AAT3603 Datasheet, PDF (20/35 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

PRODUCT DATASHEET
AAT3603178
Total Power Solution for Portable Applications
The startup sequence for the AAT3603 core (Buck and
LDO1) is typically initiated by pulling the EN_KEY pin low
with a pushbutton switch, see Figure 1. The Buck (Core)
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 (PowerDigital) reaches 90% of its
final value, the 65ms RESET timer is initiated holding the
microprocessor in reset. When the RESET pin goes High,
the μP can begin a power up sequence. After the startup
sequence has commenced, LDO2 (PowerAnalog), LDO3
(TCXO), LDO4 (TX) and LDO5 (RX) 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 con-
trol of EN_HOLD, providing protection against inadver-
tent momentary assertions of the pushbutton. Once
EN_HOLD is high the startup sequence is complete. If
the μP is unable to complete its power-up routine suc-
cessfully before the user lets go of the push-button, the
AAT3603 will automatically shut itself down. (EN_KEY
and EN_HOLD are OR’d internally to enable the two core
converters.)
Alternatively, the startup sequence is automatically
started 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 startup 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 AAT3603. The user can initi-
ate 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 AAT3603
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 voltage
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 AAT3603. 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 internally pulled
to ground with 10k during shutdown to discharge the out-
put capacitors and ensure a fast turn-off response time.
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3603.2008.06.1.0