SX8724C Datasheet, PDF (16/67 Pages) Semtech Corporation – ZoomingADC for sensing data acquisition

SX8724C
ZoomingADC for sensing data acquisition
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Data stored in the LSB bits of RegOut register are outputted at GPIO block if D[x]Dir= 1. The default values after power
on reset is low (0).
The digital pins are able to deliver a driving current up to 8 mA.
When the bits VrefD0Out and VrefD1In in the RegMode (address 0x70) register are set to 1 the D0 and D1 pins digital
behavior are automatically bypassed in order to either input or output the voltage reference signals.
6.3.1 Optional Operating Mode: External Vref
D0 and D1 are multi-functional pins with the following functions in different operating modes (see RegMode register
for control settings):
0
D0/VREFOUT
1
GPIO
0
D0/VREFOUT
1
GPIO
RegMode[1] = 0
Internal
V_BG
+
Bandgap
reference ^-
0 VREF
ZoomingADC
1
RegMode[1] = 0
Internal ₊
Bandgap
reference ^-
0 VREF
ZoomingADC
1
RegMode[0] = 0
RegMode[0] = 1
D1/VREFIN
1
GPIO
0
Figure 6. D0 and D1 are Digital Inputs / Outputs
D1/VREFIN
1
GPIO
0
Figure 7. D1 is Reference Voltage Input and D0 is Digital
Input / Output
0
D0/VREFOUT
1
GPIO
0
D0/VREFOUT
1
GPIO
RegMode[1] = 1
Internal
V_BG
+
Bandgap
reference ^-
0 VREF
ZoomingADC
1
RegMode[1] = 1
Internal
V_BG
+
Bandgap
reference ^-
0 VREF
ZoomingADC
1
RegMode[0] = 0
RegMode[0] = 1
D1/VREFIN
1
GPIO
0
D1/VREFIN
1
GPIO
0
Figure 8. D1 is Digital Input / Output and D0 Reference Figure 9. D0 is Reference Voltage Output and D1 is Reference
Voltage Output
Voltage Input
This allows external monitoring of the internal bandgap reference or the ability to use an external reference input for
the ADC, or the option to filter the internal VREF output before feeding back as VREF,ADC input. The internally generated
VREF is a trimmed as ADC reference with a nominal value of 1.22V. When using an external VREF,ADC input, it may have
any value between 0V and VBATT. Simply substitute the external value for 1.22 V in the ADC conversion calculations.
Revision 1.01
© Semtech
January 2011
Page 16
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