LTC2260-12_15 [Linear]
12-Bit, 125/105/80Msps Ultralow Power 1.8V ADCs;型号: | LTC2260-12_15 |
厂家: | Linear |
描述: | 12-Bit, 125/105/80Msps Ultralow Power 1.8V ADCs |
文件: | 总34页 (文件大小:1122K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC2261-12
LTC2260-12/LTC2259-12
12-Bit, 125/105/80Msps
Ultralow Power 1.8V ADCs
FeaTures
DescripTion
The LTC®2261-12/LTC2260-12/LTC2259-12 are sam-
pling 12-bit A/D converters designed for digitizing high
frequency, wide dynamic range signals. They are perfect
for demanding communications applications with AC
performancethatincludes70.8dBSNRand85dBspurious
n
70.8dB SNR
n
85dB SFDR
n
Low Power: 124mW/103mW/87mW
n
Single 1.8V Supply
n
CMOS, DDR CMOS or DDR LVDS Outputs
n
free dynamic range (SFDR). Ultralow jitter of 0.17ps
Selectable Input Ranges: 1V to 2V
RMS
P-P
P-P
n
n
n
n
n
n
n
allows undersampling of IF frequencies with excellent
800MHz Full-Power Bandwidth S/H
noise performance.
Optional Data Output Randomizer
Optional Clock Duty Cycle Stabilizer
Shutdown and Nap Modes
DC specs include 0.3LSB INL (typical), 0.1LSB DNL
(typical) and no missing codes over temperature. The
transition noise is a low 0.3LSB
Serial SPI Port for Configuration
.
RMS
Pin Compatible 14-Bit and 12-Bit Versions
The digital outputs can be either full-rate CMOS, double-
data rate CMOS, or double-data rate LVDS. A separate
output power supply allows the CMOS output swing to
range from 1.2V to 1.8V.
40-Pin (6mm × 6mm) QFN Package
applicaTions
n
+
–
Communications
The ENC and ENC inputs may be driven differentially or
single ended with a sine wave, PECL, LVDS, TTL or CMOS
inputs. An optional clock duty cycle stabilizer allows high
performance at full speed for a wide range of clock duty
cycles.
n
Cellular Base Stations
n
Software Defined Radios
Portable Medical Imaging
Multi-Channel Data Acquisition
Nondestructive Testing
n
n
n
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
1.8V
2-Tone FFT, fIN = 70MHz and 75MHz
1.2V
TO 1.8V
V
DD
0
OV
DD
–10
–20
–30
–40
–50
–60
–70
D11
+
–
12-BIT
PIPELINED
ADC CORE
CMOS
OR
LVDS
•
•
•
CORRECTION
LOGIC
ANALOG
INPUT
OUTPUT
DRIVERS
INPUT
S/H
D0
OGND
–80
–90
CLOCK/DUTY
CYCLE
CONTROL
–100
–110
–120
226112 TA01a
GND
0
20
30
40
50
60
10
125MHz
CLOCK
FREQUENCY (MHz)
226112 TA01b
226112fc
1
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
absoluTe MaxiMuM raTings (Notes 1, 2)
Supply Voltages (V , OV )....................... –0.3V to 2V
Digital Output Voltage................ –0.3V to (OV + 0.3V)
DD
DD
DD
+
–
Analog Input Voltage (A , A
,
Operating Temperature Range:
IN
IN
PAR/SER, SENSE) (Note 3).......... –0.3V to (V + 0.2V)
LTC2261C, LTC2260C, LTC2259C............ 0°C to 70°C
LTC2261I, LTC2260I, LTC2259I ...........–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
DD
+
–
Digital Input Voltage (ENC , ENC , CS,
SDI, SCK) (Note 4).................................... –0.3V to 3.9V
SDO (Note 4)............................................. –0.3V to 3.9V
pin conFiguraTions
DOUBLE-DATA RATE CMOS OUTPUT MODE
TOP VIEW
FULL-RATE CMOS OUTPUT MODE
TOP VIEW
40 39 38 37 36 35 34 33 32 31
+
40 39 38 37 36 35 34 33 32 31
+
A
A
1
2
30
29
28
D7
IN
A
A
1
2
30
29
28
D6_7
IN
IN
–
–
D6
IN
DNC
+
–
+
–
GND
REFH
3
CLKOUT
GND
REFH
3
CLKOUT
4
27 CLKOUT
4
27 CLKOUT
REFH
5
26 OV
DD
REFH
5
26 OV
DD
41
GND
41
GND
REFL
6
25
OGND
24 D5
23
REFL
6
25
OGND
REFL
7
REFL
7
24 D4_5
PAR/SER
8
D4
22 D3
21
PAR/SER
8
23
22
21
DNC
D2_3
DNC
V
DD
9
V
DD
9
V
10
D2
DD
V
10
DD
11 12 13 14 15 16 17 18 19 20
11 12 13 14 15 16 17 18 19 20
UJ PACKAGE
40-LEAD (6mm × 6mm) PLASTIC QFN
UJ PACKAGE
40-LEAD (6mm × 6mm) PLASTIC QFN
T
= 150°C, θ = 32°C/W
JA
JMAX
T
= 150°C, θ = 32°C/W
JMAX JA
EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB
DOUBLE-DATA RATE LVDS OUTPUT MODE
TOP VIEW
40 39 38 37 36 35 34 33 32 31
+
–
+
–
A
A
1
2
30
29
28
D6_7
D6_7
IN
IN
+
–
GND
REFH
3
CLKOUT
4
27 CLKOUT
REFH
5
26 OV
DD
41
GND
REFL
6
25
OGND
+
REFL
7
24 D4_5
–
+
–
PAR/SER
8
23
D4_5
22 D2_3
21
V
DD
9
V
DD
10
D2_3
11 12 13 14 15 16 17 18 19 20
UJ PACKAGE
40-LEAD (6mm × 6mm) PLASTIC QFN
T
= 150°C, θ = 32°C/W
JA
JMAX
EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB
226112fc
2
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
orDer inForMaTion
LEAD FREE FINISH
LTC2261CUJ-12#PBF
LTC2261IUJ-12#PBF
LTC2260CUJ-12#PBF
LTC2260IUJ-12#PBF
LTC2259CUJ-12#PBF
LTC2259IUJ-12#PBF
TAPE AND REEL
PART MARKING*
LTC2261UJ-12
LTC2261UJ-12
LTC2260UJ-12
LTC2260UJ-12
LTC2259UJ-12
LTC2259UJ-12
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
LTC2261CUJ-12#TRPBF
LTC2261IUJ-12#TRPBF
LTC2260CUJ-12#TRPBF
LTC2260IUJ-12#TRPBF
LTC2259CUJ-12#TRPBF
LTC2259IUJ-12#TRPBF
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container.
Consult LTC Marketing for information on non-standard 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/
converTer characTerisTics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2261-12
TYP
LTC2260-12
TYP
LTC2259-12
MIN TYP MAX
PARAMETER
CONDITIONS
MIN
12
MAX
MIN
12
MAX
UNITS
Bits
l
l
l
l
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
12
–1
Differential Analog Input (Note 6)
Differential Analog Input
(Note 7)
–1
0.3
0.1
1.5
1
0.4
9
–1
0.3
0.1
1.5
1
0.4
9
0.3
0.1
1.5
1
0.4
9
LSB
LSB
mV
–0.4
–9
–0.4
–9
–0.4
–9
Gain Error
Internal Reference
External Reference
1.5
0.4
1.5
0.4
1.5
0.4
%FS
%FS
l
–1.5
1.5
–1.5
1.5
–1.5
1.5
Offset Drift
20
20
20
µV/°C
Full-Scale Drift
Internal Reference
External Reference
30
10
30
10
30
10
ppm/°C
ppm/°C
Transition Noise
External Reference
0.3
0.3
0.3
LSB
RMS
226112fc
3
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
analog inpuT The l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
1.7V < V < 1.9V
MIN
TYP
MAX
UNITS
+
–
l
l
l
V
V
V
Analog Input Range (A – A
)
1 to 2
V
P-P
IN
IN
IN
DD
+
–
Analog Input Common Mode (A + A )/2 Differential Analog Input (Note 8)
V
– 100mV
0.625
V
CM
V
+ 100mV
1.300
V
IN(CM)
SENSE
INCM
IN
IN
CM
CM
External Voltage Reference Applied to SENSE External Reference Mode
1.250
V
I
Analog Input Common Mode Current
Per Pin, 125Msps
Per Pin, 105Msps
Per Pin, 80Msps
155
130
100
µA
µA
µA
+
–
l
l
l
I
I
I
t
t
Analog Input Leakage Current
0 < A , A < V , No Encode
–1
–3
–6
1
3
6
µA
µA
µA
ns
IN1
IN
IN
DD
DD
PAR/SER Input Leakage Current
SENSE Input Leakage Current
0 < PAR/SER < V
IN2
0.625V < SENSE < 1.3V
IN3
Sample-and-Hold Acquisition Delay Time
Sample-and-Hold Acquisition Delay Jitter
Analog Input Common Mode Rejection Ratio
Full-Power Bandwidth
0
AP
0.17
80
ps
RMS
JITTER
CMRR
BW-3B
dB
Figure 6 Test Circuit
800
MHz
DynaMic accuracy The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5)
LTC2261-12
TYP
LTC2260-12
TYP
LTC2259-12
SYMBOL PARAMETER
CONDITIONS
MIN
MAX
MIN
MAX
MIN
TYP MAX UNITS
SNR
Signal-to-Noise Ratio
5MHz Input
70.8
70.7
70.4
70.8
70.7
70.4
70.6
70.5
70.2
dB
dB
dB
l
l
l
l
70MHz Input
140MHz Input
69.4
69.4
69.1
SFDR
Spurious Free Dynamic Range 5MHz Input
