Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - AD converter (ADC) External TSSOP 20

VREFP

AVSS

REFOUT

AVDD

VREFN

ReferenceSelect

EXTREFRegisterBit

(1=SwitchOpenforExternalReference)

ReferenceBias

RBIASRegisterBit

(1=BiasOn)

2.5V

Reference

ADCReferenceInput

(+)

( )-

1 F

REFOUT

)

ReferenceOutput

(+)

( )-

2kW

ReferenceInput

(+)

( )-

1 F

REFIN

)

ADS1259

SBAS424D –JUNE 2009– REVISED AUGUST 2011

www.ti.com

REFERENCE the ADC reference input pins, VREFP and VREFN.

(Note that these device pins are not intended to drive

The ADS1259 includes an onboard voltage reference

external circuits.) An external 1μF capacitor,

with a low temperature coefficient. The reference

connected from VREFP to VREFN, is recommended

voltage is 2.5V with the capability of sinking and

for noise reduction. The capacitor can be increased

sourcing 10mA via the REFOUT pin. The ADS1259

for increased noise filtering, but the settling time of

can also operate from an external reference. The

the reference may also increase. The settling time

external reference is the default selection. Refer to

should be considered upon activating the internal

Figure 38 for a reference block diagram.

reference.

Internal Reference See Figure 29 for typical reference settling C

REFIN

1µF. The capacitor dielectric absorption results in

The reference output is provided between pins

increased settling time for RC filter circuits.

REFOUT and AVSS. Because the reference output

return shares the same pin as AVSS, route the To activate the internal reference, set the register bit

reference return trace and the AVSS trace RBIAS = 1. This enables the reference bias. Once

independently as Kelvin-connected printed circuit biased, the internal reference can then be selected as

board (PCB) traces. For stability reasons, connect a the ADC reference by the register bit EXTREF.

1μF capacitor between REFOUT and AVSS. EXTREF = 0 closes the internal switches.

An internal switch connects the internal reference to

Figure 38. Reference Block Diagram

Table 2. Reference Selection for Figure 38

ADS1259 REFERENCE RBIAS REGISTER BIT EXTREF REGISTER BIT

Internal 1 0

External See

(1)

(1) If the reference output is not required, set RBIAS = 0. If the reference output is enabled (RBIAS = 1), an external 1µF capacitor must be

used between REFOUT and AVSS.