Specifications

Table Of Contents

Reference Circuit configuration 5

Configurations summary for reference circuit 5

Config no.

Main Supply

EXT Supply Output USB

VDDH VDD

Config.5 USB(VDDH = VBUS) N/A Yes Yes

Explanation of symbols in reference circuit 5 schematic

Symbol Parameter Min. Typ. Max. Units

BUS

Supply voltage on VBUS pin 4.35 5 5.5 V

EXT

Voltage output on VDD when supplied from internal

regulator (REG0). V

BUS

is the input to REG0.

1.8 3.3 V

Some general guidance is summarized here:

 Main supply voltage is connected to VDD/VDDH. The system will enter one of two supply voltage

modes, normal or high voltage mode, depending on how the supply voltage is connected to these

pins. Normal voltage mode is entered when the supply voltage is connected to both the VDD and

VDDH pins (so that VDD equals VDDH).High voltage mode is entered when the supply voltage is

only connected to the VDDH pin and the VDD pin is not connected to any voltage supply.

 By default, the LDO regulators in the chip are enabled and the DC/DC regulators are disabled.

Registers DC/DCEN0 and DC/DCEN are used to independently enable the DC/DC regulators.

External LC filters has been connected in the Module for DC/DC regulators being used.

 The GPIO high reference voltage always equals the level on the VDD pin. In normal voltage

mode, the GPIO high level equals the voltage supplied to the VDD pin, and in high voltage mode

it equals the level specified in the register REGOUT0 UICR registers.

http://www.freqchina.com