AX5151-TSSOP24-TU AXSEM, AX5151-TSSOP24-TU Datasheet - Page 22

• Manufacturer Part Number: AX5151-TSSOP24-TU
• Description: RF Transmitter TSSOP-Class-IC
• Manufacturer: AXSEM
• Type: Single Chip Transceiverr

Specifications of AX5151-TSSOP24-TU

• Package / Case: TSSOP-24
• Operating Frequency: 400 MHz to 940 MHz
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 2.3 V to 3.6 V
• Supply Current: 100 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

22
Circuit Description
VCO
An on-chip VCO converts the control voltage generated by the charge pump and loop filter
into an output frequency. This frequency is used for transmit as well as for receive operation.
The frequency can be programmed in 1 Hz steps in the FREQ registers. For operation in the
433 MHz band, the BANDSEL bit in the PLLLOOP register must be programmed.
VCO Auto-Ranging
The AX5151 has an integrated auto-ranging function, which allows to set the correct VCO
range for specific frequency generation subsystem settings automatically. Typically it has to
be executed after power-up. The function is initiated by setting the RNG_START bit in the
PLLRANGING register. The bit is readable and a 0 indicates the end of the ranging process.
The RNGERR bit indicates the correct execution of the auto-ranging.
Loop Filter and Charge Pump
The AX5151 internal loop filter configuration together with the charge pump current sets the
synthesizer loop band width. The loop-filter has three configurations that can be
programmed via the register bits FLT[1:0] in register PLLLOOP, the charge pump current can
be programmed using register bits PLLCPI[1:0] also in register PLLLOOP. Synthesizer
bandwidths are typically 50 - 500 kHz depending on the PLLLOOP settings, for details see the
section 4.3: AC Characteristics.
Registers
Register
PLLLOOP
FREQ
IFFREQHI, IFFREQLO
PLLRANGING
Version 1.0
3. Adaptation of the bandwidth to the data-rate. For transmission of FSK and MSK it is
required that the synthesizer bandwidth must be in the order of the data-rate.
FLT[1:0]
PLLCPI[2:0]
BANDSEL
Bits
Synthesizer loop filter bandwidth, recommended usage is to increase the bandwidth
for faster settling time, bandwidth increases of factor 2 and 5 are possible.
Synthesizer charge pump current, recommended usage is to decrease the bandwidth
(and improve the phase-noise) for low data-rate transmissions.
Switches between 868 MHz/915 MHz and 433 MHz bands
Programming of the carrier frequency
Programming of the IF frequency
Initiate VCO auto-ranging and check results
Purpose
Datasheet AX5151