sx8725 Semtech Corporation, sx8725 Datasheet - Page 16

• Manufacturer Part Number: sx8725
• Description: Sx8725 Zoomingadc? For Pressure And Temperature Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
The output of the PGA stages is directly fed to the analog-to-digital converter (ADC), which converts the signal
V
Like most ADCs intended for instrumentation or sensing applications, the ZoomingADC is an over-sampled
converter (See Note
both positive and negative differential input voltages). In first approximation, the ADC output result relative to
full-scale (FS) delivers the quantity:
in two's complement (see Equation 4 and Equation 5 for details). The output code OUT
V
relationship:
where GD
1 Note: Over-sampled converters are operated with a sampling frequency f
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.
V1.5 © 2007 Semtech Corp.
IN,ADC
IN,ADC
into digital.
-V
TOT
REF,ADC
is the total PGA gain, and GDoff
/2 to +V
1
). The ADC is a so-called incremental converter; with bipolar operation (the ADC accepts
REF,ADC
V
IN
/2 respectively. As will be shown, V
,
ADC
GD
ZoomingADC™ for Pressure and Temperature Sensing
OUT
TOT
F
TOT
S
V
2 /
ADC
is the total PGA offset.
Equation 1
Equation 2
IN
16
GDoff
V
REF
V
IN
,
S
ADC
,
TOT
much higher than the input signal's Nyquist rate (typically f
ADC
2 /
V
REF
IN,ADC
,
ADC
is related to input voltage V
(V)
ADC
is -FS/2 to +FS/2 for
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SX8725
IN
by the
S
is