LINEAR TECHNOLOGY LTC1745 Technical data

Final Electrical Specifications

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LTC1745

Low Noise,12-Bit, 25Msps ADC

FEATURES

■

Sample Rate: 25Msps

■

72.5dB SNR and 96dB SFDR (3.2V Range)

■

71dB SNR and 96dB SFDR (2V Range)

■

No Missing Codes

■

Single 5V Supply

■

Low Power Dissipation: 380mW

■

Selectable Input Ranges: ±1V or ±1.6V

■

240MHz Full Power Bandwidth S/H

■

Output Enable

■

Two’s Complement or Offset Binary Outputs

■

Out-of-Range Indicator

■

Data Ready Output Clock

■

48-Pin TSSOP Package

■

50Msps Pin-for-Pin Upgrade (LTC1743)

■

14-Bit Plug Compatible Upgrade (LTC1746)

U

APPLICATIO S

■

Telecommunications

■

Medical Imaging

■

Receivers

■

Cellular Base Stations

■

Spectrum Analysis

■

Imaging Systems

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

U

January 2003

DESCRIPTION

The LTC®1745 is a 25Msps, sampling 12-bit A/D con­verter designed for digitizing high frequency, wide dy­namic range signals. Pin selectable input ranges of ±1V
and ±1.6V along with a resistor programmable mode
allow the LTC1745’s input range to be optimized for a wide
variety of applications.

The LTC1745 is perfect for demanding communications
applications with AC performance that includes 72.5dB
SNR and 96dB spurious free dynamic range. Ultralow jitter
of 0.3ps
to 70MHz with excellent noise performance. DC specs
include ±1LSB INL and ±0.75LSB DNL over temperature.

The digital interface is compatible with 5V, 3V and 2V logic
systems. The ENC and ENC inputs may be driven differen­tially from PECL, GTL and other low swing logic families or
from single-ended TTL or CMOS. The low noise, high gain
ENC and ENC inputs may also be driven by a sinusoidal
signal without degrading performance. A separate output
power supply can be operated from 0.5V to 5V, making it
easy to connect directly to any low voltage DSPs or FIFOs.

The TSSOP package with a flow-through pinout simplifies
the board layout.

allows undersampling of IF frequencies of up

RMS

BLOCK DIAGRA

+

A

IN

±1V

DIFFERENTIAL

ANALOG INPUT

4.7µF

A

SENSE

V

–

IN

CM

2.35V

RANGE
SELECT

W

25Msps, 12-Bit ADC with a ±1V Differential Input Range

S/H

AMP

BUFFER

DIFF AMP

REF

0.1µF0.1µF

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.

12-BIT

PIPELINED ADC

REFHAREFLB

REFLA REFHB

4.7µF

1µF1µF

CONTROL LOGIC

ENC

DIFFERENTIAL

ENCODE INPUT

ENC

12

OUTPUT

LATCHES

OV

DD

OF
D11

•

•

•
D0

CLKOUT

OGND

V

DD

GND

1745 BD

OEMSBINV

0.1µF

1µF 1µF 1µF

0.5V TO 5V

0.1µF

5V

1745i

1

LTC1745

WW

W

U

ABSOLUTE MAXIMUM RATINGS

OVDD = VDD (Notes 1, 2)

Supply Voltage (VDD)............................................. 5.5V

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

Digital Input Voltage (Note 4) ..... –0.3V to (VDD + 0.3V)

Digital Output Voltage................. –0.3V to (VDD + 0.3V)

OGND Voltage...........................................–0.3V to 0.3V

Power Dissipation............................................ 2000mW

Operating Temperature Range

LTC1745C ............................................... 0°C to 70°C

LTC1745I............................................ – 40°C to 85°C

Storage Temperature Range ................. –65°C to 150°C

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

U

W

PACKAGE/ORDER INFORMATION

SENSE

V
GND
A
A
GND

V

V
GND

REFLB

REFHA

GND
GND

REFLA

REFHB

GND

V

V
GND

V
GND

MSBINV

ENC

ENC

TOP VIEW

1
2

CM

3

+

4

IN

–

5

IN

6
7

DD

8

DD

9
10
11
12
13
14
15
16
17

DD

18

DD

19
20

DD

21
22
23
24

FW PACKAGE

48-LEAD PLASTIC TSSOP

T

= 150°C, θJA = 35°C/W

JMAX

48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25

OF
OGND
D11
D10
D9
OV

DD

D8
D7
D6
D5
OGND
GND
GND
D4
D3
D2
OV

DD

D1
D0
NC
NC
OGND
CLKOUT
OE

ORDER PART

NUMBER

LTC1745CFW
LTC1745IFW

U

Consult LTC Marketing for parts specified with wider operating temperature ranges.

