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mdanish
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Hello,

I have one question regarding the crystal placement.

Can someone please check our current crystal placement? Is it advisable to place the load capacitors near to the crystal pins or near to the IC? Kindly review the screenshot for our current placement and advise.

Also as per Infineon checklist, it is recommended to use crystal having drive current of around 600uW but in 4-SMD package we are not able to find the desired part. We are only able to get maximum of 300uW, so we added a series resistor for current limiting. Is it a right way? Also which one is better to use with this IC, Crystal or Oscillator?

Crystal Placement MCU2.png

 Thanks in advance

 

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Ajeethkumar
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Hi,

The crystal and the load capacitors must be placed close to the pins of the HX2LP(1 cm) and the load capacitors should be placed near the crystal. By placing the crystal as close as possible to the XI/XO pins of the HX2LP PHY, thereby achieving short traces, the stray capacitance can be minimized.

A crystal with a low drive level may result in accelerated aging or may burn out and not function. It is not recommended to use series resistors as it can affect the HX2LP device functionality. Please find the capacitors with recommended values here.

We recommend you to use Crystal for HX2LP with the following parameters:

  • 12 pF rating on the crystal
  • 24 MHz ± 0.05%
  • Parallel resonant, fundamental mode
  • 12 pF capacitors for load caps
  • 500 µW drive

Thanks,
Ajeeth

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Ajeethkumar
Moderator
Moderator 100 replies posted 100 sign-ins 25 solutions authored
Moderator

Hi,

The crystal and the load capacitors must be placed close to the pins of the HX2LP(1 cm) and the load capacitors should be placed near the crystal. By placing the crystal as close as possible to the XI/XO pins of the HX2LP PHY, thereby achieving short traces, the stray capacitance can be minimized.

A crystal with a low drive level may result in accelerated aging or may burn out and not function. It is not recommended to use series resistors as it can affect the HX2LP device functionality. Please find the capacitors with recommended values here.

We recommend you to use Crystal for HX2LP with the following parameters:

  • 12 pF rating on the crystal
  • 24 MHz ± 0.05%
  • Parallel resonant, fundamental mode
  • 12 pF capacitors for load caps
  • 500 µW drive

Thanks,
Ajeeth

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mdanish
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Hi Ajeeth,

 

We are not able to find any crystal parts (Automotive grade) with the above mentioned specifications. Can you please suggest us any crystal part? Also I checked the BOM of "Infineon-CY4605_Board_Design_Files_(Schematic_Layout_Gerber_BOM)-PCBDesignData-v01_00-EN"  and found that the crystal part used in the development board (FX2400026) is having drive level of 100uW only. 

 

Also can you please answer if oscillator can be used with CY7C65620 IC? 

 

Regards,

Danish

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Ajeethkumar
Moderator
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Hi Danish,

It is highly recommended to use the crystal of the Min. 500uW Drive level. The crystal part(FX2400026 - Download datasheet from here) used in CY4605 has a drive level of 500uW as mentioned in our guidelines.

You can use any external oscillator to generate a clock other than the crystal, but the clock requirements like frequency, minimum drive level, accuracy, etc., should be met. Please refer to the datasheet for external clock connections(as shown below).

Ajeethkumar_1-1656500710067.png

Thanks,
Ajeeth

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mdanish
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Thanks Ajeeth.

 

Also could you please suggest the placement for the Load capacitors which I asked earlier? Whether we should place the crystal first close to the IC and then load capacitors or load capacitors close to the IC and then crystal?

Regards,

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Ajeethkumar
Moderator
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Moderator

Hi Danish,

The load capacitors should be present near the crystal and the crystal should be present near the HX2LP device(1 cm). Please refer to our DVK CY4605 layout for the crystal placement(a snapshot of crystal placement in CY4605 is given below).

Ajeethkumar_0-1656502898155.png

Thanks,
Ajeeth

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