Datasheet

2.5V Max
V
CM
+ 0.5V
V
CM
V
CM
- 0.5V
0V Min
2.5V Max
V
CM
+ 1V
V
CM
V
CM
- 1V
0V Min
ADC10065
www.ti.com SNAS225H –JULY 2003–REVISED APRIL 2013
FUNCTIONAL DESCRIPTION
The ADC10065 uses a pipeline architecture and has error correction circuitry to help ensure maximum
performance. Differential analog input signals are digitized to 10 bits. In differential mode, each analog input
signal should have a peak-to-peak voltage equal to 1.0V, 0.75V or 0.5V, depending on the state of the IRS pin
(pin 5), and be centered around V
CM
and be 180° out of phase with each other. If single ended operation is
desired, V
IN
- may be tied to the V
COM
pin (pin 4). A single ended input signal may then be applied to V
IN
+, and
should have an average value in the range of V
CM
. The signal amplitude should be 2.0V, 1.5V or 1.0V peak-to-
peak, depending on the state or the IRS pin (pin 5).
Applications Information
ANALOG INPUTS
The ADC10065 has two analog signal inputs, V
IN
+ and V
IN
−. These two pins form a differential input pair. There
is one common mode pin V
COM
that may be used to set the common mode input voltage.
REFERENCE PINS
The ADC10065 is designed to operate with a 1.2V reference. The voltages at V
COM
, V
REFT
, and V
REFB
are
derived from the reference voltage. It is very important that all grounds associated with the reference voltage and
the input signal make connection to the analog ground plane at a single point to minimize the effects of noise
currents in the ground path. The three Reference Bypass Pins V
REF
, V
REFT
and V
REFB
, are made available for
bypass purposes only. These pins should each be bypassed to ground with a 0.1 µF capacitor. DO NOT LOAD
these pins.
V
COM
PIN
This pin supplies a voltage for possible use to set the common mode input voltage. This pin may also be
connected to V
IN
-, so that V
IN
+ may be used as a single ended input. This pin should be bypassed with at least a
0.1 µF capacitor. Do not load this pin.
SIGNAL INPUTS
The signal inputs are V
IN
+ and V
IN
−. The input signal amplitude is defined as V
IN
+ − V
IN
− and is represented
schematically in Figure 40:
Figure 40. Input Voltage Waveforms for a 2V
P-P
Figure 41. Input Voltage Waveform for a 2V
P-P
differential Input Single Ended Input
A single ended input signal is shown in Figure 41.
The internal switching action at the analog inputs causes energy to be output from the input pins. As the driving
source tries to compensate for this, it adds noise to the signal. To prevent this, use 18Ω series resistors at each
of the signal input pins with a 25 pF capacitor across the inputs, as shown in Figure 42. These components
should be placed close to the ADC because the input pins of the ADC is the most sensitive part of the system
and this is the last opportunity to filter the input. The two 18Ω resistors and the 25 pF capacitor form a low-pass
filter with a -3 dB frequency of 177 MHz.
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