U

CO VERTER CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. (Note 5)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resolution (No Missing Codes) ● 12 Bits
Integral Linearity Error (Note 6) ● –1 ±0.4 1 LSB
Differential Linearity Error ● –0.75 ±0.2 0.75 LSB
Offset Error (Note 7) ● –30 ±530 mV
Gain Error External Reference (SENSE = 1.6V) ● –2.5 ±1 2.5 %FS
Full-Scale Tempco I

The ● indicates specifications which apply over the full operating

= 0 ±40 ppm/°C

OUT(REF)

UU

A ALOG I PUT

specifications are at TA = 25°C. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IN

I

IN

C

IN

t

ACQ

t

AP

t

JITTER

CMRR Analog Input Common Mode Rejection Ratio 1.0V < (A

Analog Input Range (Note 8) 4.75V ≤ VDD ≤ 5.25V ● ±1 to ±1.6 V
Analog Input Leakage Current ● –1 1 µA
Analog Input Capacitance Sample Mode ENC < ENC 8 pF

Sample-and-Hold Acquisition Time ● 15 18 ns
Sample-and-Hold Acquisition Delay Time 0 ns
Sample-and-Hold Acquisition Delay Time Jitter 0.3 ps

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

Hold Mode ENC > ENC 4 pF

–

+

= A

IN

) < 3.5V 80 dB

IN

RMS

1745i

2

LTC1745

UW

DY A IC ACCURACY

otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

SNR Signal-to-Noise Ratio 5MHz Input Signal (2V Range) 71 dB

SFDR Spurious Free Dynamic Range 5MHz Input Signal (2V Range) 96.5 dB

S/(N + D) Signal-to-(Noise + Distortion) Ratio 5MHz Input Signal (2V Range) 71 dB

THD Total Harmonic Distortion 5MHz Input Signal, First 5 Harmonics (2V Range) –95 dB

IMD Intermodulation Distortion f

Sample-and-Hold Bandwidth R

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

5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range) 71 dB

30MHz Input Signal (3.2V Range) 72 dB
70MHz Input Signal (2V Range) 70 dB

70MHz Input Signal (3.2V Range) 71.5 dB

5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range) 93.5 dB

30MHz Input Signal (3.2V Range) 87.5 dB
70MHz Input Signal (2V Range) 78.5 dB

70MHz Input Signal (3.2V Range) 70.5 dB

5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range) 71 dB

30MHz Input Signal (3.2V Range) 72 dB
70MHz Input Signal (2V Range) 69.5 dB

70MHz Input Signal (3.2V Range) 68.5 dB

5MHz Input Signal, First 5 Harmonics (3.2V Range) –93 dB
30MHz Input Signal, First 5 Harmonics (2V Range) –92 dB

30MHz Input Signal, First 5 Harmonics (3.2V Range) –87 dB
70MHz Input Signal, First 5 Harmonics (2V Range) –77.5 dB

70MHz Input Signal, First 5 Harmonics (3.2V Range) –70 dB

= 4MHz, f

IN1

= 4MHz, f

f

IN1

SOURCE

= 5.1MHz (2V Range) 97 dBc

IN2

= 5.1MHz (3.2V Range) 93 dBc

IN2

= 50Ω 240 MHz

● 71 72.5 dB

● 78 96.5 dB

● 71 72.5 dB

UU U

I TER AL REFERE CE CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

VCM Output Voltage I
VCM Output Tempco I
VCM Line Regulation 4.75V ≤ VDD ≤ 5.25V 3 mV/V
VCM Output Resistance 1mA ≤ I

= 0 2.29 2.35 2.41 V

OUT

= 0 ±30 ppm/°C

OUT

 ≤ 1mA 4 Ω

OUT

(Note 5)

1745i

3

LTC1745

UU

DIGITAL I PUTS A D DIGITAL OUTPUTS

operating temperature range, otherwise specifications are at TA = 25°C. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IH

V

IL

I

IN

C

IN

V

OH

V

OL

I

OZ

C

OZ

I

SOURCE

I

SINK

High Level Input Voltage VDD = 5.25V ● 2.4 V
Low Level Input Voltage VDD = 4.75V ● 0.8 V
Digital Input Current VIN = 0V to V
Digital Input Capacitance MSBINV and OE Only 1.5 pF
High Level Output Voltage OVDD = 4.75V IO = –10µA 4.74 V

Low Level Output Voltage OVDD = 4.75V IO = 160µA 0.05 V

Hi-Z Output Leakage D11 to D0 V
Hi-Z Output Capacitance D11 to D0 OE = High (Note 8) ● 15 pF
Output Source Current V
Output Sink Current V

OUT

OUT

OUT

DD

= 0V to VDD, OE = High ● ±10 µA

= 0V –50 mA
= 5V 50 mA

The ● indicates specifications which apply over the full

● ±10 µA

IO = –200µA ● 4V

IO = 1.6mA ● 0.1 0.4 V

WU

POWER REQUIRE E TS

range, otherwise specifications are at TA = 25°C. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
I

DD

P
OV

DD

DIS

DD

Positive Supply Voltage 4.75 5.25 V
Positive Supply Current 2V Range, Full-Scale Input ● 76 91 mA
Power Dissipation 2V Range, Full-Scale Input 380 455 mW
Digital Output Supply Voltage 0.5 V

The ● indicates specifications which apply over the full operating temperature

DD

UW

TI I G CHARACTERISTICS

range, otherwise specifications are at TA = 25°C. (Note 5)

