LINEAR TECHNOLOGY LTC2288, LTC2287, LTC2286 Technical data

FEATURES

■

Integrated Dual 10-Bit ADCs

■

Sample Rate: 65Msps/40Msps/25Msps

■

Single 3V Supply (2.7V to 3.4V)

■

Low Power: 400mW/235mW/150mW

■

61.6dB SNR at 70MHz Input

■

85dB SFDR at 70MHz Input

■

110dB Channel Isolation at 100MHz

■

Multiplexed or Separate Data Bus

■

Flexible Input: 1V

■

575MHz Full Power Bandwidth S/H

■

Clock Duty Cycle Stabilizer

■

Shutdown and Nap Modes

■

Pin Compatible Family

P-P

to 2V

P-P

Range

80Msps: LTC2294 (12-Bit), LTC2289 (10-Bit)
65Msps: LTC2293 (12-Bit), LTC2288 (10-Bit)
40Msps: LTC2292 (12-Bit), LTC2287 (10-Bit)
25Msps: LTC2291 (12-Bit), LTC2286 (10-Bit)

■

64-Pin (9mm × 9mm) QFN Package

U

APPLICATIO S

■

Wireless and Wired Broadband Communication

■

Imaging Systems

■

Spectral Analysis

■

Portable Instrumentation

LTC2288/LTC2287/LTC2286

Dual 10-Bit, 65/40/25Msps

Low Noise 3V ADCs

U

DESCRIPTIO

The LTC®2288/LTC2287/LTC2286 are 10-bit 65Msps/
40Msps/25Msps, low noise dual 3V A/D converters de­signed for digitizing high frequency, wide dynamic range
signals. The LTC2288/LTC2287/LTC2286 are perfect for
demanding imaging and communications applications
with AC performance that includes 61.6dB SNR and 85dB
SFDR for signals well beyond the Nyquist frequency.

DC specs include ±0.1LSB INL (typ), ±0.05LSB DNL (typ)
and ±0.6 LSB INL, ±0.5 LSB DNL over temperature. The
transition noise is a low 0.07LSB

A single 3V supply allows low power operation. A separate
output supply allows the outputs to drive 0.5V to 3.3V
logic. An optional multiplexer allows both channels to
share one digital output bus.

A single-ended CLK input controls converter operation. An
optional clock duty cycle stabilizer allows high perfor­mance at full speed for a wide range of clock duty cycles.

, LTC and LT are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

RMS

.

TYPICAL APPLICATIO

ANALOG
INPUT A

CLK A

CLK B

ANALOG
INPUT B

+

INPUT

S/H

–

CLOCK/DUTY CYCLE

CONTROL

CLOCK/DUTY CYCLE

CONTROL

+

INPUT

S/H

–

10-BIT
PIPELINED
ADC CORE

10-BIT
PIPELINED
ADC CORE

U

OUTPUT

DRIVERS

OUTPUT

DRIVERS

228876 TA01

OV

D9A

•

•

•

D0A

OGND

MUX

OV

D9B

•

•

•

D0B

OGND

DD

LTC2288: SNR vs Input Frequency,

–1dB, 2V Range, 65Msps

62.5

61.5

60.5

59.5

SNR (dBFS)

DD

58.5

57.5
50

0

INPUT FREQUENCY (MHz)

100

150

200

228876 TA02

228876f

1

LTC2288/LTC2287/LTC2286

WW

W

U

ABSOLUTE AXI U RATI GS

OVDD = VDD (Notes 1, 2)

Supply Voltage (VDD) ................................................. 4V

Digital Output Ground Voltage (OGND) ....... –0.3V to 1V

Analog Input Voltage (Note 3) ..... –0.3V to (V

Digital Input Voltage .................... –0.3V to (V

Digital Output Voltage ................– 0.3V to (OV

Power Dissipation............................................ 1500mW

Operating Temperature Range

LTC2288C, LTC2287C, LTC2286C........... 0°C to 70°C

LTC2288I, LTC2287I, LTC2286I .......... –40°C to 85°C

Storage Temperature Range ..................–65°C to 125°C

Lead Temperature (Soldering, 10 sec).................. 300°C

+ 0.3V)

DD

+ 0.3V)

DD

+ 0.3V)

DD

UUW

PACKAGE/ORDER I FOR ATIO

TOP VIEW

DD

64 GND

63 VDD62 SENSEA

61 VCMA

60 MODE

59 SHDNA

58 OEA

57 OFA

56 DA9

55 DA8

54 DA7

53 DA6

52 DA5

51 DA4

50 OGND

49 OV

1

A

INA+

–

A

2

INA

REFHA 3
REFHA 4
REFLA 5
REFLA 6

V

7

DD

CLKA

8

CLKB 9

V

10

DD

REFLB 11
REFLB 12
REFHB 13
REFHB 14

–

A

15

INB

+

A

16

INB

19

17

18

DD

V

GND

SENSEB

64-LEAD (9mm × 9mm) PLASTIC QFN

EXPOSED PAD (PIN 65) IS GND AND MUST BE SOLDERED TO PCB

T

65

20

NC 24

OEB 23

MUX 21

VCMB

SHDNB 22

UP PACKAGE

= 125°C, θJA = 20°C/W

JMAX

NC 25

NC 26

NC 27

DB0 28

ORDER PART

NUMBER

DB1 29

48 DA3
47 DA2
46 DA1
45 DA0
44 NC
43 NC
42 NC
41 NC
40 OFB
39 DB9
38 DB8
37 DB7
36 DB6
35 DB5
34 DB4
33 DB3

32

DD

DB2 30

OV

OGND 31

QFN PART*

MARKING

LTC2288CUP
LTC2288IUP
LTC2287CUP

LTC2288UP
LTC2287UP

LTC2286UP
LTC2287IUP
LTC2286CUP
LTC2286IUP

Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature grade is identified by a label on the shipping container.

U

CO VERTER CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. (Note 4)

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS

Resolution ● 10 10 10 Bits
(No Missing Codes)

Integral Linearity Error Differential Analog Input (Note 5) ● –0.6 ±0.1 0.6 – 0.6 ±0.1 0.6 –0.6 ±0.1 0.6 LSB
Differential Differential Analog Input ● – 0.5 ±0.05 0.5 –0.5 ±0.05 0.5 –0.5 ±0.05 0.5 LSB

Linearity Error
Offset Error (Note 6) ● –12 ±212–12±212–12±212 mV
Gain Error External Reference ● –2.5 ±0.5 2.5 –2.5 ±0.5 2.5 –2.5 ±0.5 2.5 %FS
Offset Drift ±10 ±10 ±10 µV/°C
Full-Scale Drift Internal Reference ±30 ±30 ±30 ppm/°C

External Reference ±15 ±15 ±15 ppm/°C
Gain Matching External Reference ±0.3 ±0.3 ±0.3 %FS
Offset Matching ±2 ±2 ±2mV
Transition Noise SENSE = 1V 0.07 0.07 0.07 LSB

The ● denotes the specifications which apply over the full operating

LTC2288 LTC2287 LTC2286

RMS

228876f

2

LTC2288/LTC2287/LTC2286

UU

A ALOG I PUT

specifications are at TA = 25°C. (Note 4)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IN

V

IN,CM

I

IN

I

SENSE

I

MODE

t

AP

t

JITTER

CMRR Analog Input Common Mode Rejection Ratio 80 dB

U

Analog Input Range (A

Analog Input Common Mode Differential Input (Note 7) ● 1 1.5 1.9 V

Analog Input Leakage Current 0V < A

SENSEA, SENSEB Input Leakage 0V < SENSEA, SENSEB < 1V ● –3 3 µA

MODE Input Leakage Current 0V < MODE < V

Sample-and-Hold Acquisition Delay Time 0 ns

Sample-and-Hold Acquisition Delay Time Jitter 0.2 ps

Full Power Bandwidth Figure 8 Test Circuit 575 MHz

W

DY A IC ACCURACY

otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 4)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS

SNR Signal-to-Noise Ratio 5MHz Input 61.8 61.8 61.8 dB

SFDR 5MHz Input 85 85 85 dB

SFDR 5MHz Input 85 85 85 dB

S/(N+D) 5MHz Input 61.8 61.8 61.8 dB

I

MD

Spurious Free
Dynamic Range
2nd or 3rd
Harmonic

Spurious Free
Dynamic Range
4th Harmonic
or Higher

Signal-to-Noise
Plus Distortion
Ratio

Intermodulation
Distortion

Crosstalk fIN = Nyquist –110 –110 –110 dB

The ● denotes the specifications which apply over the full operating temperature range, otherwise

