ADP3408(Rev0) 查看數據表（PDF） - Analog Devices
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ADP3408 Datasheet PDF : 16 Pages
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ADP3408
NON-CHARGING
MODE
CHARGER
DETECTER
NO
CHRIN > BATSNS
YES
VBAT > UVLO
YES
NO
LOW CURRENT
CHARGE MODE
VSENSE = 20mV
CHGEN = HIGH
NIMH
CHARGING MODE
GATEIN = PULSED
NIMH
BATTERY
TYPE
LI+
CHGEN = LOW
HIGH CURRENT
CHARGE MODE
VSENSE = 160mV
NO
VBAT > 4.2V
NO
VBAT > 5.5V
YES
NIMH
CHARGER OFF
GATEIN = HIGH
YES
CONSTANT
VOLTAGE MODE
NO ICHARGE < I END
OF CHARGE
NO
VBAT < 5.5V
YES
EOC = HIGH
YES
TERMINATE CHARGE
CHREN = HIGH
GATEIN = HIGH
Figure 5. Battery Charger Flow Chart
Digital Core LDO (VCORE)
The digital core LDO supplies the baseband circuitry in the hand-
set (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 peripheral subsystems of the
baseband processor including GPIO, display, and SIM interfaces as
well as memory. The LDO has also been optimized for low quies-
cent 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
130 mA load, which is sufficient to supply the complete analog
section of the baseband converter such as the AD652l.
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 5 mA of output current and is turned
on along with the analog LDO when TCXOEN is asserted.
RTC LDO (VRTC)
The RTC LDO charges up a capacitor-type backup coin cell to
run the real-time clock module. It has been designed to charge electric
double layer capacitors such as the PAS621 from Kanebo. The
PAS621 has a small physical size (6.8 mm diameter) and a nominal
capacity of 0.3 F, giving many hours of backup time.
The ADP3408 supplies current both for charging the coin cell
and for the RTC module when the digital supply is off. The
nominal charging voltage is 2.45 V, which ensures long cell life
while obtaining in excess of 90% of the nominal capacity. 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 3 V SIMs. It is
rated for 20 mA of supply current and can be controlled com-
pletely independently of the other LDOs.
Reference Output (REFOUT)
The reference output is a low noise, high precision reference with
a guaranteed accuracy of 1.5% over temperature. The reference
can be used with the baseband converter, if the converter’s own
reference is not accurate. This will significantly reduce calibration
time needed for the baseband converter during production.
Note that the reference in the AD6521 has an initial accuracy of
10%, but can be calibrated to within 1%.
Power ON/OFF
The ADP3408 handles all issues regarding the powering ON
and OFF of the handset. It is possible to turn on the ADP3408
in three different ways:
• Pulling the PWRONKEY Low
• Pulling PWRONIN High
• CHRIN exceeds CHRDET Threshold
Pulling the PWRONKEY low is the normal way of turning on the
handset. This will turn all the LDOs on, 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 ADP3408 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 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.
–12–
REV. 0
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