TEXAS INSTRUMENTS THS1401, THS1403, THS1408 Technical data

Download

查询THS1401供应商

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

features

14-Bit Resolution

1, 3, and 8 MSPS Speed Grades Available

Differential Nonlinearity (DNL) ±0.6 LSB Typ

Integral Nonlinearity (INL) ±1.5 LSB Typ

Internal Reference

Differential Inputs

Programmable Gain Amplifier

µP Compatible Parallel Interface

Timing Compatible With TMS320C6000 DSP

3.3-V Single Supply

Power-Down Mode

Monolithic CMOS Design

IN–

VBG

CML REF+ REF–

AGND AGND DGND

OV D13 D12

2 3 4 5 6 7 8 9 10 11 12

PFB PACKAGE

IN+AVAGND

47 46 45 44 4348 42

14 15

AGND

D D D D

(TOP VIEW)

AGND

17 18 19 20

applications

xDSL Front Ends Communication Industrial Control Instrumentation

A0A1NC

40 39 3841

22 23 24

36 35 34 33 32 31 30 29 28 27 26 25

WR OE DGND DGND CLK DV

D0 D1 D2 DV

DGND

NC – No internal connection

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

D10

DGND

D9D8D7

D11

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

D5D4D3

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

description

The THS1401, THS1403, and THS1408 are 14-bit, 1/3/8 MSPS, single supply analog-to-digital converters with an internal reference, differential inputs, programmable input gain, and an on-chip sample and hold amplifier .

Implemented with a CMOS process, the device has outstanding price/performance and power/speed ratios. The THS1401, THS1403, and THS1408 are designed for use with 3.3-V systems, and with a high-speed µP compatible parallel interface, making them the first choice for solutions based on high-performance DSPs like the TI TMS320C6000 series.

The THS1401, THS1403, and THS1408 are available in a TQFP-48 package in standard commercial and industrial temperature ranges.

functional block diagram

VBG

IN+

IN–

CLK

1.5 V BG

PGA

0..7 dB

REF+

REF

14-Bit

ADC

CONTROL

LOGIC

AVAILABLE OPTIONS

0°C to 70°C

–40°C to 85°C

14 15

Buffer

PACKAGED DEVICE

TQFP (PFB)

THS1401CPFB, THS1403CPFB, THS1408CPFB,

THS1401IPFB, THS1403IPFB, THS1408IPFB

REF–

D[13:0] + OV bit

A[1:0]

CS WR OE

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

I/O

DESCRIPTION

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

Terminal Functions

TERMINAL

NAME NO.

A[1:0] 40, 41 I Address input AGND 7,8, 44,

CLK 32 I Clock input CML 4 Reference midpoint. This pin requires a 0.1-µF capacitor to AGND. CS 37 I Chip select input. Active low DGND 9, 15, 25,

D[13:0] 11, 12, 13,

NC 38, 39 No connection, do not use. Reserved IN+ 48 I Positive differential analog input IN– 1 I Negative dif ferential analog input OE 35 I Output enable. Active low OV 10 O Out of range output REF+ 5 O Positive reference output. This pin requires a 0.1-µF capacitor to AGND. REF– 6 O Negative reference output. This pin requires a 0.1-µF capacitor to AGND. VBG 3 I Reference input. This pin requires a 1-µF capacitor to AGND. WR 36 I Write signal. Active low

45, 46

2, 43, 47 P Analog power supply

33, 34

14, 20, 26,

30, 31, 42

16, 17, 18,

19,21, 22,

23, 24, 27,

28, 29

P Analog ground

P Digital ground

P Digital power supply

I/O Data inputs/outputs

SLAS248 – DECEMBER 1999

absolute maximum ratings over operating free-air temperature (unless otherwise noted)

†

Supply voltage, (AVDD to AGND) 4V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Supply voltage, (DVDD to DGND) 4V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reference input voltage range, VBG – 0.3 V to AV Analog input voltage range – 0.3 V to AV Digital input voltage range – 0.3 V to DV

DD DD DD

+ 0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+ 0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating free-air temperature range, TA: C suffix 0°C to 70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I suffix –40°C to 85°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, T

stg

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lead temperature 1.6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

†

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

Operating free-air temperature

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

recommended operating conditions

PARAMETER MIN NOM MAX UNIT

Supply voltage, AVDD, DV High level digital input, V Low level digital input, V Load capacitance, C

