LTC1412
12-Bit, 3Msps,
Sampling A/D Converter
FEATURES
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DESCRIPTION
The LTC
®
1412 is a 12-bit, 3Msps, sampling A/D con-
verter. This high performance device includes a high
dynamic range sample-and-hold and a precision refer-
ence. Operating from
±5V
supplies it draws only 150mW.
The
±2.5V
input range is optimized for low noise and low
distortion. Most high performance op amps also perform
best over this range, allowing direct coupling to the analog
inputs and eliminating the need for special translation
circuitry. Outstanding AC performance includes 72dB
S/(N + D) and 82dB SFDR at the Nyquist input frequency
of 1.5MHz.
The unique differential input sample-and-hold can acquire
single-ended or differential input signals up to its 40MHz
bandwidth. The 60dB common mode rejection allows
users to eliminate ground loops and common mode noise
by measuring signals differentially from the source.
The ADC has a high speed 12-bit parallel output port. There
is no pipeline delay in the conversion results. A separate
convert start input and converter status signal (BUSY)
ease connections to FIFOs, DSPs and microprocessors. A
digital output driver power supply pin allows direct con-
nection to 3V logic.
Sample Rate: 3Msps
72dB S/(N + D) and 82dB SFDR at Nyquist
±0.35LSB
INL and
±0.25LSB
DNL (Typ)
Power Dissipation: 150mW
External or Internal Reference Operation
True Differential Inputs Reject Common Mode Noise
40MHz Full Power Bandwidth Sampling
±2.5V
Bipolar Input Range
No Pipeline Delay
28-Pin SSOP Package
APPLICATIONS
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Telecommunications
Digital Signal Processing
Mulitplexed Data Acquisition Systems
High Speed Data Acquisition
Spectrum Analysis
Imaging Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
5V
10µF
AV
DD
LTC1412
EFFECTIVE NUMBER OF BITS
A
IN+
S/H
A
IN–
4.0625V
COMP
10µF
V
REF
BUFFER
2k
BUSY
CS
CONVST
OGND
1412 TA01
OPTIONAL
3V LOGIC
SUPPLY
DV
DD
OV
DD
Effective Bits and Signal-to-Noise + Distortion
vs Input Frequency
12
10
8
6
4
2
0
1k
10k
100k
1M
INPUT FREQUENCY (Hz)
10M
1412 G01
12
12-BIT ADC
OUTPUT
BUFFERS
•
•
•
D11 (MSB)
D0 (LSB)
2.5V
REFERENCE
AGND
TIMING AND
LOGIC
DGND
V
SS
10µF
– 5V
U
U
U
74
68
62
56
S/(N + D) (dB)
1
LTC1412
ABSOLUTE
MAXIMUM
RATINGS
AV
DD
= DV
DD
= V
DD
(Notes 1, 2)
PACKAGE/ORDER INFORMATION
TOP VIEW
A
IN+
A
IN–
V
REF
REFCOMP
AGND
D11 (MSB)
D10
D9
D8
1
2
3
4
5
6
7
8
9
28 AV
DD
27 DV
DD
26 V
SS
25 BUSY
24 CS
23 CONVST
22 OGND
21 OV
DD
20 DV
DD
19 DGND
18 D0
17 D1
16 D2
15 D3
Supply Voltage (V
DD
) ................................................. 6V
Negative Supply Voltage (V
SS
) ................................ – 6V
Total Supply Voltage (V
DD
to V
SS
) .......................... 12V
Analog Input Voltage
(Note 3) ......................... (V
SS
– 0.3V) to (V
DD
+ 0.3V)
Digital Input Voltage (Note 4) ..........(V
SS
– 0.3V) to 10V
Digital Output Voltage ........ (V
SS
– 0.3V) to (V
DD
+ 0.3V)
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC1412C ............................................... 0°C to 70°C
LTC1412I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1412CG
LTC1412IG
D7 10
D6 11
D5 12
D4 13
DGND 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 110°C,
θ
JA
= 95°C/ W
Consult factory for Military grade parts.