+

–

–A

IN

) 2.7V < V

IN

< 3.4V (Note 7) ● 1V to 2V V

DD

+

–

, A

< V

IN

IN

DD

DD

● –1 1 µA

● –3 3 µA

RMS

The ● denotes the specifications which apply over the full operating temperature range,

LTC2288 LTC2287 LTC2286

12.5MHz Input ● 60 61.8 dB

20MHz Input ● 60 61.8 dB

30MHz Input ● 60 61.8 dB

70MHz Input 61.7 61.7 61.6 dB

140MHz Input 61.6 61.6 61.6 dB

12.5MHz Input ● 69 85 dB

20MHz Input ● 69 85 dB

30MHz Input ● 69 85 dB

70MHz Input 85 85 85 dB

140MHz Input 80 80 80 dB

12.5MHz Input ● 74 85 dB

20MHz Input ● 74 85 dB

30MHz Input ● 74 85 dB

70MHz Input 85 85 85 dB

140MHz Input 85 85 85 dB

12.5MHz Input ● 60 61.8 dB

20MHz Input ● 60 61.7 dB

30MHz Input ● 60 61.8 dB

70MHz Input 61.7 61.6 61.6 dB

140MHz Input 61.6 61.6 61.5 dB

fIN = Nyquist, 85 85 85 dB
Nyquist + 1MHz

228876f

3

LTC2288/LTC2287/LTC2286

UU U

I TER AL REFERE CE CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

VCM Output Voltage I

VCM Output Tempco ±30 ppm/°C

VCM Line Regulation 2.7V < VDD < 3.3V 3 mV/V

VCM Output Resistance –1mA < I

= 0 1.475 1.500 1.525 V

OUT

(Note 4)

< 1mA 4 Ω

OUT

UU

DIGITAL I PUTS A D DIGITAL OUTPUTS

full operating temperature range, otherwise specifications are at TA = 25°C. (Note 4)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

LOGIC INPUTS (CLK, OE, SHDN, MUX)

V

IH

V

IL

I

IN

C

IN

LOGIC OUTPUTS

OVDD = 3V

C

OZ

I

SOURCE

I

SINK

V

OH

V

OL

OV

= 2.5V

DD

V

OH

V

OL

OVDD = 1.8V

V

OH

V

OL

High Level Input Voltage VDD = 3V ● 2V

Low Level Input Voltage VDD = 3V ● 0.8 V

Input Current VIN = 0V to V

Input Capacitance (Note 7) 3 pF

Hi-Z Output Capacitance OE = High (Note 7) 3 pF

Output Source Current V

Output Sink Current V

High Level Output Voltage IO = –10µA 2.995 V

Low Level Output Voltage IO = 10µA 0.005 V

High Level Output Voltage IO = –200µA 2.49 V

Low Level Output Voltage IO = 1.6mA 0.09 V

High Level Output Voltage IO = –200µA 1.79 V

Low Level Output Voltage IO = 1.6mA 0.09 V

= 0V 50 mA

OUT

= 3V 50 mA

OUT

= –200µA ● 2.7 2.99 V

I

O

= 1.6mA ● 0.09 0.4 V

I

O

The ● denotes the specifications which apply over the

DD

● –10 10 µA

4

228876f

LTC2288/LTC2287/LTC2286

WU

POWER REQUIRE E TS

range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS

V

OV

IV

P

P

P

DD

DD

DD

DISS

SHDN

NAP

Analog Supply (Note 9) ● 2.7 3 3.4 2.7 3 3.4 2.7 3 3.4 V
Voltage

Output Supply (Note 9) ● 0.5 3 3.6 0.5 3 3.6 0.5 3 3.6 V
Voltage

Supply Current Both ADCs at f

Power Dissipation Both ADCs at f

Shutdown Power SHDN = H, 2 2 2 mW
(Each Channel) OE = H, No CLK

Nap Mode Power SHDN = H, 15 15 15 mW
(Each Channel) OE = L, No CLK

= 25°C. (Note 8)

A

The ● denotes the specifications which apply over the full operating temperature

LTC2288 LTC2287 LTC2286

S(MAX)

S(MAX)

● 133 150 78 95 50 60 mA

● 400 450 235 285 150 180 mW

UW

TI I G CHARACTERISTICS

range, otherwise specifications are at TA = 25°C. (Note 4)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS

f

s

t

L

t

H

t

AP

t

D

t

MD

Pipeline 6 6 6 Cycles
Latency

Sampling Frequency (Note 9) ● 165140125MHz

CLK Low Time Duty Cycle Stabilizer Off ● 7.3 7.7 500 11.8 12.5 500 18.9 20 500 ns

Duty Cycle Stabilizer On
(Note 7)

CLK High Time Duty Cycle Stabilizer Off ● 7.3 7.7 500 11.8 12.5 500 18.9 20 500 ns

Duty Cycle Stabilizer On
(Note 7)

Sample-and-Hold 0 0 0 ns
Aperture Delay

CLK to DATA Delay CL = 5pF (Note 7) ● 1.4 2.7 5.4 1.4 2.7 5.4 1.4 2.7 5.4 ns

MUX to DATA Delay CL = 5pF (Note 7) ● 1.4 2.7 5.4 1.4 2.7 5.4 1.4 2.7 5.4 ns

Data Access Time CL = 5pF (Note 7) ● 4.3 10 4.3 10 4.3 10 ns
After OE↓

BUS Relinquish Time (Note 7) ● 3.3 8.5 3.3 8.5 3.3 8.5 ns

The ● denotes the specifications which apply over the full operating temperature

LTC2288 LTC2287 LTC2286

● 5 7.7 500 5 12.5 500 5 20 500 ns

● 5 7.7 500 5 12.5 500 5 20 500 ns

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 GND and OGND
wired together (unless otherwise noted).

Note 3: When these pin voltages are taken below GND or above V
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above V

Note 4: VDD = 3V, f
25MHz (LTC2286), input range = 2V
otherwise noted.

= 65MHz (LTC2288), 40MHz (LTC2287), or

SAMPLE

with differential drive, unless

P-P

without latchup.

DD

DD

, they

Note 5: 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 6: Offset error is the offset voltage measured from –0.5 LSB when
the output code flickers between 00 0000 0000 and 11 1111 1111.

Note 7: Guaranteed by design, not subject to test.
Note 8: V

25MHz (LTC2286), input range = 1V
current and power dissipation are the sum total for both channels with
both channels active.

Note 9: Recommended operating conditions.

= 3V, f

DD

= 65MHz (LTC2288), 40MHz (LTC2287), or

SAMPLE

with differential drive. The supply

P-P

228876f

5

LTC2288/LTC2287/LTC2286

CODE

70000

60000

50000

40000

30000

20000

10000

0

512

65520

513

228876 G09

511

0

0

COUNT

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2288/LTC2287/LTC2286:
Crosstalk vs Input Frequency

–100

–105

–110

–115

CROSSTALK (dB)

–120

–125

–130

0

20 40 60 80

INPUT FREQUENCY (MHz)

LTC2288: 8192 Point FFT,
fIN = 5MHz, –1dB, 2V Range,
65Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

0

5

15

10

FREQUENCY (MHz)

LTC2288: 8192 Point FFT,
fIN = 140MHz, –1dB, 2V Range,
65Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

6

15

0

10

5

FREQUENCY (MHz)

LTC2288: Typical INL,
2V Range, 65Msps

1.00

0.75

0.50

0.25

0

–0.25

INL ERROR (LSB)

–0.50

–0.75

228876 G01

100

–1.00

0

256

512

CODE

768

1024

228876 G02

LTC2288: 8192 Point FFT,
fIN = 30MHz, –1dB, 2V Range,
65Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

20

25

30

228876 G04

0

10

5

FREQUENCY (MHz)

20

15

25

30

228876 G05

LTC2288: Typical DNL,
2V Range, 65Msps

1.00

0.75

0.50

0.25

0

–0.25

DNL ERROR (LSB)

–0.50

–0.75

–1.00

0

256

512

CODE

LTC2288: 8192 Point FFT,
fIN = 70MHz, –1dB, 2V Range,
65Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

0

5

15

10

FREQUENCY (MHz)

768

20

1024

22876 G03

25

30

228876 G06

LTC2288: 8192 Point 2-Tone FFT,
f

= 28.2MHz and 26.8MHz,

IN

–1dB, 2V Range 65Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

20

25

30

228876 G07

–120

0

10

5

FREQUENCY (MHz)

25

30

228876 G08

20

15

LTC2288: Grounded Input
Histogram, 65Msps

228876f

LTC2288/LTC2287/LTC2286

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2288: SNR vs Input Frequency,
–1dB, 2V Range, 65Msps