Clock frequency, f

Clock duty cycle 40% 50% 60%

CLK

THS1401 0.1 1 1 MHz THS1403 0.1 3 3 MHz THS1408 0.1 8 8 MHz

C suffix 0 25 70 °C I suffix –40 25 85 °C

electrical characteristics over recommended operating conditions

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Power Supply

DDA

DDD

DC Characteristics

DNL Differential nonlinearity ±0.6 ±1 LSB

INL Integral nonlinearity

AC Characteristics

ENOB Effective number of bits 11.2 1 1.5 Bits

THD Total harmonic distortion

SNR Signal-to-noise ratio

SINAD Signal-to-noise ratio + distortion

SFDR Spurious free dynamic range

Analog supply current 81 90 mA Digital supply current 5 10 mA Power 270 360 mW Power down current 20 µA

Resolution 14 Bits

THS1401 ±1.5 ±2.5 LSB THS1403

THS1408 ±3 ±5 LSB Offset error IN+ = IN–, PGA = 0 dB 0.3 %FSR Gain error PGA = 0 dB 1 %FSR

THS1401/3/8 fi = 100 kHz –81

THS1403/8

THS1408 fi = 4 MHz –77

THS1401/3/8 fi = 100 kHz 72

THS1403/8

THS1408 fi = 4 MHz 71

THS1401/3/8 fi = 100 kHz 70

THS1403/8

THS1408 fi = 4 MHz 70

THS1401/3/8 fi = 100 kHz 80

THS1403/8

THS1408 fi = 4 MHz 80 Analog input bandwidth 140 MHz

Best fit

fi = 1 MHz –78

fi = 1 MHz 70 72

fi = 1 MHz 69 70

fi = 1 MHz 73 80

3 3.3 3.6 V 2 3.3 V

0.8

5 15 pF

±1.5 ±2.5 LSB

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

VBG

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

electrical characteristics (continued)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Reference Voltage

Bandgap voltage, internal mode 1.425 1.5 1.575 V Input impedance 40 kΩ Positive reference voltage, REF+ 2.5 V Negative reference voltage, REF– 0.5 V Reference difference, ∆REF, REF+ – REF– 2 V Accuracy, internal reference 5% Temperature coefficient 40 ppm/°C Voltage coefficient 200 ppm/V

Analog Inputs

Positive analog input, IN+ 0 AV Negative analog input, IN– 0 AV Analog input voltage difference ∆Ain = IN+ – IN–, V Input impedance 25 kΩ PGA range 0 7 dB PGA step size 1 dB PGA gain error ±0.25 dB

Digital Inputs

Digital Outputs

Clock Timing (CS low)

CLK

High-level digital input 2 V Low-level digital input 0.8 V Input capacitance 5 pF Input current ±1 µA

High-level digital output IOH = 50 µA 2.6 V Low-level digital output IOL = 50 µA 0.4 V Output current, high impedance ±10 µA

Clock frequency

Output delay time 25 ns Latency 9.5 Cycles

THS1401, THS1403, THS1408

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

ref

V V V

DD DD

= REF+ – REF– –V

ref

THS1401 0.1 1 1 MHz THS1403 THS1408 0.1 8 8 MHz

ref

0.1 3 3 MHz

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

PARAMETER MEASUREMENT INFORMATION

sample timing

The THS1401/3/8 core is based on a pipeline architecture with a latency of 9.5 samples. The conversion results appear on the digital output 9.5 clock cycles after the input signal was sampled.

Analog

Input

S11

S10

S12

CLK

Data

Out

w(CLK)

C1 C2

Figure 1. Sample Timing

The parallel interface of the THS1401/3/8 ADC features 3-state buffers making it possible to directly connect it to a data bus. The output buffers are enabled by driving the OE input low.

Besides the sample results, it is also possible to read back the values of the control register, the PGA register, and the control register. Which register is read is determined by the address inputs A[1,0]. The ADC results are available at address 0.

The timing of the control signals is described in the following sections.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

PARAMETER MEASUREMENT INFORMATION

read timing (15-pF load)

PARAMETER MIN TYP MAX UNIT

su(OE–ACS)

dis

h(A)

h(CS)

NOTE: All timing parameters refer to a 50% level.

Address and chip select setup time 4 ns Output enable 15 ns Output disable Address hold time 1 15 ns Chip select hold time 0 ns

THS1401, THS1403, THS1408

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

h(CS)

D[13:0]

O V

A[1:0]

su(OE–ACS)

X X

DATA

ADDRESS

Figure 2. Read Timing

h(A)

dis

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

PARAMETER MEASUREMENT INFORMATION

write timing (15-pF load)

PARAMETER MIN TYP MAX UNIT

su(WE–CS)

su(DA)

h(DA)

h(CS)

wH(WE)

NOTE: All timing parameters refer to a 50% level.

