Microsemi LX1710 Evaluation kit Datasheet

LXE1710 EVALUATION BOARD
USER GUIDE
A
Copyright  2000
Rev. 1.1, 2000-12-01
M I C R O S E M I
C O M P A N Y
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LXE1710 EVALUATION BOARD
USER GUIDE
INTRODUCING LX1710/1711 AUDIOMAX
Thank you for your interest in the latest generation of AudioMAX products. The enclosed LXE1710 evaluation
board is a fully functional mono amplifier designed to demonstrate the “new and improved” Switching Class-D
Power Amplifier IC from Linfinity Microsemi. The LX1710/1711 is a completely new controller design with
superior performance over the LX1720 stereo controller IC. Key improvements include better SNR, lower noise
floor, and reduced THD therefore resulting in a much “quieter” and “cleaner” sounding amplifier.
The evaluation board has been configured with easy-to-use terminal block connections for power supply/battery hook
up and speaker connections. An RCA jack or separate audio +/- pins allow a quick interface to your audio source.
Jumpers are also provided to enable/disable the amplifier (Sleep control) and to turn off the audio input (Mute
control). With minimal setup, the user can be listening to the amplifier in a matter of a few minutes.
Both the LX1710 and LX1711 operate from a single supply voltage.
The LXE1710 evaluation board can
!e
LX1711 can handle a higher supply voltage (7V to 25V) and provides greater than 50W continuous output power
! " " ! " change frequency response for other load optimization.
Thank you again for your interest in the new “quieter”, high efficiency Class-D Audio Amplifier from Linfinity
Microsemi. Please let us know what you think and stay tuned for future product releases to our AudioMAX family
of products.
Regards,
Linfinity Microsemi
http://www.linfinity.com
(714) 898-8121
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LXE1710 EVALUATION BOARD
USER GUIDE
TABLE OF CONTENTS
LX1710 / 1710 AudioMAX Evaluation Board Features and Circuit Description .............................4
Input Compensation
Output Stage
Filter Stage
Quick Start Guide ............................................................................................................................................5
Application Schematic ...................................................................................................................................6
Electrical Characteristics ..............................................................................................................................7
Performance Graphs ......................................................................................................................................8
Application Information
Filter Design Tradeoffs (1-Stage vs. 2-Stage).............................................................................................9
LC Filter Design...........................................................................................................................................9
MOSFET Selection....................................................................................................................................10
Inductor Selection......................................................................................................................................12
Capacitor Selection ...................................................................................................................................13
Gate Resistor ............................................................................................................................................14
Oscillator Configuration .............................................................................................................................14
Multi Channel Requirements and Frequency Synchronization..................................................................14
PCB Layout ...............................................................................................................................................15
Board Layout ..................................................................................................................................................16
Printed Circuit Board ...................................................................................................................................17
Bill of Materials ..............................................................................................................................................18
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LXE1710 EVALUATION BOARD
USER GUIDE
Part Number
Product
Description
LX1710CDB
AudioMAX High
Fidelity Controller IC
VDD = 7V to 15V, Switching Class-D Mono
Power Amplifier IC, 28-Pin SSOP Package.
LX1711CDB
AudioMAX High
Power Controller IC
VDD = 7V to 25V, Switching Class-D Mono
Power Amplifier IC, 28-Pin SSOP Package.
LXE1710
LX1710 AudioMAX
Evaluation Board
Fully Operational Mono Audio Amplifier.
LX1710/1711 AUDIOMAX EVALUATION BOARD FEATURES AND CIRCUIT DESCRIPTION
•
•
•
Fully Assembled Mono Evaluation Board with
LX1710 Class-D Controller IC
Improved SNR and Noise Floor Performance
Output Power of 25W typical (LX1710, 15VDD,
•
Output Power of 54W typical (LX1711, 25VDD,
•
•
•
•
Supports Full Audio Bandwidth
Terminal Block Connectors for
Voltage and Speaker Connection
RCA Plug for Audio Input Signal
Supply
The AudioMAX Evaluation Amplifier Board allows the
user to quickly connect and evaluate the LX1710
Switching Class-D Mono Controller IC. Easy-toconnect terminal blocks and an RCA plug are
provided for interfacing to Power, Speaker, and Audio
Input connections. The single stage output filter has
been configured to drive a 4 audio bandwidth amplification (See Application
section LC filter design for component selection,
calculations, and suggested inductor and capacitor
values for other loads). The LXE1710 Evaluation
Board operates from a single supply voltage.
