high
supply range (4.75V to 5.25V). The LTC2314-14 samples
at a 4.5Msps rate and supports an 87.5MHz data clock.
The LTC2314-14 achieves excellent dynamic performance
(77dB SINAD, 85dB THD) while dissipating only 31mW
from a 5V supply at the 4.5Msps conversion rate.
The LTC2314-14 outputs the conversion data with one
cycle of conversion latency on the SDO pin. The SDO pin
output logic levels are supplied by the dedicated OVDD
supply pin which has a wide supply range (1.71V to 5.25V)
allowing the LTC2314-14 to communicate with 1.8V, 2.5V,
3V or 5V systems.
The LTC2314-14 provides both nap and sleep power-down
modes through serial interface control to reduce power
dissipation during inactive periods.
Serial Interface
The LT2314-14 communicates with microcontrollers, DSPs
and other external circuitry via a 3-wire interface. A falling
CS edge starts a conversion and frames the serial data
transfer. SCK provides the conversion clock for the current
sample and controls the data readout on the SDO pin of
the previous sample. CS transitioning low clocks out the
first leading zero and subsequent SCK falling edges clock
out the remaining data as shown in Figures 5, 6 and 7 for
three different timing schemes. Data is serially output MSB
first through LSB last, followed by trailing zeros if further
SCK falling edges are applied. Figure 5 illustrates that during the case where SCK is held low during the acquisition
phase, only one leading zero is output. Figures 6 and 7
illustrate that for the SCK held high during acquisition or
continuous clocking mode two leading zeros are output.
Leading zeros allow the 14-bit data result to be framed
with both leading and trailing zeros for timing and data
verification. Since the rising edge of SCK will be coincident
with the falling edge of CS, delay t2 is the delay to the first
falling edge of SCK, which is simply 0.5 • tSCK. Delays t2
(CS falling edge to SCK leading edge) and t10 (16th falling
SCK edge to CS rising edge) must be observed for Figures
5, 6 and 7 and any timing implementation in order for the
conversion process and data readout to occur correctly.
The user can bring CS high after the 16th falling SCK edge
provided that timing delay t10 is observed. Prematurely
terminating the conversion by bringing CS high before the
16th falling SCK edge plus delay t10 will cause a loss of
conversion data for that sample. The sample-and-hold is
placed in sample mode when CS is brought high. As shown
in Figure 6, a sample rate of 4.5Msps can be achieved on
the LTC2314-14 by using an 87.5MHz SCK data clock
and a minimum acquisition time of 40ns which results in
the minimum throughput time (tTHROUGHPUT) of 222ns.
Note that the maximum throughput of 4.5Msps can only
be achieved with the timing implementation of SCK held
high during acquisition as shown in Figure 6.
The LTC2314-14 also supports a continuous data clock
as shown in Figure 7. With a continuous data clock the
acquisition time period and conversion time period must
be designed as an exact integer number of data clock
periods. Because the minimum acquisition time is not an
exact multiple of the minimum SCK period, the maximum
sample rate for the continuous SCK timing is less than
4.5Msps. For example, a 4.375Msps throughput is achieved
using exactly 20 data clock periods with the maximum
data clock frequency of 87.5MHz. For this particular case,
the acquisition time period and conversion clock period
are designed as 4 data clock periods (TACQ = 45.7ns) and
16data clock periods (TCONV = 182.9ns) respectively,
yielding a throughput time of 228.6ns.
