Hi All,
I have some confusion as to the EMI filter upon entering.
The datasheet states the following:
Positive power supply for the differential amplifier stage. Tie VDD1 and VDD2 to the same power supply with independent power-supply bypassing.
But on the EVB, the VDD1 and VDD2 are shorted to one provider power.
What is the right EMI filter the component should need?
The picture below is taken from the EVB scheme.
The schematic is misleading. On the actual board, the two supplies indeed have independent bypass capacitors:
First, thanks for the response. I'm inferring from your answer that the bypass should be independent of each VDD input, C5&C7 and C3&C6.
I've attached my scheme, please agree if this is the poet's intention.
Hi Netanel,
Please see the layout guidelines section in the LMH32401-Q1 datasheet I have shown below for more details on this.
In the EVM schematic that you have shown:
C1 is the large decoupling capacitor and should be placed further from the device and close to the power supply source
C3 and C6 would be the smaller decoupling capacitors that should be placed close to the device and connected to VDD1
C5 and C7 would be the smaller decoupling capacitors that should be placed close to the device and connected to VDD2
This layout is shown in the image above.
From the schematic you provide, you should not need both C2509 and C2510. One can be placed close to the power supply source and shared for both power supply rail paths. However, the smaller decoupling capacitors (C9, C10, C11, and C12) would be connected as you have shown and when designing PCB boards, please follow the recommended layout guidelines I have shown above.
Please let me know if you need any other clarification.
Thanks,
Nick