2nd or 3rd Harmonic
88
85
82
88
85
82
88
85
82
dB
dB
dB
70MHz Input
140MHz Input
76
83
76
82
79
85
Spurious Free Dynamic Range 5MHz Input
4th Harmonic or Higher
90
90
90
90
90
90
90
90
90
dB
dB
dB
70MHz Input
140MHz Input
S/(N+D) Signal-to-Noise Plus
Distortion Ratio
5MHz Input
70MHz Input
140MHz Input
70.6
70.4
70
70.6
70.4
70
70.4
70.3
69.9
dB
dB
dB
68.6
68.6
68.8
inTernal reFerence characTerisTics The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5)
PARAMETER
CONDITIONS
= 0
MIN
TYP
0.5 • V
25
MAX
UNITS
V
V
CM
V
CM
V
CM
V
REF
V
REF
V
REF
V
REF
Output Voltage
I
0.5 • V – 25mV
0.5 • V + 25mV
OUT
DD
DD
DD
Output Temperature Drift
Output Resistance
Output Voltage
ppm/°C
Ω
–600µA < I
< 1mA
< 1mA
4
OUT
I
= 0
1.225
1.250
25
1.275
V
OUT
Output Temperature Drift
Output Resistance
Line Regulation
ppm/°C
Ω
–400µA < I
7
OUT
1.7V < V < 1.9V
0.6
mV/V
DD
226112fc
4
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
DigiTal inpuTs anD ouTpuTs The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
+
–
ENCODE INPUTS (ENC , ENC )
–
Differential Encode Mode (ENC Not Tied to GND)
l
V
V
Differential Input Voltage
(Note 8)
0.2
V
ID
Common Mode Input Voltage
Internally Set
Externally Set (Note 8)
1.2
V
V
ICM
l
l
1.1
0.2
1.6
3.6
+
–
V
Input Voltage Range
Input Resistance
ENC , ENC to GND
(See Figure 10)
(Note 8)
V
kΩ
pF
IN
R
10
IN
IN
C
Input Capacitance
3.5
–
Single-Ended Encode Mode (ENC Tied to GND)
l
l
l
V
V
V
High Level Input Voltage
Low Level Input Voltage
Input Voltage Range
Input Resistance
V
V
= 1.8V
= 1.8V
1.2
0
V
V
IH
IL
IN
DD
DD
0.6
3.6
+
ENC to GND
(See Figure 11)
(Note 8)
V
R
30
kΩ
pF
IN
IN
C
Input Capacitance
3.5
DIGITAL INPUTS (CS, SDI, SCK)
l
l
l
V
V
High Level Input Voltage
Low Level Input Voltage
Input Current
V
V
V
= 1.8V
1.3
V
V
IH
IL
DD
DD
IN
= 1.8V
0.6
10
I
IN
= 0V to 3.6V
–10
µA
pF
C
IN
Input Capacitance
(Note 8)
3
200
4
SDO OUTPUT (Open-Drain Output. Requires 2k Pull-Up Resistor if SDO is Used)
R
Logic Low Output Resistance to GND
Logic High Output Leakage Current
Output Capacitance
V
= 1.8V, SDO = 0V
DD
Ω
µA
pF
OL
l
I
SDO = 0V to 3.6V
(Note 8)
–10
10
OH
C
OUT
DIGITAL DATA OUTPUTS (CMOS MODES: FULL-DATA RATE AND DOUBLE-DATA RATE)
OV = 1.8V
DD
l
l
V
OH
V
OL
High Level Output Voltage
Low Level Output Voltage
I = –500µA
1.750
1.790
0.010
V
V
O
I = 500µA
O
0.050
OV = 1.5V
DD
V
V
High Level Output Voltage
Low Level Output Voltage
I = –500µA
1.488
0.010
V
V
OH
OL
O
I = 500µA
O
OV = 1.2V
DD
V
V
High Level Output Voltage
Low Level Output Voltage
I = –500µA
1.185
0.010
V
V
OH
OL
O
I = 500µA
O
DIGITAL DATA OUTPUTS (LVDS MODE)
l
l
V
Differential Output Voltage
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
247
350
175
454
mV
mV
OD
V
Common Mode Output Voltage
On-Chip Termination Resistance
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
1.125
1.250
1.250
1.375
V
V
OS
R
Termination Enabled, OV = 1.8V
100
Ω
TERM
DD
226112fc
5
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
power requireMenTs The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 9)
LTC2261-12
TYP
LTC2260-12
TYP
LTC2259-12
MIN TYP MAX UNITS
SYMBOL PARAMETER
CONDITIONS
MIN
MAX
MIN
MAX
CMOS Output Modes: Full-Data Rate and Double-Data Rate
l
l
l
V
Analog Supply Voltage
Output Supply Voltage
Analog Supply Current
(Note 10)
(Note 10)
1.7
1.1
1.8
1.9
1.9
1.7
1.1
1.8
1.9
1.9
1.7
1.1
1.8
1.9
1.9
V
V
DD
OV
DD
I
DC Input
Sine Wave Input
68.7
70
81.1
57.1
58.3
67.4
48
49
56.6
mA
mA
VDD
I
Digital Supply Current
Power Dissipation
Sine Wave Input, OV =1.2V
3.5
2.9
2.2
mA
OVDD
DD
l
P
DC Input
124
130
146
103
108
122
87
91
102
mW
mW
DISS
Sine Wave Input, OV =1.2V
DD
LVDS Output Mode
l
l
l
V
Analog Supply Voltage
Output Supply Voltage
Analog Supply Current
Digital Supply Current
(Note 10)
1.7
1.7
1.8
1.9
1.9
1.7
1.7
1.8
1.9
1.9
1.7
1.7
1.8
1.9
1.9
V
V
DD
OV
(Note 10)
DD
I
I
Sine Wave Input
73.6
86.9
61.9
73.1
52.7 62.2
mA
VDD
OVDD
l
l
Sine Input, 1.75mA Mode
Sine Input, 3.5mA Mode
18.8
36.7
22.2
43.3
18.8
36.7
22.2
43.3
18.8 22.2
36.7 43.3
mA
mA
(0V = 1.8V)
DD
l
l
P
Power Dissipation
Sine Input, 1.75mA Mode
Sine Input, 3.5mA Mode
166
199
196
235
145
177
172
210
129
161
152
190
mW
mW
DISS
All Output Modes
P
P
P
Sleep Mode Power
Nap Mode Power
0.5
9
0.5
9
0.5
9
mW
mW
mW
SLEEP
NAP
Power Increase with Differential Encode Mode Enabled
(No Increase for Nap or Sleep Modes)
10
10
10
DIFFCLK
TiMing characTerisTics The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2261-12
TYP
LTC2260-12
TYP
LTC2259-12
MIN TYP MAX UNITS
SYMBOL PARAMETER
CONDITIONS
MIN
MAX
MIN
MAX
l
f
S
t
L
Sampling Frequency
(Note 10)
1
125
1
105
1
80
MHz
l
l
ENC Low Time (Note 8) Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
3.8
2.0
4
4
500
500
4.52
2.00
4.76
4.76
500
500
5.93
2.00
6.25
6.25
500
500
ns
ns
l
l
t
t
ENC High Time (Note 8) Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
3.8
2.0
4
4
500
500
4.52
2.00
4.76
4.76
500
500
5.93
2.00
6.25
6.25
500
500
ns
ns
H
Sample-and-Hold
Acquisition Delay Time
0
0
0
ns
AP
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Digital Data Outputs (CMOS Modes: Full-Data Rate and Double-Data Rate)
l
l
l
t
t
t
ENC to Data Delay
ENC to CLKOUT Delay
DATA to CLKOUT Skew
Pipeline Latency
C = 5pF (Note 8)
1.1
1
1.7
1.4
0.3
3.1
2.6
0.6
ns
ns
ns
D
L
C = 5pF (Note 8)
L
C
t – t (Note 8)
0
SKEW
D
C
Full-Data Rate Mode
Double-Data Rate Mode
5.0
5.5
Cycles
Cycles
226112fc
6
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
TiMing characTerisTics The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Digital Data Outputs (LVDS Mode)
l
l
l
t
t
t
ENC to Data Delay
ENC to CLKOUT Delay
DATA to CLKOUT Skew
Pipeline Latency
C = 5pF (Note 8)
1.1
1
1.8
1.5
0.3
5.5
3.2
2.7
0.6
ns
ns
D
L
C = 5pF (Note 8)
L
C
t – t (Note 8)
0
ns
SKEW
D
C
Cycles
SPI Port Timing (Note 8)
l
l
t
SCK Period
Write Mode
40
ns
ns
SCK
Readback Mode, C
= 20pF, R
= 20pF, R
= 2k
= 2k
250
SDO
PULLUP
l
l
l
l
l
t
t
t
t
t
CS to SCK Setup Time
SCK to CS Setup Time
SDI Setup Time
5
5
5
5
ns
ns
ns
ns
ns
S
H
DS
DH
DO
SDI Hold Time
SCK Falling to SDO Valid
Readback Mode, C
125
SDO
PULLUP
+
–
termination disabled, differential ENC /ENC = 2V sine wave, input
P-P
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.
range = 2V with differential drive, unless otherwise noted.
P-P
Note 6: Integral nonlinearity is defined as the deviation of a code from a
best fit straight line to the transfer curve. The deviation is measured from
the center of the quantization band.
Note 2: All voltage values are with respect to GND with GND and OGND
shorted (unless otherwise noted).
Note 3: When these pin voltages are taken below GND or above V , they
will be clamped by internal diodes. This product can handle input currents
Note 7: Offset error is the offset voltage measured from –0.5 LSB when
the output code flickers between 0000 0000 0000 and 1111 1111 1111 in
2’s complement output mode.
