1
LTC1278
S
FEATURE
D
U
ESCRIPTIO
The LTC
1278 is a 1.6
s, 500ksps, sampling 12-bit A/D
converter that draws only 75mW from a single 5V or
5V
supplies. This easy-to-use device comes complete with
a 200ns sample-and-hold, a precision reference and an
internally trimmed clock. Unipolar and bipolar conver-
sion modes add to the flexibility of the ADC. The low
power dissipation is made even more attractive by a
8.5mW power-down feature. Instant wake-up from shut-
down allows the converter to be powered down even
during brief inactive periods.
The LTC1278 converts 0V to 5V unipolar inputs from a
single 5V supply and
2.5V bipolar inputs from
5V
supplies. Maximum DC specs include
1LSB INL and
1LSB DNL. Outstanding guaranteed AC performance
includes 70dB S/(N + D) and 78dB THD at the input
frequency of 100kHz over temperature.
The internal clock is trimmed for 1.6
s conversion time.
The clock automatically synchronizes to each sample
command, eliminating problems with asynchronous clock
noise found in competitive devices. A separate convert
start input and a data ready signal (BUSY) ease connec-
tions to FIFOs, DSPs and microprocessors.
s
Single Supply 5V or
5V Operation
s
Two Speed Grades,500ksps (LTC1278-5)
400ksps (LTC1278-4)
s
70dB S/(N + D) and 74dB THD at Nyquist
s
No Missing Codes Over Temperature
s
75mW (Typ) Power Dissipation
s
Power Shutdown with Instant Wake-Up
s
Internal Reference Can Be Overdriven Externally
s
Internal Synchronized Clock; No Clock Required
s
High Impedance Analog Input
s
0V to 5V or
2.5V Input Range
s
New Flexible, Friendly Parallel Interface to DSPs
and FIFOs
s
24-Pin Narrow PDIP and SW Packages
12-Bit, 500ksps Sampling
A/D Converter with Shutdown
U
A
O
PPLICATI
TYPICAL
Effective Bits and Signal-to-(Noise + Distortion)
vs Input Frequency
INPUT FREQUENCY (Hz)
10k
0
EFFECTIVE NUMBER OF BITS
S/(N
+
D) (dB)
3
5
7
10
100k
1M
2M
LT1278 G4
1
4
6
9
12
11
62
56
74
68
8
2
f
SAMPLE
= 500kHz
NYQUIST
FREQUENCY
U
S
A
O
PPLICATI
s
High Speed Data Acquisition
s
Digital Signal Processing
s
Multiplexed Data Acquisition Systems
s
Audio and Telecom Processing
s
Spectrum Analysis
, LTC and LT are registered trademarks of Linear Technology Corporation.
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
A
IN
V
REF
AGND
D11(MSB)
D10
D9
D8
D7
D6
D5
D4
DGND
AV
DD
V
SS
BUSY
CS
RD
CONVST
SHDN
DV
DD
D0
D1
D2
D3
LTC1278-5
+
0.1
F
10
F
2.42V
REFERENCE
OUTPUT
ANALOG INPUT
(0V TO 5V)
10
F
0.1
F
5V
12-BIT
PARALLEL
BUS
P CONTROL
LINES
LTC1278 TA01
+
CONVERSION START INPUT
POWER DOWN INPUT
Single 5V Supply, 500kHz, 12-Bit Sampling A/D Converter
2
LTC1278
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER
PART NUMBER
AV
DD
= DV
DD
= V
DD
(Notes 1, 2)
Supply Voltage (V
DD
) .............................................. 12V
Negative Supply Voltage (V
SS
)
Bipolar Operation Only .......................... 6V to GND
Total Supply Voltage (V
DD
to V
SS
)
Bipolar Operation Only ....................................... 12V
Analog Input Voltage (Note 3)
Unipolar Operation ................... 0.3V to V
DD
+ 0.3V
Bipolar Operation............... V
SS
0.3V to V
DD
+ 0.3V
Digital Input Voltage (Note 4)
Unipolar Operation ................................ 0.3V to 12V
Bipolar Operation........................... V
SS
0.3V to 12V
Digital Output Voltage
Unipolar Operation ................... 0.3V to V
DD
+ 0.3V
Bipolar Operation................ V
SS
0.3V to V
DD
+ 0.3V
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC1278-4C, LTC1278-5C ..................... 0
C to 70
C
LTC1278-4I ....................................... 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec) ................. 300
C
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
SW PACKAGE
24-LEAD PLASTIC SO WIDE
N PACKAGE
24-LEAD PDIP
24
23
22
21
20
19
18
17
16
15
14
13
A
IN
V
REF
AGND
D11 (MSB)
D10
D9
D8
D7
D6
D5
D4
DGND
AV
DD
V
SS
BUSY
CS
RD
CONVST
SHDN
DV
DD
D0
D1
D2
D3
T
JMAX
= 110
C,
JA
= 100
C/W (N)
T
JMAX
= 110
C,
JA
= 130
C/W (SW)
Consult factory for Military grade parts.
