18

4891CS–GPS–01/06

ATR0622 [Preliminary]

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

connected 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 ATR0622 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

ATR0622 internal

VDDUSB

0 to 2V or 3V to 3.6V

1.5V to 3.6V

1 µF

(X7R)

ldoout

ldoen

ldoin

LDO18

LDO_IN

1 µF

(X7R)

VDDIO

LDO_EN

VDD18

LDO_OUT

USB SM and

Transceiver

1.8V to 3.3V

variable IO Domain

RTC

Backup Memory

Core

vbat18

vbat

vdd

ldobat_in

LDOBAT

LDOBAT_IN

VBAT

VBAT18

2.3V to 3.6V

1.65V to 1.95V