RFM31B-868-D QUASAR, RFM31B-868-D Datasheet - Page 38

• Manufacturer Part Number: RFM31B-868-D
• Description: MODULE, RECEIVER, -118DB, 868MHZ
• Manufacturer: QUASAR

Specifications of RFM31B-868-D

• Modulation Type: FSK, GFSK, OOK
• Sensitivity: -121dBm
• Power Supply: 1.8V To 3.6V
• Supply Current: 18.5mA
• Data Rate Max: 256Kbps
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RFM31B
8.3. General Purpose ADC
An 8-bit SAR ADC is integrated for general purpose use, as well as for digitizing the on-chip temperature sensor
reading. Registers 0Fh "ADC Configuration", 10h "Sensor Offset" and 4Fh "Amplifier Offset" can be used to
configure the ADC operation.
Every time an ADC conversion is desired, bit 7 "adcstart/adcbusy" in “Register 1Fh. Clock Recovery Gearshift
Override” must be set to 1. This is a self clearing bit that will be reset to 0 at the end of the conversion cycle of the
ADC. The conversion time for the ADC is 350 µs. After this time or when the "adcstart/adcbusy" bit is cleared, then
the ADC value may be read out of register 11h "ADC Value".
The architecture of the ADC is shown in Figure 19. The signal and reference inputs of the ADC are selected by
adcsel[2:0] and adcref[1:0] in “Register 0Fh. ADC Configuration,” respectively. The default setting is to read out the
temperature sensor using the bandgap voltage (VBG) as reference. With the VBG reference the input range of the
ADC is from 0–1.02 V with an LSB resolution of 4 mV (1.02/255). Changing the ADC reference will change the LSB
resolution accordingly.
A differential multiplexer and amplifier are provided for interfacing external bridge sensors. The gain of the amplifier
is selectable by adcgain[1:0] in Register 0Fh. The majority of sensor bridges have supply voltage (VDD) dependent
gain and offset. The reference voltage of the ADC can be changed to either V
dependent offset voltage can be added using soffs[3:0] in register 10h.
See “General Purpose ADC Configuration” for mo re details on the usage of the general purpose ADC.
38
Add
0F
10
11
R/W
R/W
R/W
Tel: [phone]
R
Function/Description
ADC Configuration
Sensor Offset
ADC Value
GPIO0
GPIO1
GPIO2
Temperature Sensor
V
V
V
DD
DD
BG
(1.2V)
/ 3
/ 2
Figure 19. General Purpose ADC Architecture
adcsel [2:0]
Diff. MUX
Fax: [phone]
adcstart/adcbusy
adc[7]
D7
aoffs [4:0]
adcgain [1:0]
Diff. Amp.
adcsel[2] adcsel[1]
adc[6]
soffs [3:0]
D6
adc[5]
D5
adcsel [2:0]
Input MUX
adcref [1:0]
Ref MUX
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adcsel[0]
adc[4]
D4
V
V
adcref[1]
in
ref
soffs[3]
adc[3]
D3
0 -1020mV / 0-255
8-bit ADC
DD
/2 or V
adcref[0]
soffs[2]
adc[2]
D2
DD
adc [7:0]
adcgain[1] adcgain[0]
/3. A programmable V
soffs[1]
adc[1]
D1
soffs[0]
adc[0]
D0
POR Def.
00h
00h
—
DD