DD
of greater than 100mA below GND or above V without latchup.
DD
Note 8: Guaranteed by design, not subject to test.
Note 4: When these pin voltages are taken below GND they will be
clamped by internal diodes. When these pin voltages are taken above V
they will not be clamped by internal diodes. This product can handle input
currents of greater than 100mA below GND without latchup.
Note 9: V = 1.8V, f
or 80MHz (LTC2259), ENC = single-ended 1.8V square wave, ENC = 0V,
= 125MHz (LTC2261), 105MHz (LTC2260),
DD
SAMPLE
+
–
DD
input range = 2V with differential drive, 5pF load on each digital output
P-P
unless otherwise noted.
Note 5: V = OV = 1.8V, f
105MHz (LTC2260), or 80MHz (LTC2259), LVDS outputs with internal
= 125MHz (LTC2261),
DD
DD
SAMPLE
Note 10: Recommended operating conditions.
TiMing DiagraMs
Full-Rate CMOS Output Mode Timing
All Outputs Are Single Ended and Have CMOS Levels
t
AP
N + 4
N + 2
ANALOG
INPUT
N
N + 3
t
H
N + 1
t
L
–
ENC
+
ENC
t
D
N – 5
N – 4
N – 3
N – 2
N – 1
D0-D11, OF
t
C
+
CLKOUT
–
CLKOUT
226112 TD01
226112fc
7
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
TiMing DiagraMs
Double-Data Rate CMOS Output Mode Timing
All Outputs Are Single Ended and Have CMOS Levels
t
AP
N + 4
N + 2
ANALOG
INPUT
N
N + 3
t
H
N + 1
t
L
–
ENC
+
ENC
t
t
D
D
D0_1
D0
D1
D0
D1
N-4
D0
N-3
D1
D0
D1
N-2
N-5
N-5
N-4
N-3
N-2
•
•
•
D10_11
OF
D10
D11
D10
OF
D11
D10
D11
D10
D11
N-2
N-5
N-5
N-4
N-4
N-3
N-3
N-2
OF
OF
OF
N-2
N-5
N-4
N-3
t
t
C
C
+
CLKOUT
–
CLKOUT
226112 TD02
Double-Data Rate LVDS Output Mode Timing
All Outputs Are Differential and Have LVDS Levels
t
AP
N + 4
N + 2
ANALOG
INPUT
N
N + 3
t
H
N + 1
t
L
–
ENC
+
ENC
t
t
D
D
+
D0_1
D0
D1
D0
N-4
D1
D0
D1
D0
D1
N-2
N-5
N-5
N-4
N-3
N-3
N-2
–
D0_1
•
•
•
+
D10_11
D10
D11
D10
D11
D10
D11
D10
D11
N-2
N-5
N-5
N-4
N-4
N-3
N-3
N-2
–
D10_11
+
OF
OF
N-5
OF
N-4
OF
N-3
OF
N-3
–
OF
t
C
t
C
+
CLKOUT
–
CLKOUT
226112 TD03
226112fc
8
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
TiMing DiagraMs
SPI Port Timing (Readback Mode)
t
S
t
DS
t
DH
t
t
H
SCK
CS
SCK
t
DO
SDI
A6
A5
A4
A3
A2
A1
A0
XX
XX
D6
XX
D5
XX
D4
XX
D3
XX
D2
XX
D1
XX
R/W
SDO
D7
D0
HIGH IMPEDANCE
SPI Port Timing (Write Mode)
CS
SCK
SDI
A6
A5
A4
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
R/W
SDO
226112 TD04
HIGH IMPEDANCE
Typical perForMance characTerisTics
LTC2261-12: Integral
Nonlinearity (INL)
LTC2261-12: Differential
Nonlinearity (DNL)
LTC2261-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 125Msps
1.0
0.8
1.0
0.8
0.6
0
–10
–20
–30
–40
–50
–60
–70
0.6
0.4
0.4
0.2
0
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–0.2
–0.4
–0.6
–80
–90
–100
–110
–120
–0.8
–1.0
0
2048
3072
4096
0
2048
3072
4096
1024
1024
0
20
30
40
50
60
10
OUTPUT CODE
OUTPUT CODE
FREQUENCY (MHz)
226112 G01
226112 G02
226112 G03
226112fc
9
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical perForMance characTerisTics
LTC2261-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 125Msps
LTC2261-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 125Msps
LTC2261-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 125Msps
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–80
–90
–80
–90
–100
–110
–120
–100
–110
–120
–100
–110
–120
0
20
30
40
50
60
0
20
30
40
50
60
10
10
0
20
30
40
50
60
10
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
226112 G05
226112 G06
226112 G04
LTC2261-12: SNR vs Input
LTC2261-12: 8k Point 2-Tone FFT,
IN = 70MHz, 75MHz, –1dBFS,
125Msps
LTC2261-12: Shorted Input
Histogram
Frequency, –1dB, 2V Range,
125Msps
f
0
–10
–20
–30
–40
–50
–60
–70
18000
16000
14000
12000
10000
8000
72
71
70
69
68
67
66
–80
–90
–100
–110
–120
6000
4000
2000
0
0
20
30
40
50
60
10
2041
2043
2045
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
50
FREQUENCY (MHz)
OUTPUT CODE
226112 G07
226112 G08
226112 G09
LTC2261-12: SFDR vs Input
Frequency, –1dB, 2V Range,
125Msps
LTC2261-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 125Msps
LTC2261-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
95
90
85
80
75
70
65
110
100
90
80
75
70
65
dBFS
80
LVDS OUTPUTS
CMOS OUTPUTS
70
dBc
60
50
40
30
20
10
0
60
55
50
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
50
–80
–60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
0
–70
0
25
50
75
100
125
SAMPLE RATE (Msps)
226112 G10
226112 G12
226112 G13
226112fc
10
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical perForMance characTerisTics
LTC2261-12: SNR vs Sample Rate
LTC2261-12: IOVDD vs Sample
and Digital Output Mode,
LTC2261-12: SNR vs SENSE,
fIN = 5MHz, –1dB
Rate, 5MHz Sine Wave Input,
–1dB, 5pF on Each Data Output
30MHz Sine Wave Input, –1dB
45
40
35
30
25
20
15
72
71
70
69
68
67
66
72
3.5mA LVDS
71
70
69
68
67
LVDS
CMOS
DDR CMOS
1.75mA LVDS
10
5
1.8V CMOS
1.2V CMOS
100 125
0
0
25
50
75
0.6 0.7 0.8 0.9
1
1.1 1.2 1.3
0
25
50
75
100
125
SAMPLE RATE (Msps)
SENSE PIN (V)
SAMPLE RATE (Msps)
226112 G14
226112 G15
226112 G18
LTC2260-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 105Msps
LTC2260-12: Differential
Nonlinearity (DNL)
LTC2260-12: Integral Nonlinearity
(INL)
0
1.0
0.8
0.6
0.4
0.2
0
1.0
0.8
0.6
–10
–20
–30
–40
–50
–60
–70
0.4
0.2
0
–0.2
–0.2
–0.4
–0.6
–0.8
–1.0
–80
–90
–100
–110
–120
–0.4
–0.6
–0.8
–1.0
0
20
30
40
50
10
0
2048
3072
4096
0
2048
3072
4096
1024
1024
FREQUENCY (MHz)
OUTPUT CODE
OUTPUT CODE
226112 G23
226112 G22
226112 G21
LTC2260-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 105Msps
LTC2260-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 105Msps
LTC2260-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 105Msps
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–80
–90
–80
–90
–100
–110
–120
–100
–110
–120
–100
–110
–120
0
20
30
40
50
0
20
30
40
50
0
20
30
40
50
10
10
10
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
226112 G26
226112 G24
226112 G25
226112fc
11
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical perForMance characTerisTics
LTC2260-12: 8k Point 2-Tone FFT,
LTC2260-12: SNR vs Input
Frequency, –1dB, 2V Range,
105Msps
fIN = 70MHz, 75MHz, –1dBFS,
LTC2260-12: Shorted Input
105Msps
Histogram
0
–10
–20
–30
–40
–50
–60
–70
72
71
70
69
68
67
66
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
–80
–90
–100
–110
–120
0
20
30
40
50
10
2044
2045
OUTPUT CODE
2048
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
50
FREQUENCY (MHz)
226112 G27
226112 G29
226112 G28
LTC2260-12: SFDR vs Input
Frequency, –1dB, 2V Range,
105Msps
LTC2260-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 105Msps
LTC2260-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
65
60
55
50
110
100
90
95
90
85
80
75
70
65
dBFS
LVDS OUTPUTS
CMOS OUTPUTS
80
70
dBc
60
50
40
30
20
10
0
45
40
–80
–60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
0
0
25
50
75
100
–70
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
50
SAMPLE RATE (Msps)
226112 G32
226112 G33
226112 G30
LTC2260-12: IOVDD vs Sample
Rate, 5MHz Sine Wave Input,
–1dB, 5pF on Each Data Output
LTC2260-12: SNR vs SENSE,
fIN = 5MHz, –1dB
LTC2259-12: Integral Nonlinearity
(INL)
45
40
35
30
25
20
15
72
1.0
0.8
0.6
0.4
0.2
0
3.5mA LVDS
71
70
69
68
1.75mA LVDS
–0.2
–0.4
–0.6
–0.8
–1.0
10
5
67
66
1.8V CMOS
1.2V CMOS
0
0
25
50
75
100
0.6 0.7 0.8 0.9
1
1.1 1.2 1.3
0
2048
3072
4096
1024
SAMPLE RATE (Msps)
SENSE PIN (V)
OUTPUT CODE
226112 G34
226112 G35
226112 G41
226112fc
12
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical perForMance characTerisTics
LTC2259-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 80Msps
LTC2259-12: Differential
Nonlinearity (DNL)
LTC2259-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 80Msps
1.0
0.8
0.6
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–80
–90
–100
–110
–120
–80
–90
–100
–110
–120
0
2048
3072
4096
0
20
30
40
1024
0
20
30
40
10
10
OUTPUT CODE
FREQUENCY (MHz)
FREQUENCY (MHz)
226112 G42
226112 G44
226112 G43
LTC2259-12: 8k Point 2-Tone FFT,
fIN = 70MHz, 75MHz, –1dBFS,
80Msps
LTC2259-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 80Msps
LTC2259-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 80Msps
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–80
–90
–80
–90
–100
–110
–120
–100
–110
–120
–100
–110
–120
0
20
30
40
0
20
30
40
10
10
0
20
30
40
10
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
226114 G47
226114 G46
226112 G45
LTC2259-12: SNR vs Input
Frequency, –1dB, 2V Range,
80Msps
LTC2259-12: SFDR vs Input
Frequency, –1dB, 2V Range,
80Msps
LTC2259-12: Shorted Input
Histogram
72
71
70
69
68
67
95
90
85
80
75
70
65
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
66
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
50
0
100 150 200 250 300 350
INPUT FREQUENCY (MHz)
2052
2054
2056
50
OUTPUT CODE
226112 G49
226112 G50
226112 G48
226112fc
13
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical perForMance characTerisTics
LTC2259-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 80Msps
LTC2259-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
55
50
45
110
100
90
dBFS
LVDS OUTPUTS
CMOS OUTPUTS
80
70
dBc
60
50
40
30
20
10
0
40
35
0
20
40
60
80
–80
–60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
0
–70
SAMPLE RATE (Msps)
226112 G53
226112 G52
LTC2259-12: IOVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB, 5pF
on Each Data Output
LTC2259-12: SNR vs SENSE,
fIN = 5MHz, –1dB
45
40
35
30
25
20
15
72
71
3.5mA LVDS
70
69
68
67
66
1.75mA LVDS
10
5
1.2V CMOS
1.8V CMOS
0
0
20
40
60
80
0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
SENSE PIN (V)
SAMPLE RATE (Msps)
226112 G54
226112 G55
226112fc
14
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
pin FuncTions
PINS THAT ARE THE SAME FOR ALL DIGITAL OUTPUT
SCK (Pin 14): In serial programming mode, (PAR/SER =
MODES
0V), SCK is the serial interface clock input. In the parallel
programming mode (PAR/SER = V ), SCK controls the
+
DD
A
A
(Pin 1): Positive Differential Analog Input.
