XE8000EV121 Semtech, XE8000EV121 Datasheet - Page 22

• Manufacturer Part Number: XE8000EV121
• Description: BOARD EVAL FOR SX8723/24
• Manufacturer: Semtech

Specifications of XE8000EV121

• Main Purpose: Interface, Sensor to ADC Interface, Programmable
• Embedded: No
• Utilized Ic / Part: SX8723, SX8724, SX8725
• Primary Attributes: Signal Conditioning for Bridge-Type Sensors
• Secondary Attributes: GUI, Up to 16-Bit, Programmable Gain of 1/12 ~ 1000, I2C Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADVANCED COMMUNICATIONS & SENSING
ADC Characteristics
The main performance characteristics of the ADC (resolution, conversion time, etc.) are determined by three
programmable parameters. The setting of these parameters and the resulting performances are described later.
Conversion Sequence
A conversion is started each time the bit START or the bit DEF is set. As depicted in Figure 11, a complete
analog-to-digital conversion sequence is made of a set of N
final quantization step. Each elementary conversion is made of (OSR+1) over-sampling periods T
The result is the mean of the elementary conversion results. An important feature is that the elementary
conversions are alternatively performed with the offset of the internal amplifiers contributing in one direction and
the other to the output code. Thus, converter internal offset is eliminated if at least two elementary sequences
are performed (i.e. if N
conversion properly.
Note:
The internal bandgap reference state may be forced High or Low, or may be set to toggle during conversion at either the same rate or half
the rate of the Elementary Conversion. This may be useful to help eliminate bandgap related internal offset voltage and 1/f
Over-Sampling Frequency
The word FIN[1:0] (see Table 10) is used to select the over-sampling frequency f
is derived from the 4MHz oscillator clock.
V1.8 © 2009 Semtech Corp.
Conversion index
Offset
Init
Over-sampling frequency f
Over-Sampling Ratio OSR
Number of Elementary Conversions NELCONV
Elementary
Conversion
1
+
ELCONV
Figure 11 - Analog-to-Digital Conversion Sequence
(RegACCfg2[7:6])
Table 10 - Over-Sampling Frequency Settings
2). A few additional clock cycles are also required to initiate and end the
s
FIN[1:0]
Elementary
Conversion
00
01
10
11
2
-
ZoomingADC™ for Pressure and Temperature Sensing
T
ELCONV
Equation 12
T
Over-Sampling Frequency f
CONV
22
OSR
fs
Elementary
Conversion
N
ELCONV
ELCONV
1
62.5 kHz
+
125 kHz
250 kHz
500 kHz
-1
(s)
elementary incremental conversions and a
s
Elementary
Conversion
(Hz)
N
ELCONV
s
. The over-sampling frequency
-
www.semtech.com
End
s
s
=1/f
noise.
Conversion
SX8725
s
, i.e.:
Result