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AN107

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Figure 4

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Power Supply Decoupling Layout

3.1.3

XTAL

Place the crystal as close as possible to the XTAL pin and keep the routing as short as possible in order to reduce

any frequency offsets that may occur. Avoid routing digital signals with sharp edges close to XIN PCB track or

underneath the crystal X1 pad, as this may shift the crystal DC operating point and result in duty-cycle variation.

The XTAL circuit is shown in the figure below.

Figure 5

．

XTAL Circuit Layout

3.1.4

Digital Signals Routing

The digital signals must be routed away from the RF, the XTAL and the VCO circuit to avoid high frequency

harmonics coupling to those sensitive signals. The solid ground should be placed among the SDA, CSB and SCL

signal routings to avoid cross-coupling if possible. R2 is a resistor for internal use only. The user does not need to

include it in the design.

Содержание CMT2210A

Страница 1: ...reless applications The chip is part of the CMOSTEK NextGenRFTM family which includes a complete line of transmitters receivers and transceivers To give the CMT2210A schematic design guidelines an exa...

Страница 2: ...d be within 60 in order to ensure a reliable start up The total tolerance is 20 ppm typically which include initial tolerance crystal loading aging and temperature dependence The acceptable tolerance...

Страница 3: ...ce clock input 10 nRSTO O Active low power on reset output to reset an external MCU 11 VCOP IO VCO tank connected to an external inductor 12 VCON 13 15 GND I Ground 14 RFIN I RF input 16 VDD I Power s...

Страница 4: ...transmission line is in proportion to the thickness of the PCB and the distance between the routing and grounding around it It is in inverse proportion to the width thickness of the routing and the di...

Страница 5: ...ignal routing should be smooth to avoid the impedance variation on the transmission lines which will result in RF signal reflection and performance inconsistency in mass production Wherever possible t...

Страница 6: ...d as this may shift the crystal DC operating point and result in duty cycle variation The XTAL circuit is shown in the figure below Figure 5 XTAL Circuit Layout 3 1 4 Digital Signals Routing The digit...

Страница 7: ...his port To minimize the radiation from the VCO circuit and maintain the high Q factor of the VCO tank L2 should be placed as close as possible to the CMT2210A The VCO tank is surrounded by a solid gr...

Страница 8: ...us ground plane metallization as possible 2 Place a series of ground vias along the PCB edges if possible The maximum distance between the vias should be less than 10 This is required to reduce the PC...

Страница 9: ...AN107 Rev 1 0 Page 9 10 www hoperf com 4 Document Change List Table 3 Document Change List Rev No Chapter Description of Changes Date 0 9 Initial released version 2014 06 14 1 0 2014 06 30...

Страница 10: ...is assumed for inaccuracies and specifications within this document are subject to change without notice The material contained herein is the exclusive property of CMOSTEK and shall not be distribute...