Fairchild Semiconductor SPT7725 Datasheet

SPT7725

8-BIT, 300 MSPS, FLASH A/D CONVERTER

TECHNICAL DATA

AUGUST 17, 2001

FEATURES

• Metastable errors reduced to 1 LSB

• Low input capacitance: 10 pF

• Wide input bandwidth: 210 MHz

• 300 MSPS conversion rate

• Typical power dissipation: 2.2 watts

GENERAL DESCRIPTION

The SPT7725 is a monolithic flash A/D converter capable
of digitizing a two volt analog input signal into 8-bit digital
words at a 300 MSPS (typ) update rate.

For most applications, no external sample-and-hold is re­quired for accurate conversion due to the device’s narrow
aperture time, wide bandwidth, and low input capacitance.
A single standard –5.2 volt power supply is required for
operation of the SPT7725, with nominal power dissipation

BLOCK DIAGRAM

V

RTS

V

RTF

Analog Input

(Force or Sense)

AGND DGND V

Preamp Comparator

256

255

EE

Clock
Buffer

APPLICATIONS

• Digital oscilloscopes

• Transient capture

• Radar, EW, ECM

• Direct RF down-conversion

• Medical electronics: ultrasound, CAT instrumentation
of 2.2 W. A proprietary decoding scheme reduces meta-

stable errors to the 1 LSB lev el.
The SPT7725 is available in 42-lead ceramic sidebrazed

DIP, surface-mount 44-lead cerquad, and 46-lead PGA
packages (all are pin-compatible with the SPT7710); the
cerquad and PGA packages allow access to additional
reference ladder taps, an overrange bit, and a data ready
output. The SPT7725 is available in the industrial tem­perature range.

LINV MINV

DRINV

MSB D7

DREAD

Convert

V
V

V

V

V

RBF

RBS

CLK
CLK

R3

R2

R1

(Sense or Force)

152

151

128

256 to

127

64

63

2

1

2

8-Bit

Encoder

V

EE

D6

D5

D4

D3

D2

D1

LSB D0

AGNDAnalog Input

ECL

Latches

and

Buffers

Overrange

D7 MSB

D6

D5

These functions are

D4

available in the PGA and
cerquad packages only.

D3

D2

D1

D0 LSB

ABSOLUTE MAXIMUM RATINGS (Beyond which damage may occur)1 25 °C

Supply Voltages

Negative Supply Voltage (VEE TO GND) –7.0 to +0.5 V

Ground Voltage Differential ....................–0.5 to +0.5 V

Input Voltage

Analog Input Voltage ...............................V

to +0.5 V

EE

Temperature

Operating Temperature,ambient............. –25 to +85 °C

junction ...................... +150 °C

Lead Temperature, (soldering 10 seconds) ..... +300 °C

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

Reference Input Voltage..........................VEE to +0.5 V

Digital Input Voltage ................................VEE to +0.5 V

Reference Current V

Output

Digital Output Current ............................... 0 to –30 mA

RTF

to V

........................25 mA

RBF

Note: 1. Operation at any Absolute Maximum Rating is not implied. See

Electrical Specifications for proper nominal applied conditions
in typical applications.

ELECTRICAL SPECIFICATIONS

TA= T

PARAMETERS CONDITIONS LEVEL MIN TYP MAX MIN TYP MAX UNITS
DC Accuracy

Analog Input

to T

MIN

, VEE=–5.2 V , R

MAX

Source

=50 Ω, V

=–2.00 V , VR2=–1.00 V , V

RBF

=0.00 V , ƒ

RTF

=250 MHz, Duty Cycle=50%, unless otherwise specified.

CLK

TEST TEST SPT7725A SPT7725B

Integral Linearity Error ƒ
Differential Linearity Error ƒ

= 100 kHz VI –0.75 ±0.60 +0.75 –0.95 ±0.80 +0.95 LSB

CLK

= 100 kHz VI –0.75 +0.75 –0.95 +0.95 LSB

CLK

No missing codes Guaranteed Guaranteed

Offset Error V
Offset Error V

RT
RB

VI –30 +30 –30 +30 mV

VI –30 +30 –30 +30 mV
Input Voltage Range VI –2.0 0.0 –2.0 0.0 Volts
Input Capacitance Over full

input range V 10 10 pF
Input Resistance V 15 15 kΩ
Input Current VI 250 500 250 500 µA
Input Slew Rate V 1,000 1,000 V/µs
Large Signal Bandwidth V
Small Signal Bandwidth V

