Fairchild Semiconductor SPT7852 Datasheet

SPT7852

DUAL 10-BIT, 20 MSPS, 160 mW A/D CONVERTER

FEATURES

• Dual 10-Bit/20 MSPS Analog-to-Digital Converter

• Monolithic CMOS

• Internal Track-and-Hold

• Low Power Dissipation: 160 mW

• 4 Vp-p Analog Input Range for Each ADC

• Single +5 Volt Power Supply with Option for 3.3 V Digital Outputs

• Tri-State, TTL-Compatible Outputs

• Overrange Bit

• Selectable Two’s Complement or Straight Binary Output

GENERAL DESCRIPTION

The SPT7852 has two 10-Bit CMOS analog-to-digital converters that can sample data at speeds up to 20 MSPS. It has excellent low noise performance with a very low typical power dissipation of only 160 mW—that’s the total power for

both

converters. The SPT7852 uses a dual configuration of the proprietary circuit design found in our 10-bit CMOS single converter family, to achieve its high performance in a CMOS process.

The SPT7852 is specifically designed for video decoding applications and is ideal for S-video decoding and decoding of multiple composite video sources. It also has excellent

APPLICATIONS

• Video Set-Top Boxes

• Cellular Base Stations

• QPSK/QAM RF Demodulation

• S-Video Digitizers

• Composite Video Digitizers

• Portable and Handheld Instrumentation

application in the area of coherent I/Q demodulation in such applications as QAM demodulation and TV set-top box converters.

Inputs and outputs are TTL/CMOS-compatible to interface with TTL/CMOS-logic systems. Output data format is selectable for either straight binary or two’s complement. The SPT7852 is available in a 44L TQFP package in commercial and industrial temperature ranges. It is also available in die form. For availability of extended temperature ranges, please contact the factory.

BLOCK DIAGRAM

MSB

Invert

INA

Reference In

INB

Clock

Reset

Output

Enable

T/H

ADC

Reference

Ladder

ADC

Timing

Generation

Output

Buffer

Output

Buffer

Overrange D

A0-9

Overrange D

B0-9

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

Supply Voltages

AVDD.........................................................................+6 V

Output

Digital Outputs .......................................................10 mA

DVDD.........................................................................+6 V

Temperature

Input Voltages

Analog Input................................. –0.5 V to AVDD +0.5 V

.............................................. –1.5 V to AVDD +0.8 V

Ref

CLK Input ...................................................................V

– DVDD......................................................±100 mV

Operating Temperature ...................................0 to 70 °C

Junction Temperature ........................................... 175 °C

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

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

Note: 1. Operation at any Absolute Maximum Rating is not implied. See Electrical Specifications for proper nominal

applied conditions in typical applications.

ELECTRICAL SPECIFICATIONS FOR EACH CHANNEL

TA = T

PARAMETERS CONDITIONS LEVEL MIN TYP MAX UNITS

Resolution 10 Bits DC Accuracy

Analog Input

Reference Input

Conversion Characteristics

Dynamic Performance

MIN

to T

, AVDD = DVDD = +5.0 V, V

MAX

=0 to 4 V, ƒS =20 MSPS, ƒ

=40 MHz, V

CLK

RHS

=4.0 V, V

=0.0 V, unless otherwise specified.

RLS

TEST TEST

Integral Nonlinearity IV ±1.0 LSB Differential Nonlinearity IV ±1.0 LSB

Input Voltage Range V V

RLS

RHS

V Input Resistance V 50 kΩ Input Capacitance V 5.0 pF Input Bandwidth Full Power V 35 MHz Offset VI ±2.0 LSB Gain Error VI ±2.0 LSB

Resistance V

RHS

– V

RLS

VI 350 425 500 Ω

Voltage Range

RLS

RHS

– V

∆(V ∆(V

RHS RHF RLS

RLS

– V

) V 150 mV

RHS

– V

) V 150 mV

RLF

Maximum Conversion Rate Minimum Conversion Rate

IV 0 - 2.0 V IV 3.0 - AV

V 1.0 4.0 5.0 V

VI 20 MHz

IV 100 kHz Pipeline Delay (Latency) IV 12 Clock Cycles Aperture Delay Time V 5 ns Aperture Jitter Time V 15 ps

Effective Number of Bits

=3.58 MHz VI 8.4 8.9 Bits

ƒIN= 10 MHz VI 7.9 8.4 Bits

2X Clock required.

