DP83826AE: DP83826AE Schematic review for robotics humanoid motor.

Alba Dervishi

Part Number: DP83826AE

Dear experts,

My customer is currently looking into the EtherCAT circuitry for a robotics humanoid motor. The key components they plan to use:

Microcontroller TMS320F28P650SK7ZEJR
Ethernet PHY DP83826AE
Oscillator LMK6CE02500CDLE
Clock Buffer LMK1C1104DQF (spreads oscillator to MCU and both PHYs)

Below you can find a quick overview to their considered bootstrap configuration.

Can you please help with the scematics review: DP83826A_Schematic_Design_Review_Checklist_v0.1.xlsx

The customer added also several additional questions in the attached file.

Strap	Pin	PHY0	PHY1	Default	PU/PD?	comment
ModeSelect	1	high	high	PU	not needed	EtherCAT -> Enhanced Mode
Strap 7	13	high	high	PD	PU	FLD enabled
Strap 8	14	low	low	PD	not needed	FLD enabled
Strap 9	15	low	low	PD	not needed	auto MDIX enable
Strap 0	16	low	low	PD	not needed	auto-negotiation enable
Strap 10	18	low	low	PD	not needed	MDIX (applicable only when auto-MDIX is disabled)
Strap 11	19	high	high	PD	PU	Energy Detect only
Strap 6	20	high	high	PD	PU	LED1 on Pin 31 - no CLK out
Strap 5	22	low	low	PD	not needed	not needed?
Strap 4	28	low	low	PD	PD	ADDR
Strap 3	29	low	low	PD	PD	ADDR
Strap 2	30	low	high	PD	PD/PU	ADDR
Strap 1	31	low	low	PU	PD	Odd Nibble Disable PHY automatically in MII

Many thanks in advance for your support,

Alba

4 months ago

0 Shane Hauser 4 months ago

TI__Mastermind 38895 points

Hi Alba,

Thank you for filling out the checklist beforehand. Here is my feedback:

1. LDO is ideal for power rails, but a DC/DC is ok with the example decoupling network

2. 6.49k 1% is needed for RBIAS, 6.2 or 6.8 is not possible

3. There is no 50 ohm integrated termination on the MII TX inputs. These are only present on the MII RX outputs.

4. You are correct that in MII mode a 25MHz oscillator or crystal should be used.

5. LED_0 is the link indicator by default. On the EVM this is routed to an LED, though this can be used as a signal to monitor the PHY link as well.

6. You do not need to use all LEDs if you do not need them. Typically I see LED_0 and 1 used.

7. You do not need a series resistor on MDC or MDIO, though it may be helpful to add these as a way to disconnect the MDIO/MDC bus from the bus controller if needed in debug. If doing this, I recommend keeping the MDIO pullup on the PHY-side of the series resistor on MDIO.

8. You can connect the RESET_N signal to an MCU or use a passive network.

9. In enhanced mode, you can configure PWRDN/INT as an interrupt pin through register access. This can be connected to the MCU

10. ESD diodes are not a requirement, though they are recommended if you intend to perform ESD testing.

I agree with the energy detect only FLD mode you are configuring. Certainly let me know if you have any other questions.

Best,

Shane

0 Alba Dervishi 4 months ago in reply to Shane Hauser

TI__Prodigy 490 points

Hi Shane,

Thanks a lot for you fast reply and the feedback.

Best regards,

Alba

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DP83826AE: DP83826AE Schematic review for robotics humanoid motor.