TMS320F2811 datasheet(68/173 Pages) TI

68 / 173 page

Peripherals

April 2001 − Revised July 2007

SPRS174O

ADCINA[7:0]

ADCINB[7:0]

ADCLO

ADCBGREFIN

ADC External Current Bias Resistor

ADCRESEXT

ADCREFP

VDDA1

VDDA2

VSSA1

VSSA2

AVDDREFBG

AVSSREFBG

VDDAIO

VSSAIO

VDD1

VSS1

Test Pin

ADC Reference Positive Input

ADCREFM

ADC Reference Medium Input

ADC Analog Power

ADC Reference Power

ADC Analog I/O Power

ADC Digital Power

Analog Input 0−3 V With Respect to ADCLO

Connect to Analog Ground

24.9 k

W/20 kW (C)

Analog 3.3 V

Analog Ground

1.8 V Can use the same 1.8-V (or 1.9-V)

supply as the digital core but separate the

two with a ferrite bead or a filter

Digital Ground

ADC 16-Channel Analog Inputs

mF −10 mF

2 V

1 V

mF − 10 mF

NOTES: A. External decoupling capacitors are recommended on all power pins.

B. Analog inputs must be driven from an operational amplifier that does not degrade the ADC performance.

C. Use 24.9 k

Ω for ADC clock range 1 − 18.75 MHz; use 20 kΩ for ADC clock range 18.75 − 25 MHz.

D. It is recommended that buffered external references be provided with a voltage difference of (ADCREFP-ADCREFM)

= 1 V

$ 0.1% or better.

External reference is enabled using bit 8 in the ADCTRL3 Register at ADC power up. In this mode, the accuracy of

external reference is critical for overall gain. The voltage ADCREFP−ADCREFM will determine the overall accuracy.

Do not enable internal references when external references are connected to ADCREFP and ADCREFM. See the

TMS320x281x DSP Analog-to-Digital Converter (ADC) Reference Guide (literature number SPRU060) for more

information.

(D)

Figure 4−6. ADC Pin Connections With External Reference

TMS320F2811 数据表(PDF) 68 Page - Texas Instruments

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