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ELECTRICAL SPECIFICATIONS

TA=T

MIN

to T

, AVDD = DVDD = +5.0 V, V

MAX

=0 to 4 V, ƒS =20 MSPS, ƒ

=40 MHz, V

CLK

RHS

= 4.0 V, V

=0.0 V, unless otherwise specified.

RLS

TEST TEST

PARAMETERS CONDITIONS LEVEL MIN TYP MAX UNITS

Dynamic Performance

Signal-to-Noise Ratio (without Harmonics)

=3.58 MHz VI 53 57 dB

ƒIN=10 MHz VI 52 56 dB

Harmonic Distortion

ƒIN=3.58 MHz VI 56 59 dB ƒIN=10 MHz VI 52 54 dB

Signal-to-Noise and Distortion

(SINAD) ƒIN=3.58 MHz VI 52 55 dB

ƒIN=10 MHz VI 49 52 dB Channel-to-Channel Crosstalk ƒIN=3.58 MHz IV 70 dB Channel-to-Channel Gain Matching Full Scale IV 0.04 dB Spurious Free Dynamic Range ƒIN=3.58 MHz @ –3 dB FS V 66 dB Differential Phase V 0.2 Degree Differential Gain V 0.3 %

Digital Inputs

Logic "1" Voltage VI 2.0 V Logic "0" Voltage VI 0.8 V Maximum Input Current Low V

=0 V VI –10 +10 µA

Maximum Input Current High VIH=5 V VI –10 +10 µA Input Capacitance V 5 pF

Digital Outputs

Logic "1" Voltage IOH=0.5 mA VI OVDD–0.5 V Logic "0" Voltage IOS=1.6 mA VI 0.4 V t

RISE/tFALL

15 pF Load V 10 ns

Output Enable to Data Output Delay 20 pF Load, TA=+25 °C V 10 ns

50 pF Load Over Temp. V 22 ns

Power Supply Requirements

Voltages DV

AV OV

Currents AI

DD DD

Total for Both Converter VI 15 18 mA Channels VI 17 20 mA

IV 4.75 5.0 5.25 V IV 4.75 5.0 5.25 V IV 2.7 5.0 5.25 V

Power Dissipation VI 160 190 mW

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.

TEST LEVEL

III

TEST PROCEDURE

100% production tested at the specified temperature. 100% production tested at T

=+25 °C, and sample tested at

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

acterization data. Parameter is a typical value for information purposes only. 100% production tested at T

= +25 °C. Parameter is guaran-

teed over specified temperature range.

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Figure 1 –Typical Interface Circuit

+A5

3-st

Ref In (+4 V)

IN1

IN2

Clock

RHF

RHS

RLS

RLF

CAL

INA

INB

CLK

MSBINV Reset

SPT7852

.1 µF .1 µF

4.7 µF 4.7 µF

+A5

GND OV

Digital

Output A

DAV

Digital

Output B

Interfacing

Logic

3.3 V/5 V

1. Place the ferrite bead (*) as close to the ADC as possible.

2. Place 0.1 µF decoupling capacitors as close to the ADC as possible.

3. All capacitors are 0.1 µF surface-mount unless otherwise specified.

4. All analog input pins (references, analog input, clock input) must be protected. (See absolute maximum ratings.)

TYPICAL INTERFACE CIRCUIT

Very few external components are required to achieve the stated device performance. Figure 1 shows the typical interface requirements when using the SPT7852 in normal circuit operation. The following sections provide descriptions of the major functions and outline critical performance criteria to consider for achieving the optimal device performance.

POWER SUPPLIES AND GROUNDING

Fairchild suggests that both the digital and the analog supply voltages on the SPT7852 be derived from a single analog supply as shown in figure 1. A separate digital supply must be used for all interface circuitry. Fairchild suggests using this power supply configuration to prevent a possible latch-up condition on powerup.

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