CO VERTER CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
Full-Scale Error
Full-Scale Tempco
(Note 8)
(Note 7)
With internal reference (Notes 5, 6)
MIN
q
q
q
q
CONDITIONS
TYP
±0.35
±0.25
±2
MAX
±1
±1
±6
±8
±15
UNITS
Bits
LSB
LSB
LSB
LSB
LSB
ppm/°C
12
I
OUT(REF)
= 0
q
±15
A ALOG I PUT
SYMBOL PARAMETER
V
IN
I
IN
C
IN
t
ACQ
t
AP
t
jitter
CMRR
(Note 5)
CONDITIONS
4.75V
≤
V
DD
≤
5.25V, – 5.25V
≤
V
SS
≤
– 4.75V
CS = High
Between Conversions
During Conversions
q
q
q
MIN
TYP
±2.5
MAX
±1
UNITS
V
µA
pF
pF
Analog Input Range (Note 9)
Analog Input Leakage Current
Analog Input Capacitance
Sample-and-Hold Acquisition Time
Sample-and-Hold Aperture Delay Time
Sample-and-Hold Aperture Delay Time Jitter
Analog Input Common Mode Rejection Ratio
10
4
20
– 0.5
1
50
ps
RMS
dB
– 2.5V < (A
IN–
= A
IN
) < 2.5V
63
2
U
W
U
U
W W
W
U
U
U
ns
ns
LTC1412
DY A IC ACCURACY
SYMBOL PARAMETER
S/(N + D) Signal-to-Noise Plus Distortion Ratio
THD
SFDR
IMD
Total Harmonic Distortion
Spurious Free Dynamic Range
Intermodulation Distortion
Full Power Bandwidth
Full Linear Bandwidth
I TER AL REFERE CE CHARACTERISTICS
PARAMETER
V
REF
Output Voltage
V
REF
Output Tempco
V
REF
Line Regulation
V
REF
Output Resistance
COMP Output Voltage
CONDITIONS
I
OUT
= 0
I
OUT
= 0
4.75V
≤
V
DD
≤
5.25V
– 5.25V
≤
V
SS
≤
– 4.75V
0.1mA
≤
I
OUT
≤
0.1mA
I
OUT
= 0
DIGITAL I PUTS AND OUTPUTS
SYMBOL PARAMETER
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
C
OZ
I
SOURCE
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 D11 to D0
Hi-Z Output Capacitance D11 to D0
Output Source Current
V
DD
= 5.25V
POWER REQUIRE E TS
SYMBOL PARAMETER
V
DD
V
SS
I
DD
I
SS
P
D
Positive Supply Voltage
Negative Supply Voltage
Positive Supply Current
Negative Supply Current
Power Dissipation
UW
U
U
U
W U
(Note 5)
CONDITIONS
100kHz Input Signal
1.465MHz Input Signal
100kHz Input Signal, First 5 Harmonics
1.465MHz Input Signal, First 5 Harmonics
1.465MHz Input Signal
f
IN1
= 29.37kHz, f
IN2
= 32.446kHz
S/(N + D)
≥
68dB
MIN
70
TYP
72.5
72
– 90
– 80
82
– 84
40
4
MAX
UNITS
dB
dB
dB
dB
dB
dB
MHz
MHz
U
U
(Note 5)
MIN
2.480
TYP
2.500
±15
0.01
0.01
2
4.06
MAX
2.520
UNITS
V
ppm/°C
LSB/ V
LSB/ V
kΩ
V
(Note 5)
MIN
q
q
q
CONDITIONS
V
DD
= 4.75V
V
IN
= 0V to V
DD
V
DD
= 4.75V, I
O
= – 10µA
V
DD
= 4.75V, I
O
= – 200µA
V
DD
= 4.75V, I
O
= 160µA
V
DD
= 4.75V, I
O
= 1.6mA
V
OUT
= 0V to V
DD
, CS High
CS High (Note 9)
V
OUT
= 0V
TYP
MAX
0.8
±10
UNITS
V
V
µA
pF
V
V
2.4
1.4
q
q
q
4.0
4.75
4.71
0.05
0.10
7
– 10
0.4
±10
V
V
µA
pF
mA
(Note 5)
CONDITIONS
(Note 10)
(Note 10)
CS High
CS High
q
q
q
MIN
4.75
– 4.75
TYP
MAX
5.25
– 5.25
UNITS
V
V
mA
mA
mW
12
18
150
16
28
220
3
LTC1412
TI I G CHARACTERISTICS
SYMBOL
f
SAMPLE(MAX)
t
THROUGHPUT
t
CONV
t
ACQ
t
1
t
2
t
3
t
4
t
5
t
6
t
7
PARAMETER
Maximum Sampling Frequency
t
8
t
9
The
q
denotes specifications which apply over the full operating
temperature range; all other limits and typicals T
A
= 25°C.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltage values are with respect to ground with DGND and
AGND wired together (unless otherwise noted).
Note 3:
When these pin voltages are taken below V
SS
or above V
DD
, they
will be clamped by internal diodes. This product can handle input currents
greater than 100mA below V
SS
or above V
DD
without latchup.
Note 4:
When these pin voltages are taken below V
SS
they will be clamped
by internal diodes. This product can handle input currents greater than
100mA below V
SS
without latchup. These pins are not clamped to V
DD
.