Chip select setup time 4 ns Data and address setup time 29 ns Data and address hold time 0 ns Chip select hold time 0 ns Write pulse duration high 15 ns

su(WE–CS)

su(DA)

h(CS)

D[13:0]

h(DA)

X X

DATA

ADDRESS

Figure 3. Write Timing

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

TYPICAL CHARACTERISTICS

POWER

FREQUENCY

284

282

280

278

276

Power – mW

274

272

270

268

0.1 1 10 f – Frequency – MHz

Figure 4

fs = 1 MSPS,

–20

fI = 100 kHz, –1 dB

–40 –60

– Supply Current – mA

0 50 100 150 200 250 300

FAST FOURIER TRANSFORM

SUPPLY CURRENT

TIME

t – Time – ns

Figure 5

–80

Output – dB

–100 –120

–140

0 100 200 300

f – Frequency – kHz

Figure 6

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

400 500

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

TYPICAL CHARACTERISTICS

FAST FOURIER TRANSFORM

fs = 3 MSPS,

–20

fI = 1 MHz, –1 dB

–40 –60 –80

Output – dB

–100 –120

–140

0.1 0.4 0.7 1 f – Frequency – MHz

Figure 7

FAST FOURIER TRANSFORM

fs = 8 MSPS,

–20

fI = 1 MHz, –1 dB

–40 –60

1.3

–80

Output – dB

–100 –120

–140

0.1 0.4 0.7 1 1.6 1.9 2.5

1.3 f – Frequency – MHz

Figure 8

INTEGRAL NONLINEARITY

1.5

0.5

–0.5

–1

–1.5

–2

INL – Integral Nonlinearity – LSB

fs = 1 MSPS

0 2048 4096 6144 8192 10240

Samples

Figure 9

2.2

2.8 3.1 3.7 4

12288 14336 16384

3.4

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

TYPICAL CHARACTERISTICS

INTEGRAL NONLINEARITY

1.5 1

0.5 0

–0.5

–1

–1.5

–2

INL – Integral Nonlinearity – LSB

0 2048 4096 6144 8192 10240

Samples

Figure 10

INTEGRAL NONLINEARITY

4 3 2 1

0 –1 –2

–3 –4

INL – Integral Nonlinearity – LSB

0 2048 4096 6144 8192 10240

Samples

fs = 3 MSPS

12288 14336 16384

fs = 8 MSPS

12288 14336 16384

Figure 11

DIFFERENTIAL NONLINEARITY

fs = 1 MSPS

0.8

0.6

0.4

0.2 0

–0.2 –0.4 –0.6 –0.8

–1

0 2048 4096 6144 8192 10240

DNL – Differential Nonlinearity – LSB

Samples

Figure 12

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

12288 14336 16384

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

TYPICAL CHARACTERISTICS

DIFFERENTIAL NONLINEARITY

0.8

0.6

0.4

0.2 0

–0.2 –0.4 –0.6

–0.8

–1

0 2048 4096 6144 8192 10240

DNL – Differential Nonlinearity – LSB

Samples

Figure 13

DIFFERENTIAL NONLINEARITY

0.8

0.6

0.4

0.2

–0.2 –0.4 –0.6

–0.8

–1

DNL – Differential Nonlinearity – LSB

fs = 8 MSPS

0 2048 4096 6144 8192 10240

Samples

fs = 3 MSPS

12288 14336 16384

Figure 14

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

TYPICAL CHARACTERISTICS

TOTAL HARMONIC DISTORTION

FREQUENCY

–70

fs = 3 MSPS,

–72

fI at –1 dB –74

–76 –78 –80

–82

–84 –86

THD – Total Harmonic Distortion – dB

–88 –90

f – Frequency – Hz

Figure 15

SIGNAL-TO-NOISE RATIO

FREQUENCY

fs = 3 MSPS,

fI at –1 dB

100 1000

1500

TOTAL HARMONIC DISTORTION

FREQUENCY

–70

fs = 8 MSPS, fI at –1 dB

–72

–74

–76

–78 –80

–82

–84

–86

THD – Total Harmonic Distortion – dB

–88

–90

10 100

f – Frequency – Hz

Figure 16

SIGNAL-TO-NOISE RATIO

FREQUENCY

fs = 8 MSPS,

fI at –1 dB

1000

4000

74 72 70

66 64

SNR – Signal-to-Noise Ratio – dB

62 60

100

f – Frequency – Hz

Figure 17

1000

1500

72 70

SNR – Signal-to-Noise Ratio – dB

100

f – Frequency – Hz

Figure 18

1000

4000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

PRINCIPLES OF OPERATION

registers

The device contains several registers. The A register is selected by the values of bits A1 and A0:

A1 A0 Register

0 0 Conversion result 0 1 PGA 1 0 Offset 1 1 Control

T ables 1 and 2 describe how to read the conversion results and how to configure the data converter . The default values (were applicable) show the state after a power-on reset.