LTC1278-4CN
LTC1278-5CN
LTC1278-4IN
LTC1278-4CSW
LTC1278-5CSW
LTC1278-4ISW
LTC1278-4/LTC1278-5
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Resolution (No Missing Codes)
q
12
Bit
Integral Linearity Error
(Note 7)
q
1
LSB
Differential Linearity Error
q
1
LSB
Offset Error
(Note 8)
4
LSB
q
6
LSB
Gain Error
15
LSB
Gain Error Tempco
I
OUT(REF)
= 0
q
10
45
ppm/
C
C
C
HARA TERISTICS
CO
U
VERTER
With Internal Reference (Notes 5, 6)
LTC1278-4/LTC1278-5
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Analog Input Range (Note 9)
4.95V
V
DD
5.25V (Unipolar)
q
0 to 5
V
4.75V
V
DD
5.25V, 5.25V
V
SS
2.45V (Bipolar)
q
2.5
V
I
IN
Analog Input Leakage Current
CS = High
q
1
A
C
IN
Analog Input Capacitance
Between Conversions (Sample Mode)
45
pF
During Conversions (Hold Mode)
5
pF
PUT
U
I
A
A
U
LOG
(Note 5)
3
LTC1278
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
S/(N + D)
Signal-to-Noise Plus Distortion Ratio
100kHz Input Signal
q
70
72
dB
250kHz Input Signal
70
dB
THD
Total Harmonic Distortion
100kHz Input Signal
q
80
78
dB
First 5 Harmonics
250kHz Input Signal
74
dB
Peak Harmonic or Spurious Noise
100kHz Input Signal
q
84
78
dB
250kHz Input Signal
74
dB
IMD
Intermodulation Distortion
f
IN1
= 99.37kHz, f
IN2
= 102.4kHz
82
dB
f
IN1
= 249.37kHz, f
IN2
= 252.4kHz
70
dB
Full Power Bandwidth
4
MHz
Full Linear Bandwidth (S/(N + D)
68dB)
350
kHz
(Note 5)
LTC1278-4/LTC1278-5
ACCURACY
IC
DY
U
W
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
REF
Output Voltage
I
OUT
= 0
2.400
2.420
2.440
V
V
REF
Output Tempco
I
OUT
= 0
q
10
45
ppm/
C
V
REF
Line Regulation
4.95V
V
DD
5.25V
0.01
LSB/V
5.25V
V
SS
4.95V
0.01
LSB/V
V
REF
Load Regulation
0V
|
I
OUT
|
1mA
2
LSB/mA
LTC1278-4/LTC1278-5
I TER AL REFERE CE CHARACTERISTICS
U
U
U
(Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
V
DD
= 5.25V
q
2.4
V
V
IL
Low Level Input Voltage
V
DD
= 4.95V
q
0.8
V
I
IN
Digital Input Current
V
IN
= 0V to V
DD
q
10
A
C
IN
Digital Input Capacitance
5
pF
V
OH
High Level Output Voltage
V
DD
= 4.95V
I
O
= 10
A
4.7
V
I
O
= 200
A
q
4
V
V
OL
Low Level Output Voltage
V
DD
= 4.95V
I
O
= 160
A
0.05
V
I
O
= 1.6mA
q
0.10
0.4
V
I
OZ
High Z Output Leakage D11 to D0
V
OUT
= 0V to V
DD
, CS High
q
10
A
C
OZ
High Z Output Capacitance D11 to D0
CS High (Note 9 )
q
15
pF
I
SOURCE
Output Source Current
V
OUT
= 0V
10
mA
I
SINK
Output Sink Current
V
OUT
= V
DD
10
mA
LTC1278-4/LTC1278-5
(Note 5)
DIGITAL I PUTS A D DIGITAL OUTPUTS
U
U
4
LTC1278
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
DD
Positive Supply Voltage (Notes 10, 11)
Unipolar
4.95
5.25
V
Bipolar
4.75
5.25
V
V
SS
Negative Supply Voltage (Note 10)
Bipolar Only
2.45
5.25
V
I
DD
Positive Supply Current
f
SAMPLE
= 500ksps
q
15.0
29.5
mA
SHDN = 0V
q
1.7
3.0
mA
I
SS
Negative Supply Current
f
SAMPLE
= 500ksps, V
SS
= 5V
q
0.12
0.30
mA
P
D
Power Dissipation
f
SAMPLE
= 500ksps
q
75.0
150
mW
SHDN = 0V
q
8.5
15
mW
(Note 5)
POWER REQUIRE E TS
W U
LTC1278-4/LTC1278-5
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
SAMPLE(MAX)
Maximum Sampling Frequency
LTC1278-4
q
400
kHz
LTC1278-5
q
500
t
SAMPLE(MIN)
Minimum Throughput Time
LTC1278-4
q
2.5
s
(Acquisition Time Plus Conversion Time)
