AAT2601B Datasheet, PDF (21/39 Pages) Skyworks Solutions Inc. – Total Power Solution for Portable Applications

DATA SHEET
AAT2601B
Total Power Solution for Portable Applications
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.
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,
CHGIN provides power to SYSOUT through an internal
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 AAT2601B supports a variety of push-button or
enable/disable schemes. A typical startup and shutdown
process proceeds as illustrated in Figures 1 and 2. System
startup is initiated whenever one of the following condi-
tions occurs:
1) A push-button is used to assert EN_KEY low.
2) A valid supply (>CHGIN UVLO) is connected to the
charger input CHGIN.
3) A hands free device or headset is connected, assert-
ing EN_TEST high.
The startup sequence for the AAT2601B Buck and LDO1
is typically initiated by pulling the EN_KEY pin low with
a pushbutton switch, as shown in Figure 1. The Buck is
the first block to be turned on. When the output of the
Buck reaches 90% of its final value, then LDO1 is
enabled. When LDO1 reaches 90% of its final value, the
65ms RESET timer is initiated holding the microproces-
sor in reset. When the RESET pin goes High, the μP can
begin a power up sequence. After the startup sequence
has commenced, LDO2, LDO3, LDO4, and LDO5 can be
enabled and disabled as desired using their independent
enable pins, even while the Buck and LDO1 are still
starting up. However, if they are shut down, then LDO2,
LDO3, LDO4, and LDO5 cannot be enabled. The μP must
pull the EN_HOLD signal high before the EN_KEY signal
can be released by the push-button. This procedure
requires that the push-button be held until the μP
assumes control of EN_HOLD, providing protection
against inadvertent momentary assertions of the push-
button. Once EN_HOLD is high the startup sequence is
complete. If the μP is unable to complete its power-up
routine successfully before the user lets go of the push-
button, the AAT2601B will automatically shut down.
(EN_KEY and EN_HOLD are OR’d internally to enable the
two core converters.)
Alternately, the startup sequence is automatically start-
ed without the pushbutton switch when the CHGIN pin
rises above its UVLO threshold. The system cannot be
disabled until the voltage at the CHGIN pin drops below
the falling UVLO threshold. Thirdly, the EN_TEST pin can
be used to start up the device for test purposes or for
hands-free operation such as when connecting a headset
to the system.
Typical Power Down Sequence
If only the battery is connected and the voltage level is
above the BAT UVLO , then the EN_KEY pin can be held
low in order to power down AAT2601B. The user can
initiate a shutdown process by pressing the push-button
a second time. Upon detecting a second assertion of
EN_KEY (by depressing the push-button), the AAT2601B
asserts ON_KEY to interrupt the microprocessor which
initiates an interrupt service routine that the user
pressed the push-button. If EN_TEST and CHGIN are
both low, the microprocessor then initiates a power-
down routine, the final step of which will be to de-assert
EN_HOLD, disabling LDO2, LDO3, LDO4, and LDO5.
When the voltage at the CHGIN pin is above the CHGIN
UVLO, the device cannot be powered down. If the volt-
age at the CHGIN pin is below the CHGIN UVLO, both the
EN_KEY and EN_HOLD pins must be held low in order to
power down the AAT2601B. If LDO2, LDO3, LDO4, and
LDO5 have not been disabled individually prior to global
power down, then they will be turned off simultaneously
with the Buck. The outputs of LDO4 and LDO5 are inter-
nally pulled to ground with 10k during shutdown to dis-
charge the output capacitors and ensure a fast turn-off
response time.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
202181B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 19, 2013
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