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USB EZ-PD Type-C

New Contributor II

Hi,

I am using a custom solution for the CYPD3175, modifying the CYPD3171-CLA sample. The PD profiles are sent to the device over I2C, I want to set the current limits over I2C as well but am having an issue finding where in the API the parameters for current limits must be set.

I thought that using the function call:

psrc_set_current(0,100);

Would set the port 0 current limit to 1A, but when I draw 2A on the port, the current limit is not triggered (shutdown of Vbus)

I have set the Rsense to 5mR which is what we are using.

#define VBUS_CSA_RSENSE       (50u)

I would appreciate some guidance on how to set the parameters via the PD API so that the Alert flag is set and the Vbus is disabled when a value is exceeded.

Regards

TG

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Moderator
Moderator

Hi TG,

1. void psrc_set_current (uint8_t port, uint16_t cur_10mA) is the correct API to add your I2C operations. You could make a function which is for I2C write or Read and then use it in void psrc_set_current (uint8_t port, uint16_t cur_10mA). So that when Type-C PD stack state machine call back function void psrc_set_current (uint8_t port, uint16_t cur_10mA), the I2C operations will be formed.

2. You do not need to call  function psrc_set_current (0, 100) for Type-C port with 1A current set. Since the Type-C PD stack will call it if the PD contract is current with 1A.

You could take a look the function and find that the ocp_cur is calculated in this function. ocp_cur is over current protection threshold. Meanwhile, you could open Ez-PD configuration Utility to see what value you have set in your project.

pastedImage_0.png

3. The Rsense to 5mR is okay. But you need confirm it with your board. The value shall be Rsense + Resistance on the trace. And please make sure the GND return ground is single loop and cross the Rsense.

Best Regards,

Lisa

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3 Replies
Moderator
Moderator

Hi TG,

1. void psrc_set_current (uint8_t port, uint16_t cur_10mA) is the correct API to add your I2C operations. You could make a function which is for I2C write or Read and then use it in void psrc_set_current (uint8_t port, uint16_t cur_10mA). So that when Type-C PD stack state machine call back function void psrc_set_current (uint8_t port, uint16_t cur_10mA), the I2C operations will be formed.

2. You do not need to call  function psrc_set_current (0, 100) for Type-C port with 1A current set. Since the Type-C PD stack will call it if the PD contract is current with 1A.

You could take a look the function and find that the ocp_cur is calculated in this function. ocp_cur is over current protection threshold. Meanwhile, you could open Ez-PD configuration Utility to see what value you have set in your project.

pastedImage_0.png

3. The Rsense to 5mR is okay. But you need confirm it with your board. The value shall be Rsense + Resistance on the trace. And please make sure the GND return ground is single loop and cross the Rsense.

Best Regards,

Lisa

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New Contributor II

I  have copied the config.c content for the following:

2019-03-22 14_34_28-EZ-PD™ Analyzer Utility.png

The OCP is not triggering on more the 2x the current.

I will have to wait for the accurate LCR meter to check the trace resistance.

Regards

TG

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New Contributor II

After reviewing the schematic I found an error in the BoM that caused a 0.5mR res to be placed instead of a 5mR, Fixing this resolved the issue. Thanks for your help.