aoz1050pi Alpha & Omega Semiconductor, aoz1050pi Datasheet - Page 6

• Manufacturer Part Number: aoz1050pi
• Description: Ezbucktm 2 A Synchronous Buck Regulator
• Manufacturer: Alpha & Omega Semiconductor

Efficiency
Detailed Description
The AOZ1050PI is a current-mode step down regulator
with an integrated high-side PMOS switch and a low-side
NMOS switch. The AOZ1050PI operates from a 4.5 V to
18 V input voltage range and supplies up to 2 A of load
current. Features include enable control, power-on reset,
input under voltage lockout, output over voltage
protection, external soft-start and thermal shut down.
The AOZ1050PI is available in an exposed pad SO-8
package.
Enable and Soft Start
The AOZ1050PI has an external soft start feature to limit
in-rush current and ensure the output voltage ramps up
smoothly to regulation voltage. The soft start process
begins when the input voltage rises to 4.1 V and voltage
on the EN pin is HIGH. In the soft start process, the
FB voltage is ramped to follow the voltage of the soft start
pin until it reaches 0.8 V. The voltage of the soft-start pin
is charged by an internal 5 µA current.
The EN pin of the AOZ1050PI is active high. Connect the
EN pin to VIN if the enable function is not used. Pulling
EN to ground will disable the AOZ1050PI. Do not leave
EN open. The voltage on the EN pin must be above 2 V
to enable the AOZ1050PI. When the EN pin voltage falls
below 0.6 V, the AOZ1050PI is disabled.
Rev. 1.0 June 2011
100
95
90
85
80
75
70
65
60
0.2
0.4
Efficiency (V
0.6
www.aosmd.com
0.8
Load Current (A)
IN
1.0
= 12V) vs. Load Current
Steady-State Operation
Under heavy load steady-state conditions, the converter
operates in fixed frequency and Continuous-Conduction
Mode (CCM).
The AOZ1050PI integrates an internal P-MOSFET as the
high-side switch. Inductor current is sensed by amplifying
the voltage drop across the drain to source of the high
side power MOSFET. Output voltage is divided down by
the external voltage divider at the FB pin. The difference
of the FB pin voltage and reference voltage is amplified
by the internal transconductance error amplifier. The
error voltage, which shows on the COMP pin, is
compared against the current signal, which is the sum of
inductor current signal and ramp compensation signal, at
the PWM comparator input. If the current signal is less
than the error voltage, the internal high-side switch is on.
The inductor current flows from the input through the
inductor to the output. When the current signal exceeds
the error voltage, the high-side switch is off. The inductor
current is freewheeling through the internal low-side
N-MOSFET switch to output. The internal adaptive FET
driver guarantees no turn on overlap of both the
high-side and the low-side switch.
1.2
1.4
5V OUTPUT
3.3V OUTPUT
1.8V OUTPUT
1.2V OUTPUT
1.6
1.8
2.0
AOZ1050PI
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