(Pin 2): Negative Differential Analog Input.
IN
digital output mode. When SCK is low, the full-rate CMOS
output mode is enabled. When SCK is high, the double-
data rate LVDS output mode (with 3.5mA output current)
is enabled. SCK can be driven with 1.8V to 3.3V logic.
–
IN
GND (Pin 3): ADC Power Ground.
REFH (Pins 4, 5): ADC High Reference. Bypass to Pins
6, 7 with a 2.2µF ceramic capacitor and to ground with a
0.1µF ceramic capacitor.
SDI (Pin 15): In serial programming mode, (PAR/SER =
0V), SDI is the serial interface data input. Data on SDI is
clocked into the mode control registers on the rising edge
of SCK. In the parallel programming mode (PAR/SER =
REFL (Pins 6, 7): ADC Low Reference. Bypass to Pins
4, 5 with a 2.2µF ceramic capacitor and to ground with a
0.1µF ceramic capacitor.
V ), SDI can be used to power down the part. When SDI
DD
is low, the part operates normally. When SDI is high, the
part enters sleep mode. SDI can be driven with 1.8V to
3.3V logic.
PAR/SER(Pin8):ProgrammingModeSelectionPin. Con-
nect to ground to enable the serial programming mode.
CS, SCK, SDI, SDO become a serial interface that control
SDO (Pin 16): In serial programming mode, (PAR/SER
= 0V), SDO is the optional serial interface data output.
Data on SDO is read back from the mode control registers
and can be latched on the falling edge of SCK. SDO is an
open-drain NMOS output that requires an external 2k
pull-up resistor to 1.8V-3.3V. If read back from the mode
control registers is not needed, the pull-up resistor is not
necessaryandSDOcanbeleftunconnected.Intheparallel
the A/D operating modes. Connect to V to enable the
DD
parallel programming mode where CS, SCK, SDI become
parallel logic inputs that control a reduced set of the A/D
operating modes. PAR/SER should be connected directly
to ground or the V of the part and not be driven by a
DD
logic signal.
V
(Pins 9, 10, 40): 1.8V Analog Power Supply. Bypass
DD
programming mode (PAR/SER = V ), SDO is not used
DD
to ground with 0.1µF ceramic capacitors. Pins 9 and 10
and should not be connected.
can share a bypass capacitor.
OGND (Pin 25): Output Driver Ground.
+
ENC (Pin 11): Encode Input. Conversion starts on the
OV (Pin 26): Output Driver Supply. Bypass to ground
rising edge.
DD
with a 0.1µF ceramic capacitor.
–
ENC (Pin 12): Encode Complement Input. Conversion
V
(Pin 37): Common Mode Bias Output, Nominally
starts on the falling edge.
CM
Equal to V /2. V should be used to bias the common
DD
CM
CS (Pin 13): In serial programming mode, (PAR/SER =
0V), CS is the serial interface chip select input. When
CS is low, SCK is enabled for shifting data on SDI into
the mode control registers. In the parallel programming
mode of the analog inputs. Bypass to ground with a 0.1µF
ceramic capacitor.
V
(Pin38):ReferenceVoltageOutput.Bypasstoground
REF
with a 1µF ceramic capacitor, nominally 1.25V.
mode (PAR/SER = V ), CS controls the clock duty cycle
DD
stabilizer. When CSislow, theclockduty cyclestabilizeris
turned off. When CS is high, the clock duty cycle stabilizer
is turned on. CS can be driven with 1.8V to 3.3V logic.
SENSE(Pin39):ReferenceProgrammingPin.Connecting
SENSEtoV selectstheinternalreferenceanda 1Vinput
DD
range. Connecting SENSE to ground selects the internal
reference and a 0.5V input range. An external reference
between 0.625V and 1.3V applied to SENSE selects an
input range of ±0.8 • V
.
SENSE
226112fc
15
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
pin FuncTions
+
FULL-RATE CMOS OUTPUT MODE
CLKOUT (Pin 28): Data Output Clock. The digital outputs
normally transition at the same time as the falling and ris-
+
+
All Pins Below Have CMOS Output Levels (OGND to
ing edges of CLKOUT . The phase of CLKOUT can also
be delayed relative to the digital outputs by programming
the mode control registers.
OV )
DD
D0 to D11 (Pins 19-24, 29-34): Digital Outputs. D11 is
the MSB.
DNC (Pins 17, 18, 19, 21, 23, 29, 31, 33, 35): Do not
connect these pins.
–
+
CLKOUT (Pin 27): Inverted Version of CLKOUT .
+
OF (Pin 36): Over/Under Flow Digital Output. OF is high
CLKOUT (Pin 28): Data Output Clock. The digital outputs
when an overflow or underflow has occurred.
normally transition at the same time as the falling edge
+
+
of CLKOUT . The phase of CLKOUT can also be delayed
relative to the digital outputs by programming the mode
control registers.
DOUBLE-DATA RATE LVDS OUTPUT MODE
All Pins Below Have LVDS Output Levels. The Output
Current Level is Programmable. There is an Optional
Internal 100Ω Termination Resistor Between the Pins
of Each LVDS Output Pair.
DNC (Pins 17, 18, 35): Do not connect these pins.
OF (Pin 36): Over/Under Flow Digital Output. OF is high
when an overflow or underflow has occurred.
–
+
–
+
D0_1 /D0_1 to D10_11 /D10_11 (Pins 19/20, 21/22,
23/24, 29/30, 31/32, 33/34): Double-Data Rate Digital
Outputs.Two databitsaremultiplexedontoeachdifferential
output pair. The even data bits (D0, D2, D4, D6, D8, D10)
DOUBLE-DATA RATE CMOS OUTPUT MODE
All Pins Below Have CMOS Output Levels (OGND to
OV )
DD
+
appear when CLKOUT is low. The odd data bits (D1, D3,
D5, D7, D9, D11) appear when CLKOUT is high.
D0_1 to D10_11 (Pins 20, 22, 24, 30, 32, 34): Double-
Data Rate Digital Outputs. Two data bits are multiplexed
onto each output pin. The even data bits (D0, D2, D4, D6,
+
–
+
CLKOUT /CLKOUT (Pins 27/28): Data Output Clock.
+
The digital outputs normally transition at the same time
D8, D10) appear when CLKOUT is low. The odd data bits
+
+
as the falling and rising edges of CLKOUT . The phase of
(D1, D3, D5, D7, D9, D11) appear when CLKOUT is high.
+
CLKOUT canalsobedelayedrelativetothedigitaloutputs
–
+
CLKOUT (Pin 27): Inverted Version of CLKOUT .
by programming the mode control registers.
–
+
+
OF /OF (Pins 35/36): Over/Under Flow Digital Output.
OF is high when an overflow or underflow has occurred.
