Texas Instruments TMS320C2801, TMS320F2809 ADC Connections if the ADC Is Not Used, Adcresext

TMS320F2809, TMS320F2808, TMS320F2806
TMS320F2802, TMS320F2801, TMS320C2802
TMS320C2801, TMS320F28016, TMS320F28015
SPRS230L –OCTOBER 2003 –REVISED DECEMBER 2009			www.ti.com
ADC 16-Channel Analog Inputs	ADCINA[7:0]	Analog input 0−3 V with respect to ADCLO
	ADCINB[7:0]
	ADCLO	Connect to Analog Ground
	ADCREFIN	Connect to 1.500, 1.024, or 2.048-V precision source (D)
		22 kW
ADC External Current Bias Resistor	ADCRESEXT	2.2 mF (A)
ADC Reference Positive Output	ADCREFP
		2.2 mF (A)	ADCREFP and ADCREFM should not
ADC Reference Medium Output	ADCREFM
			be loaded by external circuitry
	VDD1A18		ADC Analog Power Pin (1.8 V)
ADC Analog Power	VDD2A18		ADC Analog Power Pin (1.8 V)
	VSS1AGND		ADC Analog Ground Pin
	VSS2AGND		ADC Analog Ground Pin
	VDDA2		ADC Analog Power Pin (3.3 V)
	VSSA2		ADC Analog Ground Pin
ADC Analog and Reference I/O Power	VDDAIO		ADC Analog Power Pin (3.3 V)
	VSSAIO		ADC Analog I/O Ground Pin

A.TAIYO YUDEN LMK212BJ225MG-T or equivalent

B.External decoupling capacitors are recommended on all power pins.

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

D.External voltage on ADCREFIN is enabled by changing bits 15:14 in the ADC Reference Select register depending on the voltage used on this pin. TI recommends TI part REF3020 or equivalent for 2.048-V generation. Overall gain accuracy will be determined by accuracy of this voltage source.

Figure 4-9. ADC Pin Connections With External Reference

NOTE

The temperature rating of any recommended component must match the rating of the end product.

4.6.1ADC Connections if the ADC Is Not Used

It is recommended to keep the connections for the analog power pins, even if the ADC is not used. Following is a summary of how the ADC pins should be connected, if the ADC is not used in an application:

•VDD1A18/VDD2A18 – Connect to VDD

•VDDA2, VDDAIO – Connect to VDDIO

•VSS1AGND/VSS2AGND, VSSA2, VSSAIO – Connect to VSS

•ADCLO – Connect to VSS

•ADCREFIN – Connect to VSS

•ADCREFP/ADCREFM – Connect a 100-nF cap to VSS

•ADCRESEXT – Connect a 20-kΩ resistor (very loose tolerance) to VSS.

•ADCINAn, ADCINBn - Connect to VSS

When the ADC is not used, be sure that the clock to the ADC module is not turned on to realize power savings.

When the ADC module is used in an application, unused ADC input pins should be connected to analog

ground (VSS1AGND/VSS2AGND)

66 Peripherals Copyright © 2003–2009, Texas Instruments Incorporated

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TMS320C2801 TMS320F28016 TMS320F28015