The Class-D Amplifier Controller IC requires a
minimal number of external components to create a
complete amplifier solution. See LXE1710 Evaluation
Board Schematic and Bill of Materials for circuit
specifics.
A Class-D Amplifier is a “switching”
amplifier that converts a low-level, analog audio input
signal into a high power, pulse-width modulated
(PWM) output. The switching frequency (500kHz
typical but can be adjusted) is much higher than the
audio bandwidth (20Hz to 20kHz), and is easily
filtered out with a simple LC filter. The support
circuitry can be generally grouped into three areas
(input circuit, output power stage, and output filter).
INPUT COMPENSATION
The first group is the compensation network and
control setting components. These resistors and
Copyright  2000
Rev. 1.1, 2000-12-01
capacitors set up the controller operating frequency,
response characteristics, and comparator ramp
fundamental to Class-D operation.
OUTPUT STAGE
The next section is the output stage. The controller
IC generates a PWM output by controlling external
FETs connected in a full bridge configuration. The full
bridge configuration is connected between the single
supply voltage (PVDD) and ground (PGND) with the
output of the bridge driving the LC filter stage.
Because the FETs are either fully “on” or fully “off”,
Class-D topology is extremely efficient (up to 85%
typical), circuit power dissipation is minimal, and
maximum power is delivered to the speaker. The
bridge output also drives the RC low pass filter, which
provides the feedback for the control loop through the
FBK+ and FBK- inputs.
FILTER STAGE
The single stage, second order LC filter is used to
remove the switching frequency. The frequency
response and corner frequency can be easily
adjusted for optimization of various loads. The LC
evaluation board component values have been
chosen for a 4 ! " # $
for component selection.
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LXE1710 EVALUATION BOARD
USER GUIDE
QUICK START GUIDE
can be used to drive other speaker loads but
frequency response may not be optimal. See
LC filter design section for recommended
inductor and capacitor modifications.
The LXE1710 Evaluation Board is a fully functional,
Class-D Amplifier. Connection to a single supply
voltage (VDD from either a battery or power supply),
speakers, and your audio source is all that is required
to begin evaluating the amplifier and listening to music.
The following outlines the necessary connections and
control jumpers.
4) Audio Input Connection: Connect your audio
source to the RCA Jack CN1, Audio In. For
other type interfaces, the audio input signal can
also be connected to the amplifier board using
the J3 (In- and In+) location. Strip Line Plugs
can be inserted into J3 for connectivity.
1) Verify contents of Evaluation Kit: The easy-touse amplifier is all contained on a single board.
Visually inspect to see if the board or any
components were damaged during shipping.
All components are located on the top side of
the PCB except for the decoupling capacitor,
C17. A copy of the LX1710/1711 Datasheet
should also be enclosed or a PDF version can
be downloaded from the Microsemi.com
website
5) Jumper Selection Controls: The “on/off” or
enable to the module is controlled with the
SLEEP/ signal.
Jumper J1 connects the
SLEEP/ to “on” or “ off”. SLEEP/ is an active
Low control. Jumper J2 connects the MUTE
control which enables/disables the audio input
to the amplifier. MUTE is an active High signal.
See table below.
(http://www.microsemi.com/datasheets/MSC1580.PDF).
2) Power and Ground Connections: The voltage
supply and ground connections are made
through terminal block TB1. Connect your “+”
(+7V to +15V) power supply or battery to the
+V input of TB1. Connect your supply or
battery ground to the GND input of TB1.
Please ensure the correct positive and ground
connections are made before turning on the
power supply.
6) Power Source: If a power supply is being used,
make sure it is set to the correct voltage level
and turn the power supply on.
7) Audio Source: Make sure the audio source
signal is set to a minimum level. Start or “play”
audio source and adjust source volume to
desired level.
8) Listen to AudioMAX: If the amplifier is not
operating properly, verify preceding steps or
contact Linfinity for technical assistance (714)
898-8121.