226112fc
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LTC2261-12
LTC2260-12/LTC2259-12
FuncTional block DiagraM
+
A
IN
V
DD
INPUT
S/H
FIRST PIPELINED
ADC STAGE
SECOND PIPELINED
ADC STAGE
THIRD PIPELINED
ADC STAGE
FOURTH PIPELINED
ADC STAGE
FIFTH PIPELINED
ADC STAGE
–
A
IN
GND
V
CM
V
/2
DD
0.1µF
V
REF
1.25V
REFERENCE
SHIFT REGISTER
AND CORRECTION
1µF
RANGE
SELECT
REFH
REFL INTERNAL CLOCK SIGNALS
REF
BUF
OV
OF
DD
SENSE
D11
•
•
•
DIFF
CLOCK/DUTY
CYCLE
CONTROL
MODE
OUTPUT
DRIVERS
REF
CONTROL
AMP
REGISTERS
D0
+
–
CLKOUT
CLKOUT
226112 F01
0.1µF
2.2µF
REFH
REFL
OGND
+
–
PAR/SER
SCK SDI
SDO
ENC
ENC
CS
0.1µF
0.1µF
Figure 1. Functional Block Diagram
226112fc
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CONVERTER OPERATION
the inputs should swing from V – 0.5V to V + 0.5V.
CM CM
Thereshouldbe180°phasedifferencebetweentheinputs.
TheLTC2261-12/LTC2260-12/LTC2259-12arelowpower
12-bit125Msps/105Msps/80MspsA/Dconvertersthatare
poweredbyasingle1.8Vsupply.Theanaloginputsshould
be driven differentially. The encode input can be driven
differentially or single ended for lower power consump-
tion. The digital outputs can be CMOS, double-data rate
CMOS(tohalvethenumberofoutputlines),ordouble-data
rate LVDS (to reduce digital noise in the system.) Many
additional features can be chosen by programming the
mode control registers through a serial SPI port. See the
Serial Programming Mode section.
INPUT DRIVE CIRCUITS
Input Filtering
If possible, there should be an RC lowpass filter right at
the analog inputs. This lowpass filter isolates the drive
circuitry from the A/D sample-and-hold switching, and
alsolimitswidebandnoisefromthedrivecircuitry.Figure 3
showsanexampleofaninputRCfilter.TheRCcomponent
values should be chosen based on the application’s input
frequency.
ANALOG INPUT
Transformer Coupled Circuits
The analog input is a differential CMOS sample-and-hold
circuit(Figure2).Theinputsshouldbedrivendifferentially
around a common mode voltage set by the V output
pin, which is nominally V /2. For the 2V input range,
Figure 3 shows the analog input being driven by an RF
transformer with a center-tapped secondary. The center
CM
tap is biased with V , setting the A/D input at its optimal
CM
DD
DC level. At higher input frequencies a transmission line
50Ω
V
CM
LTC2261-12
V
0.1µF
DD
C
C
SAMPLE
3.5pF
0.1µF
R
T1
1:1
ON
+
25Ω
A
10Ω
10Ω
IN
25Ω
ANALOG
INPUT
+
–
A
A
IN
LTC2261-12
C
0.1µF
25Ω
25Ω
PARASITIC
1.8pF
V
DD
12pF
SAMPLE
3.5pF
R
25Ω
ON
–
25Ω
A
IN
IN
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
C
PARASITIC
226112 F03
1.8pF
V
DD
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz
1.2V
10k
+
–
ENC
ENC
10k
1.2V
226112 F02
Figure 2. Equivalent Input Circuit
226112fc
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LTC2261-12
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balun transformer (Figures 4 to 6) has better balance,
resulting in lower A/D distortion.
At very high frequencies an RF gain block will often have
lower distortion than a differential amplifier. If the gain
blockissingleended, thenatransformercircuit(Figures 4
to 6) should convert the signal to differential before driv-
ing the A/D.
Amplifier Circuits
Figure 7 shows the analog input being driven by a high
speed differential amplifier. The output of the amplifier is
AC coupled to the A/D so the amplifier’s output common
mode voltage can be optimally set to minimize distortion.
50Ω
V
CM
0.1µF
0.1µF
0.1µF
+
A
ANALOG
INPUT
IN
T2
50Ω
V
CM
LTC2261-12
T1
0.1µF
25Ω
25Ω
0.1µF
1.8pF
0.1µF
0.1µF
+
–
A
ANALOG
INPUT
IN
T2
A
IN
LTC2261-12
T1
0.1µF
25Ω
25Ω
226112 F05
4.7pF
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1LB
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
–
A
IN
226112 F04
Figure 5. Recommended Front-End Circuit for Input
Frequencies from 170MHz to 270MHz
T1: MA/COM MABA-007159-000000
T2: MA/COM MABAES0060
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
Figure 4. Recommended Front-End Circuit for Input
Frequencies from 70MHz to 170MHz
50Ω
V
CM
0.1µF
0.1µF
0.1µF
2.7nH
0.1µF
+
–
A
A
IN
IN
ANALOG
INPUT
LTC2261-12
25Ω
25Ω
T1
2.7nH
T1: MA/COM ETC1-1-13
226112 F06
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
Figure 6. Recommended Front-End Circuit for Input
Frequencies Above 270MHz
226112fc
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Reference
The V , REFH and REFL pins should be bypassed as
REF
shown in Figure 8. The 0.1µF capacitor between REFH
and REFL should be as close to the pins as possible (not
on the back side of the circuit board).
The LTC2261-12/LTC2260-12/LTC2259-12 have an inter-
nal 1.25V voltage reference. For a 2V input range using
the internal reference, connect SENSE to V . For a 1V
DD
input range using the internal reference, connect SENSE
to ground. For a 2V input range with an external reference,
apply a 1.25V reference voltage to SENSE (Figure 9.)
LTC2261-12
5Ω
V
REF
1.25V BANDGAP
REFERENCE
1.25V
The input range can be adjusted by applying a voltage to
SENSE that is between 0.625V and 1.30V. The input range
1µF
0.625V
will then be 1.6 • V
.
SENSE
RANGE
DETECT
AND
CONTROL
TIE TO V FOR 2V RANGE;
DD
TIE TO GND FOR 1V RANGE;
SENSE
V
CM
RANGE = 1.6 • V
FOR
SENSE
BUFFER
0.65V < V
< 1.300V
HIGH SPEED
DIFFERENTIAL
AMPLIFIER
SENSE
0.1µF
200Ω 200Ω
25Ω
INTERNAL ADC
HIGH REFERENCE
0.1µF
0.1µF
+
–
0.1µF
A
IN
REFH
0.1µF
LTC2261-12
ANALOG
INPUT
+
+
12pF
2.2µF
–
–
0.8x
DIFF AMP
25Ω
A
IN
0.1µF
226112 F07
REFL
Figure 7. Front-End Circuit Using a High Speed
Differential Amplifier
INTERNAL ADC
LOW REFERENCE
226112 F08
Figure 8. Reference Circuit
V
REF
1µF
LTC2261-12
1.25V
EXTERNAL
REFERENCE
SENSE
1µF
226112 F09
Figure 9. Using an External 1.25V Reference
226112fc
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Encode Input
Thesingle-endedencodemodeshouldbeusedwithCMOS
–
encode inputs. To select this mode, ENC is connected
The signal quality of the encode inputs strongly affects
the A/D noise performance. The encode inputs should
be treated as analog signals—do not route them next to
digital traces on the circuit board. There are two modes
of operation for the encode inputs: the differential encode
mode (Figure 10) and the single-ended encode mode
(Figure 11).
+
to ground and ENC is driven with a square wave encode
+
input. ENC can be taken above V (up to 3.6V) so 1.8V
DD
+
to3.3VCMOSlogiclevelscanbeused.TheENC threshold
+
is0.9V. ForgoodjitterperformanceENC shouldhavefast
rise and fall times.
Clock Duty Cycle Stabilizer
The differential encode mode is recommended for sinu-
soidal, PECL or LVDS encode inputs (Figures 12, 13). The
encode inputs are internally biased to 1.2V through 10k
equivalent resistance. The encode inputs can be taken
For good performance the encode signal should have a
50%( 5%) duty cycle. If the optional clock duty cycle
stabilizer circuit is enabled, the encode duty cycle can
vary from 30% to 70% and the duty cycle stabilizer will
maintain a constant 50% internal duty cycle. If the encode
signal changes frequency or is turned off, the duty cycle
stabilizer circuit requires one hundred clock cycles to lock
onto the input clock. The duty cycle stabilizer is enabled
by mode control register A2 (serial programming mode),
or by CS (parallel programming mode).
above V (up to 3.6V), and the common mode range
DD
is from 1.1V to 1.6V. In the differential encode mode,
–
ENC should stay at least 200mV above ground to avoid
falselytriggeringthesingle-endedencodemode.Forgood
+
–
jitter performance ENC and ENC should have fast rise
and fall times.
0.1µF
LTC2261-12
+
25Ω
V
ENC
DD
T1
1:4
DIFFERENTIAL
COMPARATOR
100Ω
D1
V
DD
LTC2261-12
100Ω
–
ENC
15k
30k
+
–
0.1µF
ENC
226112 F12
T1: COILCRAFT WBC4 - 1WL
D1: AVAGO HSMS - 2822
ENC
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
Figure 12. Sinusoidal Encode Drive
226112 F10
Figure 10. Equivalent Encode Input Circuit
for Differential Encode Mode
0.1µF
+
ENC
LTC2261-12
+
PECL OR
LTC2261-12
LVDS
CLOCK
0.1µF
1.8V TO 3.3V
0V
ENC
–
ENC
–
30k
ENC
CMOS LOGIC
BUFFER
226112 F13
226112 F11
Figure 13. PECL or LVDS Encode Drive
Figure 11. Equivalent Encode Input Circuit
for Single-Ended Encode Mode
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Forapplicationswherethesamplerateneedstobechanged
quickly, the clock duty cycle stabilizer can be disabled. If
the duty cycle stabilizer is disabled, care should be taken
to make the sampling clock have a 50%( 5%) duty cycle.
