LTC1272
12-Bit, 3µs, 250kHz
Sampling A/D Converter
FEATURES
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DESCRIPTION
The
LTC1272
is a 3µs, 12-bit, successive approximation
sampling A/D converter. It has the same pinout as the
industry standard AD7572 and offers faster conversion
time, on-chip sample-and-hold, and single supply opera-
tion. It uses LTBiCMOS™ switched-capacitor technology
to combine a high speed 12-bit ADC with a fast, accurate
sample-and-hold and a precision reference.
The LTC1272 operates with a single 5V supply but can
also accept the 5V/–15V supplies required by the AD7572
(Pin 23, the negative supply pin of the AD7572, is not con-
nected on the LTC1272). The LTC1272 has the same 0V to
5V input range as the AD7572 but, to achieve single supply
operation, it provides a 2.42V reference output instead of
the – 5.25V of the AD7572. It plugs in for the AD7572 if the
reference capacitor polarity is reversed and a 1µs sample-
and-hold acquisition time is allowed between conversions.
The output data can be read as a 12-bit word or as two
8-bit bytes. This allows easy interface to both 8-bit and
higher processors. The LTC1272 can be used with a crystal
or an external clock and comes in speed grades of 3ms
and 8ms.
AD7572 Pinout
12-Bit Resolution
3µs and 8µs Conversion Times
On-Chip Sample-and-Hold
Up to 250kHz Sample Rates
5V Single Supply Operation
No Negative Supply Required
On-Chip 25ppm/°C Reference
75mW (Typ) Power Consumption
ESD Protected on All Pins
24-Pin Narrow DIP and SOL Packages
APPLICATIONS
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High Speed Data Acquisition
Digital Signal Processing (DSP)
Multiplexed Data Acquisition Systems
Single Supply Systems
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
LTBiCMOS is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
Single 5V Supply, 3µs, 12-Bit Sampling ADC
LTC1272
2.42V
V
REF
OUTPUT
ANALOG INPUT
(0V TO 5V)
0.1µF
A
IN
V
REF
10µF
AGND
D11 (MSB)
D10
D9
D8
D7
8 OR 12-BIT
PARALLEL
BUS
D6
D5
D4
DGND
V
DD
NC
BUSY
CS
RD
HBEN
CLK OUT
CLK IN
D0/8
D1/9
D2/10
D3/11
LTC1272 • F01
1024 Point FFT, f
S
= 250kHz, f
IN
= 10kHz
5V
0
–20
0.1µF
AMPLITUDE (dB)
–40
–60
–80
–100
–120
–140
0
20
40
60
80
100
120
LTC1272 • F02
+
10µF
+
S = 72.1
(N+D)
µP
CONTROL
LINES
FREQUENCY (kHz)
1272fc
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1
LTC1272
ABSOLUTE MAXIMUM RATINGS
(Notes 1 and 2)
Supply Voltage (V
DD
) ..................................................6V
Analog Input Voltage (Note 3) .................... –0.3V to 15V
Digital Input Voltage................................... –0.3V to 12V
Digital Output Voltage .....................–0.3V to V
DD
+ 0.3V
Power Dissipation ...............................................500mW
Operating Temperature Range
LTC1272-XAC, CC .................................... 0°C to 70°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
TOP VIEW
A
IN
V
REF
AGND
(MSB) D11
D10
D9
D8
D7
D6
1
2
3
4
5
6
7
8
9
24 V
DD
23 NC
22
BUSY
21
CS
20
RD
19 HBEN
18 CLK OUT
