The VPP supply can be sourced on-board or externally.
The VPP pin can be left floating (HiZ) or pulled down to ground through a resistor during processor power-up, power-down, and during normal processor operation.
The following hardware requirements must be met when programming keys in the OTP eFuses:
- The VPP power supply must applied only after completion of processor power-up sequence.
- It is recommended to use a fixed LDO with higher input supply (2.5V or 3.3V) and enable input. The enable input is required to be controlled by the processor GPIO for timing.
- The VPP power supply is expected to see high load current transients and local bulk capacitors are likely required near the VPP pin to support the LDO transient response.
- Select the power supply with quick discharge capability or use a discharge resistor.
- A maximum current of 400mA is specified during programming.
- When an external power supply is used, the supply is recommended to be applied after the processor power supplies ramp and are stable.
- When an external power supply is used, add an onboard bulk capacitor, decoupling capacitor, and discharge resistor near to the processor VPP supply pin. Add a test point to connect the external power supply and provision to connect one of the processor GPIOs to control the timing of the external supply.
- It is recommended to disable the VPP supply (left floating (HiZ) or grounded) when not programming the OTP eFuses.
For more information, see the [FAQ] AM625 / AM623 / AM625SIP / AM625-Q1 / AM620-Q1 Custom board hardware design – Queries regarding VPP eFuse programming power supply selection and application. This is a generic FAQ and can also be used for AM64x or AM243x family of processors.
For more information, refer to the VPP Specifications for One-Time Programmable (OTP) eFuses section in the Specifications chapter of the device-specific data sheet.