REV. 0

ADP3522

–13–

Digital Core LDO (VCORE)

The digital core LDO supplies the baseband circuitry in the

handset (baseband processor and baseband converter). The

LDO has been optimized for very low quiescent current at light

loads as this LDO is on whenever the handset is switched on.

Memory LDO (VMEM)

The memory LDO supplies the system memory as well as the

subsystems of the baseband processor including memory IO,

display, and melody interfaces. It is capable of delivering up to

150 mA of current and is available for either 1.8 V or 3 V based

systems. The LDO has also been optimized for low quiescent

current and will power up at the same time as the core LDO.

Analog LDO (VAN)

This LDO has the same features as the core LDO. It has fur-

thermore been optimized for good low frequency ripple

rejection for use with the baseband converter sections in order

to reject the ripple coming from the RF power amplifier. VAN is

rated to 180 mA, which is sufficient to supply the analog section

of the baseband converter, such as the AD6521, as well as the

microphone and speaker.

TCXO LDO (VTCXO)

The TCXO LDO is intended as a supply for a temperature

compensated crystal oscillator, which needs its own ultralow

noise supply. VTCXO is rated for 20 mA of output current and

is turned on along with the analog LDO when TCXOEN is

asserted. Note that the ADP3522 has been optimized for use

with the AD6534 (Othello One™).

RTC LDO (VRTC)

The RTC LDO is capable of charging rechargeable Lithium or

capacitor-type backup coin cells to run the real-time clock mod-

ule. The RTC LDO supplies current both for charging the coin

cell and for the RTC module. In addition, it features a very low

quiescent current since this LDO is running all the time, even

when the handset is switched off. It also has reverse current

protection with low leakage, which is needed when the main

battery is removed and the coin cell supplies the RTC module.

SIM LDO (VSIM)

The SIM LDO generates the voltage needed for 1.8 V or 3 V

SIMs. It is rated for 20 mA of supply current and can be con-

trolled completely independently of the other LDOs.

Applying a low to SIMEN shuts down the SIM LDO. A dis-

charge circuit is active when SIMEN is low. This pulls the SIM

LDO’s output down when the LDO is disabled.

SIMVSEL allows the SIM LDO to be programmed for either

1.8 V or 2.8 V. Asserting a high on SIMVSEL sets the output

for 2.8 V.

SIMEN and SIMVSEL allow the baseband processor to prop-

erly sequence the SIM supply when determining which type of

SIM module is present.

Reference Output (REFOUT)

The reference output is a low noise, high precision reference with

a guaranteed accuracy of 1.5% overtemperature. The maximum

output current of the REFOUT supply is limited to 50

µA.

Power ON/OFF

The ADP3522 handles all issues regarding the powering ON

and OFF of the handset. It is possible to turn on the ADP3522

in three different ways:

• Pulling the PWRONKEY low

• Pulling the PWRONIN high

• CHRIN exceeds CHRDET threshold

Pulling the

PWRONKEY low is the normal way of turning on the

handset. This will turn on all the LDOs, except the SIM LDO, as

long as the

PWRONKEY is held low. When the VCORE LDO

comes into regulation, the

RESET timer is started. After timing

out, the

RESET pin goes high, allowing the baseband processor to

start up. With the baseband processor running, it can poll the

ROWX pin of the ADP3522 to determine if the PWRONKEY has

been depressed and pull PWRONIN high. Once the PWRONIN is

taken high, the

PWRONKEY can be released. Note that by moni-

toring the

ROWX pin, the baseband processor can detect a second

PWRONKEY and press and turn the LDOs off in an orderly manner.

In this way, the

PWRONKEY can be used for ON/OFF control.

Pulling the PWRONIN pin high is how the alarm in the real-

time clock module will turn the handset on. Asserting

PWRONIN will turn the core and memory LDOs on, starting

up the baseband processor.

1.6

3.5

4.0

1.2

1.8

4.5

5.0

3.0

1.4

0.8

0.4

1.0

0.6

5.5

6.0

0.2

0

INPUT VOLTAGE – V

ADP3522-1.8

ADP3522-2.8

Figure 3. Power Dissipation vs. Input Voltage

1.6

020

1.2

1.8

40

60

–20

1.4

0.8

0.4

1.0

0.6

80

0.2

0

AMBIENT TEMPERATURE – C

LFCSP

32 C/W

Figure 4. Allowable Package Power Dissipation

vs. Temperature