The duty cycle stabilizer should not be used below 5Msps.
When using double-data rate CMOS at high sample rates
the SNR will degrade slightly (see Typical Performance
Characteristics section). DDR CMOS is not recommended
for sample frequencies above 100MHz.
Double-Data Rate LVDS Mode
DIGITAL OUTPUTS
In double-data rate LVDS mode, two data bits are
multiplexed and output on each differential output pair.
Digital Output Modes
+
–
There are 6 LVDS output pairs (D0_1 /D0_1 through
+
–
–
D10_11 /D10_11 ) for the digital output data. Overflow
The LTC2261-12/LTC2260-12/LTC2259-12 can operate
in three digital output modes: full-rate CMOS, double-
data rate CMOS (to halve the number of output lines),
or double-data rate LVDS (to reduce digital noise in the
system). The output mode is set by mode control regis-
ter A3 (serial programming mode), or by SCK (parallel
programming mode). Note that double-data rate CMOS
cannot be selected in the parallel programming mode.
+
+
–
(OF /OF )andthedataoutputclock(CLKOUT /CLKOUT )
each have an LVDS output pair.
By default the outputs are standard LVDS levels: 3.5mA
output current and a 1.25V output common mode volt-
age. An external 100Ω differential termination resistor
is required for each LVDS output pair. The termination
resistors should be located as close as possible to the
LVDS receiver.
Full-Rate CMOS Mode
The outputs are powered by OV and OGND which are
DD
In full-rate CMOS mode the 12 digital outputs (D0-D11),
+
isolated from the A/D core power and ground. In LVDS
overflow (OF), and the data output clocks (CLKOUT ,
–
mode, OV must be 1.8V.
DD
CLKOUT ) have CMOS output levels. The outputs are
powered by OV and OGND which are isolated from the
DD
Programmable LVDS Output Current
A/D core power and ground. OV can range from 1.1V
DD
to 1.9V, allowing 1.2V through 1.8V CMOS logic outputs.
In LVDS mode, the default output driver current is 3.5mA.
Thiscurrentcanbeadjustedbyseriallyprogrammingmode
control register A3. Available current levels are 1.75mA,
2.1mA, 2.5mA, 3mA, 3.5mA, 4mA and 4.5mA.
For good performance the digital outputs should drive
minimal capacitive loads. If the load capacitance is larger
than 10pF a digital buffer should be used.
Optional LVDS Driver Internal Termination
Double-Data Rate CMOS Mode
In most cases using just an external 100Ω termination
resistor will give excellent LVDS signal integrity. In addi-
tion, an optional internal 100Ω termination resistor can
beenabledbyseriallyprogrammingmodecontrolregister
A3. The internal termination helps absorb any reflections
caused by imperfect termination at the receiver. When the
internal termination is enabled, the output driver current
is increased by 1.6x to maintain about the same output
voltage swing.
In double-data rate CMOS mode, two data bits are
multiplexed and output on each data pin. This reduces
the number of data lines by seven, simplifying board
routing and reducing the number of input pins needed
to receive the data. The 6 digital outputs (D0_1, D2_3,
D4_5, D6_7, D8_9, D10_11), overflow (OF), and the data
+
–
output clocks (CLKOUT , CLKOUT ) have CMOS output
levels. TheoutputsarepoweredbyOV andOGNDwhich
DD
are isolated from the A/D core power and ground. OV
DD
can range from 1.1V to 1.9V, allowing 1.2V through 1.8V
CMOS logic outputs.
For good performance the digital outputs should drive
minimal capacitive loads. If the load capacitance is larger
than 10pF a digital buffer should be used.
226112fc
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+
–
Overflow Bit
CLKOUT and CLKOUT , independently of the phase shift.
Thecombinationofthesetwofeaturesenablesphaseshifts
of 45° up to 315° (Figure 14).
The overflow output bit (OF) outputs a logic high when
the analog input is either overranged or underranged. The
overflow bit has the same pipeline latency as the data bits.
DATA FORMAT
Table 1 shows the relationship between the analog input
voltage, the digital data output bits and the overflow bit.
By default the output data format is offset binary. The 2’s
complement format can be selected by serially program-
ming mode control register A4.
Phase Shifting the Output Clock
In full-rate CMOS mode the data output bits normally
+
change at the same time as the falling edge of CLKOUT ,
+
so the rising edge of CLKOUT can be used to latch the
output data. In double-data rate CMOS and LVDS modes
the data output bits normally change at the same time as
Table 1. Output Codes vs Input Voltage
+
–
A
– A
D11-D0
D11-D0
IN
IN
+
thefallingandrisingedgesofCLKOUT .To allowadequate
setup-and-hold time when latching the data, the CLKOUT
signal may need to be phase shifted relative to the data
outputbits. MostFPGAshavethisfeature;thisisgenerally
the best place to adjust the timing.
(2V RANGE)
>+1.000000V
+0.999512V
+0.999024V
+0.000488V
0.000000V
OF (OFFSET BINARY)
(2’s COMPLEMENT)
+
1
0
0
0
0
0
0
0
0
1
1111 1111 1111
1111 1111 1111
1111 1111 1110
1000 0000 0001
1000 0000 0000
0111 1111 1111
0111 1111 1110
0000 0000 0001
0000 0000 0000
0000 0000 0000
0111 1111 1111
0111 1111 1111
0111 1111 1110
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 1110
1000 0000 0001
1000 0000 0000
1000 0000 0000
TheLTC2261-12/LTC2260-12/LTC2259-12canalsophase
+
–
–0.000488V
–0.000976V
–0.999512V
–1.000000V
≤–1.000000V
shift the CLKOUT /CLKOUT signals by serially program-
ming mode control register A2. The output clock can be
shifted by 0°, 45°, 90° or 135°. To use the phase shifting
feature the clock duty cycle stabilizer must be turned
on. Another control register bit can invert the polarity of
+
ENC
D0-D11, OF
MODE CONTROL BITS
PHASE
SHIFT
CLKINV
CLKPHASE1 CLKPHASE0
0°
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
45°
90°
135°
180°
225°
270°
315°
+
CLKOUT
226112 F14
Figure 14. Phase Shifting CLKOUT
226112fc
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Digital Output Randomizer
Alternate Bit Polarity
Interference from the A/D digital outputs is sometimes
unavoidable.Digitalinterferencemaybefromcapacitiveor
inductive coupling or coupling through the ground plane.
Even a tiny coupling factor can cause unwanted tones
in the ADC output spectrum. By randomizing the digital
output before it is transmitted off chip, these unwanted
tones can be randomized which reduces the unwanted
tone amplitude.
Anotherfeaturethatreducesdigitalfeedbackonthecircuit
board is the alternate bit polarity mode. When this mode
is enabled, all of the odd bits (D1, D3, D5, D7, D9, D11)
are inverted before the output buffers. The even bits (D0,
D2, D4, D6, D8, D10), OF and CLKOUT are not affected.
Thiscanreducedigitalcurrentsinthecircuitboardground
plane and reduce digital noise, particularly for very small
analog input signals.
Thedigitaloutput israndomized byapplying an exclusive-
OR logic operation between the LSB and all other data
outputbits.To decode,thereverseoperationisapplied—an
exclusive-OR operation is applied between the LSB and
all other bits. The LSB, OF and CLKOUT outputs are not
affected. The output randomizer is enabled by serially
programming mode control register A4.
When there is a very small signal at the input of the A/D
thatiscenteredaroundmid-scale,thedigitaloutputstoggle
between mostly 1s and mostly 0s. This simultaneous
switchingofmostofthebitswillcauselargecurrentsinthe
ground plane. By inverting every other bit, the alternate bit
polarity mode makes half of the bits transition high while
half of the bits transition low. To first order, this cancels
currentflowinthegroundplane,reducingthedigitalnoise.
CLKOUT
CLKOUT
OF
PC BOARD
FPGA
CLKOUT
OF
OF
D11
D11/D0
D10/D0
D11/D0
D11
D10
D10
D2
•
•
•
D10/D0
LTC2261-12
•
•
•
D2/D0
D1/D0
D2/D0
D1/D0
RANDOMIZER
ON
D2
D1
D0
D1
D0
D0
D0
116112 F15
116112 F15
Figure 15. Functional Equivalent of Digital Output Randomizer
Figure 16. Unrandomizing a Randomized Digital
Output Signal
226112fc
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depends on the size of the bypass capacitors on V
REFH, and REFL. For the suggested values in Figure 8,
the A/D will stabilize after 2ms.
,
The digital output is decoded at the receiver by inverting
the odd bits (D1, D3, D5, D7, D9, D11). The alternate
bit polarity mode is independent of the digital output
randomizer—either, both or neither function can be on
at the same time. When alternate bit polarity mode is on,
the data format is offset binary and the 2’s complement
control bit has no effect. The alternate bit polarity mode is
enabledbyseriallyprogrammingmodecontrolregisterA4.
REF
InnapmodetheA/Dcoreispowereddownwhiletheinternal
referencecircuitsstayactive,allowingfasterwake-upthan
from sleep mode. Recovering from nap mode requires at
least 100 clock cycles. If the application demands very
accurate DC settling then an additional 50µs should be
allowedsotheon-chipreferencescansettlefromtheslight
temperature shift caused by the change in supply current
astheA/Dleavesnapmode. Napmodeisenabledbymode
control register A1 in the serial programming mode.
Digital Output Test Patterns
To allow in-circuit testing of the digital interface to the
A/D, there are several test modes that force the A/D data
outputs (OF, D11-D0) to known values:
DEVICE PROGRAMMING MODES
All 1s: All outputs are 1
All 0s: All outputs are 0
The operating modes of the LTC2261-12 can be pro-
grammed by either a parallel interface or a simple serial
interface. The serial interface has more flexibility and
can program all available modes. The parallel interface
is more limited and can only program some of the more
commonly used modes.