17 CLK IN
16 D0/8
15 D1/9
14 D2/10
13 D3/11
N PACKAGE
24-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 100°C/W
A
IN
V
REF
AGND
(MSB) D11
D10
D9
D8
D7
D6
1
2
3
4
5
6
7
8
9
TOP VIEW
24 V
DD
23 NC
22
BUSY
21
CS
20
RD
19 HBEN
18 CLK OUT
17 CLK IN
16 D0/8
15 D1/9
14 D2/10
13 D3/11
D5 10
D4 11
DGND 12
D5 10
D4 11
DGND 12
SW PACKAGE
24-LEAD PLASTIC SO WIDE
T
JMAX
= 110°C,
θ
JA
= 130°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC1272ACN-3#PBF
LTC1272CCN-3#PBF
LTC1272ACN-8#PBF
LTC1272CCN-8#PBF
LTC1272ACSW-3#PBF
LTC1272CCSW-3#PBF
LTC1272ACSW-8#PBF
LTC1272CCSW-8#PBF
TAPE AND REEL
LTC1272ACN-3#TRPBF
LTC1272CCN-3#TRPBF
LTC1272ACN-8#TRPBF
LTC1272CCN-8#TRPBF
LTC1272ACSW-3#TRPBF
LTC1272CCSW-3#TRPBF
LTC1272ACSW-8#TRPBF
LTC1272CCSW-8#TRPBF
PART MARKING
LTC1272-3ACN
LTC1272-3CCN
LTC1272-8ACN
LTC1272-8CCN
LTC1272-3ACSW
LTC1272-3CCSW
LTC1272-8ACSW
LTC1272-8CCSW
PACKAGE DESCRIPTION
24-Lead PDIP
24-Lead PDIP
24-Lead PDIP
24-Lead PDIP
24-Lead Plastic SO Wide
24-Lead Plastic SO Wide
24-Lead Plastic SO Wide
24-Lead Plastic SO Wide
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/
1272fc
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LTC1272
temperature range, otherwise specifications are at T
A
= 25°C. With Internal Reference (Note 4)
LTC1272-XA
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
l
CONVERTER CHARACTERISTICS
The
l
denotes the specifications which apply over the full operating
LTC1272-XC
MAX
±1/2
±1
±3
±4
±10
I
OUT
(Reference) = 0
l
CONDITIONS
l
MIN
12
l
l
TYP
MIN
12
TYP
MAX
±1
±1
±4
±6
±15
UNITS
Bits
LSB
LSB
LSB
LSB
LSB
ppm/°C
(Note 5)
Gain Error
Full-Scale Tempco
±5
±25
±10
±45
INTERNAL REFERENCE CHARACTERISTICS
PARAMETER
V
REF
Output Voltage (Note 6)
V
REF
Output Tempco
V
REF
Line Regulation
CONDITIONS
I
OUT
= 0
I
OUT
= 0
4.75V ≤ V
DD
≤ 5.25V, I
OUT
= 0
l
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
LTC1272-XA
MIN
2.400
TYP
2.420
5
0.01
2
MAX
2.440
25
MIN
2.400
LTC1272-XC
TYP
2.420
10
0.01
2
MAX
2.440
45
UNITS
V
ppm/°C
LSB/V
LSB/mA
V
REF
Load Regulation (Sourcing Current) 0 ≤
I
OUT
≤ 1mA
DIGITAL AND DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
IH
V
IL
I
IN
V
OH
V
OL
I
OZ
C
OZ
I
SOURCE
I
SINK
I
DD
P
D
PARAMETER
High Level Input Voltage
CS, RD,
HBEN, CLK IN
Low Level Input Voltage
CS, RD,
HBEN, CLK IN
Input Current
CS, RD,
HBEN
Input Current CLK IN
High Level Output Voltage All Logic Outputs
Low Level Output Voltage All Logic Outputs
High-Z Output Leakage D11-D0/8
High-Z Output Capacitance (Note 7)
Output Source Current
Output Sink Current
Positive Supply Current
Power Dissipation
V
OUT
= 0V
V
OUT
= V
DD
CS
=
RD
= V
DD
, A
IN
= 5V
CONDITIONS
V
DD
= 5.25V
V
DD
= 4.75V
V
IN
= 0V to V
DD
V
IN
= 0V to V
DD
V
DD
= 4.75V
I
OUT
= – 10μA
I
OUT
= – 200μA
The
l
denotes the specifications which
apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
LTC1272-XA/C
MIN
l
l
l
l
l
l
l
l
TYP
MAX
0.8
± 10
± 20
UNITS
V
V
µA
µA
V
V
2.4
4.7
4.0
0.4
±10
15
–10
10
V
DD
= 4.75V, I
OUT
= 1.6mA
V
OUT
= 0V to V
DD
V
µA
pF
mA
mA
l
15
75
30