3) Speaker Connection: The amplifier is designed
$ ! #" “+” and “-“ to the +OUT and –OUT input of
terminal block TB2 respectively. The amplifier
To Speaker +
To Speaker -
To Power Supply +V
J1 Jumper:
SLEEP/
J2 Jumper:
MUTE
Jumper
toward
OFF
Jumper
toward
ON
Amplifier
enabled
(SLEEP/ is
OFF)
Audio Input
enabled
(MUTE is
OFF)
Amplifier
disabled
(SLEEP/ is
ON)
Audio Input
disabled
(MUTE is ON)
7V-15V for LX1710
7V-25V for LX1711
Jumper
floating
Amplifier
disabled
(SLEEP/ is
ON)
Audio Input
enabled
(MUTE is
OFF)
To Power Supply
Ground
Jumper Settings
Copyright  2000
Rev. 1.1, 2000-12-01
Optional
Audio In Optional
Audio In +
To Audio
Source
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LXE1710 EVALUATION BOARD
USER GUIDE
SCHEMATIC
V IN 7V to 15V
C9
0.1µ F
35V
+
C 22
.1µ F
C 13
2.2µ F
25
C LO C K 28 N C
VDD
24 P V D D
+
+
C 11
4.7µ F
IS 26
5
R 5 34.8 K
C1
1µ F
C 16
100 pF
C 17
220 µ F
25V
6
1
4
C2
1µ F
2
27
C 12
.1µ F
P + 23
CP
R 12
10 o hm
RPW M
Q1
L1 1 5µ H
CPW M
VREF
N+
V 25
GND
LX1710
P-
R3
24.3 K
Q2
22
R 11
10 o hm
SLEEP
10
R S1
.034 7
C8
.1µ F
50V
C7
220 pF
20
R6
10 o hm
S LE E P
MU TE
C 20
.68µ F
C 18
.47µ F
C 21
.68µ F
Q3
R 13
15 o hm
1W
C 19
.47µ F
11 M U T E
AU DIO
IN PUT
NC
R 8 10K
9 IN A M P O U T
7
IN P U T+
N-
R 10
10 o hm
C3
470 nF
C 26
330 pF
8
R 9 10K
C 14
470 nF
3
PGND
IN P U T-
R 1 56.2 K
C4
150 pF
14
NC
13
15
EAOUT
E A IN
FA O U T
19
C 10
4.7µ F
CN
C5
18p F
Q4
21
FB K +
FB K S TA TU S
L2 1 5µ H
R4
24.3 K
C6
220 pF
+
18
16
17
12
NC
R 2 10K
– Evaluation Board Schematic
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
LXE1710 EVALUATION BOARD
USER GUIDE
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C<TA<70°C.
For test circuit, see LXE1710 Evaluation Board Schematic diagram.
PARAMETER
SYMBOL
Supply Voltage LX1710
VDD
Supply Current
IDD
Quiescent Current
IQ
Output Power
PO
Efficiency
Total Harmonic Distortion Plus
Noise
Signal-To-Noise Ratio
MIN.
TYP.
7
UNITS
15
V
3
A
VIN=15V, No Input
43
mA
14
W
25
W
VIN=15V, RL 10Hz to 22kHz
VIN=15V, RL 10Hz to 22kHz
VIN=15V, RL 10Hz to 22kHz
VIN=15V, fIN=1kHz, PO=10W
38
W
82
%
VIN=15V, fIN=1kHz, PO=20W
85
%
fIN=1kHz, PO=1W
0.05
fIN=20Hz to 20kHz, PO=1W
PSRR
MAX
VIN=15V, PO=38W, RL
THD+N=1%
SNR
Power Supply Rejection Ratio
Copyright  2000
Rev. 1.1, 2000-12-01
THD+N
TEST CONDITIONS
VIN=15V, VRIPPLE=1VRMS,
10Hz to 10kHz
%
0.3
%
81
dBV
-70
dB
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LXE1710 EVALUATION BOARD
USER GUIDE
PERFORMANCE GRAPHS
90%
60
85%
50
Output Power (W)
Efficency (%)
80%
75%
70%
65%
60%
55%
40
30
20
10
50%
0
45%
0
5
10
15
20
25
30
6
11
Output Power (W)
16
21
26
Supply Voltage (VIN)
fIN=1kHz
RL%
THD+N=1%
VIN = 15V
+20
100
50
+15
20
10
5
+5
2
-0.08
1
0.5
THD + N (%)
Voltage Amplification (dBr)
+10
-0.59
-5
0.26
0.1
0.04
-10
0.02
0.01
-15
0.005
-20
10
0.002
18.2
50
100 200
500
1k 2k
5k
10k 17.88k
50k
80k
0.001
50m
100m 200m 500m
1.13 2
5
10 20
24.56 30
Frequency (Hz)
Output Power (W )
VIN=15V
RL%
RO=1W RMS
Copyright  2000
Rev. 1.1, 2000-12-01
VIN=15V
fIN=1kHz
RL%
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LXE1710 EVALUATION BOARD
USER GUIDE
APPLICATION INFORMATION
! &' ( LX1710 Filter Implementation, 1-stage vs. 2- stage
100
50
20
10
5
2
1
Percent (%)
0.5
0.55626
2-Stage
0.2
0.12572
0.1
1-Stage
0.05
0.02
0.01
0.005
0.002
0.001
50m
100m
200m
500m
11.15
Watts(W)
2
•
Low Cost: The 1-stage LC filter uses one half
the number of inductors/capacitors resulting in
a substantial cost savings over a 2-stage
design. Key parameters such as THD+N,
frequency response, and nose performance
do not change significantly.