The ● indicates specifications which apply over the full operating temperature

V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

f

SAMPLE(MAX)

t

1

t

2

t

3

t

4

t

5

t

6

t

7

t

8

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
(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: When these pin voltages are taken below GND, they will be
clamped by internal diodes. This product can handle input currents of
>100mA below GND without latchup. These pins are not clamped to V

Maximum Sampling Frequency (Note 9) ● 25 MHz
ENC Low Time (Note 9) ● 19 20 1000 ns
ENC High Time (Note 9) ● 19 20 1000 ns
Aperture Delay of Sample-and-Hold 0 ns
Delay to Data Output CL = 10pF (Note 8) ● 0.5 1.5 5 ns
ENC to CLKOUT Delay (Note 8) ● 013ns
CLKOUT to Data Delay (Note 8) ● 0 0.5 ns
DATA Access Time After OE ↓ CL = 5pF (Note 8) 10 25 ns
BUS Relinquish Time (Note 8) 10 25 ns

without latchup.

DD

DD

, they

DD

Note 5: V
sine wave, input range = ±1.6V differential, unless otherwise specified.

Note 6: 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 7: Bipolar offset is the offset voltage measured from –0.5 LSB
when the output code flickers between 0000 0000 0000 and
1111 1111 1111.

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

.

Note 9: Recommended operating conditions.

= 5V, f

DD

= 25MHz, differential ENC/ENC = 2V

SAMPLE

P-P

25MHz

1745i

4

UW

TYPICAL PERFOR A CE CHARACTERISTICS

1.0

0.5

0

INL ERROR (LSB)

–0.5

–1.0

0

1000 2000

CODE

Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,
2V Range

0

–10
–20
–30
–40
–50
–60

–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

4

2

FREQUENCY (MHz)

6

Nonaveraged, 32768 Point FFT,
Input Frequency = 70MHz,
2V Range

0

–10
–20
–30
–40
–50
–60

–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

4

2

FREQUENCY (MHz)

6

3000 4000

1745 G01

10

812

1745 G04

10

812

1745 G07

1.0

0.5

0

DNL ERROR (LSB)

–0.5

–1.0

0

1000 2000

CODE

Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,

3.2V Range

0
–10
–20
–30
–40
–50
–60
–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

4

2

FREQUENCY (MHz)

6

Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 3.2V Range

0
–10
–20
–30
–40
–50
–60
–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

4

2

FREQUENCY (MHz)

6

3000 4000

10

812

10

812

1745 G02

1745 G05

1745 G08

LTC1745

Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,

3.2V RangeTypical INL Typical DNL

0
–10
–20
–30
–40
–50
–60
–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,
2V Range

0
–10
–20
–30
–40
–50
–60
–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 2V Range

0
–10
–20
–30
–40
–50
–60
–70

AMPLITUDE (dB)

–80
–90

–100
–110
–120

0

4

2

FREQUENCY (MHz)

4

2

FREQUENCY (MHz)

4

2

FREQUENCY (MHz)

6

6

6

10

812

1745 G03

10

812

1745 G06

10

812

1745 G09

1745i

5

LTC1745

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Grounded Input Histogram

35000

30000

25000

20000

COUNT

15000

10000

5000

0

2041

Power vs Sample Rate,
Input Frequency = 5MHz

500
480
460
440
420
400
380

POWER (mW)

360
340
320
300

0

10

20

SAMPLE RATE (Msps)

2042 2043

CODE

2V RANGE3.2V RANGE

30 40

SNR vs Sample Rate,
Input Frequency = 5MHz, –1dB

73

3.2V RANGE

2V RANGE

20 30 40

10

SAMPLE RATE (Msps)

50 60

1745 G11

1745 G10

72

71

70

69

SNR (dBFS)

68

67

66

0

SNR vs Input Frequency

3.2V Range

80

75

–1dBFS

70

65

SNR (dB)

60

55

60

50

1745 G13

50

20 40 60 80

INPUT FREQUENCY (MHz)

–6dBFS

–20dBFS

10010030507090

1745 G14

SFDR vs Sample Rate,
Input Frequency = 5MHz, –1dB

110

100

90

SFDR (dB)

80

70

60

0

10

3.2V RANGE

2V RANGE

20 30 40

SAMPLE RATE (Msps)

SNR vs Input Frequency
2V Range

80

75

70

65

SNR (dB)

60

55

50

20 40 60 80

INPUT FREQUENCY (MHz)

–1dBFS

–6dBFS

–20dBFS

50 60

1745 G12

10010030507090

1745 G15

6

SFDR vs Input Frequency
and Amplitude, 3.2V Range

110

100

90

80

70

SFDR (dBFS)

60

50

40

0

10

20

INPUT FREQUENCY (MHz)

–6dBFS

–1dBFS

30

50

40

–20dBFS

70

60 80

90

1746 G16

100

SFDR vs Input Frequency
and Amplitude, 2V Range

110

100

90

80

70

SFDR (dBFS)

60

50

40

0

–1dBFS

50
INPUT FREQUENCY (MHz)

100

–20dBFS

–6dBFS

150

200

1745 G17

1745i