62.5

61.5

60.5

LTC2288: SFDR vs Input Frequency,
–1dB, 2V Range, 65Msps

100

95

90

85

LTC2288: SNR and SFDR vs
Sample Rate, 2V Range,
f

= 5MHz, –1dB

IN

100

90

80

SFDR

59.5

SNR (dBFS)

58.5

57.5
0

50
INPUT FREQUENCY (MHz)

100

150

200

228876 G10

LTC2288: SNR vs Input Level,
fIN = 30MHz, 2V Range, 65Msps

80

70

60

50

40

30

SNR (dBc AND dBFS)

20

10

0

–50 –40

–60

LTC2288: I

dBFS

–30

INPUT LEVEL (dBFS)

vs Sample Rate,

VDD

5MHz Sine Wave Input, –1dB

155

dBc

–20

80

SFDR (dBFS)

75

70

65

0

–10

0

228876 G13

50 100 200

INPUT FREQUENCY (MHz)

150

228876 G11

LTC2288: SFDR vs Input Level,
fIN = 30MHz, 2V Range, 65Msps

120

110

100

90

80

70

60

50

40

SFDR (dBc AND dBFS)

30

20

10

0

–60

–50

LTC2288: I
5MHz Sine Wave Input, –1dB,
O

= 1.8V

VDD

12

70

SNR AND SFDR (dBFS)

60

50

10 20 30

0

dBFS

dBc

80dBc SFDR

REFERENCE LINE

–40 –30

INPUT LEVEL (dBFS)

OVDD

–20

vs Sample Rate,

SNR

60 70 90 100

40 50

SAMPLE RATE (Msps)

–10 0

228876 G14

80

110

228876 G12

145

135

(mA)

125

VDD

I

115

105

95

2V RANGE

0

10 30

20

40

SAMPLE RATE (Msps)

1V RANGE

50

10

8

(mA)

6

OVDD

I

4

2

70

60

80

228876 G15

0

0

10 30

20

SAMPLE RATE (Msps)

70

40

60

50

228876 G16

80

228876f

7

LTC2288/LTC2287/LTC2286

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2287: Typical INL,
2V Range, 40Msps

1.00

0.75

0.50

0.25

0

–0.25

INL ERROR (LSB)

–0.50

–0.75

–1.00

0

256

512

CODE

LTC2287: 8192 Point FFT,
fIN = 30MHz, –1dB, 2V Range,
40Msps

0
–10
–20

–30
–40

–50

–60
–70

AMPLITUDE (dB)

–80

–90

–100

–110

–120

0

5

10

FREQUENCY (MHz)

LTC2287: 8192 Point 2-Tone FFT,
fIN = 21.6MHz and 23.6MHz,
–1dB, 2V Range, 40Msps

0
–10
–20

–30
–40

–50

–60
–70

AMPLITUDE (dB)

–80

–90

–100

–110

–120

0

5

10

FREQUENCY (MHz)

768

15

15

1024

228876 G17

20

228876 G20

20

228876 G23

LTC2287: Typical DNL,
2V Range, 40Msps

1.00

0.75

0.50

0.25

0

–0.25

DNL ERROR (LSB)

–0.50

–0.75

–1.00

0

256

512

CODE

LTC2287: 8192 Point FFT,
fIN = 70MHz, –1dB, 2V Range,
40Msps

0
–10
–20

–30
–40

–50

–60
–70

AMPLITUDE (dB)

–80

–90

–100

–110

–120

0

5

10

FREQUENCY (MHz)

LTC2287: Grounded Input
Histogram, 40Msps

70000

60000

50000

40000

COUNT

30000

20000

10000

0

0

510

65520

511

CODE

768

15

0

512

228876 G18

228876 G21

228876 G24

1024

20

LTC2287: 8192 Point FFT,
fIN = 5MHz, –1dB, 2V Range,
40Msps

0
–10
–20

–30
–40

–50

–60
–70

AMPLITUDE (dB)

–80

–90

–100

–110

–120

0

5

10

FREQUENCY (MHz)

LTC2287: 8192 Point FFT,
fIN = 140MHz, –1dB, 2V Range,
40Msps

0
–10
–20

–30
–40

–50

–60
–70

AMPLITUDE (dB)

–80

–90

–100

–110

–120

0

5

10

FREQUENCY (MHz)

LTC2287: SNR vs Input Frequency,
–1dB, 2V Range, 40Msps

62.5

61.5

60.5

59.5

SNR (dBFS)

58.5

57.5
0

50
INPUT FREQUENCY (MHz)

100

150

15

15

20

228876 G19

20

228876 G22

200

228876 G25

228876f

8

LTC2288/LTC2287/LTC2286

FREQUENCY (MHz)

0

AMPLITUDE (dB)

–80

–20

–10

0

4

8

10

228876 G34

–100

–110

–40

–60

–90

–30

–120

–50

–70

2

6

12

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2287: SNR and SFDR vs
LTC2287: SFDR vs Input Frequency,
–1dB, 2V Range, 40Msps

100

95

90

85

80

SFDR (dBFS)

75

70

65

50 100 200

0

INPUT FREQUENCY (MHz)

150

228876 G26

Sample Rate, 2V Range,

fIN = 5MHz, –1dB

100

90

80

70

SNR AND SFDR (dBFS)

60

50

10 20 30

0

SAMPLE RATE (Msps)

SFDR

SNR

40 50

60 70

228876 G27

80

LTC2287: SNR vs Input Level,
fIN = 5MHz, 2V Range, 40Msps

80

70

60

50

40

30

SNR (dBc AND dBFS)

20

10

0

–50 –40

–60

dBFS

dBc

–30

INPUT LEVEL (dBFS)

–20

–10

0

228876 G28

LTC2287: SFDR vs Input Level,
fIN = 5MHz, 2V Range, 40Msps

120

110

100

90

80

70

60

50

40

SFDR (dBc AND dBFS)

30

20

10

0

–60

–50

dBFS

dBc

–40 –30

INPUT LEVEL (dBFS)

LTC2286: Typical INL,
2V Range, 25Msps

1.00

0.75

0.50

0.25

0

–0.25

INL ERROR (LSB)

–0.50

–0.75

–1.00

0

256

512

CODE

80dBc SFDR

REFERENCE LINE

–20

–10 0

228876 G29

768

228876 G32

1024

LTC2287: I

vs Sample Rate,

VDD

5MHz Sine Wave Input, –1dB

100

90

(mA)

VDD

I

80

70

60

0

2V RANGE

10

20

SAMPLE RATE (Msps)

LTC2286: Typical DNL,
2V Range, 25Msps

1.00

0.75

0.50

0.25

0

–0.25

DNL ERROR (LSB)

–0.50

–0.75

–1.00

0

256

512

CODE

1V RANGE

30

768

40

228876 G30

228876 G33

50

1024

LTC2287: I

vs Sample Rate,

OVDD

5MHz Sine Wave Input, –1dB,
O

= 1.8V

VDD

8

6

(mA)

4

OVDD

I

2

0

10

0

20

SAMPLE RATE (Msps)

LTC2286: 8192 Point FFT,
fIN = 5MHz, –1dB, 2V Range,
25Msps

30

40

50

228876 G31

228876f

9

LTC2288/LTC2287/LTC2286

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2286: 8192 Point FFT,
fIN = 30MHz, –1dB, 2V Range,
25Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

0

4

2

FREQUENCY (MHz)

8

6

LTC2286: 8192 Point 2-Tone FFT,
fIN = 10.9MHz and 13.8MHz,
–1dB, 2V Range, 25Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

0

4

2

FREQUENCY (MHz)

8

6

LTC2286: SFDR vs Input
Frequency, –1dB, 2V Range,
25Msps

100

95

90

85

80

SFDR (dBFS)

75

70

65

50 100 200

0

INPUT FREQUENCY (MHz)

150

LTC2286: 8192 Point FFT,

= 70MHz, –1dB, 2V Range,

f

IN

25Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

10

12

228876 G35

0

4

2

FREQUENCY (MHz)

8

6

10

12

228876 G36

LTC2286: Grounded Input

Histogram, 25Msps

70000

60000

50000

40000

COUNT

30000

20000

10000

0

0

10

12

228876 G38

511

65520

512

CODE

0

513

228876 G39

LTC2286: 8192 Point FFT,
fIN = 140MHz, –1dB, 2V Range,
25Msps

0

–10

–20

–30

–40

–50

–60

–70

–80

AMPLITUDE (dB)

–90

–100

–110

–120

0

4

2

FREQUENCY (MHz)

8

6

LTC2286: SNR vs Input Frequency,
–1dB, 2V Range, 25Msps

62.5

61.5

60.5

59.5

SNR (dBFS)

