ADS5294IPFPR datasheet(59/81 Pages) TI1

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ADS5294

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SLAS776D – NOVEMBER 2011 – REVISED SEPTEMBER 2015

In addition to the above, the SYNC also synchronizes the RAMP test patterns across channels. In order to

synchronize the test patterns, TP_HARD_SYNC must be set as '1'. Setting TP_HARD_SYNC = 1 actually

disables the sync of the filters.

9.6.1.14 External Reference Mode of Operation

The ADS5294 supports an external reference mode of operation in one of two ways:

a. By forcing the reference voltages on the REFT and REFB pins.

b. By applying the reference voltage on VCM pin.

This mode can be used to operate multiple ADS5294 chips with the same (externally applied) reference voltage.

Using the REF pins:

For normal operation, the device requires two reference voltages: REFT and REFB. By default, the device

generates these two voltages internally. To enable the external reference mode, set the register bits as shown in

Table 23 which powers down the internal reference amplifier and the two reference voltages are forced directly

on the REFT and REFB pins as VREFT = 1.45 V ± 50 mV and VREFB = 0.45 V ±50 mV.

Note that the relation between the ADC full-scale input voltage and the applied reference voltages is

Full-scale input voltage = 2 × (VREFT – VREFB)

(5)

Using the VCM pin:

In this mode, an external reference voltage VREFIN can be applied to the VCM pin such that

Full-scale input voltage = 2 × VREFIN x (2 / 3)

(6)

To enable this mode, set the register bits as shown in Table 23 which changes the function of the VCM pin to an

external reference input pin. The voltage applied on VCM must be 1.5 V ±50 mV.

Table 23. External Reference Function

EN_HIGH_ADDRS (

EN_EXT_REF (0xF0[15])

EXT_REF_VCM

Function

0x1[4])

(0x42[15,3])

External reference using REFT and REFB pins

External reference using VCM pin

9.6.1.15 Data Output Format Modes

Table 24. Data Output Format Modes

ADDR.

D15

D14

D13

D12

D11

D10

NAME

(HEX)

BTC_MODE

MSB_FIRST

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