The following table illustrates the maximum throughput
achievable for each of the three timing patterns. Note
that in order to achieve the maximum throughput rate of
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10
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LTC2314-14
APPLICATIONS INFORMATION
t10
CS
tCONV = 15.5 • tSCK + t2 + t10
t2
t6
1
SCK
2
0
SDO
tACQ-MIN
3
4
t5
t3
tACQ-MIN = 40ns
tCONV
t4
B13*
B12
14
15
16
t9
t7
B11
B0
(MSB)
0
HI-Z STATE
tTHROUGHPUT
*NOTE: SDO REPRESENTS THE ANALOG INPUT FROM THE PREVIOUS CONVERSION
231414 F05
Figure 5: LTC2314-14 Serial Interface Timing Diagram (SCK Low During tACQ)
t10
CS
tCONV(MIN) = 15 • tSCK + t2 + t10
t2
SCK
t6
1
2
0
3
0
tACQ-MIN
4
5
t5
t3
SDO
tACQ-MIN = 40ns
tCONV
t4
B13*
B12
15
16
t9
t7
B11
B1
(MSB)
B0
0
HI-Z STATE
tTHROUGHPUT
*NOTE: SDO REPRESENTS THE ANALOG INPUT FROM THE PREVIOUS CONVERSION
231414 TD06
Figure 6: LTC2314-14 Serial Interface Timing Diagram (SCK High During tACQ)
CS
tCONV = 16 • tSCK
t2
SCK
1
2
3
4
t5
t3
SDO
tCONV
t6
20
0
0
(MSB)
B12
B11
tACQ
t10
5
t4
B13*
tACQ = 4 • tSCK
15
16
17
18
19
20
t9
t7
B1
B0
0
HI-Z STATE
tTHROUGHPUT = 20 • tSCK
*NOTE: SDO REPRESENTS THE ANALOG INPUT FROM THE PREVIOUS CONVERSION
231414 TD07
Figure 7: LTC2314-14 Serial Interface Timing Diagram (SCK Continuous)
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11
LTC2314-14
APPLICATIONS INFORMATION
4.5Msps, the timing pattern where SCK is held high during
the acquisition time must be used.
Table 1: Maximum Throughput vs Timing Pattern
TIMING PATTERN
MAXIMUM
THROUGHPUT
SCK high during TACQ
4.5Msps
SCK low during TACQ
4.375Msps
SCK continuous (tTHROUGHPUT = 20 periods)
4.375Msps
Serial Data Output (SDO)
The SDO output is always forced into the high impedance
state while CS is high. The falling edge of CS starts the
conversion and enables SDO. The A/D conversion result
is shifted out on the SDO pin as a serial data stream with
the MSB first. The data stream consists of either one
leading zero (SCK held low during acquisition, Fig. 5) or
two leading zeros (SCK held high during acquisition, Fig.
6) followed by 14 bits of conversion data. There is 1 cycle
of conversion latency. Subsequent falling SCK edges after
the LSB is output will output zeros on the SDO pin. The
SDO output returns to the high impedance state after the
16th falling edge of SCK.
The output swing on the SDO pin is controlled by the
OVDD pin voltage and supports a wide operating range
from 1.71V to 5.25V independent of the VDD pin voltage.
Power Considerations
The LTC2314-14 provides two sets of power supply pins:
the analog 5V power supply (VDD) and the digital input/
output interface power supply (OVDD). The flexible OVDD
supply allows the LTC2314-14 to communicate with any
digital logic operating between 1.8V and 5V, including
2.5V and 3.3V systems.
Entering Nap/Sleep Mode
Pulsing CS two times and holding SCK static places the
LTC2314-14 into nap mode. Pulsing CS four times and
holding SCK static places the LTC2314-14 into sleep mode.
In sleep mode, all bias circuitry is shut down, including the
internal bandgap and reference buffer, and only leakage
currents remain (0.8µA typical). Because the reference
buffer is externally bypassed with a large capacitor (2.2µF),
the LTC2314-14 requires a significant wait time (1.1ms) to
recharge this capacitance before an accurate conversion
can be made. In contrast, nap mode does not power down
the internal bandgap or reference buffer allowing for a fast
wake-up and accurate conversion within one conversion clock
cycle. Supply current during nap mode is nominally 1.8mA.
Exiting Nap/Sleep Mode
Waking up the LTC2314-14 from either nap or sleep mode,
as shown in Figures 8 and 9, requires SCK to be pulsed
one time. A conversion may be started immediately following nap mode as shown in Figure 8. A period of time
allowing the reference voltage to recover must follow
waking up from sleep mode as shown in Figure 9. The
wait period required before initiating a conversion for the
recommended value of CREF of 2.2µF is 1.1ms.
