LX1710-1 Microsemi Corporation, LX1710-1 Datasheet - Page 11

• Manufacturer Part Number: LX1710-1
• Description: EVALUATION KIT
• Manufacturer: Microsemi Corporation

LXE1710 E
As seen in previous sections, the user can design the
output filter of the amplifier to meet performance or
costs targets. In addition, the amplifier’s power stage
(selection of MOSFETs) can be selected depending on
these tradeoffs. The efficiency of the amplifier circuit
can be approximated by the following equation.
The overall efficiency is a function of primarily the
MOSFETs and output filter inductors. The “Inductor”
section’s contribution will be considered later.
MOSFET Power loss is a function of the on-resistance
and gate charge.

   
The LX1710 Evaluation Board is designed using
FDS4953
MOSFETS.

 
Drain-Source On-Resistance


MOSFET
Drain Current (continuous)
Copyright
Rev. 1.1, 2000-12-01
MOSFET S
Drain-Source Voltage
Where
R
R
R
P
P
R
Total Gate Charge
P
NDS
PDS
IND
CROSS
L
OUT
IN
Manufacturer
MOSFET Component Options
Then
2000
=
=
=
=
=
p-channel
Power
I
ELECTION
2
If
[
DC Resistance of Speaker
n-channel MOSFET on-resistance
p-channel MOSFET on-resistance
DC Resistance of Inductor
MOSFET Switching Loss
VALUATION
( 2


R
I
Loss
NDS
P
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
O
and
P
R
R
P
PDS
25
DS
RDS(ON)@VGS = +/-10V
I
W
FDS6612A
2
25
ID(continuous) (A)
4
R
R
Q
at
I
B
L
IND
g
2
VDSS (V)
(typical) (nC)
[
4
OARD
( 2
)
2

5 .
R
R
NDS
A
L
]
Linfinity Microelectronics Division
n-channel
P
R
CROSS
PDS
Microsemi
The
FDS6612A FDS4953
)]
n-channel p-channel n-channel p-channel n-channel p-channel
Fairchild
0.022
8.4
30
9
MOSFET power loss is proportional to on-resistance.
      
MOSFET switching loss is proportional to total gate
charge, supply voltage, and switching frequency.
There are a few other important parameters to
consider when selecting the output power components
besides the on-resistance and gate charge of the
MOSFETs.
ample margin for circuit noise and high speed
switching transients. Since the amplifier configuration
requires output bridge operation at the supply voltage,
the MOSFETs should have a drain-source voltage of
at least 50% greater than the supply voltage.
power dissipation of the MOSFETs should also be
able to dissipate the heat generated by the internal
losses and be greater than the sum of P
Linfinity recommends that in selecting MOSFETs, R
several MOSFET options
Fairchild
0.053
P
-30
MOSFET
-5
CROSS
8
Where
Assume
R
P
NDS
DS
1 (
Siliconix
Vishay
(
The drain-source voltage must provide
0.053
. 2
. 0
4.9
30
Switching
8
Si4532ADY
10
C
V
f
n
C
V
f
g
) 5
03
S
S
<10nC.
2
9
[
= Input Capacitance
= Supply Voltage
= Switching Frequency
= Number of MOSFETS
= 1000pF
= 15VDC
= 500kHz
)(
( 2
,

15
Siliconix
. 0
Vishay
R
0.08
-3.9
-30
.
03
2
10
PDS
Loss
)(
500
The table below provides
. 0
. 0
International
095
P
095
Rectifier
10
U
CROSS
0.10
3.5
9.4
25
)]
3
SER
)(
IRF7105
) 4
. 1
DS
56
CV
G
and P
International
. 0
W
Rectifier
UIDE
Page 11
2
45
0.25
-2.3
-25
10
n f
S
W
CROSS
The
DS
.