REV. 0

ADP3510

–11–

AMBIENT TEMPERATURE – C

1.2

0.0

–20

100

0

20

40

60

80

1.0

0.8

0.6

0.4

0.2

Figure 4. Power Dissipation vs. Temperature

However, high battery voltages normally occur only when the battery

is being charged and the handset is not in conversation mode. In

this mode, there is a relatively light load on the LDOs. A fully

charged Li-Ion battery is 4.245 V, where the ADP3510 can deliver

the maximum power (0.52 W) up to 85

∞C ambient temperature.

Low Dropout Regulators (LDOs)

The ADP3510 high performance LDOs are optimized for their

given functions by balancing quiescent current, dropout voltage,

regulation, ripple rejection, and output noise. 2.2

mF tantalum or

MLCC ceramic capacitors are recommended for use with the core,

memory, IO, and analog LDOs. A 0.22

mF capacitor is recom-

mended for the TCXO LDO.

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 at all times.

Memory LDO (VMEM)

The memory LDO supplies the memory of the baseband pro-

cessor. The memory LDO is capable of supplying 60 mA of

current and 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 further-

more 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

75 mA load, which is sufficient to supply the complete analog

section of the baseband converter. The analog LDO is controlled

by the power-on delay block of the ADP3510.

TCXO LDO (VTCXO)

The TCXO LDO is intended as a supply for a temperature compen-

sated crystal oscillator, which needs its own ultralow noise supply.

VTCXO is rated for 10 mA of output current and is turned on

when TCXOEN is asserted.

RTC LDO (VRTC)

The RTC LDO charges up a rechargeable lithium type coin

cell to run the realtime clock module. It has been designed to

charge manganese lithium batteries such as the ML series

(ML614, ML621, or ML1220) from Sanyo. The ML621 has a

small physical size (6.8 mm diameter) and will give many hours

of backup time.

The ADP3510 supplies current both for charging the coin cell

and for the RTC module. The nominal charging voltage is 2.85 V,

which ensures long cell life while obtaining in excess of 90% of

the nominal capacity. In addition, it features a very low quies-

cent 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.

IO LDO (VIO)

The IO LDO generates the voltage needed for the peripheral

subsystems of the baseband processor, including GPIO, display,

and serial interfaces. It is rated for 25 mA of supply current and

is controlled by the power-on delay block of the ADP3510.

Reference Output (REFOUT)

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

a guaranteed accuracy of 1.65% over temperature. The reference

can be used with the baseband converter, if the converter’s own

reference is not accurate. This may significantly reduce the calibra-

tion time needed for the baseband converter during production.

Power ON/OFF

The ADP3510 handles all issues regarding the powering ON and

OFF of the handset. It is possible to turn on the ADP3510 in

four different ways:

∑ Pulling the PWRONKEY Low

∑ Pulling PWRONIN High

∑ Pulling ALARM 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, as long as the PWRONKEY

is held low. When the VIO 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 ADP3510 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 monitoring the ROWX pin, the baseband

processor can detect a second PWRONKEY press and turn the

LDOs off in an orderly manner. In this way, the PWRONKEY

can be used for ON/OFF control.

Pulling the ALARM pin high is how the alarm in the realtime

clock module will turn the handset on. Asserting ALARM will

turn the core, IO, memory, and analog LDOs on, starting up

the baseband processor.

Applying an external charger can also turn the handset on. This

will turn on all the LDOs, again starting up the baseband processor.

Note that if the battery voltage is below the undervoltage lockout

threshold, applying the adapter will not start up the LDOs.