LTC1278
12-Bit, 500ksps Sampling
A/D Converter with Shutdown
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
Single Supply 5V or
±5V
Operation
Two Speed Grades,500ksps (LTC1278-5)
400ksps (LTC1278-4)
70dB S/(N + D) and 74dB THD at Nyquist
No Missing Codes Over Temperature
75mW (Typ) Power Dissipation
Power Shutdown with Instant Wake-Up
Internal Reference Can Be Overdriven Externally
Internal Synchronized Clock; No Clock Required
High Impedance Analog Input
0V to 5V or
±2.5V
Input Range
New Flexible, Friendly Parallel Interface to DSPs
and FIFOs
24-Pin Narrow PDIP and SW Packages
The LTC
®
1278 is a 1.6µs, 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 1.6µs 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.
APPLICATI
s
s
s
s
s
S
High Speed Data Acquisition
Digital Signal Processing
Multiplexed Data Acquisition Systems
Audio and Telecom Processing
Spectrum Analysis
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
2.42V
REFERENCE
OUTPUT
Single 5V Supply, 500kHz, 12-Bit Sampling A/D Converter
LTC1278-5
1
ANALOG INPUT
AV
DD
A
(0V TO 5V) 2
IN
V
REF
V
SS
3
AGND
BUSY
0.1µF
4
D11(MSB) CS
5
D10
RD
6
D9
CONVST
7
D8
SHDN
8
D7
DV
DD
9
D6
D0
10
12-BIT
D5
D1
PARALLEL
11
D4
D2
BUS
12
DGND
D3
5V
24
23
22
21
20
19
18
17
16
15
14
13
10µF
µP
CONTROL
LINES
CONVERSION START INPUT
POWER DOWN INPUT
Effective Bits and Signal-to-(Noise + Distortion)
vs Input Frequency
12
74
68
NYQUIST
FREQUENCY
62
56
+
+
10µF
0.1µF
EFFECTIVE NUMBER OF BITS
11
10
9
8
7
6
5
4
3
2
1
0
10k
f
SAMPLE
= 500kHz
100k
INPUT FREQUENCY (Hz)
1M
LTC1278 • TA01
U
S/(N+D) (dB)
2M
LT1278 G4
UO
UO
1
LTC1278
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
A
IN
V
REF
AGND
D11(MSB)
D10
D9
D8
D7
D6
1
2
3
4
5
6
7
8
9
24 AV
DD
23 V
SS
22 BUSY
21 CS
20 RD
19 CONVST
18 SHDN
17 DV
DD
16 D0
15 D1
14 D2
13 D3
SW PACKAGE
24-LEAD PLASTIC SO WIDE
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
ORDER
PART NUMBER
LTC1278-4CN
LTC1278-5CN
LTC1278-4IN
LTC1278-4CSW
LTC1278-5CSW
LTC1278-4ISW
D5 10
D4 11
DGND 12
N PACKAGE
24-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 100°C/W (N)
T
JMAX
= 110°C,
θ
JA
= 130°C/W (SW)
Consult factory for Military grade parts.
CO VERTER CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
Gain Error
Gain Error Tempco
I
OUT(REF)
= 0
(Note 8)
(Note 7)
CONDITIONS
With Internal Reference (Notes 5, 6)
LTC1278-4/LTC1278-5
MIN
TYP
MAX
q
q
q
q
UNITS
Bit
LSB
LSB
LSB
LSB
LSB
ppm/°C
12
±1
±1
±4
±6
±15
±10
±45
q
A ALOG I PUT
SYMBOL PARAMETER
V
IN
I
IN
C
IN
(Note 5)
CONDITIONS
4.95V
≤
V
DD
≤
5.25V (Unipolar)
4.75V
≤
V
DD
≤
5.25V, – 5.25V
≤
V
SS
≤
– 2.45V (Bipolar)
CS = High
Between Conversions (Sample Mode)
During Conversions (Hold Mode)
q
q
q
LTC1278-4/LTC1278-5
MIN
TYP
MAX
0 to 5
±2.5
±1
45
5
UNITS
V
V
µA
pF
pF
Analog Input Range (Note 9)
Analog Input Leakage Current
Analog Input Capacitance
2
U
W
U
U
W W
W
U
U
U
LTC1278
DY A IC ACCURACY
SYMBOL
S/(N + D)
THD
PARAMETER
Signal-to-Noise Plus Distortion Ratio
Total Harmonic Distortion
First 5 Harmonics
Peak Harmonic or Spurious Noise
IMD
Intermodulation Distortion
Full Power Bandwidth
Full Linear Bandwidth (S/(N + D)
≥
68dB)
I TER AL REFERE CE CHARACTERISTICS
PARAMETER
V
REF
Output Voltage
V
REF
Output Tempco
V
REF
Line Regulation
V
REF
Load Regulation
CONDITIONS
I
OUT
= 0
I
OUT
= 0
4.95V
≤
V
DD
≤
5.25V
– 5.25V
≤
V
SS
≤
– 4.95V
0V
≤
|
I
OUT
|
≤
1mA
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL PARAMETER
V
IH
V
IL
I
IN
C
IN
V
OH
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
Digital Input Capacitance