58.5

57.5
0

50
INPUT FREQUENCY (MHz)

100

150

10

12

228876 G37

200

228876 G40

LTC2286: SNR and SFDR vs

228876 G41

Sample Rate, 2V Range,
fIN = 5MHz, –1dB

100

90

80

70

SNR AND SFDR (dBFS)

60

50

51015

0

20 25

SAMPLE RATE (Msps)

SFDR

SNR

30 35 45 50

40

228876 G42

LTC2286: SNR vs Input Level,
fIN = 5MHz, 2V Range, 25Msps

80

70

60

50

40

30

SNR (dBc AND dBFS)

20

10

0

–50 –40

–60

dBFS

dBc

–30

INPUT LEVEL (dBFS)

–20

–10

0

228876 G43

228876f

10

LTC2288/LTC2287/LTC2286

0

10

20

515

25

30

35

SAMPLE RATE (Msps)

I

OVDD

(mA)

228876 G46

6

4

2

0

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2286: SFDR vs Input Level,

= 5MHz, 2V Range, 25Msps

f

IN

120

110

100

90

80

70

60

50

40

SFDR (dBc AND dBFS)

30

20

10

0

–60

U

dBFS

dBc

–40 –30

–50

INPUT LEVEL (dBFS)

80dBc SFDR

REFERENCE LINE

UU

–20

–10 0

228876 G44

LTC2286: I
5MHz Sine Wave Input, –1dB

70

60

(mA)

50

VDD

I

40

30

0

PI FU CTIO S

+

A

(Pin 1): Channel A Positive Differential Analog

INA

Input.

–

A

(Pin 2): Channel A Negative Differential Analog

INA

Input.

REFHA (Pins 3, 4): Channel A High Reference. Short
together and bypass to Pins 5, 6 with a 0.1µF ceramic chip
capacitor as close to the pin as possible. Also bypass to
Pins 5, 6 with an additional 2.2µF ceramic chip capacitor
and to ground with a 1µF ceramic chip capacitor.

REFLA (Pins 5, 6): Channel A Low Reference. Short
together and bypass to Pins 3, 4 with a 0.1µF ceramic chip
capacitor as close to the pin as possible. Also bypass to
Pins 3, 4 with an additional 2.2µF ceramic chip capacitor
and to ground with a 1µF ceramic chip capacitor.

VDD (Pins 7, 10, 18, 63): Analog 3V Supply. Bypass to
GND with 0.1µF ceramic chip capacitors.

CLKA (Pin 8): Channel A Clock Input. The input sample
starts on the positive edge.

CLKB (Pin 9): Channel B Clock Input. The input sample
starts on the positive edge.

REFLB (Pins 11, 12): Channel B Low Reference. Short
together and bypass to Pins 13, 14 with a 0.1µF ceramic

vs Sample Rate,

VDD

2V RANGE

1V RANGE

515

10

SAMPLE RATE (Msps)

20

chip capacitor as close to the pin as possible. Also bypass
to Pins 13, 14 with an additional 2.2µF ceramic chip ca-
pacitor and to ground with a 1µF ceramic chip capacitor.

REFHB (Pins 13, 14): Channel B High Reference. Short
together and bypass to Pins 11, 12 with a 0.1µF ceramic
chip capacitor as close to the pin as possible. Also bypass
to Pins 11, 12 with an additional 2.2µF ceramic chip ca-
pacitor and to ground with a 1µF ceramic chip capacitor.

–

A

INB

Input.

+

A

INB

Input.

GND (Pins 17, 64): ADC Power Ground.

SENSEB (Pin 19): Channel B Reference Programming Pin.

Connecting SENSEB to V
and a ±0.5V input range. VDD selects the internal reference
and a ±1V input range. An external reference greater than

0.5V and less than 1V applied to SENSEB selects an input
range of ±V

V

CMB

Mode Bias. Bypass to ground with 2.2µF ceramic chip
capacitor. Do not connect to V

LTC2286: I

vs Sample Rate,

OVDD

5MHz Sine Wave Input, –1dB,
O

= 1.8V

VDD

30

25

35

228876 G45

(Pin 15): Channel B Negative Differential Analog

(Pin 16): Channel B Positive Differential Analog

selects the internal reference

CMB

SENSEB

. ±1V is the largest valid input range.

(Pin 20): Channel B 1.5V Output and Input Common

.

CMA

228876f

11

LTC2288/LTC2287/LTC2286

U

UU

PI FU CTIO S

MUX (Pin 21): Digital Output Multiplexer Control. If MUX
is High, Channel A comes out on DA0-DA13, OFA; Channel B
comes out on DB0-DB13, OFB. If MUX is Low, the output
busses are swapped and Channel A comes out on DB0­DB13, OFB; Channel B comes out on DA0-DA13, OFA. To
multiplex both channels onto a single output bus, connect
MUX, CLKA and CLKB together.

SHDNB (Pin 22): Channel B Shutdown Mode Selection
Pin. Connecting SHDNB to GND and OEB to GND results
in normal operation with the outputs enabled. Connecting
SHDNB to GND and OEB to VDD results in normal opera­tion with the outputs at high impedance. Connecting
SHDNB to VDD and OEB to GND results in nap mode with
the outputs at high impedance. Connecting SHDNB to V
and OEB to VDD results in sleep mode with the outputs at
high impedance.

OEB (Pin 23): Channel B Output Enable Pin. Refer to
SHDNB pin function.

NC (Pins 24 to 27, 41 to 44): Do Not Connect These Pins.

DB0 – DB9 (Pins 28 to 30, 33 to 39): Channel B Digital

Outputs. DB9 is the MSB.

OGND (Pins 31, 50): Output Driver Ground.

OVDD (Pins 32, 49): Positive Supply for the Output Driv-

ers. Bypass to ground with 0.1µF ceramic chip capacitor.

OFB (Pin 40): Channel B Overflow/Underflow Output.
High when an overflow or underflow has occurred.

DA0 – DA9 (Pins 45 to 48, 51 to 56): Channel A Digital
Outputs. DA9 is the MSB.

OFA (Pin 57): Channel A Overflow/Underflow Output.
High when an overflow or underflow has occurred.

DD

SHDNA (Pin 59): Channel A Shutdown Mode Selection
Pin. Connecting SHDNA to GND and OEA to GND results
in normal operation with the outputs enabled. Connecting
SHDNA to GND and OEA to VDD results in normal opera­tion with the outputs at high impedance. Connecting
SHDNA to V
the outputs at high impedance. Connecting SHDNA to V
and OEA to VDD results in sleep mode with the outputs at
high impedance.

MODE (Pin 60): Output Format and Clock Duty Cycle
Stabilizer Selection Pin. Note that MODE controls both
channels. Connecting MODE to GND selects straight bi­nary output format and turns the clock duty cycle stabilizer
off. 1/3 VDD selects straight binary output format and turns
the clock duty cycle stabilizer on. 2/3 VDD selects 2’s
complement output format and turns the clock duty cycle
stabilizer on. VDD selects 2’s complement output format
and turns the clock duty cycle stabilizer off.

V

(Pin 61): Channel A 1.5V Output and Input Common

CMA

Mode Bias. Bypass to ground with 2.2µF ceramic chip
capacitor. Do not connect to V

SENSEA (Pin 62): Channel A Reference Programming Pin.
Connecting SENSEA to V
and a ±0.5V input range. VDD selects the internal reference
and a ±1V input range. An external reference greater than

0.5V and less than 1V applied to SENSEA selects an input
range of ±V

GND (Exposed Pad) (Pin 65): ADC Power Ground. The
Exposed Pad on the bottom of the package needs to be
soldered to ground.

and OEA to GND results in nap mode with

DD

.

CMB

selects the internal reference

CMA

SENSEA

. ±1V is the largest valid input range.

DD

OEA (Pin 58): Channel A Output Enable Pin. Refer to
SHDNA pin function.