Power Supply Sequencing
The LTC2314-14 does not have any specific power supply sequencing requirements. Care should be taken to
observe the maximum voltage relationships described in
the Absolute Maximum Ratings section.
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12
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LTC2314-14
APPLICATIONS INFORMATION
1
CS
2
NAP MODE
SCK
START tACQ
HOLD STATIC HIGH or LOW
Z
SDO
0
Z
HOLD STATIC HIGH or LOW
HI-Z STATE
0
231414 F08
Figure 8: LTC2314-14 Entering/Exiting Nap Mode
1
CS
2
3
4
VREF RECOVERY
NAP MODE
SCK
SDO
SLEEP MODE
tWAIT
START tACQ
HOLD STATIC HIGH or LOW
Z
0
Z
0
HI-Z STATE
231414 F09
Figure 9: LTC2314-14 Entering/Exiting Sleep Mode
Single-Ended Analog Input Drive
Choosing an Input Amplifier
The analog input of the LTC2314-14 is easy to drive. The
input draws only one small current spike while charging
the sample-and-hold capacitor at the end of conversion.
During the conversion, the analog input draws only a small
leakage current. If the source impedance of the driving
circuit is low, then the input of the LTC2314-14 can be
driven directly. As the source impedance increases, so
will the acquisition time. For minimum acquisition time
with high source impedance, a buffer amplifier should be
used. The main requirement is that the amplifier driving
the analog input must settle after the small current spike
before the next conversion starts. Settling time must be less
than tACQ-MIN (40ns) for full performance at the maximum
throughput rate. While choosing an input amplifier, also
keep in mind the amount of noise and harmonic distortion
the amplifier contributes.
Choosing an input amplifier is easy if a few requirements
are taken into consideration. First, to limit the magnitude
of the voltage spike seen by the amplifier from charging
the sampling capacitor, choose an amplifier that has a low
output impedance (<50Ω) at the closed-loop bandwidth
frequency. For example, if an amplifier is used in a gain
of 1 and has a unity-gain bandwidth of 100MHz, then the
output impedance at 100MHz must be less than 50Ω. The
second requirement is that the closed-loop bandwidth
must be greater than 100MHz to ensure adequate small
signal settling for full throughput rate. If slower op amps
are used, more time for settling can be provided by increasing the time between conversions. The best choice
for an op amp to drive the LTC2314-14 will depend on the
application. Generally, applications fall into two categories:
AC applications where dynamic specifications are most
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13
LTC2314-14
APPLICATIONS INFORMATION
critical and time domain applications where DC accuracy
and settling time are most critical. The following list is a
summary of the op amps that are suitable for driving the
LTC2314-14. (More detailed information is available on
the Linear Technology website at www.linear.com.)
LT6230: 215MHz GBWP, –80dBc Distortion at 1MHz,
Unity-Gain Stable, Rail-to-Rail Input and Output, 3.5mA/
Amplifier, 1.1nV/√Hz.
LT6200: 165MHz GBWP, –85dBc Distortion at 1MHz, UnityGain Stable, R-R In and Out, 15mA/Amplifier, 0.95nV/√Hz.
LT1818/1819: 400MHz GBWP, –85dBc Distortion at 5MHz,
Unity-Gain Stable, 9mA/Amplifier, Single/Dual Voltage
Mode Operational Amplifier.
Input Drive Circuits
The analog input of the LTC2314-14 is designed to be driven
single-ended with respect to GND. A low impedance source
can directly drive the high impedance analog input of the
LTC2314-14 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.
For best performance, a buffer amplifier should be used
to drive the analog input of the LTC2314-14. The amplifier
provides low output impedance to allow for fast settling
of the analog signal during the acquisition phase. It also
provides isolation between the signal source and the ADC
inputs which draw a small current spike during acquisition.
Input Filtering
The noise and distortion of the buffer amplifier and other
circuitry must be considered since they add to the ADC
noise and distortion. Noisy input circuitry should be filtered
prior to the analog inputs to minimize noise. A simple
1-pole RC filter is sufficient for many applications.