•
Power Loss: Since current will flow in two
inductors and not four, the inductor power loss
will be less in the single stage design. The
overall amplifier will have a wider dynamic
range and improved efficiency.
•
Filter Design: This easy-to-design filter can
limit audio signal changes within +/- 3dB
across the audio band with impedance
vari" ) *+ ,! a steeper rolloff with the 2-stage filter,
Copyright  2000
Rev. 1.1, 2000-12-01
2025.04 30
THD: There are minimal differences between
the 1-stage and 2-stage implementations with
other parameters such as THD+N as seen in
the above graph.
Single Stage Filter Disadvantages
•
Single Stage Filter Advantages
•
10
impedance changes could result in a +/- 6dB
change.
FILTER DESIGN TRADEOFFS (1-STAGE VS. 2-STAGE)
A 1-stage or 2-stage filter may be used depending on
your application and performance targets. The main
tradeoff in this selection is price (number of
components, component costs, PCB area) vs.
performance. The primary advantage of the single
stage filter is lower cost whereas the main benefit to a
2-stage filter is that it will provide steeper attenuation.
This allows the corner frequency to be selected further
outside of the audio band (to minimize the effects of
impedance variations in the passband) and still
provide adequate RF attenuation.
5
EMI and Switching Frequency: For the 1stage, the switching frequency must be higher
than 400kHz to ensure the corner frequency
will provide adequate amplifier performance in
the high end of the audio frequency range. If
fS < 400kHz, then fC < fS /10 = 40kHz which is
too close to the desired audio band. A higher
oscillation frequency could translate into
greater MOSFET switching losses, slightly
lower efficiency, and increased EMI effects.
With a 2-stage 4th order filter, the switching
frequency fS can be reduced to 120kHz. If fS =
120kHz, then fC = fS /3 = 40kHz. The lower
oscillation frequency could help minimize EMI
issues.
LC FILTER DESIGN
The output filter helps to reconstruct the amplified
audio signal and filter out the switching frequency.
The design of the filter depends on the type of
attenuation and frequency response desired at the
output. The output filter designed into the LXE1710
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evaluation board is a second order, LC type filter as
shown below. Tradeoffs between performance and
component cost must be considered when determining
the complexity or type of filter selected.
the required audio response and is used in the
calculation below.
Q
Q
0.707
=
=
= 0.56µ F
Rω R(2πfC ) 4(2π )(50000)
C = 0.68µF is used in the Evaluation Board
C=
OUT+
L
15µH
C
0.68µF
To Compute the Inductor Value:
L=
R
L
C
0.68µF
15µH
1
1
1
=
=
= 14.9µ H
2
2
ω C (2πfC ) C [(2π )(50000)]2 (.68µ )
L = 15µH is used in the Evaluation Board
OUT-
LXE1710 Evaluation Board
Frequency Response
Its Laplace Transform function is:
+15
+12.5
S
S
C
C
H(S) =
=
ω
1
1
2
2
S +
S+
S + S +ω2
RC
LC
Q
+10
Voltage Amplification (dBr)
+7.5
+5
+2.5
+0
-2.5
-5
-7.5
-10
-12.5
Where
ω=
-15
1
LC
20
50
10
20
50
1k
Frequency (Hz)
2k
5k
10
k
20
k
50 80
k k
Frequency response of the audio amplifier was
Q = RCω
The Class-D amplifier evaluation board design has a
pass-band of 20Hz to 20kHz to support the audio
frequency range and is configured to utilize a switching
or oscillator frequency fs = 500kHz. Depending on the
application, this oscillator frequency may be adjusted
(see section on Oscillator Configuration) to optimize
amplifier performance or modified for other
considerations such as EMI effects.
