LTC1608
High Speed, 16-Bit, 500ksps
Sampling A/D Converter
with Shutdown
FEATURES
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
A Complete, 500ksps 16-Bit ADC
90dB S/(N+D) and –100dB THD (Typ)
Power Dissipation: 270mW (Typ)
No Pipeline Delay
No Missing Codes Over Temperature
Nap (7mW) and Sleep (10
µ
W) Shutdown Modes
Operates with Internal 15ppm/°C Reference
or External Reference
True Differential Inputs Reject Common Mode Noise
5MHz Full Power Bandwidth
±2.5V
Bipolar Input Range
36-Pin SSOP Package
Pin Compatible with the LTC1604
The LTC
®
1608 is a 500ksps, 16-bit sampling A/D con-
verter that draws only 270mW from
±5V
supplies. This
high performance device includes a high dynamic range
sample-and-hold, a precision reference and a high speed
parallel output. Two digitally selectable power shutdown
modes provide power savings for low power systems.
The LTC1608’s full-scale input range is
±
2.5V. Outstand-
ing AC performance includes 90dB S/(N+D) and – 100dB
THD at a sample rate of 500ksps.
The unique differential input sample-and-hold can acquire
single-ended or differential input signals up to its 15MHz
bandwidth. The 68dB common mode rejection allows
users to eliminate ground loops and common mode noise
by measuring signals differentially from the source.
The ADC has
µP
compatible,16-bit parallel output port.
There is no pipeline delay in conversion results. A separate
convert start input and a data ready signal (BUSY) ease
connections to FlFOs, DSPs and microprocessors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Circuitry in the LTC1608 is covered under US Patent #5,764,175
APPLICATIO S
s
s
s
s
s
s
Telecommunications
Digital Signal Processing
Multiplexed Data Acquisition Systems
High Speed Data Acquisition
Spectrum Analysis
Imaging Systems
TYPICAL APPLICATIO
2.2µF
10µF
10Ω
36
3
V
REF
5V 10µF
5V
10µF
+
35
AV
DD
+
9
+
10
DGND
SHDN
33
AV
DD
DV
DD
LTC1608
4
REFCOMP
7.5k
1.75X
2.5V
REF
22µF
BUSY
27
OV
DD
29
5V OR
3V
10µF
AMPLITUDE (dB)
+
CONTROL
LOGIC
AND
TIMING
CS
32
CONVST
31
RD
30
µP
CONTROL
LINES
+
1
A
IN
DIFFERENTIAL
ANALOG INPUT
±
2.5V
+
–
OGND 28
16-BIT
SAMPLING
ADC
AGND
5
AGND
6
B15 TO B0
OUTPUT
BUFFERS
16-BIT
PARALLEL
BUS
11 TO 26
1608 TA01
2
A
IN–
D15 TO D0
AGND
7
AGND V
SS
8
34
+
–5V
10µF
U
LTC1608 4096 Point FFT
0
–20
–40
–60
–80
–100
–120
–140
0
50
150
FREQUENCY (kHz)
100
200
250
1608 TA02
+
U
U
f
SAMPLE
= 500kHz
f
IN
= 98.754kHz
SINAD = 86.7dB
THD = –92.6dB
1
LTC1608
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
A
IN+
A
IN–
V
REF
REFCOMP
AGND
AGND
AGND
AGND
DV
DD
1
2
3
4
5
6
7
8
9
36 AV
DD
35 AV
DD
34 V
SS
33 SHDN
32 CS
31 CONV
30 RD
29 OV
DD
28 OGND
27 BUSY
26 D0
25 D1
24 D2
23 D3
22 D4
21 D5
20 D6
19 D7
G PACKAGE
36-LEAD PLASTIC SSOP
AV
DD
= DV
DD
= OV
DD
= V
DD
(Notes 1, 2)
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)
V
REF
Voltage (Note 4) ................. – 0.3V to (V
DD
+ 0.3V)
REFCOMP Voltage (Note 4) ......... – 0.3V to (V
DD
+ 0.3V)
Digital Input Voltage (Note 4) ....................– 0.3V to 10V
Digital Output Voltage .................. – 0.3V to (V
DD
+ 0.3V)
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC1608C .............................................. 0°C to 70°C
LTC1608I ............................................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER
PART NUMBER
LTC1608CG
LTC1608ACG
LTC1608IG
LTC1608AIG
DGND 10
D15 (MSB) 11
D14 12
D13 13
D12 14
D11 15
D10 16
D9 17
D8 18
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult factory for parts specified with wider operating temperature ranges.
CO VERTER CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Transition Noise
Offset Error
Offset Tempco
Full-Scale Error
Full-Scale Tempco
(Note 7)
(Note 8)
(Note 9)
(Note 9)
Internal Reference
External Reference
CONDITIONS
The
q
denotes specifications that apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. With Internal Reference (Notes 5, 6), unless otherwise noted.
