SX8724E082TRT Semtech, SX8724E082TRT Datasheet - Page 21

• Manufacturer Part Number: SX8724E082TRT
• Description: IC DAS PRESSURE/TEMP SENS 16MLPQ
• Manufacturer: Semtech
• Series: ZoomingADC™r
• Type: Pressure/Temperature Sensorr

Specifications of SX8724E082TRT

• Input Type: Differential
• Output Type: Digital
• Interface: 2-Wire
• Mounting Type: Surface Mount
• Package / Case: 16-MLPQ
• For Use With: XE8000EV121 - BOARD EVAL FOR SX8723/24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Other names: SX8724E082TR

ADVANCED COMMUNICATIONS & SENSING
PGA & ADC Enabling
Depending on the application objectives, the user may enable or bypass each PGA stage. This is done
according to the word ENABLE and the coding given in Table 4. To reduce power dissipation, the ADC can also
be inactivated while idle.
PGA1
The first stage can have a buffer function (unity gain) or provide a gain of 10 (see Table 5). The voltage V
the output of PGA1 is:
where GD
PGA2
The second PGA has a finer gain and offset tuning capability, as shown in Table 6 and Table 7. The voltage V
at the output of PGA2 is given by:
where GD
words PGA2_GAIN[1:0] and PGA2_OFFSET[3:0].
PGA3
The finest gain and offset tuning is performed with the third and last PGA stage, according to the coding of
Table 8 and Table 9. The output of PGA3 is also the input of the ADC. Thus, similarly to PGA2, we find that the
voltage entering the ADC is given by:
where GD
PGA3_GAIN[6:0] and PGA3_OFFSET[6:0]. To remain within the signal compliance of the PGA stages, the
condition:
must be verified.
Finally, combining equations 5 to 7 for the three PGA stages, the input voltage V
V
where the total PGA gain is defined as:
and the total PGA offset is:
V1.23 © 2009 Semtech Corp.
IN
by:
1
2
3
is the gain of PGA1 (in V/V) controlled with the bit PGA1_GAIN.
and GDoff
and GDoff
2
3
are respectively the gain and offset of PGA2 (in V/V). These are controlled with the
are respectively the gain and offset of PGA3 (in V/V). The control words are
V
V
IN
IN
GDoff
,
,
V
ADC
ADC
D
2
GD
TOT
GD
GD
ZoomingADC™ for Pressure and Temperature Sensing
GD
TOT
V
D
TOT
3
2
1
GDoff
V
V
V
GD
D
D
GD
D
V
1
2
Equation 10
Equation 11
1
Equation 5
Equation 6
Equation 7
Equation 8
Equation 9
,
IN
V
3
1
D
GDoff
GDoff
3
GD
21
2
V
GDoff
IN
GD
2
V
DD
GD
3
2
3
TOT
V
V
(V)
GDoff
1
REF
REF
V
(V)
,
,
ADC
ADC
REF
(V/V)
2
,
ADC
(V/V)
(V)
(V)
(V)
IN,ADC
of the ADC is related to
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SX8724
D1
at
D2