SX8724 SEMTECH [Semtech Corporation], SX8724 Datasheet - Page 15

• Manufacturer Part Number: SX8724
• Manufacturer: SEMTECH [Semtech Corporation]

ADVANCED COMMUNICATIONS & SENSING
ZoomingADC
Features
The ZoomingADC is a complete and versatile low-power analog front-end interface typically intended for sensing
applications.
In the following text the ZoomingADC will be referred as ZADC.
The key features of the ZADC are:
Overview
The total acquisition chain consists of an input multiplexer, 3 programmable gain amplifier stages and an over
sampled A/D converter. The reference voltage can be selected on two different channels. Two offset compensation
amplifiers allow for a wide offset compensation range. The programmable gain and offset allow the application to
zoom in on a small portion of the reference voltage defined input range.
ZADC Description
Acquisition Chain
Figure 8 shows the general block diagram of the acquisition chain (AC). A control block (not shown in Figure 8)
manages all communications with the 2-WIRE peripheral. The clocking is derived from the internal 4 MHz
Oscillator.
Analog inputs can be selected through an 8 input multiplexer, while reference input is selected between two
differential channels. It should however be noted that only 7 acquisition channels (including the V
when configured as single ended since the input amplifier is always operating in differential mode with both positive
and negative input selected through the multiplexer.
The core of the zooming section is made of three differential programmable amplifiers (PGA). After selection of an
input and reference signals
V1.23 © 2009 Semtech Corp.
Reference
Analog
Inputs
Inputs
Programmable 6 to 16-bit dynamic range over-sampled ADC
Flexible gain programming between 0.5 and 1000
Flexible and large range offset compensation
4-channel differential or 7-channel single-ended input
2-channel differential reference inputs
Power saving modes
V
V
V
V
V
V
AC
AC
AC
AC
AC
AC
BATT
SS
REF
SS
SS
REF
2
3
4
5
6
7
Reference
Selection
Selection
AC
AC
+
-
+
-
Input
0
1
V
IN
V
f
s
REF,ADC
V
Figure 8 - ZADC General Functional Block Diagram
IN
GD1
and V
Gain 1
PGA1
REF,ADC
ZoomingADC™ for Pressure and Temperature Sensing
V
D1
combination, the input voltage is modulated and amplified through
GD2
Gain 2 Offset 2
PGA2
15
OFF2
ZOOM
+
-
V
D2
GD3
Gain 3 Offset 3
PGA3
OFF3
+
-
V
www.semtech.com
IN,ADC
REF
) are available
SX8724
ADC
f
s
16