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ADCINA[7:0]
ADCINB[7:0]
ADCLO
ADCREFIN
ADC External Current Bias Resistor
ADCRESEXT
ADCREFP
V
DD1A18
V
DD2A18
V
SS1AGND
V
SS2AGND
V
DDAIO
V
SSAIO
V
DDA2
V
SSA2
ADC Reference Positive Output
ADCREFM
ADC Reference Medium Output
ADC Analog Power
ADC Analog and Reference I/O Power
Analog input 03 V with respect to ADCLO
Connect to Analog Ground
Connect to 1.500, 1.024, or 2.048-V precision source
(D)
22 k
2.2 F
(A)
2.2 F
(A)
ADCREFP and ADCREFM should not
be loaded by external circuitry
ADC 16-Channel Analog Inputs
ADC Analog Power Pin (1.8 V)
ADC Analog Power Pin (1.8 V)
ADC Analog Ground Pin
ADC Analog Ground Pin
ADC Analog I/O Ground Pin
ADC Analog Power Pin (3.3 V)
ADC Analog Ground Pin
ADC Analog Power Pin (3.3 V)
4.5
ADC Connections if the ADC Is Not Used
TMS320F28044
Digital Signal Processor
SPRS357B–AUGUST 2006–REVISED MAY 2007
A.
B.
C.
D.
TAIYO YUDEN LMK212BJ225MG-T or equivalent
External decoupling capacitors are recommended on all power pins.
Analog inputs must be driven from an operational amplifier that does not degrade the ADC performance.
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 4-7. ADC Pin Connections With External Reference
NOTE
The temperature rating of any recommended component must match the rating of the end
product.
It is recommended that the connections for the analog power pins be kept 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:
V
DD1A18
/V
DD2A18
– Connect to V
DD
V
DDA2
, V
DDAIO
– Connect to V
DDIO
V
SS1AGND
/V
SS2AGND
, V
SSA2
, V
SSAIO
– Connect to V
SS
ADCLO – Connect to V
SS
ADCREFIN – Connect to V
SS
ADCREFP/ADCREFM – Connect a 100 nF cap to V
SS
ADCRESEXT – Connect a 20-k
resistor (very loose tolerance) to V
SS
.
ADCINAn, ADCINBn - Connect to V
SS
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 (V
SS1AGND
/V
SS2AGND
)
The ADC operation is configured, controlled, and monitored by the registers listed in
Table 4-6
.
Peripherals
52
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