Rainbow Electronics ATR0630 - Manual (Page 21)

21
4920A–GPS–01/06
ATR0630 [Preliminary]
Figure 4-1. Connecting Example: Separate Power Supplies for RF and Digital Part Using the Internal LDOs
The ATR0630 contains a built in low dropout voltage regulator LDO18. This regulator can be
used if the host system does not provide the core voltage VDD18 of 1.8V nominal. In such case,
LDO18 will provide a 1.8V supply voltage from any input voltage VDD between 2.3V and 3.6V.
The LDO_EN input can be used to shut down VDD18 if the system is in standby mode.
If the host system does supply a 1.8V core voltage directly, this voltage has to be connected to
the VDD18 supply pins of the Core. LDO_EN must be connected to GND. LDO_IN can be con-
nected to GND. LDO_OUT must not be connected.
A second built in low dropout voltage regulator LDOBAT provides the supply voltage for the RTC
and backup SRAM from any input voltage VBAT between 1.5V and 3.6V. The backup battery
delivers the supply current if LDOBAT_IN is not powered.
ATR0630 internal
VDDUSB 0V or 3V to 3.6V
1.5V to 3.6V
1 µF
(X7R)
ldoout
ldoen
ldoin
LDO18
LDO_IN
1 µF
(X7R)
VDDIO
2.3V to 3.6V
LDO_EN NSHDN
VDD18
LDO_OUT
USB SM and
transceiver
1.8V to 3.3V
variable I/O domain
RTC
backup memory
Core
vbat18
vbat
VDD
ldobat_in
LDOBAT
LDOBAT_IN
VBAT
VBAT18
RF
VCC1
VCC2
VBP
VDIG
2.7V to 3.3V