AAT2601B Datasheet, PDF (29/39 Pages) Skyworks Solutions Inc. – Total Power Solution for Portable Applications

DATA SHEET
AAT2601B
Total Power Solution for Portable Applications
Control Loop
The converter is a peak current mode step-down con-
verter. The inner, wide bandwidth loop controls the induc-
tor peak current. The inductor current is sensed through
the P-channel MOSFET (high side) which is also used for
short circuit and overload protection. A fixed slope com-
pensation signal is added to the sensed current to main-
tain stability for duty cycles greater than 50%. The peak
current mode loop appears as a voltage programmed
current source in parallel with the output capacitor.
The output of the voltage error amplifier programs the
current mode loop for the necessary peak inductor cur-
rent to force a constant output voltage for all load and
line conditions. The voltage feedback resistive divider is
internal and the error amplifier reference voltage is
0.45V. The voltage loop has a high DC gain making for
excellent DC load and line regulation. The internal volt-
age loop compensation is located at the output of the
transconductance voltage error amplifier.
Soft Start
Soft start slowly increases the internal reference voltage
when the input voltage or enable input is initially applied.
It limits the current surge seen at the input and elimi-
nates output voltage overshoot.
Current Limit and
Over-Temperature Protection
For overload conditions the peak input current is limited.
As load impedance decreases and the output voltage
falls closer to zero, more power is dissipated internally,
raising the device temperature. Thermal protection com-
pletely disables switching when internal dissipation
becomes excessive, protecting the device from damage.
The junction over-temperature threshold is 140°C with
15°C of hysteresis.
Linear LDO Regulators (OUT1-5)
The advanced circuit design of the linear regulators has
been specifically optimized for very fast start-up and
shutdown timing. These proprietary LDOs are tailored for
superior transient response characteristics. These traits
are particularly important for applications which require
fast power supply timing.
The high-speed turn-on capability is enabled through the
implementation of a fast start control circuit, which
accelerates the power up behavior of fundamental con-
trol and feedback circuits within the LDO regulator. For
LDO4 and LDO5, fast turn-off time response is achieved
by an active output pull down circuit, which is enabled
when the LDO regulator is placed in the shutdown mode.
This active fast shutdown circuit has no adverse effect on
normal device operation.
Input/Output Capacitors
The LDO regulator output has been specifically optimized
to function with low cost, low ESR ceramic capacitors.
However, the design will allow for operation over a wide
range of capacitor types. The input capacitor is shared
with all LDO inputs and the step-down converter. A 10μF
is sufficient. A 4.7μF ceramic output capacitor is recom-
mended for LDO2-5 and a 22μF output capacitor for
LDO1.
Current Limit and
Over-Temperature Protection
The regulator comes with complete short circuit and
thermal protection. The combination of these two internal
protection circuits gives a comprehensive safety system
to guard against extreme adverse operating conditions.
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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