Further
requirements of the filter are that the pass band
attenuation of switching frequency fs should be lower
than 40dB and the corner frequency of the LC filter
should be set higher than 20kHz to avoid attenuating
audio signals in the desired audio band by more than
1dB. A speaker DC impedance o '- C =
50kHz corner frequency are defined for the evaluation
board.
The Q (selectivity factor or ratio of the center
frequency divided by the bandwidth) of the filter must
also be considered when designing a filter. Too high a
Q will result in a boost of the audio signal across the
audio band whereas a low Q will cause too much
attenuation of the signal. A Q value of 0.707 provides
Copyright  2000
Rev. 1.1, 2000-12-01
10
$ " )
,! - $- + - - "" ' . ! - ,
) " + )/ . –4dB
attenuation respectively.
Therefore, to improve
frequency response performance for other loads, the
value of Q must be increased/decreased by changing
the capacitor. Since a different value C will affect the
corner frequency, values for L and C must be
recalculated. Below are recommended inductor and
capacitor values for 2 , -
single stage LC filter design.
Capacitor C (µF)
Inductor L (µH)
1.0
0.68
0.47
10
15
22
Filter Component Values
Please note: These recommended values are guidelines
for speaker loads.
Actual speakers have varying
impedances, which may require revised filter calculations
and optimization. Furthermore, your application may have
different design goals than those chosen for the LX1710
evaluation board.
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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LXE1710 EVALUATION BOARD
USER GUIDE
RNDS = 0.03Ω, RPDS = 0.095Ω
MOSFET SELECTION
PDS = (2.5) 2 [2(0.03 + 0.095)] = 1.56W
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.
MOSFET power loss is proportional to on-resistance.
POUT
I 2 RL
=
= 2
PIN
I [2( RNDS + RPDS + RIND ) + RL ] + PCROSS
MOSFET SwitchingLoss = PCROSS = CV 2 fSn
Where
Where
RL
=
RNDS =
DC Resistance of Speaker
n-channel MOSFET on-resistance
RPDS
=
p-channel MOSFET on-resistance
RIND
=
DC Resistance of Inductor
PCROSS =
MOSFET Switching Loss
Assume
C
V
fS
n
=
=
=
=
C
V
fS
= 1000pF
= 15VDC
= 500kHz
Input Capacitance
Supply Voltage
Switching Frequency
Number of MOSFETS
PCROSS = (1× 10 −9 )(152 )(500 ×103 )(4) = 0.45W
The overall efficiency is a function of primarily the
MOSFETs and output filter inductors. The “Inductor”
section’s contribution will be considered later. The
MOSFET Power loss is a function of the on-resistance
and gate charge.
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. The drain-source voltage must provide
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. The
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 PDS and PCROSS.
Linfinity recommends that in selecting MOSFETs, RDS
0 1!1 2g <10nC. The table below provides
several MOSFET options.
MOSFET Power Loss = PDS = I 2 [2( RNDS + RPDS )]
PO = 25W at 4Ω
If
Then
P
25
=
= 2.5 A
R
4
I=
The LX1710 Evaluation Board is designed using
FDS4953 p-channel and FDS6612A n-channel
MOSFETS.
FDS6612A FDS4953
Si4532ADY
IRF7105
n-channel p-channel n-channel p-channel n-channel p-channel
Drain-Source On-Resistance
RDS(ON)@VGS = +/-10V
0.022
0.053
0.053
0.08
0.10
0.25
Drain-Source Voltage
VDSS (V)
30
-30
30
-30
25
-25
Drain Current (continuous)
ID(continuous) (A)
8.4
-5
4.9
-3.9
3.5
-2.3
Total Gate Charge
Qg (typical) (nC)
9
8
8
10
9.4
10
Fairchild
Vishay
Siliconix
Vishay
Siliconix
Manufacturer
Fairchild
MOSFET Component Options
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
International International
Rectifier
Rectifier
Page 11
LXE1710 EVALUATION BOARD
USER GUIDE
INDUCTOR SELECTION
The output filter inductors are key elements in the
performance of the Class-D audio power amplifier.
Inductor Power Loss = PIND = ( I 2 )(2)( RIND )
Inductor selection criteria also involves tradeoffs
between performance (efficiency) and component
costs. The critical specifications for the inductor are
the DC resistance, DC current, and peak current
ratings. The inductors should be able to handle the
amplifier’s power as well as operate within its linear
region.
