TLC1518IPW datasheet(34/40 Pages) TI2

34 / 40 page

TLC1514, TLC1518

5-V, 10-BIT, 400 KSPS, 4/8 CHANNEL, LOW POWER,

SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTO POWER DOWN

SLAS252 – DECEMBER 1999

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

Driving Source†

TLC1514/18

VI = Input Voltage at AIN

VS = External Driving Source Voltage

Rs = Source Resistance

ri = Input Resistance (MUX on Resistance)

Ci = Input Capacitance

VC= Capacitance Charging Voltage

† Driving source requirements:

• Noise and distortion for the source must be equivalent to the resolution of the converter.

• Rs must be real at the input frequency.

Figure 38. Equivalent Input Circuit Including the Driving Source

maximum conversion throughput

For a supply voltage of 5 V, if the source impedance is less than 1 k

Ω, and the ADC analog input capacitance

Ci is less than 50 pF, this equates to a minimum sampling time tch(0.5 LSB) of 0.571

µs. Since the sampling

time requires 12 SCLKs, the fastest SCLK frequency is 12/tch = 20 MHz.

The minimal total cycle time is given as:

+ tcommand ) tch ) tconv ) td(EOCH–CSL) + 4

f (SCLK)

) 12

f (SCLK)

) 1.4 ms ) 0.1 ms

+ 16

MHz

) 1.5 ms + 2.3 ms

This is equivalent to a maximum throughput of 400 KSPS. The throughput can be even higher with a smaller

source impedance.

TLC1518IPW Datasheet(PDF) 34 Page - Texas Instruments