=F.S. V 210 210 MHz

IN

=500 mV

IN

P-P

V 335 335 MHz

Clock Synchronous

Input Currents V 40 40 µA

Reference Input

Ladder Resistance VI 100 200 300 100 200 300 Ω
Reference Bandwidth V 10 10 MHz

Timing Characteristics

Maximum Sample Rate IV 250 300 250 300 MSPS
Clock to Data Delay V 2.4 2.4 ns
Output Delay Tempco V 2 2 ps/°C
CLK-to-Data Ready Delay (t

) V 2.0 2.0 ns

D

Aperture Jitter V 5 5 ps
Acquisition Time V 1.5 1.5 ns

Dynamic Performance

Signal-to-Noise Ratio ƒ

= 3.58 MHz VI 45 47 44 46 dB

IN

= 50 MHz VI 39 42 38 41 dB

ƒ

IN

Total Harmonic Distortion ƒIN = 3.58 MHz VI –52 –48 –50 –46 dB

= 50 MHz VI –43 –40 –42 –39 dB

ƒ

IN

Signal-to-Noise and Distortion ƒ

= 3.58 MHz VI 44 46 42 44 dB

IN

(SINAD) ƒIN = 50 MHz VI 37 39 35 37 dB

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SPT7725

ELECTRICAL SPECIFICATIONS

TA= T

MIN

to T

MAX

, VEE=–5.2 V , R

Source

=50 Ω, V

=–2.00 V , VR2=–1.00 V , V

RBF

=0.00 V , ƒ

RTF

=250 MHz, Duty Cycle=50%, unless otherwise specified.

CLK

TEST TEST SPT7725A SPT7725B

PARAMETERS CONDITIONS LEVEL MIN TYP MAX MIN TYP MAX UNITS
Digital Inputs

Digital Input High Voltage
(MINV, LINV) VI –1.1 –0.7 –1.1 –0.7 Volts
Digital Input Low Voltage
(MINV, LINV) VI –2.0 –1.5 –2.0 –1.5 Volts
Clock Low Width, t
Clock High Width, t

PWL

PWH

VI 2.2 2.0 2 1.8 ns
VI 2.2 2.0 2 1.8 ns

Digital Outputs

Digital Output High Voltage 50 Ω to –2 V VI –1.1 –1.1 Volts
Digital Output Low Voltage 50 Ω to –2 V VI –1.5 –1.5 Volts

Power Supply Requirements

Supply Current +25 °C VI 425 550 425 550 mA
Power Dissipation +25 °C VI 2.2 2.9 2.2 2.9 W

TEST LEVEL CODES

All electrical characteristics are subject to the
following conditions:

All parameters having min/max specifications
are guaranteed. The Test Level column indi­cates the specific device testing actually per­formed during production and Quality Assur­ance inspection. Any blank section in the data
column indicates that the specification is not
tested at the specified condition.

LEVEL TEST PROCEDURE

I 100% production tested at the specified temperature.

II 100% production tested at TA = +25 °C, and sample tested at the

specified temperatures.
III QA sample tested only at the specified temperatures.
IV Parameter is guaranteed (but not tested) by design and characteri-

zation data.

V Parameter is a typical value for information purposes only.

VI 100% production tested at TA = +25 °C. Parameter is guaranteed

over specified temperature range.

Unless otherwise noted, all test are pulsed
tests; therefore, T

= TC = TA.

J

SPT7725

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TYPICAL PERFORMANCE CHARACTERISTICS

SNR vs Input Frequency

52

50

S = 250 MSPS

48

46

44

42

40

Signal-to-Noise Ratio (dB)

38

36

34

1 10 100

Input Frequency (MHz)

THD vs Input Frequency

75

70

65

60

55

50

45

40

Total Harmonic Distortion (dB)

35

30

1 10 100

S = 250 MSPS

Input Frequency (MHz)

SINAD vs Input Frequency SNR, THD, SINAD vs Temperature

52

50

S = 250 MSPS

48

46

44

42

40

38

Signal-to-Noise and Distortion (dB)

36

34

1 10 100

Input Frequency (MHz)

50

45

40

SNR, THD, SINAD (dB)

35

30

40 20 0 20 40 60 80

Temperature (°C)

S = 250 MSPS
IN = 100 MHz

THD

SNR

SINAD

SPT7725

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