unicore UFirebird II, Справочный проект, Страница: 7 / 15

2 Reference Design UC-06-C21 EN R1.0
1.2 DC/DC Mode
Under the DC/DC mode:

DCDC_IN and VDD_IO use the same power supply;
 Use the internal DC/DC to power the system;
 Power the external TCXO by LDO_X;

Connect RTC Crystal externally;

Connect LNA and SAW externally;
 Use the UART interfaces to communicate;
 Lower power consumption but higher cost due to the use of power inductor
comparing with LDO mode;
RF Short 50ohm Line
TCXO
V_CORE
LDO_X
VMAIN
DCDC_OUT
LDO_RE T LDO_X VDD_ANT
LDO_C LDO_EX
VMAIN
VMAIN
V_DE T V_BCKP
VBCKP
：
1.7V~3 .6V
VMAIN ： 2.7V~3 .6V
V_DET
：
2.7V~3 .6V
Figure 1-2 Reference design of DCDC mode

If the antenna feed supply and the chip’s main supply use the same power rail, the
ESD, surge and overvoltage from the antenna will have an effect on the main supply,
which may cause damage to the chip. Therefore, it is recommended to design an
independent power rail for the antenna feed supply to reduce the possibility of chip
damage.