mA
mW
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LTC1272
DYNAMIC ACCURACY
SYMBOL
S/(N+D)
THD
PARAMETER
Signal-to-Noise Plus Distortion Ratio
Total Harmonic Distortion (Up to 5th Harmonic)
Peak Harmonic or Spurious Noise
(Note 4) f
SAMPLE
= 250kHz (LTC1272-3), 111kHz (LTC1272-8)
LTC1272-XA/C
CONDITIONS
10kHz Input Signal
10kHz Input Signal
10kHz Input Signal
MIN
TYP
72
–82
–82
MAX
UNITS
dB
dB
dB
ANALOG INPUT
SYMBOL
V
IN
I
IN
C
IN
t
ACQ
PARAMETER
The
l
denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 4)
LTC1272-XA/B/C
CONDITIONS
4.75V ≤ V
DD
≤ 5.25V
l
l
MIN
0
TYP
MAX
5
3.5
UNITS
V
mA
pF
µs
Input Voltage Range
Input Current
Input Capacitance
Sample-and-Hold Acquisition Time
50
l
0.45
1
TIMING CHARACTERISTICS
SYMBOL
t
1
t
2
t
3
PARAMETER
CS
to
RD
Setup Time
RD
to
BUSY
Delay
Data Access Time After
RD
↓
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 8)
LTC1272-XA/C
CONDITIONS
l
MIN
0
TYP
80
MAX
190
230
90
110
125
150
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
C
L
= 50pF
COM Grade
C
L
= 20pF
COM Grade
C
L
= 100pF
COM Grade
l
50
l
70
l
l
l
t
4
t
5
t
6
t
7
t
8
t
9
t
10
t
11
t
12
t
13
t
CONV
RD
Pulse Width
CS
to
RD
Hold Time
Data Setup Time After
BUSY
Bus Relinquish Time
HBEN to
RD
Setup Time
HBEN to
RD
Hold Time
Delay Between
RD
Operations
Delay Between Conversions
Aperture Delay of Sample and Hold
CLK to
BUSY
Delay
Conversion Time
COM Grade
t
3
t
3
0
40
70
90
75
85
COM Grade
COM Grade
l
l
l
l
l
ns
ns
ns
ns
ns
ns
ns
µs
20
20
0
0
200
1
30
Jitter <50ps
COM Grade
l
l
25
80
12
170
220
13
ns
ns
ns
CLK
CYCLES
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LTC1272
ELECTRICAL CHARACTERISTICS
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 with DGND and
AGND wired together, unless otherwise noted.
Note 3:
When the analog input voltage is taken below ground it will be
clamped by an internal diode. This product can handle, with no external
diode, input currents of greater than 60mA below ground without latch-up.
Note 4:
V
DD
= 5V, f
CLK
= 4MHz for LTC1272-3, and 1.6MHz for
LTC1272-8, t
r
= t
f
= 5ns unless otherwise specified. For best analog
performance, the LTC1272 clock should be synchronized to the
RD
and
CS
control inputs with at least 40ns separating convert start from the
nearest clock edge.
Note 5:
Linearity error is specified between the actual end points of the
A/D transfer curve.
Note 6:
The LTC1272 has the same 0V to 5V input range as the AD7572
but, to achieve single supply operation, it provides a 2.42V reference
output instead of the –5.25V of the AD7572. This requires that the polarity
of the reference bypass capacitor be reversed when plugging an LTC1272
into an AD7572 socket.
Note 7:
Guaranteed by design, not subject to test.
Note 8:
V
DD
= 5V. Timing specifications are sample tested at 25°C to
ensure compliance. All input control signals are specified with t
r
= t
f
= 5ns
(10% to 90% of 5V) and timed from a voltage level of 1.6V. See Figures 13
through 17.
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