Power Supply Scheme

UC6580x-00 supports two power supply schemes, including internal DC-DC mode and LDO mode.

DCDC_IN and VDD_IO use the same power.

V_BACK can use an independent power, or use the same power as DCDC_IN and VDD_IO.

TCXO is powered by LDO_X. The voltage could be 1.8 V or 2.8 V.

To prevent a reversed current from VDD_IO to V_BACK, the supply voltage of V_BACK should be no lower than VDD_IO (not considering the problem of voltage reduction when the backup battery is short of power) or you should add a forward biased diode before V_BACK. Meanwhile, make sure that V_BACK is within the range of 1.7 V to 3.6 V. The diode is recommended to be of low power (mA-level forward current), low forward voltage drop (300 mV), and low reverse leakage current (< 100 μA within the working temperature).

If you do not use the hot start and backup function, connect the V_BACK to VDD_IO

DC-DC Mode

In this mode, the main power (V_Main) connects to the pin DCDC_IN, and the output of the DCDC module DCDC_Out provides the power to the rest circuits. At this time, the system is powered by the internal DC-DC:

• The system power supply is input by DCDC_IN, and DCDC_Out is connected to the V_CORE input pin.

LDO Mode

In this mode, the main power (V_Main) connects to DCDC_IN while DCDC_IN and DCDC_Out are short-circuited and the internal DC-DC is bypassed, so that the V_Main provides the power to the rest circuits directly. At this time:

• DCDC_IN and DCDC_OUT are short-circuited together.
• The system power supply is input by VDD_IO and output to V_CORE through LDO_EX.

For specific design scheme of the above modes, please refer to UC6580x-00 Hardware Reference Design.