ATR0625P Datasheet, PDF (18/27 Pages) ATMEL Corporation – GPS Baseband Processor SuperSense

The baseband IC 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 however supply a 1.8V core voltage directly, this voltage has to be con-
nected to the VDD18 supply pins of the baseband IC. LDO_EN must be connected to GND.
LDO_IN can be connected 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 LDOBAT_IN between 2.3V and 3.6V or from VBAT
between 1.5V and 3.6V. The backup battery connected to VBAT is only discharged if the supply
connected to LDOBAT_IN is shut-down.
Only after VDD18 has been supplied to ATR0625P the RTC section will be initialized properly. If
only VBAT is applied first, the current consumption of the RTC and backup SRAM is
undetermined.
Figure 4-2. External Wiring Example Using 1.8V from Host System and Backup Power
Supply
ATR0625P internal
LDO_IN
LDO_EN
LDO_OUT
ldoin
ldoen
ldoout
LDO18
1.65V to 1.95V
VDD18
Core
2.3V to 3.6V
1.5V to 3.6V
1 µF
(X7R)
VDDIO
1 µF
(X7R)
LDOBAT_IN
VBAT
VBAT18
1.8V to 3.3V
variable IO Domain
ldobat_in
vbat
vbat18
LDOBAT
vdd
RTC
Backup Memory
0V or 3V to 3.6V
VDDUSB
USB SM and
Transceiver
18 ATR0625P
4925G–GPS–06/08