VPP power supply can be sourced
on-board or externally. VPP pin can be left floating (HiZ) or pulled down to ground
through a resistor during processor power-up and power-down sequences 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 up after completion of proper processor power-up sequence.
- The VPP power supply has high
load current transients and local bulk capacitors are likely required near
the VPP pin to assist the LDO transient response.
- Select the power supply with
quick discharge capability or use a discharge resistor. A maximum current of
400 mA is specified for programming. It is recommended to use a fixed LDO
with higher input supply (2.5 V or 3.3 V) and enable input.
- If an external power supply
is used, the supply is recommended to be applied after the processor power
supplies are stable.
- When external power supply is
applied for VPP, recommend adding bulk capacitor, decoupling capacitor and
discharge resistor on-board near to the processor. Add a test point to
connect external power supply and provision to connect one of the processor
IO to control timing of the external supply.
- It is recommended to disable
the VPP supply (left floating (HiZ) or grounded) when not programming the
OTP.
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.
For more information, refer the
VPP Specifications for One-Time Programmable (OTP) eFuses section in the
Specifications chapter of the device-specific data sheet.