12

228876f

LTC2288/LTC2287/LTC2286

UU

W

FUNCTIONAL BLOCK DIAGRA

+

A

IN

A

V

2.2µF

SENSE

INPUT

S/H

–

IN

CM

1.5V

REFERENCE

RANGE
SELECT

FIRST PIPELINED

ADC STAGE

REF

BUF

SECOND PIPELINED

ADC STAGE

DIFF

REF

AMP

THIRD PIPELINED

ADC STAGE

INTERNAL CLOCK SIGNALSREFH REFL

FOURTH PIPELINED

CLOCK/DUTY

CYCLE

CONTROL

ADC STAGE

CONTROL

LOGIC

FIFTH PIPELINED

ADC STAGE

SIXTH PIPELINED

ADC STAGE

SHIFT REGISTER

AND CORRECTION

OUTPUT

DRIVERS

OV

DD

OF

D9

•

•

•

D0

REFH

1µF1µF

0.1µF

2.2µF

REFL

CLK

SHDN

OEMODE

Figure 1. Functional Block Diagram (Only One Channel is Shown)

OGND

228876 F01

228876f

13

LTC2288/LTC2287/LTC2286

WUW

TI I G DIAGRA S

Dual Digital Output Bus Timing

(Only One Channel is Shown)

t

AP

ANALOG

INPUT

CLK

D0-D9, OF

ANALOG
INPUT A

ANALOG
INPUT B

N

t

H

t

D

N – 6

N + 1

t

L

Multiplexed Digital Output Bus Timing

t

APA

A

t

APB

B

A + 1

B + 1

N + 2

N – 5 N – 4 N – 3 N – 2

A + 2

B + 2

N + 3

N + 4

N + 5

N – 1

228876 TD01

A + 4

A + 3

B + 4

B + 3

CLKA = CLKB = MUX

D0A-D9A, OFA

D0B-D9B, OFB

t

H

A – 6

B – 6

t

L

B – 6

t

D

A – 6

A – 5

B – 5

B – 5

A – 5

A – 4

B – 4

t

MD

B – 4

A – 4

A – 3

B – 3

B – 3

A – 3

A – 2

B – 2

228876 TD02

14

228876f

WUUU

APPLICATIO S I FOR ATIO

LTC2288/LTC2287/LTC2286

DYNAMIC PERFORMANCE

Signal-to-Noise Plus Distortion Ratio

The signal-to-noise plus distortion ratio [S/(N + D)] is the
ratio between the RMS amplitude of the fundamental input
frequency and the RMS amplitude of all other frequency
components at the ADC output. The output is band limited
to frequencies above DC to below half the sampling
frequency.

Signal-to-Noise Ratio

The signal-to-noise ratio (SNR) is the ratio between the
RMS amplitude of the fundamental input frequency and
the RMS amplitude of all other frequency components
except the first five harmonics and DC.

Total Harmonic Distortion

Total harmonic distortion is the ratio of the RMS sum of all
harmonics of the input signal to the fundamental itself. The
out-of-band harmonics alias into the frequency band
between DC and half the sampling frequency. THD is
expressed as:

2fb + fa, 2fa – fb and 2fb – fa. The intermodulation
distortion is defined as the ratio of the RMS value of either
input tone to the RMS value of the largest 3rd order
intermodulation product.

Spurious Free Dynamic Range (SFDR)

Spurious free dynamic range is the peak harmonic or
spurious noise that is the largest spectral component
excluding the input signal and DC. This value is expressed
in decibels relative to the RMS value of a full scale input
signal.

Input Bandwidth

The input bandwidth is that input frequency at which the
amplitude of the reconstructed fundamental is reduced by
3dB for a full scale input signal.

Aperture Delay Time

The time from when CLK reaches midsupply to the instant
that the input signal is held by the sample and hold circuit.

Aperture Delay Jitter

THD = 20Log √(V22 + V32 + V42 + . . . Vn2)/V1

where V1 is the RMS amplitude of the fundamental fre­quency and V2 through Vn are the amplitudes of the
second through nth harmonics. The THD calculated in this
data sheet uses all the harmonics up to the fifth.

Intermodulation Distortion

If the ADC input signal consists of more than one spectral
component, the ADC transfer function nonlinearity can
produce intermodulation distortion (IMD) in addition to
THD. IMD is the change in one sinusoidal input caused by
the presence of another sinusoidal input at a different
frequency.

If two pure sine waves of frequencies fa and fb are applied
to the ADC input, nonlinearities in the ADC transfer func­tion can create distortion products at the sum and differ­ence frequencies of mfa ± nfb, where m and n = 0, 1, 2, 3,
etc. The 3rd order intermodulation products are 2fa + fb,

The variation in the aperture delay time from conversion to
conversion. This random variation will result in noise
when sampling an AC input. The signal to noise ratio due
to the jitter alone will be:

SNR

Crosstalk

Crosstalk is the coupling from one channel (being driven
by a full-scale signal) onto the other channel (being driven
by a –1dBFS signal).

CONVERTER OPERATION

As shown in Figure 1, the LTC2288/LTC2287/LTC2286 are
dual CMOS pipelined multistep converters. The convert­ers have six pipelined ADC stages; a sampled analog input
will result in a digitized value six cycles later (see the
Timing Diagram section). For optimal AC performance the
analog inputs should be driven differentially. For cost

= –20log (2π) • fIN • t

JITTER

JITTER

228876f

15

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

sensitive applications, the analog inputs can be driven
single-ended with slightly worse harmonic distortion. The
CLK input is single-ended. The LTC2288/LTC2287/
LTC2286 have two phases of operation, determined by the
state of the CLK input pin.

Each pipelined stage shown in Figure 1 contains an ADC,
a reconstruction DAC and an interstage residue amplifier.
In operation, the ADC quantizes the input to the stage and
the quantized value is subtracted from the input by the
DAC to produce a residue. The residue is amplified and
output by the residue amplifier. Successive stages operate
out of phase so that when the odd stages are outputting
their residue, the even stages are acquiring that residue
and vice versa.

When CLK is low, the analog input is sampled differentially
directly onto the input sample-and-hold capacitors, inside
the “Input S/H” shown in the block diagram. At the instant
that CLK transitions from low to high, the sampled input is
held. While CLK is high, the held input voltage is buffered
by the S/H amplifier which drives the first pipelined ADC
stage. The first stage acquires the output of the S/H during
this high phase of CLK. When CLK goes back low, the first
stage produces its residue which is acquired by the
second stage. At the same time, the input S/H goes back
to acquiring the analog input. When CLK goes back high,
the second stage produces its residue which is acquired
by the third stage. An identical process is repeated for the

third, fourth and fifth stages, resulting in a fifth stage
residue that is sent to the sixth stage ADC for final
evaluation.

Each ADC stage following the first has additional range to
accommodate flash and amplifier offset errors. Results
from all of the ADC stages are digitally synchronized such
that the results can be properly combined in the correction
logic before being sent to the output buffer.

SAMPLE/HOLD OPERATION AND INPUT DRIVE

Sample/Hold Operation

Figure 2 shows an equivalent circuit for the LTC2288/
LTC2287/LTC2286 CMOS differential sample-and-hold.
The analog inputs are connected to the sampling capaci­tors (C

SAMPLE

shown attached to each input (C

) through NMOS transistors. The capacitors

PARASITIC

) are the summa-

tion of all other capacitance associated with each input.

During the sample phase when CLK is low, the transistors
connect the analog inputs to the sampling capacitors and
they charge to and track the differential input voltage.
When CLK transitions from low to high, the sampled input
voltage is held on the sampling capacitors. During the hold
phase when CLK is high, the sampling capacitors are
disconnected from the input and the held voltage is passed
to the ADC core for processing. As CLK transitions from
high to low, the inputs are reconnected to the sampling

16

LTC2288/LTC2287/LTC2286

15Ω

+

A

IN

15Ω

–

A

IN

CLK

V

DD

C

PARASITIC

V

DD

Figure 2. Equivalent Input Circuit

1pF

C

PARASITIC

1pF

V

DD

C

SAMPLE

4pF

C

SAMPLE

4pF

228876 F02

228876f

WUUU

APPLICATIO S I FOR ATIO

LTC2288/LTC2287/LTC2286

capacitors to acquire a new sample. Since the sampling
capacitors still hold the previous sample, a charging glitch
proportional to the change in voltage between samples will
be seen at this time. If the change between the last sample
and the new sample is small, the charging glitch seen at
the input will be small. If the input change is large, such as
the change seen with input frequencies near Nyquist, then
a larger charging glitch will be seen.

Single-Ended Input

For cost sensitive applications, the analog inputs can be
driven single-ended. With a single-ended input the har­monic distortion and INL will degrade, but the SNR and
DNL will remain unchanged. For a single-ended input, A
should be driven with the input signal and A

–

should be

IN

IN

+

connected to 1.5V or VCM.

Common Mode Bias

For optimal performance the analog inputs should be
driven differentially. Each input should swing ±0.5V for
the 2V range or ±0.25V for the 1V range, around a
common mode voltage of 1.5V. The VCM output pin may
be used to provide the common mode bias level. VCM can
be tied directly to the center tap of a transformer to set the
DC input level or as a reference level to an op amp
differential driver circuit. The VCM pin must be bypassed to
ground close to the ADC with a 2.2µF or greater capacitor.

