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TPS65982: TPS65982 OCP(Over Current Protection) Question

Satoshi Yone
Expert 3600 points

Part Number: TPS65982

Hi, Team,

A customer has questions for OCP

・By default, what size is the margin up to OCP from RDO value? (VBUS sourcing from PP5V0)

・Is there any register which can alter or lock the OCP value of VBUS Sourcing Mode?

Best Regards,

Satoshi Yone

  • 0
    TI__Mastermind 36756 points
    Hi Yone-san,

    ・By default, what size is the margin up to OCP from RDO value? (VBUS sourcing from PP5V0)
    - Default setting is 3A with 100% Peak Current. The OCP will trigger above 3A.

    ・Is there any register which can alter or lock the OCP value of VBUS Sourcing Mode?
    - You can adjust the OCP value in the Source Capabilities register through the operating current and peak current settings. For example, if you set operating current to 2A and peak current at 150%, the OCP will trip at 3A. Likewise, if you set operating current to 1A and peak current to 200%, the OCP will trip at 2A.

    Thank you,
    Eric
  • 0
    TI__Genius 16370 points

    Satoshi,

    The configuration tool allows you to configure the peak current and over-current timeout for an OCP to trigger.

    The timeout shall be configred in 'Internal 5V Power Path Over-Current Timeout' field of the 'System Configuration' register. The peak current shall be configured in ‘TypeC Current – Peak Current’ field of ‘System Configuration’ register. Note that the firmware sets the current-limit to the highest percentage for a given configuration - .i.e. If 01 (110% - 150% IOC) is chosen for bit:21-20, we set 150% IOC limit. The result is then used to  choose an ILIM setting/range depending on the configured switch – For ex., if PP5V switch is being used and Type-C current is set to 1.5A w/ peak-current configured as 130% IOC, the firmware uses (1500mA * 150% = 2250mA) to choose an ILIM code, which in this case is ‘Setting 11’, and referring section:6.11 of 982’s datasheet, this translates to an ILIM range of 2.39mA – 2.92mA.

    Few additional points:

    • As is indicated in section-6.4.1.2.3.6 of PD spec (Rev 2.0; Version 1.2), the source uses this field to advertise its overloading capabilities. And. as mentioned in section-7.2.8 of the specification, sinks shall only make use of a source overload capability when the corresponding fixed supply PDO peak current bits are set.
    • While in implicit contract, IOC is the ‘Type-C Current’ – This value gets factored in while computing the switch’s current limits based on the configuration setting for ‘TypeC Current – Peak Current’.
    • While in explicit contract, IOC is the ‘Operating Current’ of the active-contract RDO, and current limits would be set depending on the ‘Supply Type’ of active-contract PDO. For fixed-supply PDO, this operating-current gets factored in while computing the switch’s current limits based on the configuration setting for ‘TypeC Current – Peak Current’.

    Let me know if you need additional information.

    -/Praneet

  • 0 in reply to Praneet Kumar
    TI__Expert 3600 points
    Hi, Eric, Praneet,

    Thank you for the answer. A customer has additional questions.

    1. TPS65982 can not change margin of OCP. Is our understanding correct?

    2. MAX Operating Current of RDO does not affect with a source function. MAX Operating Current is for reference. Is our understanding correct?

    3. For your comments "chosen for bit:21-20", is this 21:20 PeakCurrent of 0x37 Auto Negotiate Sink Register? It seems 0x37 Auto Negotiate Sink Register affects with the sink. Does it affect with the source?

    Best Regards,
    Satoshi Yone
  • 0 in reply to Satoshi Yone
    TI__Genius 16370 points

    Satoshi,

    Please find my responses inline:

    1. TPS65982 can not change margin of OCP. Is our understanding correct?

    [APK]: Yes

    2. MAX Operating Current of RDO does not affect with a source function. MAX Operating Current is for reference. Is our understanding correct?

    [APK]: Yes - OCP is applied/enabled on the source side only – The sink is expected to keep an eye on the peaks and duty-cycle. Meaning: By setting 'Peak Current' field as ‘01’ in 'Source PDO', the source is saying that it is capable of handling the peak-currents of 150%, 125% and 110% IOC as listed in the table below. That means, the sink is:

    • Either, allowed to draw a current @ 150% IOC for a maximum of 1ms, and since that spike should have a duty-cycle of 5%, the sink should average out the power consumption by drawing lesser current @ 97% IOC for 19ms.
    • Or, allowed to draw a current @ 125% IOC for a maximum of 2ms, and since that spike should have a duty-cycle of 10%, the sink should average out the power consumption by drawing lesser current @ 97% IOC for 18ms.
    • Or, allowed to draw a current @ 110% IOC for a maximum of 10ms, and since that spike should have a duty-cycle of 50%, the sink should average out the power consumption by drawing lesser current @ 90% IOC for 10ms.

    3. For your comments "chosen for bit:21-20", is this 21:20 PeakCurrent of 0x37 Auto Negotiate Sink Register? It seems 0x37 Auto Negotiate Sink Register affects with the sink. Does it affect with the source?

    [APK]: I meant  'Peak Current' field of Source-PDO - Please see Table 6-9 of the PD specification. The device updates these bits based on configuration Type-C Current settings in configuration registers 0x28 and 0x32.

    -/Praneet

  • 0 in reply to Praneet Kumar
    TI__Expert 3600 points
    Hi, Praneet,

    Thanks for the answer!

    Best Regards,
    Satoshi Yone