Table 1. Conversion Result Register, Address 0, Read

BIT D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Function MSB ... … … … … … … … … … … … LSB

The output can be configured for two’s complement or straight binary format (see D11/control register). The output code is given by:

2s complement: Straight binary: –8192 at ∆IN = –∆REF 0 at ∆IN = –∆REF 0 at ∆IN = 0 8192 at ∆IN = 0 8191 ∆IN = –∆REF – 1 LSB 16383 at ∆IN = –∆REF – 1 LSB

1LSB

2DREF

16384

Table 2. PGA Gain Register, Address 1, Read/Write

BIT D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Function X X X X X X X X X X X G2 G1 G0

Default 0 0 0 0 0 0 0 0 0 0 0 0 0 0

The PGA gain is determined by writing to G2–0. Gain (dB) = 1dB × G2–0. max = 7dB. The range of G2–0 is 0 to 7.

Table 3. Offset Register, Address 2, Read/Write

BIT D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Function X X X X X X MSB … … … … … … LSB

Default 0 0 0 0 0 0 0 0 0 0 0 0 0 0

The offset correction range is from –128 to 127 LSB. This value is added to the conversion results from the ADC.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

PRINCIPLES OF OPERATION

Table 4. Control Register, Address 3, Read

BIT D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Function PWD REF FOR TM2 TM1 TM0 OFF RES RES RES RES RES RES RES

Table 5. Control Register, Address 3, Write

BIT D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Function PWD REF FOR TM2 TM1 TM0 OFF RES RES RES RES RES RES RES

Default 0 0 0 0 0 0 0 0 0 0 0 0 0 0

PWD: Power down 0 = normal operation 1 = power down REF: Reference select 0 = internal reference 1 = external reference FOR: Output format 0 = straight binary 1 = 2s complement TM2–0: Test mode 000 = normal operation

001 = both inputs = REF– 010 = IN+ at V 011 = IN+ at REF+, IN– at REF– 100 = normal operation 101 = both inputs = REF+ 110 = IN+ at REF–, IN– at V

111 = IN+ at REF–, IN– at REF+ OF: Offset correction 0 = enable 1 = disable RES Reserved Must be set to 0.

/2, IN– at REF–

ref

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

APPLICATION INFORMATION

driving the analog input

The THS1401/3/8 ADCs have a fully differential input. A differential input is advantageous with respect to SNR, SFDR, and THD performance because the signal peak-to-peak level is 50% of a comparable single-ended input.

There are three basic input configurations:

Fully differential

Transformer coupled single-ended to differential

Single-ended

fully differential configuration

In this configuration, the ADC converts the difference (∆IN) of the two input signals on IN+ and IN–.

22 Ω

100 pF

22 Ω

100 pF

IN+

THS1401/3/8

IN–

Figure 19. Differential Input

The resistors and capacitors on the inputs decouple the driving source output from the ADC input and also serve as first order low pass filters to attenuate out of band noise.

The input range on both inputs is 0 V to A VDD. The full-scale value is determined by the voltage reference. The positive full-scale output is reached, if ∆IN equals ∆REF , the negative full-scale output is reached, if ∆IN equals –∆REF.

∆IN [V] OUTPUT

–∆REF – full scale

0 0

∆REF + full scale

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

APPLICATION INFORMATION

transformer coupled single-ended to differential configuration

If the application requires the best SNR, SFDR, and THD performance, the input should be transformer coupled. The signal amplitude on both inputs of the ADC is one half as high as in a single-ended configuration thus

increasing the ADC ac performance.

22 Ω

100 pF

22 Ω

100 pF

1 µF 0.1 µF

Figure 20. Transformer Coupled

IN+

THS1401/3/8

IN–

CML

IN [V

–∆REF – full scale

†

n = 1 (winding ratio)

] OUTPUT [

PEAK

0 0

∆REF + full scale

PEAK

]

†

The resistor R of the transformer coupled input configuration must be set to match the signal source impedance R = n2 Rs, where Rs is the source impedance and n is the transformer winding ratio.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

APPLICATION INFORMATION

single-ended configuration

In this configuration, the input signal is level shifted by ∆REF/2.