Input Drive Impedance

As with all high performance, high speed ADCs, the
dynamic performance of the LTC2288/LTC2287/LTC2286
can be influenced by the input drive circuitry, particularly
the second and third harmonics. Source impedance and
reactance can influence SFDR. At the falling edge of CLK,
the sample-and-hold circuit will connect the 4pF sampling
capacitor to the input pin and start the sampling period.
The sampling period ends when CLK rises, holding the
sampled input on the sampling capacitor. Ideally the input
circuitry should be fast enough to fully charge
the sampling capacitor during the sampling period
1/(2F

ENCODE

); however, this is not always possible and the

incomplete settling may degrade the SFDR. The sampling

glitch has been designed to be as linear as possible to
minimize the effects of incomplete settling.

For the best performance, it is recommended to have a
source impedance of 100Ω or less for each input. The
source impedance should be matched for the differential
inputs. Poor matching will result in higher even order
harmonics, especially the second.

Input Drive Circuits

Figure 3 shows the LTC2288/LTC2287/LTC2286 being
driven by an RF transformer with a center tapped second­ary. The secondary center tap is DC biased with VCM,
setting the ADC input signal at its optimum DC level.
Terminating on the transformer secondary is desirable, as
this provides a common mode path for charging glitches
caused by the sample and hold. Figure 3 shows a 1:1 turns
ratio transformer. Other turns ratios can be used if the
source impedance seen by the ADC does not exceed 100Ω
for each ADC input. A disadvantage of using a transformer
is the loss of low frequency response. Most small RF
transformers have poor performance at frequencies be­low 1MHz.

V

CM

2.2µF

0.1µFT1

ANALOG

INPUT

Figure 3. Single-Ended to Differential Conversion
Using a Transformer

1:1

T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE

25Ω

25Ω

25Ω

0.1µF

25Ω

12pF

+

A

IN

LTC2288
LTC2287
LTC2286

–

A

IN

228876 F03

Figure 4 demonstrates the use of a differential amplifier to
convert a single ended input signal into a differential input
signal. The advantage of this method is that it provides low
frequency input response; however, the limited gain band­width of most op amps will limit the SFDR at high input
frequencies.

228876f

17

LTC2288/LTC2287/LTC2286

WUUU

APPLICATIO S I FOR ATIO

V

CM

2.2µF

A

12pF

A

+

IN

LTC2288
LTC2287
LTC2286

–

IN

228876 F04

ANALOG

INPUT

HIGH SPEED

DIFFERENTIAL

AMPLIFIER

+

+

CM

–

–

25Ω

25Ω

Figure 4. Differential Drive with an Amplifier

Figure 5 shows a single-ended input circuit. The imped­ance seen by the analog inputs should be matched. This
circuit is not recommended if low distortion is required.

V

CM

2.2µF

12pF

+

A

IN

LTC2288
LTC2287
LTC2286

–

A

IN

228876 F05

ANALOG

INPUT

1k

0.1µF

1k

25Ω

25Ω

0.1µF

Figure 5. Single-Ended Drive

V

CM

2.2µF

ANALOG

INPUT

0.1µF

T1

0.1µF

T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE

25Ω

25Ω

0.1µF

12Ω

12Ω

8pF

A

IN

A

IN

Figure 6. Recommended Front End Circuit for
Input Frequencies Between 70MHz and 170MHz

V

CM

2.2µF

ANALOG

INPUT

0.1µF

T1

0.1µF

T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE

25Ω

25Ω

0.1µF

A

IN

A

IN

Figure 7. Recommended Front End Circuit for
Input Frequencies Between 170MHz and 300MHz

+

–

+

–

LTC2288
LTC2287
LTC2286

228876 F06

LTC2288
LTC2287
LTC2286

228876 F07

The 25Ω resistors and 12pF capacitor on the analog inputs
serve two purposes: isolating the drive circuitry from the
sample-and-hold charging glitches and limiting the
wideband noise at the converter input.

For input frequencies above 70MHz, the input circuits of
Figure 6, 7 and 8 are recommended. The balun trans­former gives better high frequency response than a flux
coupled center tapped transformer. The coupling capaci­tors allow the analog inputs to be DC biased at 1.5V. In
Figure 8, the series inductors are impedance matching
elements that maximize the ADC bandwidth.

18

ANALOG

0.1µF

INPUT

T1

0.1µF

T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS, INDUCTORS
ARE 0402 PACKAGE SIZE

25Ω

25Ω

6.8nH

0.1µF

6.8nH

Figure 8. Recommended Front End Circuit for
Input Frequencies Above 300MHz

V

2.2µF

A

A

CM

IN

IN

+

–

LTC2288
LTC2287
LTC2286

228876 F08

228876f

WUUU

APPLICATIO S I FOR ATIO

LTC2288/LTC2287/LTC2286

Reference Operation

Figure 9 shows the LTC2288/LTC2287/LTC2286 refer­ence circuitry consisting of a 1.5V bandgap reference, a
difference amplifier and switching and control circuit. The
internal voltage reference can be configured for two pin
selectable input ranges of 2V (±1V differential) or 1V
(±0.5V differential). Tying the SENSE pin to VDD selects
the 2V range; tying the SENSE pin to V

selects the 1V

CM

range.

The 1.5V bandgap reference serves two functions: its
output provides a DC bias point for setting the common
mode voltage of any external input circuitry; additionally,
the reference is used with a difference amplifier to gener­ate the differential reference levels needed by the internal
ADC circuitry. An external bypass capacitor is required for
the 1.5V reference output, V

. This provides a high

CM

frequency low impedance path to ground for internal and
external circuitry.

LTC2288/LTC2287/LTC2286

4Ω

V

TIE TO V

TIE TO V

CM

RANGE = 2 • V

0.5V < V

1.5V

FOR 2V RANGE;

DD

FOR 1V RANGE;

SENSE

SENSE

1µF

CM

2.2µF

SENSE

FOR

< 1V

REFH

RANGE

DETECT

AND

CONTROL

1.5V BANDGAP
REFERENCE

1V

INTERNAL ADC
HIGH REFERENCE

0.5V

BUFFER

The difference amplifier generates the high and low refer­ence for the ADC. High speed switching circuits are
connected to these outputs and they must be externally
bypassed. Each output has two pins. The multiple output
pins are needed to reduce package inductance. Bypass
capacitors must be connected as shown in Figure 9. Each
ADC channel has an independent reference with its own
bypass capacitors. The two channels can be used with the
same or different input ranges.

Other voltage ranges between the pin selectable ranges
can be programmed with two external resistors as shown
in Figure 10. An external reference can be used by applying
its output directly or through a resistor divider to SENSE.
It is not recommended to drive the SENSE pin with a logic
device. The SENSE pin should be tied to the appropriate
level as close to the converter as possible. If the SENSE pin
is driven externally, it should be bypassed to ground as
close to the device as possible with a 1µF ceramic capacitor.
For the best channel matching, connect an external reference
to SENSEA and SENSEB.

1.5V

12k

0.75V

12k

Figure 10. 1.5V Range ADC

V

2.2µF

SENSE

1µF

CM

LTC2288
LTC2287
LTC2286

228876 F10

Input Range

2.2µF

1µF

0.1µF

REFL

DIFF AMP

INTERNAL ADC
LOW REFERENCE

Figure 9. Equivalent Reference Circuit

228876 F09

The input range can be set based on the application. The
2V input range will provide the best signal-to-noise perfor­mance while maintaining excellent SFDR. The 1V input
range will have better SFDR performance, but the SNR will
degrade by 0.6dB. See the Typical Performance Charac­teristics section.

Driving the Clock Input

The CLK inputs can be driven directly with a CMOS or TTL
level signal. A sinusoidal clock can also be used along with
a low jitter squaring circuit before the CLK pin (Figure 11).

228876f

19

LTC2288/LTC2287/LTC2286

WUUU

APPLICATIO S I FOR ATIO

CLEAN

FERRITE

BEAD

0.1µF

CLK

SUPPLY

LTC2288
LTC2287
LTC2286

228876 F11

4.7µF

1k

1k

NC7SVU04

SINUSOIDAL

CLOCK

INPUT

Figure 11. Sinusoidal Single-Ended CLK Drive

0.1µF

50Ω

The noise performance of the LTC2288/LTC2287/LTC2286
can depend on the clock signal quality as much as on the
analog input. Any noise present on the clock signal will
result in additional aperture jitter that will be RMS summed
with the inherent ADC aperture jitter.

In applications where jitter is critical, such as when digitiz­ing high input frequencies, use as large an amplitude as
possible. Also, if the ADC is clocked with a sinusoidal
signal, filter the CLK signal to reduce wideband noise and
distortion products generated by the source.