High Level Output Voltage
V
DD
= 4.95V
I
O
= – 10µA
I
O
= – 200µA
V
DD
= 4.95V
I
O
= 160µA
I
O
= 1.6mA
V
OUT
= 0V to V
DD
, CS High
CS High (Note 9 )
V
OUT
= 0V
V
OUT
= V
DD
CONDITIONS
V
DD
= 5.25V
V
DD
= 4.95V
V
IN
= 0V to V
DD
V
OL
Low Level Output Voltage
I
OZ
C
OZ
I
SOURCE
I
SINK
High Z Output Leakage D11 to D0
High Z Output Capacitance D11 to D0
Output Source Current
Output Sink Current
U
U
U
W U
(Note 5)
CONDITIONS
100kHz Input Signal
250kHz Input Signal
100kHz Input Signal
250kHz Input Signal
100kHz Input Signal
250kHz Input Signal
f
IN1
= 99.37kHz, f
IN2
= 102.4kHz
f
IN1
= 249.37kHz, f
IN2
= 252.4kHz
q
q
q
LTC1278-4/LTC1278-5
MIN
TYP
MAX
70
72
70
– 80
– 74
– 84
– 74
– 82
– 70
4
350
– 78
– 78
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
MHz
kHz
U
U
(Note 5)
LTC1278-4/LTC1278-5
MIN
TYP
MAX
2.400
q
UNITS
V
ppm/°C
LSB/V
LSB/V
LSB/mA
2.420
±10
0.01
0.01
2
2.440
±45
(Note 5)
LTC1278-4/LTC1278-5
MIN
TYP
MAX
q
q
q
UNITS
V
V
µA
pF
V
V
V
V
µA
pF
mA
mA
2.4
0.8
±10
5
4.7
q
4
0.05
0.10
q
q
q
0.4
±10
15
– 10
10
3
LTC1278
POWER REQUIRE E TS
SYMBOL PARAMETER
V
DD
V
SS
I
DD
I
SS
P
D
Positive Supply Voltage (Notes 10, 11)
Negative Supply Voltage (Note 10)
Positive Supply Current
Negative Supply Current
Power Dissipation
TI I G CHARACTERISTICS
SYMBOL
f
SAMPLE(MAX)
t
SAMPLE(MIN)
t
CONV
t
ACQ
t
1
t
2
t
3
t
4
t
5
PARAMETER
Maximum Sampling Frequency
Minimum Throughput Time
(Acquisition Time Plus Conversion Time)
Conversion Time
Acquisition Time
CS↓ to RD↓ Setup Time
CS↓ to CONVST↓ Setup Time
SHDN↑ to CONVST↓ Wake-Up Time
CONVST Low Time
CONVST↓ to BUSY↓ Delay
t
6
t
7
t
8
Data Ready Before BUSY↑
Wait Time RD↓ After BUSY↑
Data Access Time After RD↓
t
9
Bus Relinquish Time
Commercial
Industrial
q
q
q
q
t
10
t
11
t
12
RD Low Time
CONVST High Time
Aperture Delay of Sample-and-Hold
4
U W
(Note 5)
CONDITIONS
Unipolar
Bipolar
Bipolar Only
f
SAMPLE
= 500ksps
SHDN = 0V
f
SAMPLE
= 500ksps, V
SS
= – 5V
f
SAMPLE
= 500ksps
SHDN = 0V
q
q
q
q
q
LTC1278-4/LTC1278-5
MIN
TYP
MAX
4.95
4.75
– 2.45
15.0
1.7
0.12
75.0
8.5
5.25
5.25
– 5.25
29.5
3.0
0.30
150
15
UNITS
V
V
V
mA
mA
mA
mW
mW
UW
(Note 5)
CONDITIONS
LTC1278-4
LTC1278-5
LTC1278-4
LTC1278-5
LTC1278-4
LTC1278-5
(Notes 9, 10)
(Notes 9, 10)
(Note 10)
(Notes 10, 12)
C
L
= 100pF
Commercial
Industrial
C
L
= 100pF
Mode 2, (see Figure 14) (Note 9)
C
L
= 20pF (Note 9)
Commercial
Industrial
C
L
= 100pF
Commercial
Industrial
q
q
q
q
q
q
q
q
q
q
q
q
q
LTC1278-4/LTC1278-5
MIN
TYP
MAX
400
500
2.5
2.0
2.0
1.6
200
0
20
350
40
40
110
130
140
2.3
1.85
UNITS
kHz
µs
µs
µs
µs
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
20
– 20
40
50
90
110
120
125
150
170
75
85
90
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
70
q
q
20
20
20
t
8
40
30
(Note 9)
(Notes 9, 12)
Jitter < 50ps
15
ns
LTC1278
TI I G CHARACTERISTICS
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.
TYPICAL PERFORMANCE CHARACTERISTICS
Integral Nonlinearity vs
Output Code
1.0
f
SAMPLE
= 500kHz
0.5
0.5
DNL ERROR (LSB)
EFFECTIVE NUMBER OF BITS
INL ERROR (LSB)
0
–0.5
–1.0
0
512 1024 1536 2048 2560 3072 3584 4096
CODE
LT1278 G1
U W
UW
(Note 5)
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.
Differential Nonlinearity vs
Output Code
1.0
12
ENOBs and S/(N
+
D) vs
Input Frequency
74
68
NYQUIST
FREQUENCY
62
56
S/(N+D) (dB)
f
SAMPLE
= 500kHz
11
10
9
8
7
6
5
4
3
2
1
f
SAMPLE
= 500kHz
100k
INPUT FREQUENCY (Hz)
1M
0
–0.5
–1.0
0
512 1024 1536 2048 2560 3072 3584 4096
CODE
LT1278 G2
0
10k
2M
LT1278 G4
5
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