AAT3601_08 Datasheet, PDF (20/37 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

PRODUCT DATASHEET
AAT3601178
Total Power Solution for Portable Applications
Functional Description
The AAT3601 is a complete power management solution.
It seamlessly integrates an intelligent, stand-alone CC/
CV (Constant-Current/Constant-Voltage), linear-mode
single-cell battery charger with one step-down Buck con-
verter and five low-dropout (LDO) regulators to provide
power from either a wall adapter or a single-cell Lithium-
Ion/Polymer battery. Internal load switches allow the
LDO regulators and DC-DC converter to operate from the
best available power source of either an AC wall adapter,
USB port supply, or battery.
If only the battery is available, then the voltage regula-
tors and converter are powered directly from the battery
through a 100mΩ load switch. (The charger is put into
sleep mode and draws less than 1μA quiescent current.)
If the system is connected to a wall adapter, then the
voltage converters are powered directly from the adapt-
er through a 500mΩ load switch and the battery is dis-
connected from the voltage converter inputs. This allows
the system to operate regardless of the charging state of
the battery or with no battery. The LDOs and DC/DC
converter are separated into Permanently-Enabled (PE)
system-on supplies and Non-Permanent (NP) separate
enable supplies referring to the two independent enable
functions.
System Output (SYSOUT)
Intelligent control of the integrated load switches is
managed by the switch control circuitry to allow the
step-down converter and the LDOs to have the best
available power source. When the CHGIN pin voltage is
above 4.5V, the system automatically turns on and the
power to the SYSOUT pin will be provided by either the
CHGIN pin or the BAT pin. When the USE_USB pin is low,
the CHGIN provides power to SYSOUT through an inter-
nal LDO regulated to 3.9V. When the USE_USB pin is
high or if forced through use of an I²C command, the BAT
pin is shorted to SYSOUT through a 100mΩ switch. If a
CHGIN voltage is not present and the system is enabled,
SYSOUT will be shorted to BAT.
This system allows the step-down converter and LDOs to
always have the best available source of power. This also
allows the voltage converters to operate with no battery,
or with a battery voltage that falls below the precondi-
tion trickle charge threshold.
Typical Power Up Sequence
The AAT3601 supports two enable/disable schemes.
System startup is initiated whenever one of the following
conditions occurs:
1. A push-button is used to assert EN_SYS low when a
valid supply (>CHGIN UVLO) is not connected to the
charger input CHGIN.
2. A valid adaptor supply (>CHGIN UVLO) is connected
to the charger input CHGIN.
Case 1
The startup sequence for the AAT3601 is typically initiated
by pulling the EN_SYS pin low with a pushbutton switch
(see Figure 1). The SYSOUT is the first block to be turned
on. When the output of the SYSOUT reaches 90% of its
final value, then the PE supplies LDO1, LDO3 and LDO5
are enabled if EN_PE is low. When the PE supplies reach
90% of their final value, the 800ms RSTLPW timer is initi-
ated holding the microprocessor in reset. When the
RSTLPW pin goes High, the NP sequence supplies LDO2,
LDO4 and OUTBUCK can be enabled and disabled as
desired using the EN_NP pin. When the NP supplies reach
90% of their final value, the 10ms RSTIN timer is released.
The NP outputs should not be started up until after the
RSTLPW pin goes high. Do not start all the outputs up at
the same time. The state of EN_SYS is latched as long as
either CHGIN or BAT is connected to the device.
Case 2
Alternatively, the startup sequence is automatically
started without the pushbutton switch when the CHGIN
pin rises above its UVLO threshold. The battery charger
is started when CHGIN_OK is internally enabled. The
STAT pin goes high and the system is enabled.
Sequence of startup depends on whether or not the
adapter input is connected or open. The timing diagrams
in Figures 2 and 3 illustrate the two cases. A typical
startup and shutdown process proceeds as follows
(referring to Figures 1, 2 and 3).
Typical Power Down Sequence
If only the battery is connected and the voltage level is
above the BAT UVLO, then the EN_PE pin can be held low
in order to power down AAT3601. When the voltage at
the CHGIN pin is above the CHGIN UVLO, the device can-
not be powered down but the EN_PE and EN_NP pins can
be used to disable the PE and NP supplies. If the adapter
supply at the CHGIN pin is disconnected, the device will
power down even if BAT is connected if the EN_SYS state
was not first latched into the device by pulling it low
when either BAT or CHGIN is connected. If CHGIN falls
below UVLO without being disconnected, the EN_SYS will
still be latched and the device will remain powered. The
outputs of the LDOs are internally pulled to ground with
10k during shutdown to discharge the output capacitors
and ensure a fast turn-off response time.
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