THS1031

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

CMOS ANALOG-TO-DIGITAL CONVERTER

SLAS242E – NOVEMBER 1999 – REVISED MARCH 2002

23

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

operating configuration examples (continued)

to be applied to REFTS and REFBS. The differential input goes from – 0.8 V to 0.8 V, giving a total input signal

span of 1.6 V. Using a PGA gain of 1, REFTF – REFBF should therefore, equal 1.6 V. REFSENSE is connected

AIN

REFTS

REFBS

REFTF

REFBF

REFSENSE

MODE

1.4 V

0.6 V

0.1

µF

10

µF

0.1

µF

0.1

µF

VREF = 1.6 V

RA

RB

1 V

1.4 V

0.6 V

1 V

AIN+

AIN–

AVDD

2

Figure 25. Differential Operation

Figure 26 shows a center span configuration for an input waveform swinging between 0.2 and 1.9 V. Pins

REFTS and REFBS are connected to a voltage source of 1.05 V, equal to the mid-scale of the input waveform.

With the PGA gain set to its default value of 1, REFTF – REFBF should be set equal to the span of the input

to disable the ORG output to VREF (see Figure 23) to allow this external source to be applied.

AIN

REFTS

REFBS

REFTF

REFBF

REFSENSE

MODE

1.9 V

0.2 V

0.1

µF

10

µF

0.1

µF

0.1

µF

1.05 V

DC SOURCE = 1.05 V

VREF

DC SOURCE = 1.7 V

AVDD

AVDD

2

Figure 26. Center Span Operation