Alternating: Outputs change from all 1s to all 0s on
alternating samples
Checkerboard: Outputs change from 1010101010101
to 0101010101010 on alternating samples
The digital output test patterns are enabled by serially
programming mode control register A4. When enabled,
the test patterns override all other formatting modes: 2’s
complement, randomizer, alternate-bit-polarity.
Parallel Programming Mode
To use the parallel programming mode, PAR/SER should
be tied to V . The CS, SCK and SDI pins are binary logic
DD
inputs that set certain operating modes. These pins can
Output Disable
be tied to V or ground, or driven by 1.8V, 2.5V or 3.3V
DD
CMOS logic. Table 2 shows the modes set by CS, SCK
The digital outputs may be disabled by serially program-
mingmodecontrolregisterA3.Alldigitaloutputsincluding
OFandCLKOUTaredisabled.Thehighimpedancedisabled
state is intended for long periods of inactivity—it is too
slow to multiplex a data bus between multiple converters
at full speed.
and SDI.
Table 2. Parallel Programming Mode Control Bits (PAR/SER = VDD
)
PIN
DESCRIPTION
CS
Clock Duty Cycle Stabilizer Control Bit
0 = Clock Duty Cycle Stabilizer Off
1 = Clock Duty Cycle Stabilizer On
Digital Output Mode Control Bit
0 = Full-Rate CMOS Output Mode
Sleep and Nap Modes
SCK
SDI
The A/D may be placed in sleep or nap modes to conserve
power. In sleep mode the entire A/D converter is powered
down,resultingin0.5mWpowerconsumption.Sleepmode
is enabled by mode control register A1 (serial program-
ming mode), or by SDI (parallel programming mode).
The amount of time required to recover from sleep mode
1 = Double-Data Rate LVDS Output Mode
(3.5mA LVDS Current, Internal Termination Off)
Power Down Control Bit
0 = Normal Operation
1 = Sleep Mode
226112fc
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For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
applicaTions inForMaTion
Serial Programming Mode
diagrams). During a read back command the register is
not updated and data on SDI is ignored.
To use the serial programming mode, PAR/SER should be
tied to ground. The CS, SCK, SDI and SDO pins become a
serialinterfacethatprogramtheA/Dmodecontrolregisters.
Data is written to a register with a 16-bit serial word. Data
can also be read back from a register to verify its contents.
The SDO pin is an open-drain output that pulls to ground
with a 200Ω impedance. If register data is read back
through SDO, an external 2k pull-up resistor is required. If
serialdataisonlywrittenandreadbackisnotneeded, then
SDO can be left floating and no pull-up resistor is needed.
Serial data transfer starts when CS is taken low. The data
on the SDI pin is latched at the first 16 rising edges of
SCK. Any SCK rising edges after the first 16 are ignored.
The data transfer ends when CS is taken high again.
Table 3 shows a map of the mode control registers.
Software Reset
If serial programming is used, the mode control registers
shouldbeprogrammedassoonaspossibleafterthepower
supplies turn on and are stable. The first serial command
must be a software reset which will reset all register data
bits to logic 0. To perform a software reset, bit D7 in the
reset register is written with a logic 1. After the reset SPI
write command is complete, bit D7 is automatically set
back to zero.
The first bit of the 16-bit input word is the R/W bit. The
next seven bits are the address of the register (A6:A0).
The final eight bits are the register data (D7:D0).
If the R/W bit is low, the serial data (D7:D0) will be writ-
ten to the register set by the address bits (A6:A0). If the
R/W bit is high, data in the register set by the address bits
(A6:A0) will be read back on the SDO pin (see the timing
Table 3. Serial Programming Mode Register Map
REGISTER A0: RESET REGISTER (ADDRESS 00h)
D7
D6
X
D5
D4
X
D3
X
D2
X
D1
X
D0
X
RESET
X
Bit 7
RESET
0 = Not Used
Software Reset Bit
1 = Software Reset. All Mode Control Registers are Reset to 00h. This Bit is Automatically Set Back to Zero at the End of the SPI Write
Command.
The Reset Register Is Write Only.
Unused, Don’t Care Bits.
Bits 6-0
REGISTER A1: POWER-DOWN REGISTER (ADDRESS 01h)
D7
X
D6
D5
X
D4
X
D3
X
D2
X
D1
D0
X
PWROFF1
PWROFF0
Bits 7-2
Unused, Don’t Care Bits.
Bits 1-0
PWROFF1:PWROFF0
00 = Normal Operation
01 = Nap Mode
Power Down Control Bits
10 = Not Used
11 = Sleep Mode
226112fc
26
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
applicaTions inForMaTion
REGISTER A2: TIMING REGISTER (ADDRESS 02h)
D7
X
D6
D5
X
D4
X
D3
D2
D1
D0
X
CLKINV
CLKPHASE1
CLKPHASE0
DCS
Bits 7-4
Unused, Don’t Care Bits.
Bit 3
CLKINV
Output Clock Invert Bit
0 = Normal CLKOUT Polarity (As Shown in the Timing Diagrams)
1 = Inverted CLKOUT Polarity
Bits 2-1
CLKPHASE1:CLKPHASE0
Output Clock Phase Delay Bits
00 = No CLKOUT Delay (As Shown in the Timing Diagrams)
01 = CLKOUT+/CLKOUT– Delayed by 45° (Clock Period • 1/8)
10 = CLKOUT+/CLKOUT– Delayed by 90° (Clock Period • 1/4)
11 = CLKOUT+/CLKOUT– Delayed by 135° (Clock Period • 3/8)
Note: If the CLKOUT Phase Delay Feature is Used, the Clock Duty Cycle Stabilizer Must Also be Turned On
Bit 0
DCS
Clock Duty Cycle Stabilizer Bit
0 = Clock Duty Cycle Stabilizer Off
1 = Clock Duty Cycle Stabilizer On
REGISTER A3: OUTPUT MODE REGISTER (ADDRESS 03h)
D7
X
D6
D5
D4
D3
D2
D1
D0
ILVDS2
ILVDS1
ILVDS0
TERMON
OUTOFF
OUTMODE1
OUTMODE0
Bit 7
Unused, Don’t Care Bit.
Bits 6-4
ILVDS2:ILVDS0 LVDS Output Current Bits
000 = 3.5mA LVDS Output Driver Current
001 = 4.0mA LVDS Output Driver Current
010 = 4.5mA LVDS Output Driver Current
011 = Not Used
100 = 3.0mA LVDS Output Driver Current
101 = 2.5mA LVDS Output Driver Current
110 = 2.1mA LVDS Output Driver Current
111 = 1.75mA LVDS Output Driver Current
Bit 3
TERMON
0 = Internal Termination Off
1 = Internal Termination On. LVDS Output Driver Current is 1.6× the Current Set by ILVDS2:ILVDS0
LVDS Internal Termination Bit
Bit 2
OUTOFF
Output Disable Bit
0 = Digital Outputs are Enabled
1 = Digital Outputs are Disabled and Have High Output Impedance
Bits 1-0
OUTMODE1:OUTMODE0
Digital Output Mode Control Bits
00 = Full-Rate CMOS Output Mode
01 = Double-Data Rate LVDS Output Mode
10 = Double-Data Rate CMOS Output Mode
11 = Not Used
226112fc
27
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
applicaTions inForMaTion
REGISTER A4: DATA FORMAT REGISTER (ADDRESS 04h)
D7
X
D6
X
D5
D4
D3
D2
D1
D0
OUTTEST2
OUTTEST1
OUTTEST0
ABP
RAND
TWOSCOMP
Bit 7-6
Unused, Don’t Care Bits.
Bits 5-3
OUTTEST2:OUTTEST0
Digital Output Test Pattern Bits
000 = Digital Output Test Patterns Off
001 = All Digital Outputs = 0
011 = All Digital Outputs = 1
101 = Checkerboard Output Pattern. OF, D11-D0 Alternate Between 1 0101 0101 0101 and 0 1010 1010 1010
111 = Alternating Output Pattern. OF, D11-D0 Alternate Between 0 0000 0000 0000 and 1 1111 1111 1111
Note: Other Bit Combinations are not Used
Bit 2
Bit 1
Bit 0
ABP
Alternate Bit Polarity Mode Control Bit
0 = Alternate Bit Polarity Mode Off
1 = Alternate Bit Polarity Mode On
RAND
Data Output Randomizer Mode Control Bit
0 = Data Output Randomizer Mode Off
1 = Data Output Randomizer Mode On
TWOSCOMP Two’s Complement Mode Control Bit
0 = Offset Binary Data Format
1 = Two’s Complement Data Format
Note: ABP = 1 forces the output format to be Offset Binary
GROUNDING AND BYPASSING
The V capacitor should be located as close to the pin
CM
as possible. To make space for this the capacitor on V
REF
The LTC2261-12 requires a printed circuit board with a
clean unbroken ground plane. A multilayer board with
an internal ground plane is recommended. Layout for
the printed circuit board should ensure that digital and
analog signal lines are separated as much as possible. In
particular, care should be taken not to run any digital track
alongside an analog signal track or underneath the ADC.
can be further away or on the back of the PC board. The
traces connecting the pins and bypass capacitors must
be kept short and should be made as wide as possible.
The analog inputs, encode signals, and digital outputs
should not be routed next to each other. Ground fill and
grounded vias should be used as barriers to isolate these
signals from each other.
High quality ceramic bypass capacitors should be used at
the V , OV , V , V , REFH and REFL pins. Bypass
DD
DD CM REF
HEAT TRANSFER
capacitorsmustbelocatedasclosetothepinsaspossible.