An optional clock duty cycle stabilizer circuit can be used
if the input clock has a non 50% duty cycle. This circuit
uses the rising edge of the CLK pin to sample the analog
input. The falling edge of CLK is ignored and the internal
falling edge is generated by a phase-locked loop. The
input clock duty cycle can vary from 40% to 60% and the
clock duty cycle stabilizer will maintain a constant 50%
internal duty cycle. If the clock is turned off for a long
period of time, the duty cycle stabilizer circuit will require
a hundred clock cycles for the PLL to lock onto the input
clock. To use the clock duty cycle stabilizer, the MODE pin
should be connected to 1/3VDD or 2/3VDD using external
resistors. The MODE pin controls both Channel A and
Channel B—the duty cycle stabilizer is either on or off for
both channels.

The lower limit of the LTC2288/LTC2287/LTC2286 sample
rate is determined by droop of the sample-and-hold cir­cuits. The pipelined architecture of this ADC relies on
storing analog signals on small valued capacitors. Junc­tion leakage will discharge the capacitors. The specified
minimum operating frequency for the LTC2288/LTC2287/
LTC2286 is 1Msps.

It is recommended that CLKA and CLKB are shorted
together and driven by the same clock source. If a small
time delay is desired between when the two channels
sample the analog inputs, CLKA and CLKB can be driven
by two different signals. If this delay exceeds 1ns, the
performance of the part may degrade. CLKA and CLKB
should not be driven by asynchronous signals.

Maximum and Minimum Conversion Rates

The maximum conversion rate for the LTC2288/LTC2287/
LTC2286 is 65Msps (LTC2288), 40Msps (LTC2287), and
25Msps (LTC2286). For the ADC to operate properly, the
CLK signal should have a 50% (±5%) duty cycle. Each half
cycle must have at least 7.3ns (LTC2288), 11.8ns
(LTC2287), and 18.9ns (LTC2286) for the ADC internal
circuitry to have enough settling time for proper operation.

DIGITAL OUTPUTS

Digital Output Buffers

Figure 12 shows an equivalent circuit for a single output
buffer. Each buffer is powered by OVDD and OGND, iso­lated from the ADC power and ground. The additional
N-channel transistor in the output driver allows operation
down to low voltages. The internal resistor in series with
the output makes the output appear as 50Ω to external
circuitry and may eliminate the need for external damping
resistors.

As with all high speed/high resolution converters, the digi­tal output loading can affect the performance. The digital
outputs of the LTC2288/LTC2287/LTC2286 should drive a
minimal capacitive load to avoid possible interaction

20

228876f

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

LTC2288/LTC2287/LTC2286

V

DD

DATA

PREDRIVER

FROM

LATCH

between the digital outputs and sensitive input circuitry.
The output should be buffered with a device such as an
ALVCH16373 CMOS latch. For full speed operation the
capacitive load should be kept under 10pF.

LOGIC

OE

Figure 12. Digital Output Buffer

OV

DD

0.5V
TO V

0.1µF

TYPICAL
DATA
OUTPUT

DD

V

DD

OV

DD

43Ω

OGND

228876 F12

Overflow Bit

When OF outputs a logic high the converter is either
overranged or underranged.

Lower OVDD voltages will also help reduce interference
from the digital outputs.

Data Format

Using the MODE pin, the LTC2288/LTC2287/LTC2286
parallel digital output can be selected for offset binary or
2’s complement format. Note that MODE controls both
Channel A and Channel B. Connecting MODE to GND or
1/3VDD selects straight binary output format. Connecting
MODE to 2/3VDD or VDD selects 2’s complement output
format. An external resistor divider can be used to set the
1/3VDD or 2/3VDD logic values. Table 1 shows the logic
states for the MODE pin.

Table 1. MODE Pin Function

Clock Duty

MODE Pin Output Format Cycle Stabilizer

0 Straight Binary Off

1/3V

2/3V

V

DD

DD

DD

Straight Binary On

2’s Complement On

2’s Complement Off

Output Driver Power

Separate output power and ground pins allow the output
drivers to be isolated from the analog circuitry. The power
supply for the digital output buffers, OVDD, should be tied
to the same power supply as for the logic being driven. For
example, if the converter is driving a DSP powered by a 1.8V
supply, then OVDD should be tied to that same 1.8V supply.

OVDD can be powered with any voltage from 500mV up to

3.6V. OGND can be powered with any voltage from GND up
to 1V and must be less than OVDD. The logic outputs will
swing between OGND and OVDD.

Output Enable

The outputs may be disabled with the output enable pin, OE.
OE high disables all data outputs including OF. The data ac­cess and bus relinquish times are too slow to allow the
outputs to be enabled and disabled during full speed op­eration. The output Hi-Z state is intended for use during long
periods of inactivity. Channels A and B have independent
output enable pins (OEA, OEB).

228876f

21

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

Sleep and Nap Modes

The converter may be placed in shutdown or nap modes
to conserve power. Connecting SHDN to GND results in
normal operation. Connecting SHDN to VDD and OE to V
results in sleep mode, which powers down all circuitry
including the reference and typically dissipates 1mW. When
exiting sleep mode it will take milliseconds for the output
data to become valid because the reference capacitors have
to recharge and stabilize. Connecting SHDN to V
to GND results in nap mode, which typically dissipates
30mW. In nap mode, the on-chip reference circuit is kept
on, so that recovery from nap mode is faster than that from
sleep mode, typically taking 100 clock cycles. In both sleep
and nap modes, all digital outputs are disabled and enter
the Hi-Z state.

Channels A and B have independent SHDN pins (SHDNA,
SHDNB). Channel A is controlled by SHDNA and OEA, and
Channel B is controlled by SHDNB and OEB. The nap, sleep
and output enable modes of the two channels are completely
independent, so it is possible to have one channel operat­ing while the other channel is in nap or sleep mode.

Digital Output Mulitplexer

The digital outputs of the LTC2288/LTC2287/LTC2286 can
be multiplexed onto a single data bus. The MUX pin is a
digital input that swaps the two data busses. If MUX is High,
Channel A comes out on DA0-DA9, OFA; Channel B comes
out on DB0-DB9, OFB. If MUX is Low, the output busses
are swapped and Channel A comes out on DB0-DB9, OFB;
Channel B comes out on DA0-DA9, OFA. To multiplex both
channels onto a single output bus, connect MUX, CLKA and
CLKB together (see the Timing Diagram for the multiplexed
mode). The multiplexed data is available on either data
bus—the unused data bus can be disabled with its OE pin.

DD

DD

and OE

Grounding and Bypassing

The LTC2288/LTC2287/LTC2286 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.

High quality ceramic bypass capacitors should be used at
the V
tors must be located as close to the pins as possible. Of
particular importance is the 0.1µF capacitor between
REFH and REFL. This capacitor should be placed as close
to the device as possible (1.5mm or less). A size 0402
ceramic capacitor is recommended. The large 2.2µF ca-
pacitor between REFH and REFL can be somewhat further
away. The traces connecting the pins and bypass capaci­tors must be kept short and should be made as wide as
possible.

The LTC2288/LTC2287/LTC2286 differential inputs should
run parallel and close to each other. The input traces
should be as short as possible to minimize capacitance
and to minimize noise pickup.

Heat Transfer

Most of the heat generated by the LTC2288/LTC2287/
LTC2286 is transferred from the die through the bottom­side exposed pad and package leads onto the printed
circuit board. For good electrical and thermal perfor­mance, the exposed pad should be soldered to a large
grounded pad on the PC board. It is critical that all ground
pins are connected to a ground plane of sufficient area.

