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imx287  AN4199 3.2 chapter :100-mA input current limit

Question asked by xm phoenix on Jun 16, 2014


chapter 3.2 Power sources:


VDD5V—Input to the internal LinRegs. It can also be used to source the internal DC-DC with the

4.2 V regulated by the 4P2 LinReg. The 5-V source can be taken from a universal serial bus (USB)

connection, a wall charger with 5-V output, or a 5-V regulated from a supply with higher voltage.

There is a 100-mA input current limit when the system is powering up from the Power-Off state.

Product designers should pay attention to ensure the 100 mA is sufficient for the total system

consumption during cold-boot or reboot.

chapter 4.1.2 VDD5V source only:


Additionally, special consideration is needed for the hardware design in this configuration as the i.MX28

PMU is running on internal LinRegs on startup. The internal LinRegs have the following limitations:

• During the early stage of device startup, before on-chip ROM execution, the input current on

VDD5V is limited to 100 mA.

• The device is running on internal LinRegs on power up, and it needs to wait for the software to set

up the 4P2 rail before switching to the DC-DC converter as the power supply. The output current

from LinRegs is much lower than that of the DC-DC converter



I check the imx287 reference Schematic diagram 。I do not find the hardware design for limited to 100mA ?

how i deal with the limited 100mA for start up in hardware design ?