Semtech LR1121 - 32 Mhz TCXO; Figure 6-1: LR1121 Thermal Insulation on PCB Top Layer; Figure 6-2: TCXO Circuit Diagram

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
45 of 130
Semtech
Proprietary & Confidential
www.semtech.com
Refer to the LR1121 PCB reference design on www.semtech.com for an implementation example in PCB design.
Figure 6-1: LR1121 Thermal Insulation on PCB Top Layer
6.2.3 32MHz TCXO
In environments with extreme temperature variation, it may be required to use a TCXO (Temperature Compensated Crystal
Oscillator) to achieve better frequency accuracy. When a TCXO is used:
• The TCXO should be connected to pin XTA, through a 220Ω resistor and a10pF DC-cut capacitor. and associated
components.
• Pin XTB should be left open.
• The TCXO is supplied by the internal regulator on the VTCXO pin.
• The regulated VTCXO is programmable from 1.6 to 3.3V using command SetTcxoMode().
• VBAT should always be 200mV higher than the programmed voltage to ensure proper operation.
• The nominal current drain is 1.5mA, but the regulator can support up to 4mA of load.
• Clipped-sine output TCXO are required, with the output amplitude not exceeding 1.2V peak-to-peak.
Figure 6-2: TCXO Circuit Diagram
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