THS1030 Datasheet, PDF (15/22 Pages) Texas Instruments – 2.7 V . 5.5 V, 10-BIT, 30 MSPS CMOS ANALOG-TO-DIGITAL CONVERTER

THS1030
2.7 V – 5.5 V, 10-BIT, 30 MSPS
CMOS ANALOG-TO-DIGITAL CONVERTER
SLAS243A – NOVEMBER 1999 – REVISED JANUARY 2000
PRINCIPLES OF OPERATION
ADC reference
The MODE pin is used to select the reference source for the ADC.
D Internal ADC Reference: Connect the MODE pin to AV_DD to use the reference source for ADC generated
on the V_REF pin. (See V_REF REFERENCE described in Table 2) such that (REFTF–REFBF) = V_REF and
(REFTF+REFBF)/2 is set to a voltage for optimum operation of the ADC (near AV_DD/2).
D External ADC Reference: To supply an external reference source to the ADC, connect the MODE pin to
AGND. An external reference source should be connected to REFTF/REFTS and REFBF/REFBS.
MODE = AGND closes internal switches to allow a Kelvin connection through REFTS/REFBS, and disables
the on-chip amplifiers which drive on to the ADC references. Differential input is not supported
analog input mode
single-ended input
The single-ended input can be configured to work with either an external ADC reference or internal ADC
reference.
D External ADC Reference Mode: A single-ended analog input is accepted at the AIN pin where the input
signal is bounded by the voltages on the REFTS and REFBS pins. Figure 14 shows an example of applying
external reference to REFTS and REFBS pins in which REFTS is connected to the low-impedance 2-V
source and REFBS is connected to the low-impedance 2-V source. REFTS and REFBS may be driven to
any voltage within the supply as long as the difference (REFTS – REFBS) is between 1 V and 2 V as
specified in Table 2. Figure 15 shows an example of an external reference using a Kelvin connection to
eliminate line voltage drop errors.
2V
AIN
1V
2V
REFTS
1V
REFBS
MODE
THS1030
SHA
A/D
0.1 µF
0.1 µF
0.1 µF
REFTF
10 µF
REFBF
SW3
Figure 14. External ADC Reference Mode
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