THS1031IPW Datasheet, PDF (20/41 Pages) Texas Instruments – 3-V TO 5.5-V, 10-BIT, 30 MSPS CMOS ANALOG-TO-DIGITAL CONVERTER

THS1031
3-V TO 5.5-V, 10-BIT, 30 MSPS
CMOS ANALOG-TO-DIGITAL CONVERTER
SLAS242E – NOVEMBER 1999 – REVISED MARCH 2002
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
VREF pin
AGND
External divider junction
AVDD
ORG OUTPUT TO VREF
1V
2V
(1 + RA/RB)
Open circuit
REFER TO:
Figure 20
Figure 21
Figure 22
Figure 23
REFSENSE = AV_DD powers the ORG down, saving power when the ORG function is not required.
If MODE = AV_DD/2, the voltage on VREF determines the ADC reference voltages:
+ ) REFTF
AVDD
2
VREF
2
(7)
+ * REFBF
AVDD
2
VREF
2
* + REFTF REFBF VREF
VBG
+
_
Internal
Reference
Buffer
Mode =
AVDD
2
+
_
VREF = 1 V
REFSENSE
0.1 µF 1 µF
Tantalum
AGND
Figure 20. 1-V VREF Using ORG
20
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