A simple 1-pole RC filter is sufficient for many applications.
For example, Figure 10 shows a recommended singleended buffered drive circuit using the LT1818 in unity gain
mode. The 47pF capacitor from AIN to ground and 50Ω
source resistor limits the input bandwidth to 68MHz. The
47pF capacitor also acts as a charge reservoir for the input
sample-and-hold and isolates the LT1818 from sampling
glitch kick-back. The 50Ω source resistor is used to help
stabilize the settling response of the drive amplifier. When
choosing values of source resistance and shunt capacitance, the drive amplifier data sheet should be consulted
and followed for optimum settling response. If lower input
bandwidths are desired, care should be taken to optimize
the settling response of the driver amplifier with higher
values of shunt capacitance or series resistance. High
quality capacitors and resistors should be used in the RC
filter since these components can add distortion. NP0/C0G
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. When high
amplitude unwanted signals are close in frequency to the
desired signal frequency, a multiple pole filter is required.
High external source resistance, combined with external
shunt capacitance at Pin 4 and 13pF of input capacitance on
the LTC2314-14 in sample mode, will significantly reduce
the internal 130MHz input bandwidth and may increase the
required acquisition time beyond the minimum acquisition
time (tACQ-MIN) of 40ns.
ANALOG IN
Large filter RC time constants slow down the settling at
the analog inputs. It is important that the overall RC time
constants be short enough to allow the analog inputs to
completely settle to >12-bit resolution within the minimum
acquisition time (tACQ-MIN) of 40ns.
+
–
LT1818
LTC2314-14
50Ω
AIN
47pF
GND
231414 F10
Figure 10. RC Input Filter
231414fa
14
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LTC2314-14
APPLICATIONS INFORMATION
ADC Reference
A low noise, low temperature drift reference is critical to
achieving the full data sheet performance of the ADC. The
LTC2314-14 provides an excellent internal reference with
a guaranteed 20ppm/°C maximum temperature coefficient.
For added flexibility, an external reference may also be used.
The high speed, low noise internal reference buffer is used
only in the internal reference configuration. The reference
buffer must be overdriven in the external reference configuration with a voltage 50mV higher than the nominal
reference output voltage in the internal configuration.
Using the Internal Reference
The internal bandgap and reference buffer are active by
default when the LTC2314-14 is not in sleep mode. The
reference voltage at the REF pin scales automatically with
the supply voltage at the VDD pin. The scaling of the reference voltage with supply is shown in Table 2.
the internal reference voltage (see Table 2) and must be
less than or equal to the supply voltage (or 4.3V for the 5V
supply range). For example, a 3.3V external reference may
be used with a 3.3V VDD supply voltage to provide a 3.3V
analog input voltage span (i.e. 3.3V > 2.048V + 50mV).
Or alternatively, a 2.5V reference may be used with a 3V
supply voltage to provide a 2.5V input voltage range (i.e.
2.5V > 2.048V + 50mV). The LTC6655-3.3, LTC6655-2.5,
available from Linear Technology, may be suitable for
many applications requiring a high performance external
reference for either 3.3V or 2.5V input spans respectively.
Transfer Function
Figure 11 depicts the transfer function of the LTC2314-14.
The code transitions occur midway between successive
integer LSB values (i.e. 0.5LSB, 1.5LSB, 2.5LSB… FS0.5LSB). The output code is straight binary with 1LSB =
VREF/16,384.
Table 2: Reference Voltage vs Supply Range
REF VOLTAGE (VREF)
2.7V –> 3.6V
2.048V
4.75V –> 5.25V
4.096V
The reference voltage also determines the full-scale analog
input range of the LTC2314-14. For example, a 2.048V
reference voltage will accommodate an analog input range
from 0V to 2.048V. An analog input voltage that goes below
0V will be coded as all zeros and an analog input voltage
that exceeds 2.048V will be coded as all ones.
It is recommended that the REF pin be bypassed to ground
with a low ESR, 2.2µF ceramic chip capacitor for optimum
performance.