TI I G DIAGRA
CS
t
1
CONVST
t
3
BUSY
t
6
DATA
4
W
UW
UW
(Note 5)
CONDITIONS
q
q
q
q
MIN
3
TYP
MAX
333
UNITS
MHz
ns
ns
ns
ns
ns
Throughput Time (Acquisition + Conversion)
Conversion Time
Acquisition Time
CS↓ to CONVST↓ Setup Time
CONVST Low Time
CONVST to BUSY Delay
Data Ready Before BUSY↑
(Notes 9, 10)
(Note 10)
C
L
= 25pF
240
20
5
20
5
283
50
q
q
q
q
20
– 20
– 25
50
10
35
45
30
35
40
0
20
25
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Delay Between Conversions
Data Access Time After CS↓
Bus Relinquish Time
(Note 10)
C
L
= 25pF
q
q
8
LTC1412C
LTC1412I
q
q
q
CONVST High Time
Aperture Delay of Sample-and-Hold
20
–1
Note 5:
V
DD
= 5V, f
SAMPLE
= 3MHz and t
r
= t
f
= 5ns unless otherwise
specified.
Note 6:
Linearity, offset and full-scale specifications apply for a single-
ended A
IN
input with A
IN–
grounded.
Note 7:
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 8:
Bipolar offset is the offset voltage measured from – 0.5LSB
when the output code flickers between 0000 0000 0000 and
1111 1111 1111.
Note 9:
Guaranteed by design, not subject to test.
Note 10:
Recommended operating conditions.
t
CONV
t
2
t
5
t
4
DATA (N – 1)
DB11 TO DB0
DATA N
DB11 TO DB0
t
7
DATA (N + 1)
DB11 TO DB0
1412 TD
LTC1412
TYPICAL PERFOR A CE CHARACTERISTICS
S/(N + D) and Effective Number of
Bits vs Input Frequency
12
10
8
6
4
2
0
1k
100k
1M
10k
INPUT FREQUENCY (Hz)
10M
1412 G01
SIGNAL-TO-NOISE RATIO (dB)
EFFECTIVE NUMBER OF BITS
DISTORTION (dB)
Spurious-Free Dynamic Range
vs Input Frequency
0
0
–20
AMPLITUDE (dB)
– 40
– 60
– 80
SPURIOUS-FREE DYNAMIC RANGE (dB)
–10
– 20
– 30
– 40
– 50
– 60
– 70
– 80
– 90
–100
10K
–120
100K
1M
FREQUENCY (Hz)
10M
1412 G04
AMPLITUDE (dB)
Intermodulation Distortion Plot
0
–10
–20
– 30
AMPLITUDE (dB)
DNL (LSBs)
f
SMPL
= 3MHz
f
IN1
= 85.693359kHz
f
IN2
= 114.990234kHz
– 50
– 60
– 70
– 80
– 90
0
INL (LSBs)
– 40
–100
–110
0
200
400 600 800 1000 1200 1400
FREQUENCY (kHz)
1412 G05
U W
Signal-to-Noise Ratio
vs Input Frequency
74
68
62
56
S/(N + D) (dB)
Distortion vs Input Frequency
0
– 20
– 40
– 60
– 80
THD
–100
–120
3RD
2ND
80
70
60
50
40
30
20
10
0
10k
100k
1M
INPUT FREQUENCY (Hz)
10M
1412 G02
10
100
1k
INPUT FREQUENCY (Hz)
10k
1412 G03
Nonaveraged, 4096 Point FFT,
Input Frequency = 100kHz
0
f
SMPL
= 3Msps
f
IN
= 97.412kHz
SFDR = 93.3dB
SINAD = 73dB
–20
– 40
– 60
– 80
Nonaveraged, 4096 Point FFT,
Input Frequency = 1.45kHz
f
SMPL
= 3Msps
f
IN
= 1.419kHz
SFDR = 83dB
SINAD = 72.5dB
SNR = 73db
–100
–100
–120
0
200
400 600 800 1000 1200 1400
FREQUENCY (kHz)
1412 F02a
0
200
400 600 800 1000 1200 1400
FREQUENCY (kHz)
1412 F02B
Differential Nonlinearity
vs Output Code
1.0
1.0
Integral Nonlinearity
vs Output Code
0.5
0.5
0
– 0.5
– 0.5
–1.0
0
512 1024 1536 2048 2560 3072 3584 4096
OUTPUT CODE
1412 G06
–1.0
0
512 1024 1536 2048 2560 3072 3584 4096
OUTPUT CODE
1412 G07
5
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