AS3991-BQFT austriamicrosystems, AS3991-BQFT Datasheet - Page 22

• Manufacturer Part Number: AS3991-BQFT
• Description: IC UHF RFID READER 64-QFN
• Manufacturer: austriamicrosystems

Specifications of AS3991-BQFT

• Rf Type: Read / Write
• Frequency: 840MHz ~ 960MHz
• Features: ISO-18000-6
• Package / Case: 64-VFQFN, Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AS3991-BQFT; AS3991-BQFTTR

AS3990/AS3991
Data Sheet - D e t a i l e d D e s c r i p t i o n
AD Converter
AD converter intends to support the external power detector placed before or after the circulator to measure actual
output power. The analog voltage from the power detector is connected to the ADC pin. AD conversion is triggered by
the ‘Trigger AD conversion’ (87) command, and the resulted value is available in the ‘ADC readout register’ (19)
(see
Table
38). AD converter can also be used for measuring the mixers DC output levels. The source for the conversion is
selected by msel<2:0> bits in the ‘Test setting 1 and measurement selection’ register (11)
(see Table
31). Input range is
0V to two times AGD voltage (3.2V). Input level equal to AGD gives output code 00. The 7 LSB bits give absolute
output level, the MSB bit is a sign, H means positive, L means negative value. Result is valid 20µs after triggering.
AD converter can be used to measure VEXT voltage, and according to the result, the MCU can decide to use
adaptation to low supply voltage (low_vext=1 and ir<1>=1 option bits) or inform the superior system that supply needs
to be fixed or just disable transmission. The value in ‘ADC readout register’ (19) is calculated accordingly to the
equation:
ADCreg = [(VEXT-1.6)*0.8-1.6] / 0.0126
(EQ 1)
Where:
ADCreg is the value, sign should be considered as above
VEXT is in volts
Reference Oscillator
Reference frequency of 20MHz is needed for the chip. It is possible to use quartz crystal or external reference source
(TCXO). In case the crystal is used it should be connected between OSCI and OSCO pin with appropriate load
capacitors between each oscillating pin and ground. Load capacitance 15-20pF is proposed. Maximum series
resistance in resonance is 30Ω.
In case external reference source is used, it should be connected to OSCO pin. The signal should be sinusoidal shape,
1Vpp, DC level 1.6V or AC coupled.
www.austriamicrosystems.com
Revision 3.81
22 - 51