111...111
111...110
OUTPUT CODE
SUPPLY VOLTAGE (VDD)
000...001
000...000
0 1LSB
FS – 1LSB
INPUT VOLTAGE (V)
231414 F11
Figure 11. LTC2314-14 Transfer Function
External Reference
DC Performance
An external reference can be used with the LTC2314-14
if better performance is required or to accommodate a
larger input voltage span. The only constraints are that
the external reference voltage must be 50mV higher than
The noise of an ADC can be evaluated in two ways:
signal-to-noise ratio (SNR) in the frequency domain and
histogram in the time domain. The LTC2314-14 excels
in both. The noise in the time domain histogram is the
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15
LTC2314-14
APPLICATIONS INFORMATION
transition noise associated with a 14-bit resolution ADC
which can be measured with a fixed DC signal applied
to the input of the ADC. The resulting output codes are
collected over a large number of conversions. The shape
of the distribution of codes will give an indication of the
magnitude of the transition noise. In Figure 12, the distribution of output codes is shown for a DC input that has
been digitized 16,384 times. The distribution is Gaussian
and the RMS code transition noise is 0.7LSB. This corresponds to a noise level of 77.5dB relative to a full scale
voltage of 4.096V.
7000
ENOB = (SINAD – 1.76)/6.02
At the maximum sampling rate of 5MHz, the LTC2314-14
maintains an ENOB above 12 bits up to the Nyquist input
frequency of 2.25MHz. (Figure 14)
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 13 shows
that the LTC2314-14 achieves a typical SNR of 77.5dB at
a 4.5MHz sampling rate with a 500kHz input frequency.
5000
COUNTS
The effective number of bits (ENOB) is a measurement of
the resolution of an ADC and is directly related to SINAD
by the equation where ENOB is the effective number of
bits of resolution and SINAD is expressed in dB:
Signal-to-Noise Ratio (SNR)
σ = 0.7
6000
4000
3000
2000
Total Harmonic Distortion (THD)
1000
0
Effective Number of Bits (ENOB)
8194 8195 8196 8197 8198 8199 8200
CODE
231414 F12
Figure 12. Histogram for 16384 Conversions
Dynamic Performance
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:
V22 + V32 + V42 + VN2
The LTC2314-14 has excellent high speed sampling
capability. 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 and analyzing the digital output using an FFT
algorithm, the ADC’s spectral content can be examined
for frequencies outside the applied fundamental. The
LTC2314-14 provides guaranteed tested limits for both
AC distortion and noise measurements.
V1
where V1 is the RMS amplitude of the fundamental frequency and V2 through VN are the amplitudes of the second
through Nth harmonics. THD versus Input Frequency is
shown in the Typical Performance Characteristics section.
The LTC2314-14 has excellent distortion performance up
to the Nyquist frequency.
Signal-to-Noise and Distortion Ratio (SINAD)
Intermodulation Distortion (IMD)
The signal-to-noise and distortion ratio (SINAD) is the ratio between the RMS amplitude of the fundamental input 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
14 shows the LTC2314-14 maintains a SINAD above 74dB
up to the Nyquist input frequency of 2.25MHz.
16
THD=20log
If the ADC input signal consists of more than one spectral
component, the ADC transfer function nonlinearity can
produce intermodulation distortion (IMD) in addition to
THD. IMD is the change in one sinusoidal input caused
by the presence of another sinusoidal input at a different
frequency.
For more information www.linear.com/LTC2314-14
231414fa
LTC2314-14
APPLICATIONS INFORMATION
0
–20
–40
AMPLITUDE (dBFS)
If two pure sine waves of frequencies fa and fb are applied to the ADC input, nonlinearities in the ADC transfer
function can create distortion products at the sum and
difference frequencies m • fa ± n • fb, where m and n = 0,
1, 2, 3, etc. For example, the 2nd order IMD terms include
(fa ± fb). If the two input sine waves are equal in magnitude,
the value (in decibels) of the 2nd order IMD products can
be expressed by the following formula:
VDD = 5V
SNR = 77.5dBFS
SINAD = 76.9dBFS
THD = 84.9dB
SFDR = 88.1dB
–60
–80
–100
–120
IMD(fa ± fb) = 20 • log[VA (fa ± fb)/VA (fa)]
–160
–140
0
The LTC2314-14 has excellent IMD as shown in Figure 15.
