XE8000EV120 Semtech, XE8000EV120 Datasheet - Page 52

• Manufacturer Part Number: XE8000EV120
• Description: BOARD EVAL FOR SX8722I070TRLF
• Manufacturer: Semtech
• Series: ZoomingADC™r

Specifications of XE8000EV120

• Number Of Adc's: 1
• Number Of Bits: 16
• Data Interface: I²C
• Inputs Per Adc: 7 Single or 4 Differential
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: SX8722
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: XM8000EV120; XM8000EV120

The core of the zooming section is made of three differential programmable amplifiers (PGA). After selection of a
combination of input and reference signals V
Fine gain programming up to 1'000V/V is possible. In addition, the last two stages provide programmable offset. Each
amplifier can be bypassed if needed.
The output of the PGA stages is directly fed to the analog-to-digital converter (ADC), which converts the signal V
digital.
Like most ADCs intended for instrumentation or sensing applications, the ZoomingADC is an over-sampled converter (See
Note1). The ADC is a so-called incremental converter with bipolar operation (the ADC accepts both positive and negative
input voltages). In first approximation, the ADC output result relative to full-scale (FS) delivers the quantity:
in two's complement (see Section 12.8.7 for details). The output code OUT
+V
where GD
Note:
ACS - Revision 4.2
©2008 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
REF
OUT
/2 respectively. As will be shown in section 0, V
FS
V
Over-sampled converters are operated with a sampling frequency f
is 20-1'000 times the input signal bandwidth). The sampling frequency to throughput ratio is large (typically 10-500). These
converters include digital decimation filtering. They are mainly used for high resolution, and/or low-to-medium speed applications.
IN
2 /
,
ADC
TOT
ADC
(Eq. 1)
is the total PGA gain, and GDoff
≅
=
V
V
GD
REF
IN
,
TOT
ADC
2 /
(Eq. 2)
⋅
V
IN
−
GDoff
October 2008
TOT
⋅
V
REF
IN
TOT
and V
is the total PGA offset.
REF
IN,ADC
, the input voltage is modulated and amplified through stages 1 to 3.
Page 52
is related to input voltage V
S
High gain acquisition for sensor interface
much higher than the input signal's Nyquist rate (typically f
V [ ]
ADC
is -FS/2 to +FS/2 for V
IN
by the relationship:
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www.semtech.com
SX8722
IN,ADC
, -V
IN,ADC
REF
/2 to
into
S