LTC1278-5
q
2.0
s
t
CONV
Conversion Time
LTC1278-4
2.0
2.3
s
LTC1278-5
1.6
1.85
s
t
ACQ
Acquisition Time
200
ns
t
1
CS
to RD
Setup Time
(Notes 9, 10)
q
0
ns
t
2
CS
to CONVST
Setup Time
(Notes 9, 10)
q
20
ns
t
3
SHDN
to CONVST
Wake-Up Time
(Note 10)
350
ns
t
4
CONVST Low Time
(Notes 10, 12)
q
40
ns
t
5
CONVST
to BUSY
Delay
C
L
= 100pF
40
110
ns
Commercial
q
130
ns
Industrial
q
140
ns
t
6
Data Ready Before BUSY
C
L
= 100pF
q
20
40
ns
t
7
Wait Time RD
After BUSY
Mode 2, (see Figure 14) (Note 9)
q
20
ns
t
8
Data Access Time After RD
C
L
= 20pF (Note 9)
50
90
ns
Commercial
q
110
ns
Industrial
q
120
ns
C
L
= 100pF
70
125
ns
Commercial
q
150
ns
Industrial
q
170
ns
t
9
Bus Relinquish Time
20
30
75
ns
Commercial
q
20
85
ns
Industrial
q
20
90
ns
t
10
RD Low Time
(Note 9)
q
t
8
ns
t
11
CONVST High Time
(Notes 9, 12)
q
40
ns
t
12
Aperture Delay of Sample-and-Hold
Jitter < 50ps
15
ns
LTC1278-4/LTC1278-5
(Note 5)
TI I G CHARACTERISTICS
W U
5
LTC1278
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 1/2LSB 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.
Note 11: A
IN
must not exceed V
DD
or fall below V
SS
by more than 50mV for
specified accuracy. Therefore the minimum supply voltage for the unipolar
mode is 4.95V. The minimum for the bipolar mode is 4.75V, 2.45V.
Note 12: The falling CONVST edge starts a conversion. If CONVST returns
high at a bit decision point during the conversion it can create small errors.
For best performance ensure that CONVST returns high either within 120ns
after conversion start (i.e., before the first bit decision) or after BUSY rises
(i.e., after the last bit test). See mode 1a and 1b (Figures 12 and 13) timing
diagrams.
TI I G CHARACTERISTICS
W U
The
q
indicates 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
(ground for unipolar
mode) or above V
DD
, they will be clamped by internal diodes. This product
can handle input currents greater than 60mA below V
SS
(ground for
unipolar mode) or above V
DD
without latch-up.
Note 4: When these pin voltages are taken below V
SS
(ground for unipolar
mode), they will be clamped by internal diodes. This product can handle
input currents greater than 60mA below V
SS
(ground for unipolar mode)
without latch-up. These pins are not clamped to V
DD
.
Note 5: AV
DD
= DV
DD
= V
DD
= 5V, (V
SS
= 5V for bipolar mode), f
SAMPLE
=
400kHz (LTC1278-4), 500kHz (LTC1278-5), t
r
= t
f
= 5ns unless otherwise
specified.
Note 6: Linearity, offset and full-scale specifications apply for unipolar and
bipolar modes.
(Note 5)
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Integral Nonlinearity vs
Output Code
CODE
0
1.0
INL ERROR (LSB)
0.5
0
0.5
1.0
512 1024 1536 2048
LT1278 G1
2560 3072 3584 4096
f
SAMPLE
= 500kHz
CODE
0
1.0
DNL ERROR (LSB)
0.5
0
0.5
1.0
512 1024 1536 2048
LT1278 G2
2560 3072 3584 4096
f
SAMPLE
= 500kHz
Differential Nonlinearity vs
Output Code
INPUT FREQUENCY (Hz)
10k
0
EFFECTIVE NUMBER OF BITS
S/(N
+
D) (dB)
3
5
7
10
100k
1M
2M
LT1278 G4
1
4
6
9
12
11
62
56
74
68
8
2
f
SAMPLE
= 500kHz
NYQUIST
FREQUENCY
ENOBs and S/(N
+
D) vs
Input Frequency
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