250 500 750 1000 1250 1500 1750 2000 2250
FREQUENCY (kHz)
231414 F13
Figure 13. 32k Point FFT of the LTC2314-14 at fIN = 500 kHz
78
12.50
VDD = 5V
76
12.33
75
12.17
74
12.00
VDD = 3V
73
11.83
11.67
72
71
0
11.50
250 500 750 1000 1250 1500 1750 2000 2250
INPUT FREQUENCY (kHz)
231414 F14
Figure 14. LTC2314-14 ENOB/SINAD vs fIN
0
VDD = 5V
fS = 4.5Msps
fa = 471.421kHz
fb = 531.421kHz
IMD2 (fb + fa) = –79.4dBc
IMD3 (2fb –fa) = –90.8dBc
–20
MAGNITUDE (dB)
–40
–60
–80
–100
–120
–140
–160
0
1500
2000
500
1000
INPUT FREQUENCY (kHz)
2500
231414 F15
Figure 15. LTC2314-14 IMD Plot
The spurious free dynamic range is the largest spectral
component excluding DC, the input signal and the harmonics included in the THD. This value is expressed in decibels
relative to the RMS value of a full-scale input signal.
Full-Power and Full-Linear Bandwidth
ENOB
SINAD (dBFS)
77
Spurious Free Dynamic Range (SFDR)
The full-power bandwidth is the input frequency at which
the amplitude of the reconstructed fundamental is reduced
by 3dB for a full-scale input signal.
The full-linear bandwidth is the input frequency at which
the SINAD has dropped to 74dB (12 effective bits). The
LTC2314-14 has been designed to optimize the input
bandwidth, allowing the ADC to under-sample input signals
with frequencies above the converter’s Nyquist frequency.
The noise floor stays very low at high frequencies and
SINAD becomes dominated by distortion at frequencies
beyond Nyquist.
Recommended Layout
To obtain the best performance from the LTC2314-14 a
printed circuit board is required. 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.
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
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17
LTC2314-14
APPLICATIONS INFORMATION
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 DC1563, the
evaluation kit for the LTC2314-14.
Bypassing Considerations
results. These errors are due to feed-through from the
microprocessor to the successive approximation comparator. The problem can be eliminated by forcing the
microprocessor into a “Wait” state during conversion or
by using three-state buffers to isolate the ADC data bus.
High quality tantalum and ceramic bypass capacitors
should be used at the VDD, OVDD and REF pins. For optimum performance, a 2.2µF ceramic chip capacitor should
be used for the VDD and OVDD pins. The recommended
bypassing for the REF pin is also a low ESR, 2.2µF ceramic
capacitor. The traces connecting the pins and the bypass
capacitors must be kept as short as possible and should
be made as wide as possible avoiding the use of vias.
The following is an example of a recommended PCB layout.
All analog circuitry grounds should be terminated at the
LTC2314-14. The ground return from the LTC2314-14 to
the power supply should be low impedance for noise free
operation. Digital circuitry grounds must be connected to
the digital supply common.
