DS80PCI402: Inquire SCH review, EVM request and spec question

Hi Edward,

1. The DS80PCI402EVM is designed for benchtop use with SMA cables.  It was not intended to be a means to do system verification.

2a. The OUTA and OUTB pins should have 0.22uF AC coupling capacitors instead of resistors.

2b. The resistors are not typically placed in series on the INA and INB pins.

2c. Connect VIN to C6 + C7 and VCC3V3 only

2d. Connect VDD to C1 - C5 only.  Do not connect VIN to VDD.

2e. Recommend PRSNT is tied to DS80PCI402 and Endpoint.

2f. For starting signal integrity settings. Recommend DEM = Level 4, EQ = Level 2

3. It is a typo in the datasheet. OUTB is type "O" and INB is type "I".

4. The typical power consumption is 660mW

5. Yes if you want to use external pin configuration then ENSMB = 0.

6. LPBK was mainly used for testing purposes, it does provide a "loopback" function, but the signal integrity is not as good as the normal path.

7. Yes if no EEPROM is used pin 27 can remain floating.

Regards,

Lee

Hi Lee,

Thank you for your comments, please refer below question:

2a. The OUTA and OUTB pins should have 0.22uF AC coupling capacitors instead of resistors.

E: In the layout, 0.22uF AC coupling cap should close to chip or connector?

(Lee):  I prefer to see the coupling capacitor close to the connector.

2b. The resistors are not typically placed in series on the INA and INB pins.

E: So should we put 0.22uF cap in series on INA and INB pins?

(Lee)  There needs to be one set of coupling capacitors between PCIe Rx and Tx.  Typically the coupling capacitors are placed on the same PCB assembly as the PCIe Tx pins.

2d. Connect VDD to C1 - C5 only.  Do not connect VIN to VDD.

E: Does it means we can connect all VDD pin together?

(Lee): Yes all VDD pins (9/14/36/41/51) can be connected together.

2e. Recommend PRSNT is tied to DS80PCI402 and Endpoint.

E: Could you kindly share more detail description about this part?

(Lee):  Since you are not using the PRSNT# signal on the CEM connection, I would tie the PRSNT pin on the DS80PCI402 device to GND. 

3. It is a typo in the datasheet. OUTB is type "O" and INB is type "I".

E: Do we have any schedule to revised datasheet?

(Lee):  I do not have a schedule for the datasheet at this time.

Please refer latest SCH and kindly share your comments for us.

Hi Hugo,

90 Ohm impedance and 0402 size capacitors are a good combination.

I would rework the thermal pad vias into a more symmetrical arrangement to improve manufacturing.  Here is an example, you can cut down on the size of the VDD_2.5V moat, there is not a big need to connect the pins externally.

Regards,

Lee