LTC1608
MIN
TYP
MAX
q
q
LTC1608A
MIN
TYP
MAX
16
16
±0.5
0.7
±0.05 ±0.125
0.5
±0.125 ±0.25
±0.25
±15
±2
UNITS
Bits
LSB
LSB
RMS
% FSR
ppm/°C
%
%
ppm/°C
15
16
±1
0.7
±
4
q
±
0.05
±
0.125
0.5
±
0.125
±
0.25
±0.25
±15
I
OUT
(Reference) = 0, Internal Reference
A ALOG I PUT
SYMBOL PARAMETER
V
IN
I
IN
C
IN
t
ACQ
t
AP
t
jitter
CMRR
The
q
denotes specifications that apply over the full operating temperature range, otherwise
CONDITIONS
4.75
≤
V
DD
≤
5.25V, – 5.25
≤
V
SS
≤
– 4.75V,
V
SS
≤
(A
IN–
, A
IN+
)
≤
AV
DD
CS = High
Between Conversions
During Conversions
q
specifications are at T
A
= 25°C.
MIN
TYP
±2.5
±1
43
5
380
– 1.5
5
– 2.5V < (A
IN–
= A
IN+
) < 2.5V
68
MAX
UNITS
V
µA
pF
pF
ns
ns
ps
RMS
dB
Analog Input Range (Note 2)
Analog Input Leakage Current
Analog Input Capacitance
Sample-and-Hold Acquisition Time
Sample-and-Hold Acquisition Delay Time
Sample-and-Hold Acquisition Delay Time Jitter
Analog Input Common Mode Rejection Ratio
2
U
W
U
U
W W
W
U
U
U
LTC1608
DY A IC ACCURACY
SYMBOL
S/N
S/(N + D)
THD
SFDR
IMD
PARAMETER
Signal-to-Noise Ratio
I TER AL REFERE CE CHARACTERISTICS
PARAMETER
V
REF
Output Voltage
V
REF
Output Tempco
V
REF
Line Regulation
V
REF
Output Resistance
REFCOMP Output Voltage
CONDITIONS
I
OUT
= 0
I
OUT
= 0
4.75
≤
V
DD
≤
5.25V
– 5.25V
≤
V
SS
≤
– 4.75V
0
≤ I
OUT
≤
1mA
I
OUT
= 0
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
C
OZ
I
SOURCE
I
SINK
PARAMETER
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 D15 to D0
Hi-Z Output Capacitance D15 to D0
Output Source Current
Output Sink Current
CONDITIONS
V
DD
= 5.25V
V
DD
= 4.75V
V
IN
= 0V to V
DD
The
q
denotes specifications that apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
MIN
q
q
q
U
U
U
W U
U
T
A
= 25°C (Note 5)
CONDITIONS
5kHz Input Signal
100kHz Input Signal
5kHz Input Signal
100kHz Input Signal (Note 10)
5kHz Input Signal
100kHz Input Signal
100kHz Input Signal
f
IN1
= 29.37kHz, f
IN2
= 32.446kHz
MIN
TYP
90
88
90
84
– 100
– 91
94
– 88
5
350
MAX
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
MHz
kHz
Signal-to-(Noise + Distortion) Ratio
Total Harmonic Distortion
Up to 5th Harmonic
Spurious Free Dynamic Range
Intermodulation Distortion
Full Power Bandwidth
Full Linear Bandwidth (S/(N + D)
≥
84dB)
U
T
A
= 25°C (Note 5)
MIN
2.475
TYP
2.500
±15
0.01
0.01
7.5
4.375
MAX
2.515
UNITS
V
ppm/°C
LSB/V
LSB/V
kΩ
V
TYP
MAX
0.8
±1
0
UNITS
V
V
µA
pF
V
V
2.4
5
V
DD
= 4.75V, I
OUT
= – 10µA
V
DD
= 4.75V, I
OUT
= – 400µA
V
DD
= 4.75V, I
OUT
= 160µA
V
DD
= 4.75V, I
OUT
= 1.6mA
V
OUT
= 0V to V
DD
, CS High
CS High (Note 11)
V
OUT
= 0V
V
OUT
= V
DD
4.5
q
q
q
q
4.0
0.05
0.10
0.4
±10
15
–10
10
V
V
µA
pF
mA
mA
3
LTC1608
POWER REQUIRE E TS
SYMBOL
V
DD
V
SS
I
DD
PARAMETER
Positive Supply Voltage
Negative Supply Voltage
Positive Supply Current
Nap Mode
Sleep Mode
Negative Supply Current
Nap Mode
Sleep Mode
Power Dissipation
Nap Mode
Sleep Mode
The
q
denotes specifications that apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
(Notes 12, 13)
(Note 12)
CS = RD = 0V
CS = 0V, SHDN = 0V
CS = 5V, SHDN = 0V
CS = RD = 0V
CS = 0V, SHDN = 0V
CS = 5V, SHDN = 0V
CS = RD = 0V
CS = 0V, SHDN = 0V
CS = 5V, SHDN = 0V
q
I
SS
P
D
otherwise specifications are at T
A
= 25°C. (Note 5)
SYMBOL
f
SMPL(MAX)
t
CONV
t
ACQ
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
t
10
PARAMETER
Maximum Sampling Frequency
Conversion Time
Acquisition Time
CS to RD Setup Time
CS↓ to CONVST↓ Setup Time
SHDN↓ to CS↑ Setup Time
SHDN↑ to CONVST↓ Wake-Up Time
CONVST Low Time
CONVST to BUSY Delay
Data Ready Before BUSY↑
q
TI I G CHARACTERISTICS
t
ACQ+CONV(MIN)
Throughput Time (Acquisition + Conversion)
(Notes 11, 12, 15)
(Notes 11, 12)
(Notes 11, 12)
CS = Low (Note 12)
(Note 12)
C
L
= 25pF
Delay Between Conversions
Wait Time RD↓ After BUSY↑
Data Access Time After RD↓
t
11
t
12
t
13
t
14
Bus Relinquish Time
q
RD Low Time
CONVST High Time
Aperture Delay of Sample-and-Hold
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, OGND
and AGND wired together unless otherwise noted.