10 kΩ + 10 kΩ

REF+

10 kΩ 10 kΩ

–

100 pF

22 Ω

100 pF

IN+

THS1401/3/8

IN–

REF–

10 kΩ

Figure 21. Single-Ended With Level Shift

The following table shows the input voltages for negative full-scale output, zero output, and positive full-scale output:

∆IN+ [V] OUTPUT

–∆REF – full scale

0 0

∆REF + full scale

Note that the resistors of the op-amp and the op-amp all introduce gain and offset errors. Those errors can be trimmed by varying the values of the resistors.

Because of the added offset, the op-amp does not necessarily operate in the best region of its transfer curve (best linearity around zero) and therefore may introduce unacceptable distortion. For ac signals, an alternative is described in the following section.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

APPLICATION INFORMATION

AC-coupled single-ended configuration

If the application does not require the signal bandwidth to include dc, the level shift shown in Figure 4 is not necessary.

10 kΩ 10 kΩ

REF+

10 kΩ 10 kΩ

–

100 pF

10 nF

22 Ω

100 pF

Figure 22. Single-Ended With Level Shift

IN+

THS1401/3/8

IN–

10 kΩ 10 kΩ

REF–

Because the signal swing on the op-amp is centered around ground, it is more likely that the signal stays within the linear region of the op-amp transfer function, thus increasing the overall ac performance.

IN [V

–∆REF – full scale

] OUTPUT [

PEAK

0 0

∆REF + full scale

PEAK

]

Compared to the transformer-coupled configuration, the swing on IN– is twice as big, which can decrease the ac performance (SNR, SFD, and THD).

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

THS1401, THS1403, THS1408 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

APPLICATION INFORMATION

internal/external reference operation

The THS1401/3/8 ADC can either be operated using the built-in band gap reference or using an external precision reference in case very high dc accuracy is needed.

The REF+ and REF+ outputs are given by:

)

REF

VBG

If the built-in reference is used, VBG equals 1.5 V which results in REF+ = 2.5 V, REF– = 0.5 V and ∆REF = 2V.

The internal reference can be disabled by writing 1 to D12 (REF) in the control register (address 3). The band gap reference is then disconnected and can be substituted by a voltage on the VBG pin.

and REF–+VBGǒ1–

programmable gain amplifier

The on-chip programmable gain amplifier (PGA) has eight gain settings. The gain can be changed by writing to the PGA gain register (address 1). The range is 0 to 7dB in steps of one dB.

out of range indication

The OV output of the ADC indicates an out of range condition. Every time the difference on the analog inputs exceeds the differential reference, this signal is asserted. This signal is updated the same way as the digital data outputs and therefore subject to the same pipeline delay.

offset compensation

With the offset register it is possible to automatically compensate system offset errors, including errors caused by additional signal conditioning circuitry . If the offset compensation is enabled (D7 (OFF) in the control register), the value in the offset register (address 2) is automatically subtracted from the output of the ADC.

In order to set the correct value of the offset compensation register , the ADC result when the input signal is 0 must be read by the host processor and written to the offset register (address 2).

test modes

The ADC core operation can be tested by selecting one of the available test modes (see control register description). The test modes apply various voltages to the differential input depending on the setting in the control register.

digital I/O

The digital inputs and outputs of the THS1401/3/8 ADC are 3-V CMOS compatible. In order to avoid current feed back errors, the capacitive load on the digital outputs should be as low as possible (50 pF max). Series resistors (100 Ω) on the digital outputs can improve the performance by limiting the current during output transitions.

The parallel interface of the THS1401/3/8 ADC features 3-state buffers, making it possible to directly connect it to a data bus. The output buffers are enabled by driving the OE

Refer to the read and write timing diagrams in the parameter measurement information section for information on read and write access.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

input low.

THS1401, THS1403, THS1408

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SLAS248 – DECEMBER 1999

MECHANICAL DATA

PFB (S-PQFP-G48) PLASTIC QUAD FLATPACK

1,05 0,95

0,50

0,27 0,17

5,50 TYP

7,20

6,80 9,20

8,80

0,08

0,05 MIN

Seating Plane

0,13 NOM

Gage Plane

0,25

0°–7°

0,75 0,45

1,20 MAX

NOTES: A. All linear dimensions are in millimeters.

B. This drawing is subject to change without notice. C. Falls within JEDEC MS-026

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

0,08

4073176/B 10/96

IMPORTANT NOTICE

T exas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability.

TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty . Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.

CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOL VE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICA TIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERST OOD TO BE FULLY AT THE CUSTOMER’S RISK.

In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI’s publication of information regarding any third party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.

TEXAS INSTRUMENTS THS1401, THS1403, THS1408 Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual