Datasheet

ADS8363

ADS7263

ADS7223

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SBAS523B –OCTOBER 2010–REVISED JANUARY 2011

Reference and Common-Mode Selection (REFCM) Register

To allow flexible adjustment of the common-mode voltage in pseudo-differential mode while simplifying the circuit

layout, the ADS8363/7263/7223 provide this register to assign one of the CMx inputs as a reference for each of

the input signals. According to the register settings, the CMx signals are internally connected to the appropriate

negative input of each ADC.

Additionally, this register also allows for the flexible assignment of one of the internal reference DAC outputs as a

reference for each channel in both fully- and pseudo-differential modes.

Table 12. REFCM: Reference and Common-Mode Selection Register (default = 0000h)

(1)

MSB LSB

BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

CMB3 CMB2 CMB1 CMB0 CMA3 CMA2 CMA1 CMA0 RB3 RB2 RB1 RB0 RA3 RA2 RA1 RA0

(1) This register should be set after setting the SEQFIFO register.

Bits[15:8] CMxx—Common-mode source selection bits (per input channel).

These bits allow selection of the CMx input pins or the internal reference source as common-mode for pseudo-differential

inputs B[3:0] and A[3:0]. The selected signal is connected to the negative input of the corresponding ADC.

0 = external common-mode source through CMx (default).

1 = internal common-mode source = REFIOx, depending on settings of bits Rx[3 :0].

Bit 7 RB3—Internal reference DAC output selection for CHB3 in pseudo-differential mode, or channel CHB1P/N in

fully-differential mode.

0 = internal reference source REFIO1 selected (default).