TLV571

2.7 V TO 5.5 V, 1-CHANNEL, 8-BIT,

PARALLEL ANALOG-TO-DIGITAL CONVERTER

SLAS239A – SEPTEMBER 1999 – REVISED FEBRUARY 2000

13

POST OFFICE BOX 655303

software START conversion (continued)

signal-to-noise ratio + distortion (SINAD)

Signal-to-noise ratio + disortion is the ratio of the rms value of the measured input signal to the rms sum of all

other spectral components below the Nyquist frequency, including harmonics but excluding dc. The value for

SINAD is expressed in decibels.

effective number of bits (ENOB)

For a sine wave, SINAD can be expressed in terms of the number of bits. Using the following formula,

N = (SINAD – 1.76)/6.02

it is possible to get a measure of performance expressed as N, the effective number of bits. Thus, the effective

number of bits for a device for sine wave inputs at a given input frequency can be calculated directly from its

measured SINAD.

total harmonic distortion (THD)

Total harmonic distortion is the ratio of the rms sum of the first six harmonic components to the rms value of the

measured input signal and is expressed as a percentage or in decibels.

spurious free dynamic range (SFDR)

Spurious free dynamic range is the difference in dB between the rms amplitude of the input signal and the peak

spurious signal.

DSP interface

The TLV571 is a 8-bit single input channel analog-to-digital converter with throughput up to 1.25 MSPS at 5 V

and up to 625 KSPS at 3 V. To achieve 1.25 MSPS throughput, the ADC must be clocked at 20 MHz. Likewise

to achieve 625 KSPS throughout, the ADC must be clocked at 10 MHz. The TLV571 can be easily interfaced

to microcontrollers, ASICs, and DSPs. Figure 8 shows the pin connections to interface the TLV571 to the

TMS320C6x DSP.

Address

Decoder

EN

A0–A15

TMS320C6X

HW

HR

INTx

D0– D15

D0– D7

CS

WR

RD

EOC

TLV571

REF

AIN

REFP

REFM

Figure 8. TMS320C6x DSP Interface