, OVDD, VCM, REFH, and REFL pins. Bypass capaci-

DD

22

228876f

LTC2288/LTC2287/LTC2286

C21

0.1µF

C27

0.1µF

V

DD

V

DD

V

DD

V

DD

V

DD

V

CC

V

CMB

C20

2.2µF

C18 1µF

C23 1µF

C34

0.1µF

C31

12pF

C17

0.1µF

C14

0.1µF

C25

0.1µF

C30

18pF

L2

47nH

R28

24

Ω

C32

18pF

C28

2.2µF

C35

0.1µF

C24

0.1µF

C36

4.7µF

E3

V

DD

3V

E5

PWR

GND

V

DD

V

CC

V

CC

228876 AI01

C1

0.1µF

R16

33Ω

R1

1k

R2

1k

R3

1k

R10

1k

R14

49.9Ω

R20

24.9Ω

R18

24.9Ω

R24

24.9Ω

R17

OPT

R22

24.9Ω

R23

51

T2

ETC1-1T

C29

0.1µF

C33

0.1µF

J3

CLOCK

INPUT

U6

NC7SVU04

U4

NC7SV86P5X

U7

NC7SV86P5X

U3

NC7SVU04

C13

0.1µF

C15

0.1µF

C12

4.7µF

6.3V

L1

BEAD

V

DD

C19

0.1µF

C11

0.1µF

C4

0.1µF

C2

2.2µF

C10

2.2µF

C9 1µF

C13 1µF

R15

1k

J4

ANALOG

INPUT B

V

CC

1

2

3

4

••

5

V

CMB

C8

0.1µF

C6

12pF

C44

0.1µF

R6

24.9Ω

R5

24.9Ω

R9

24.9Ω

R4

OPT

R7

24.9Ω

R8

51

T1

ETC1-1T

C3

0.1µF

C7

0.1µF

J2

ANALOG

INPUT A

1

2

3

5

••

4

V

CMA

V

CMA

12

V

DD

V

DD

34

2/3V

DD

56

1/3V

DD

78

GND

JP1 MODE

C16 0.1µF

25

23

27

29

31

33

35

37

39

21

19

15

17

13

9

7

1

3

5

2

4

11

26

24

30

28

34

32

38

40

39

37

35

33

31

29

27

25

23

21

19

17

15

13

11

9

7

5

3

1

40

3201S-40G1

38

36

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

36

22

20

16

18

14

10

8

6

12

R13

10k

R11

10k

R12

10k

R30

15

Ω

R

N1D

33Ω

R

N1C

33Ω

R

N1B

33Ω

R

N1A

33Ω

R

N2D

33Ω

R

N2C

33Ω

R

N2B

33Ω

R

N2A

33Ω

R

N3D

33Ω

R

N3C

33Ω

R

N3B

33Ω

R

N3A

33Ω

R

N4D

33Ω

R

N4C

33Ω

R

N4B

33Ω

C39

1µF

C38

0.01µF

V

CC

V

DD

BYP

GND

ADJ

OUT

SHDN

GND

IN

1

2

3

4

8

U8

LT1763

7

6

5

GND

R26

100k

R25

105k

C37

10µF

6.3V

E4

GND

C40

0.1µF

C41

0.1µF

A

INA

+

A

INA

–

REFHA

REFHA

REFLA

REFLA

V

DD

CLKA

CLKB

V

DD

REFLB

REFLB

REFHB

REFHB

A

INB

–

A

INB

+

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

DA3

DA2

DA1

DA0

NC

NC

NC

NC

OFB

DB9

DB8

DB7

DB6

DB5

DB4

DB3

64

63

62

61

60

59

58

57

56

55

54

53

52

51

50

49

GND

V

DD

SENSEA

VCMA

MODE

SHDNA

OEA

OFA

DA9

DA8

DA7

DA6

DA5

DA4

OGND

OV

DD

GND

V

DD

SENSEB

VCMB

MUX

SHDNB

OEB

NC

NC

NC

NC

DB0

DB1

DB2

OGND

OV

DD

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

E2

EXT

REF B

12

V

DD

34

V

CM

V

DD

V

CMB

56

EXT REF

JP3 SENSE

E1

EXT

REF A

12

V

DD

34

V

CM

V

DD

56

EXT REF

JP2 SENSE A

C5

0.1µF

C26

0.1µF

V

CC

B3

B2

B4

B5

B6

B7

OE

B1

B0

A3

A1

A0

18

17

16

15

14

13

12

11

19

2

20

V

CC

74VCX245BQX

V

CC

3

4

5

6

7

8

9

1

10

A2

A7

T/R

GND

A5

A4

A6

B3

B2

B4

B5

B6

B7

OE

B1

B0

A3

A1

A0

18

17

16

15

14

13

12

11

19

2

20

V

CC

74VCX245BQX

V

CC

3

4

5

6

7

8

9

1

10

A2

A7

T/R

GND

A5

A4

A6

A0

A1

A2

A3

V

CC

WP

SCL

SDA

1

2

3

4

8

7

6

5

R29

51

Ω

L4

47nH

C43

8.2pF

L3

47nH

C42

8.2pF

U5

24LC025

V

CC

R31

TBD

R27

TBD

V

CC

U10

NC7SV86P5X

R32

22Ω

U1

LTC2288

U

WUU

APPLICATIO S I FOR ATIO

228876f

23

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

Silkscreen Top

Top Side

24

228876f

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

Inner Layer 2 GND

Inner Layer 3 Power

228876f

25

LTC2288/LTC2287/LTC2286

U

WUU

APPLICATIO S I FOR ATIO

Bottom Side

26

228876f

PACKAGE DESCRIPTIO

LTC2288/LTC2287/LTC2286

U

UP Package

64-Lead Plastic QFN (9mm × 9mm)

(Reference LTC DWG # 05-08-1705)

0.70 ±0.05

0.25 ±0.05

0.50 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

9 .00 ± 0.10

(4 SIDES)

PIN 1 TOP MARK
(SEE NOTE 5)

7.15 ±0.05
(4 SIDES)

8.10 ±0.05 9.50 ±0.05

PACKAGE OUTLINE

0.75 ± 0.05

7.15 ± 0.10
(4-SIDES)

R = 0.115

TYP

PIN 1

CHAMFER

6463

0.40 ± 0.10

1
2

0.200 REF

NOTE:

1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION WNJR-5

2. ALL DIMENSIONS ARE IN MILLIMETERS

3. 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

4. EXPOSED PAD SHALL BE SOLDER PLATED

5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE

6. DRAWING NOT TO SCALE

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 represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

0.25 ± 0.05

0.50 BSC

(UP64) QFN 1003

228876f

27

LTC2288/LTC2287/LTC2286

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LTC2246 14-Bit, 25Msps ADC 75mW, 74dB SNR, 5mm × 5mm QFN

LTC2247 14-Bit, 40Msps ADC 125mW, 74dB SNR, 5mm × 5mm QFN

LTC2248 14-Bit, 65Msps ADC 210mW, 74dB SNR, 5mm × 5mm QFN

LTC2249 14-Bit, 80Msps ADC 230mW, 73dB SNR, 5mm × 5mm QFN

LTC2289 Dual 10-Bit, 80Msps ADC 445mW, 61dB SNR, 9mm × 9mm QFN

LTC2290 Dual 12-Bit, 10Msps ADC 120mW, 71dB SNR, 9mm × 9mm QFN

LTC2291 Dual 12-Bit, 25Msps ADC 150mW, 71dB SNR, 9mm × 9mm QFN

LTC2292 Dual 12-Bit, 40Msps ADC 235mW, 71dB SNR, 9mm × 9mm QFN

LTC2293 Dual 12-Bit, 65Msps ADC 400mW, 71dB SNR, 9mm × 9mm QFN

LTC2294 Dual 12-Bit, 80Msps ADC 445mW, 70.6dB SNR, 9mm × 9mm QFN

LTC2295 Dual 14-Bit, 10Msps ADC 120mW, 74.4dB SNR, 9mm × 9mm QFN

LTC2296 Dual 14-Bit, 25Msps ADC 150mW, 74dB SNR, 9mm × 9mm QFN

LTC2297 Dual 14-Bit, 40Msps ADC 235mW, 74dB SNR, 9mm × 9mm QFN

LTC2298 Dual 14-Bit, 65Msps ADC 400mW, 74dB SNR, 9mm × 9mm QFN

LTC2299 Dual 14-Bit, 80Msps ADC 445mW, 73dB SNR, 9mm × 9mm QFN

LT5512 DC-3GHz High Signal Level Downconverting Mixer DC to 3GHz, 21dBm IIP3, Integrated LO Buffer

LT5514 Ultralow Distortion IF Amplifier/ADC Driver 450MHz 1dB BW, 47dB OIP3, Digital Gain

with Digitally Controlled Gain Control 10.5dB to 33dB in 1.5dB/Step

LT5515 1.5GHz to 2.5GHz Direct Conversion Quadrature Demodulator 20dBm IIP3, Integrated LO Quadrature Generator

LT5516 0.8GHz to 1.5GHz Direct Conversion Quadrature Demodulator 21.5dBm IIP3, Integrated LO Quadrature Generator

LT5517 40MHz to 900MHz Direct Conversion Quadrature Demodulator 21dBm IIP3, Integrated LO Quadrature Generator

LT5522 600MHz to 2.7GHz High Linearity Downconverting Mixer 4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB,

50Ω Single Ended RF and LO Ports

28

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

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www.linear.com

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LT/TP 0105 1K • PRINTED IN USA

© LINEAR TECHNOLOGY CORPORATION 2005