Of particular importance is the 0.1µF capacitor between
REFH and REFL. This capacitor should be on the same
side of the circuit board as the A/D, and as close to the
device as possible (1.5mm or less). Size 0402 ceramic
capacitors are recommended. The larger 2.2µF capacitor
between REFH and REFL can be somewhat further away.
Most of the heat generated by the LTC2261-12 is trans-
ferred from the die through the bottom-side exposed pad
and package leads onto the printed circuit board. For good
electricalandthermalperformance,theexposedpadmust
be soldered to a large grounded pad on the PC board.
226112fc
28
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical applicaTions
LTC2261 Schematic
T2
MABAES0060
R9 10Ω
SENSE
•
•
C23
1µF
R39
ANALOG INPUT
33.2Ω
1%
R14
1k
C51
4.7pF
R40
33.2Ω
1%
C17
1µF
R10 10Ω
V
DD
R16
100Ω
R15 100Ω
C12
0.1µF
C13
1µF
C19
0.1µF
DIGITAL
OUTPUTS
40
39
38
37
36
+
35
–
34
33
32
31
V
SENSE V
V
CM
OF
OF D11 D10 D9 D8
DD
REF
R27 10Ω
R28 10Ω
1
30
29
28
27
26
25
24
23
22
21
+
–
AIN
D7
2
3
AIN
D6
+
GND
CLKOUT
4
–
REFH
REFH
REFL
REFL
CLKOUT
5
C15
0.1µF
0V
OV
DD
DD
C20
2.2µF
LTC2261CUJ
C37
0.1µF
6
OGND
7
D5
D4
D3
D2
8
PAR/SER
C21
0.1µF
PAR/SER
9
V
V
DD
DD
10
V
DD
C18
0.1µF
+
–
GND ENC ENC CS SCK SDI SDO DNC DNC D0 D1
DIGITAL
OUTPUTS
41
11
12
13
14
15
16
17
18
19
20
R13
100Ω
ENCODE CLOCK
226112 TA02
SPI BUS
226112fc
29
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical applicaTions
Silkscreen Top
Top Side
226112 TA04
226112 TA03
Inner Layer 2 GND
Inner Layer 3
226112 TA05
226112 TA06
226112fc
30
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
Typical applicaTions
Inner Layer 4
Inner Layer 5 Power
226112 TA07
226112 TA08
Bottom Side
226112 TA09
226112fc
31
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UJ Package
40-Lead Plastic QFN (6mm × 6mm)
(Reference LTC DWG # 05-08-ꢀ728 Rev Ø)
0.70 0.05
6.50 0.05
5.ꢀ0 0.05
4.42 0.05
4.50 0.05
(4 SIDES)
4.42 0.05
PACKAGE OUTLINE
0.25 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.75 0.05
R = 0.ꢀꢀ5
TYP
6.00 0.ꢀ0
(4 SIDES)
R = 0.ꢀ0
TYP
39 40
0.40 0.ꢀ0
PIN ꢀ TOP MARK
(SEE NOTE 6)
ꢀ
2
PIN ꢀ NOTCH
R = 0.45 OR
0.35 × 45°
CHAMFER
4.42 0.ꢀ0
4.50 REF
(4-SIDES)
4.42 0.ꢀ0
(UJ40) QFN REV Ø 0406
0.200 REF
0.25 0.05
0.50 BSC
0.00 – 0.05
NOTE:
BOTTOM VIEW—EXPOSED PAD
ꢀ. DRAWING IS A JEDEC PACKAGE OUTLINE VARIATION OF (WJJD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN ꢀ LOCATION ON THE TOP AND BOTTOM OF PACKAGE
226112fc
32
For more information www.linear.com/LTC2261-12
LTC2261-12
LTC2260-12/LTC2259-12
revision hisTory (Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
08/12 Corrected RESET REGISTER A0, D7 description.
26
29
20
Attached V to pins 9,10 and 40 on schematic.
DD
C
01/14 Corrected “external reference” to “internal reference” for 1V input range.
226112fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
33
LTC2261-12
LTC2260-12/LTC2259-12
relaTeD parTs
PART NUMBER DESCRIPTION
COMMENTS
LT1993-2
LT1994
High Speed Differential Op Amp
800MHz BW, 70dBc Distortion at 70MHz, 6dB Gain
Low Distortion: –94dBc at 1MHz
Low Noise, Low Distortion Fully Differential Input/
Output Amplifier/Driver
LTC2215
LTC2216
LTC2217
LTC2202
LTC2203
LTC2204
LTC2205
LTC2206
LTC2207
LTC2208
LTC2209
LTC2220
LTC2220-1
LTC2224
LTC2249
LTC2250
LTC2251
LTC2252
LTC2253
LTC2254
LTC2255
16-Bit, 65Msps, Low Noise ADC
16-Bit, 80Msps, Low Noise ADC
16-Bit, 105Msps, Low Noise ADC
16-Bit, 10Msps, 3.3V ADC, Lowest Noise
16-Bit, 25Msps, 3.3V ADC, Lowest Noise
16-Bit, 40Msps, 3.3V ADC
700mW, 81.5dB SNR, 100dB SFDR, 64-Pin QFN
970mW, 81.3dB SNR, 100dB SFDR, 64-Pin QFN
1190mW, 81.2dB SNR, 100dB SFDR, 64-Pin QFN
140mW, 81.6dB SNR, 100dB SFDR, 48-Pin QFN
220mW, 81.6dB SNR, 100dB SFDR, 48-Pin QFN
480mW, 79dB SNR, 100dB SFDR, 48-Pin QFN
590mW, 79dB SNR, 100dB SFDR, 48-Pin QFN
725mW, 77.9dB SNR, 100dB SFDR, 48-Pin QFN
900mW, 77.9dB SNR, 100dB SFDR, 48-Pin QFN
1250mW, 77.7dB SNR, 100dB SFDR, 64-Pin QFN
1450mW, 77.1dB SNR, 100dB SFDR, 64-Pin QFN
890mW, 67.5dB SNR, 9mm × 9mm QFN Package
910mW, 67.7dB SNR, 80dB SFDR, 64-Pin QFN
630mW, 67.6dB SNR, 84dB SFDR, 48-Pin QFN
230mW, 73dB SNR, 5mm × 5mm QFN Package
320mW, 61.6dB SNR, 5mm × 5mm QFN Package
395mW, 61.6dB SNR, 5mm × 5mm QFN Package
320mW, 70.2dB SNR, 5mm × 5mm QFN Package
395mW, 70.2dB SNR, 5mm × 5mm QFN Package
320mW, 72.5dB SNR, 5mm × 5mm QFN Package
395mW, 72.5dB SNR, 88dB SFDR, 32-Pin QFN
16-Bit, 65Msps, 3.3V ADC
16-Bit, 80Msps, 3.3V ADC
16-Bit, 105Msps, 3.3V ADC
16-Bit, 130Msps, 3.3V ADC, LVDS Outputs
16-Bit, 160Msps, 3.3V ADC, LVDS Outputs
12-Bit, 170Msps ADC
12-Bit, 185Msps, 3.3V ADC, LVDS Outputs
12-Bit, 135Msps, 3.3V ADC, High IF Sampling
14-Bit, 80Msps ADC
10-Bit, 105Msps ADC
10-Bit, 125Msps ADC
12-Bit, 105Msps ADC
12-Bit, 125Msps ADC
14-Bit, 105Msps ADC
14-Bit, 125Msps, 3V ADC, Lowest Power
LTC2259-14/
LTC2260-14/
LTC2261-14
14-Bit, 80/105/125Msps 1.8V ADCs,
Ultra-Low Power
89mW/106mW/127mW, 73.4dB SNR, 85dB SFDR
DDR LVDS/DDR CMOS/CMOS Outputs, 6mm × 6mm QFN Package
LTC2284
LTC2299
LT5517
14-Bit, Dual, 105Msps, 3V ADC, Low Crosstalk
Dual 14-Bit, 80Msps ADC
540mW, 72.4dB SNR, 88dB SFDR, 64-Pin QFN
230mW, 71.6dB SNR, 5mm × 5mm QFN Package
High IIP3: 21dBm at 800MHz, Integrated LO Quadrature Generator
40MHz to 900MHz Direct Conversion Quadrature
Demodulator
LT5527
400MHz to 3.7GHz High Linearity Downconverting
Mixer
24.5dBm IIP3 at 900MHz, 23.5dBm IIP3 at 3.5GHz, NF = 12.5dB,
50Ω Single-Ended RF and LO Ports
LT5557
400MHz to 3.8GHz High Linearity Downconverting
Mixer
23.7dBm IIP3 at 2.6GHz, 23.5dBm IIP3 at 3.5GHz, NF = 13.2dB,
3.3V Supply Operation, Integrated Transformer
LT5575
800MHz to 2.7GHz Direct Conversion Quadrature
Demodulator
High IIP3: 28dBm at 900MHz, Integrated LO Quadrature Generator
Integrated RF and LO Transformer
LTC6400-20
1.8GHz Low Noise, Low Distortion Differential ADC
Driver for 300MHz IF
Fixed Gain 10V/V, 2.1nV√Hz Total Input Noise, 3mm × 3mm QFN-16 Package
LT6604-2.5/
LT6604 -5/
LT6604-10/
LT6604-15
Dual Matched 2.5MHz, 5MHz, 10MHz, 15MHz Filter Dual Matched 4th Order LP Filters with Differential Drivers. Low Noise, Low
with ADC Driver Distortion Amplifiers
226112fc
LT 0114 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
34
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC2261-12
●
●
LINEAR TECHNOLOGY CORPORATION 2008
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