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APU3048 View Datasheet(PDF) - Advanced Power Electronics Corp

Part Name
Description
Manufacturer
APU3048
A-POWER
Advanced Power Electronics Corp A-POWER
APU3048 Datasheet PDF : 17 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
APU3048
For Di1=25% of I1, we get L1=9.9mH
For Di2=25% of I2, we get: L2=5.7mH
The total conduction losses for channel 1 is:
PCON1 = 0.24W
Panasonic provides a range of inductors in different val- The total conduction losses for channel 2 is:
ues and low profile for large currents.
PCON2 = 0.24W
For L1 choose ETQP6F102HFA (10.2mH, 4A)
For L2 choose ELLATV6R8M (6.8mH, 4A)
Power MOSFET Selection
The selections criteria to meet power transfer require-
ments is based on maximum drain-source voltage (VDSS),
gate-source drive voltage (VGS), maximum output cur-
rent, On-resistance RDS(ON) and thermal management.
The MOSFET must have a maximum operating voltage
(VDSS) exceeding the maximum input voltage (VIN).
The gate drive requirement is almost the same for both
MOSFETs. Caution should be taken with devices at very
low VGS to prevent undesired turn-on of the complemen-
tary MOSFET, which results a shoot-through current.
The total power dissipation for MOSFETs includes con-
duction and switching losses. For the Buck converter
the average inductor current is equal to the DC load cur-
rent. The conduction loss is defined as:
PCOND(Upper Switch) = I2LOAD3RDS(ON)3D3q
PCOND(Lower Switch) = I2LOAD3RDS(ON)3(1 - D)3q
q = RDS(ON) Temperature Dependency
The total conduction loss is defined as:
The control MOSFET contributes to the majority of the
switching losses in synchronous Buck converter. The
synchronous MOSFET turns on under zero-voltage con-
dition, therefore the turn on losses for synchronous
MOSFET can be neglected. With a linear approxima-
tion, the total switching loss can be expressed as:
t t PSW
=
VDS(OFF)
2
3r + f
T
3 ILOAD
Where:
---(6)
VDS(OFF) = Drain to Source Voltage at off time
tr = Rise Time
tf = Fall Time
T = Switching Period
ILOAD = Load Current
VDS
90%
10%
VGS
td(ON)
tr td(OFF)
tf
Figure 4 - Switching time waveforms.
PCON(TOTAL)=PCON(Upper Switch)q +PCON(Lower Switch)q
The RDS(ON) temperature dependency should be consid-
ered for the worst case operation. This is typically given
in the MOSFET data sheet. Ensure that the conduction
losses and switching losses do not exceed the package
ratings or violate the overall thermal budget.
For this design, AP9408AGH is a good choice. These
devices provide low on-resistance in a compact
TO-252 3Pin package.
From AP9408AGH data sheet we obtain:
AP9408AGH
tr = 5ns
tf = 6ns
These values are taken under a certain condition test.
For more detail please refer to the AP9408AGH data sheet.
By using equation (6), we can calculate the switching
losses.
The MOSFETs have the following data:
AP9408AGH
VDSS = 30V
ID = 33A @ 1008C
RDS(ON) = 10mV @ VGS=10V
q = 1.5 for 1508C (Junction Temperature)
PSW1 = 52.8mW
PSW2 = 22mW
7
 

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