AOZ1017D 查看數據表（PDF） - Alpha and Omega Semiconductor
零件编号
产品描述 (功能)
比赛名单
AOZ1017D Datasheet PDF : 16 Pages
| |||
AOZ1017D
Detailed Description
The AOZ1017D is a current-mode step down regulator
with integrated high side PMOS switch. It operates from
a 4.5V to 16V input voltage range and supplies up to 3A
of load current. The duty cycle can be adjusted from 6%
to 100% allowing a wide range of output voltage. Fea-
tures include Enable Control, Power-On Reset, Input
Under Voltage Lockout, Fixed Internal Soft-Start and
Thermal Shut Down.
The AOZ1017D is available in 5x4 DFN-8 package.
Enable and Soft Start
The AOZ1017D has internal soft start feature to limit
in-rush current and ensure the output voltage ramps up
smoothly to regulation voltage. A soft start process
begins when the input voltage rises to 4.0V and voltage
on EN pin is HIGH. In the soft start process, the output
voltage is typically ramped to regulation voltage in 2.2ms.
The 2.2ms soft start time is set internally.
The EN pin of the AOZ1017D is active HIGH. Connect
the EN pin to VIN if enable function is not used. Pulling
EN to ground will disable the AOZ1017D. Do not leave it
open. The voltage on EN pin must be above 2.0 V to
enable the AOZ1017D. When voltage on EN pin falls
below 0.6V, the AOZ1017D is disabled. If an application
circuit requires the AOZ1017D to be disabled, an open
drain or open collector circuit should be used to interface
to the EN pin.
Steady-State Operation
Under steady-state conditions, the converter operates in
fixed frequency and Continuous-Conduction Mode
(CCM).
The AOZ1017D 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 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 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 external Schottky diode to
output.
The AOZ1017D uses a P-Channel MOSFET as the high
side switch. It saves the bootstrap capacitor normally
seen in a circuit which is using an NMOS switch. It allows
100% turn-on of the upper switch to achieve linear
regulation mode of operation. The minimum voltage drop
from VIN to VO is the load current x DC resistance of
MOSFET + DC resistance of buck inductor. It can be
calculated by equation below:
VO_MAX = VIN – IO × (RDS(ON) + Rinductor)
where;
VO_MAX is the maximum output voltage,
VIN is the input voltage from 4.5V to 16V,
IO is the output current from 0A to 3A,
RDS(ON) is the on resistance of internal MOSFET, the value is
between 40mΩ and 70mΩ depending on input voltage and
junction temperature, and
Rinductor is the inductor DC resistance.
Switching Frequency
The AOZ1017D switching frequency is fixed and set by
an internal oscillator. The practical switching frequency
could range from 400kHz to 600kHz due to device
variation.
Output Voltage Programming
Output voltage can be set by feeding back the output to
the FB pin with a resistor divider network. In the applica-
tion circuit shown in Figure 1. The resistor divider net-
work includes R1 and R2. Usually, a design is started by
picking a fixed R2 value and calculating the required R1
with equation below.
VO
=
0.8
×
⎜⎛ 1
⎝
+
RR-----12-⎠⎟⎞
Some standard values of R1 and R2 for most commonly
used output voltage values are listed in Table 1.
Table 1.
VO (V)
0.8
1.2
1.5
1.8
2.5
3.3
5.0
R1 (kΩ)
1.0
4.99
10
12.7
21.5
31.6
52.3
R2 (kΩ)
open
10
11.5
10.2
10
10
10
Rev. 1.1 April 2009
www.aosmd.com
Page 7 of 16
Share Link: 