4
U W
MIN
4.75
– 4.75
TYP
MAX
5.25
– 5.25
UNITS
V
V
mA
mA
µA
mA
µA
µA
mW
mW
mW
22
1.5
1
32
1
1
270
7.5
0.01
35
2.4
100
49
100
100
420
12
1
q
q
UW
The
q
denotes specifications that apply over the full operating temperature range,
CONDITIONS
q
q
MIN
500
1.0
TYP
600
1.45
1.67
MAX
1.8
400
2
UNITS
kHz
µs
ns
µs
ns
ns
ns
(Notes 11, 14)
q
q
q
q
q
0
10
10
400
40
36
80
60
32
200
–5
25
40
50
60
75
50
60
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
q
q
(Note 12)
(Note 12)
C
L
= 25pF
q
q
q
C
L
= 100pF (Note 11)
q
45
30
(Note 12)
(Note 12)
q
q
t
10
40
2
ns
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.
LTC1608
ELECTRICAL CHARACTERISTICS
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
.
Note 5:
V
DD
= 5V, V
SS
= – 5V, f
SMPL
= 500kHz, and t
r
= t
f
= 5ns unless
otherwise specified.
Note 6:
Linearity, offset and full-scale specification 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:
Typical RMS noise at the code transitions.
Note 9:
Bipolar offset is the offset voltage measured from – 0.5LSB when
the output code flickers between 0000 0000 0000 0000 and 1111 1111
1111 1111.
Note 10:
Signal-to-Noise Ratio (SNR) is measured at 5kHz and distortion
is measured at 100kHz. These results are used to calculate Signal-to-Nosie
Plus Distortion (SINAD).
Note 11:
Guaranteed by design, not subject to test.
Note 12:
Recommended operating conditions.
Note 13:
The falling CONVST edge starts a conversion. If CONVST returns
high at a critical point during the conversion it can create small errors. For
best performance ensure that CONVST returns high either within 250ns
after conversion start or after BUSY rises.
Note 14:
The acquisition time would go up to 400ns and the conversion
time would go up to 1.8µs. However, the throughput time (acquisition +
conversion) is guaranteed by test to be 2µs max.
Note 15:
If RD↓ precedes CS↓, the output enable will be gated by CS↓.
TYPICAL PERFOR A CE CHARACTERISTICS
Integral Nonlinearity
vs Output Code
2.0
1.5
1.0
DNL (LSB)
INL (LSB)
0.2
0
–0.2
–0.4
SINAD (dB)
0.5
0
–0.5
–1.0
–1.5
–2.0
–32768
–16384
0
CODE
16384
32767
1608 G01
Signal-to-Noise Ratio
vs Input Frequency
AMPLITUDE (dB BELOW THE FUNDAMENTAL)
100
90
SIGNAL-TO-NOISE RATIO (dB)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
SPURIOUS-FREE DYNAMIC RANGE (dB)
80
70
60
50
40
30
20
10
0
1k
10k
100k
FREQUENCY (Hz)
1M
1608 G04
U W
Differential Nonlinearity
vs Output Code
1.0
0.8
0.6
0.4
100
90
80
70
60
50
40
30
20
10
–16384
0
CODE
16384
32767
1608 G02
S/(N + D) vs Input Frequency
and Amplitude
V
IN
= 0dB
V
IN
= –20dB
V
IN
= –40dB
–0.6
–0.8
–1.0
–32768
0
1k
10k
100k
FREQUENCY (Hz)
1M
1608 G03
Distortion vs Input Frequency
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
Spurious-Free Dynamic Range
vs Input Frequency
THD
3RD
2ND
–110
1k
100k
INPUT FREQUENCY (Hz)
10k
1M
1608 G05
–110
1k
100k
INPUT FREQUENCY (Hz)
10k
1M
1608 G06
5
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