In applications where the ADC data outputs and control
signals are connected to a continuously active microprocessor bus, it is possible to get errors in the conversion
Figure 16. Top Silkscreen
Figure 17. Layer 1 Top Layer
Figure 18. Layer 2 GND Plane
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18
For more information www.linear.com/LTC2314-14
LTC2314-14
APPLICATIONS INFORMATION
Figure 19. Layer 3 PWR Plane
Figure 20. Layer 4 Bottom Layer
REF
U5
LT1790ACS6-2.048
9V TO 10V
4
VI
GND
GND
1
2
JP1
HD1X3-100
J4
AIN
0V TO 4.096V
C6
4.7µF
R14
0k
VO
AC
R9
1k
C8
10µF
VCCIO
C9
4.7µF
C10
OPT
C11
OPT
C12
4.7µF
DC
COUPLING
1 2 3
C18
OPT
C7
OPT
VDD
VCM
6
+
R15
49.9Ω
C17
1µF
3
2
1
U1
*
4
C19
47pF
NPO
JP2
VCM
1
2
5
VDD REF OVDD
AIN
CSL
SCK
GND
1.024V
3
SDO
231414 F21
8
CSL
7
SCK
SDO
6
R16
33Ω
2.048V
HD1X3-100
R18
1k
Figure 21. Partial 1563 Demo Board Schematic
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For more information www.linear.com/LTC2314-14
19
LTC2314-14
LTC2314-14
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637 Rev A)
0.40
MAX
2.90 BSC
(NOTE 4)
0.65
REF
1.22 REF
1.4 MIN
3.85 MAX 2.62 REF
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.22 – 0.36
8 PLCS (NOTE 3)
0.65 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
1.95 BSC
TS8 TSOT-23 0710 REV A
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
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20
For more information www.linear.com/LTC2314-14
LTC2314-14
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
10/13
Added pin-compatible family table
1
Changed TJMAX to 150°C
2
Changed SINAD condition for –3dB Input Linear Bandwidth to ≥74dB
Reordered/Renumbered Notes
3
3, 4, 5
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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 itsinformation
circuits as described
herein will not infringe on existing patent rights.
For more
www.linear.com/LTC2314-14
21
LTC2314-14
TYPICAL APPLICATION
Low-Jitter Clock Timing with RF Sine Generator Using Clock
Squaring/Level-Shifting Circuit and Re-Timing Flip-Flop
VCC
0.1µF
50Ω
1k NC7SVU04P5X
MASTER CLOCK
VCC
1k
PRE
D
>
Q
CONV
CLR
NL17SZ74
CONV ENABLE
CONTROL
LOGIC
(FPGA, CPLD,
DSP, ETC.)
CS
SCK
LTC2314-14
NC7SVUO4P5X
SDO
33Ω
231414 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2313-14
14-Bit, 2.5Msps Serial ADC
3V/5V, 14mW/25mW, 20ppm/°C Max Internal Reference,
Single-Ended Input, 8-Lead TSOT-23 Package
LTC2312-14
14-Bit, 500ksps Serial ADC
3V/5V, 9mW/15mW, 20ppm/°C Max Internal Reference,
Single-Ended Input, 8-Lead TSOT-23 Package
LTC1403A/LTC1403A-1
14-Bit, 2.8Msps Serial ADC
3V, 14mW, Unipolar/Bipolar Inputs, MSOP Package
LTC1407A/LTC1407A-1
14-Bit, 3Msps Simultaneous Sampling ADC
3V, 2-Channel Differential, Unipolar/Bipolar Inputs, 14mW,
MSOP Package
LTC2355/LTC2356
12-/14-Bit, 3.5Msps Serial ADC
3.3V Supply, Differential Input, 18mW, MSOP Package
LTC2365/LTC2366
12-Bit, 1Msps/3Msps Serial Sampling ADC
3.3V Supply, 8mW, TSOT-23 Package
LT6200/LT6201
Single/Dual Operational Amplifiers
165MHz, 0.95nV/√Hz
LT6230/LT6231
Single/Dual Operational Amplifiers
215MHz, 3.5mA/Amplifier, 1.1nV/√Hz
LT6236/LT6237
Single/Dual Operational Amplifier with
Low Wideband Noise
215MHz, 3.5mA/Amplifier, 1.1nV/√Hz
LT1818/LT1819
Single/Dual Operational Amplifiers
400MHz, 9mA/Amplifier, 6nV/√Hz
LTC6655-2.5/LTC6655-3.3
Precision Low Drift Low Noise Buffered Reference
2.5V/3.3V, 5ppm/°C, 0.25ppm Peak-to-Peak Noise,
MSOP-8 Package
LT1461-3/LT1461-3.3V
Precision Series Voltage Family
0.05% Initial Accuracy, 3ppm Drift
ADCs
Amplifiers
References
231414f
22 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC2314-14
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC2314-14
LT 1013 REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2013