THS1031CPWR datasheet(20/41 Pages) TI

20 / 41 page

THS1031

3-V TO 5.5-V, 10-BIT, 30 MSPS

CMOS ANALOG-TO-DIGITAL CONVERTER

SLAS242E – NOVEMBER 1999 – REVISED MARCH 2002

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

onboard reference generator configuration

The onboard reference generator (ORG) can supply a supply-voltage-independent and temperature-

independent voltage on pin VREF.

External connections to REFSENSE control the ORG’s output to the VREF pin as shown in Table 2.

Table 2. Effect of REFSENSE Connection on VREF Value

REFSENSE CONNECTION

ORG OUTPUT TO VREF

REFER TO:

VREF pin

1 V

Figure 20

AGND

2 V

Figure 21

External divider junction

(1 + RA/RB)

Figure 22

AVDD

Open circuit

Figure 23

REFSENSE = AVDD powers the ORG down, saving power when the ORG function is not required.

If MODE = AVDD/2, the voltage on VREF determines the ADC reference voltages:

REFTF

) VREF

REFBF

* VREF

REFTF

* REFBF + VREF

VBG

Internal

Reference

Buffer

Mode =

REFSENSE

0.1

µF 1 µF

Tantalum

AGND

VREF = 1 V

AVDD

Figure 20. 1-V VREF Using ORG

(7)

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