Saturating the inductors could decrease
performance (increase THD) and even produce a
short, which may damage either the circuit or the
speaker.
The LX1710 Evaluation board utilizes two 15µH radial
leaded R.F. inductors from Inductor Supply, Inc. (ISI).
When evaluating component options, inductors such
as from Coilcraft can be used for other performance /
price tradeoffs. See inductor table below.
Other variables when selecting an inductor depend on
the switching frequency of the designed amplifier. A
higher switching frequency implies that the corner
frequency of the LC filter is higher. With a higher fC,
the inductor value is smaller.
The amplifier’s application and design constraints will
help determine whether the inductors are selected for
size, power, or performance. Various inductors such
as those that are shielded may also have different EMI
effects and distortion performance.
The overall efficiency () of the amplifier circuit is given
in the previous MOSFET section. The inductor’s
power loss contribution is a function of the inductor’s
DC resistance, RIND.
Manufacturer
Part Number
PIND = (2.52 )(2)(.056) = 0.7W
The efficiency approximation can now be completed.
=
POUT
I 2 RL
= 2
PIN
I [2( RNDS + RPDS + RIND) + RL] + PCROSS
=
I 2 RL
PDS + PIND + PCROSS + I 2 RL
=
25
1.56 + .7 + .45 + 25
= 90.2%
The efficiency is a function of the power and switching
loss in the MOSFETs and inductors.
Q min
Test
Frequency
DC Resistance
DC Current
max (ARMS)
Self Resonant
Frequency min
(MHz)
50
2.520MHz
56
2.50
12.0
100kHz
32
4.4
20
Inductance
ISI
RL622-150K
15.0
Coilcraft
DO5022P-153HC
15.0
Inductor Component Options
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 12
LXE1710 EVALUATION BOARD
USER GUIDE
CAPACITOR SELECTION
The LC filter design section discusses filter options
and the calculation of component values. However,
the specification of capacitor type depends on the
application in the circuit.
The table provides
descriptions and guidelines for capacitors in the
AudioMAX amplifier board.
Reference
Designator
Capacitor
Comments
These ! "#! $! $ "! % #! &'!
C10, C11
FET gate drive
C3 C14
Audio input path
C18, C19,
C20, C21
Output filter
C8, C12
FET bypass
C22
LX1710 bypass
C9, C13
VDD,
PVDD bypass
These tantalum capacitors provide the bypass for the IC supply voltage and output driver
supply voltage utilizing a minimal footprint area.
C17
Output power stage
The electrolytic filter capacitor smoothes out ripple current and should be placed close to the
output FETs.
C16
Oscillator frequency
The timing capacitor (5% tolerance) sets the oscillator frequency.
C6, C7
Feedback filter
These (5%) capacitors are used in the RC filter to provide feedback for the control loop.
C4, C5
Error amplifier
These (5%) capacitors create the compensation network.
“temperature grade” is used to ensure stability.
C1, C2
Voltage references
C26
Audio input filter
These decoupling capacitors are used for the audio input +/- signals.
The output filter metal film capacitors (low ESR, 5% tolerance) work well to set an accurate
corner frequency at a low cost.
These metal film capacitors are used for the power supply bypass for the FETs. Place
adjacent to the FETs or consider lower value ESR solutions depending on the PCB
component placement.
The metal film capacitor is a high frequency bypass for the LX1710 IC.
Make sure the appropriate
The filter capacitors provide the bypass for the 5V and 2.5V references.
The RC filter minimizes high frequency noise to the amplifier.
Capacitor Description
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 13
LXE1710 EVALUATION BOARD
USER GUIDE
Gate Resistor Impact On THD+N
100
50
20
10
T HD+ N (% )
2
1
0.26978
0.1
No Gate Resistor
0.04675
W ith 10Ω Gate Resistor
0.01
0.005
0.001
50m
100m
200m
500m
11.131
2
5
10
20 24.56 30
O utput P ower (W )
VIN = 15V
fIN = 1kHz
GATE RESISTOR
Series resistors (R6, R10, R11, R12) can be added to
the gate of MOSFETs (Q1 to Q4) to control the
switching transition times.
This reduces signal
distortion as seen in the THD+N vs. Output Power
graph below.
The slower switching speeds will
however, increase power dissipation and therefore
slightly decrease the overall efficiency of the amplifier.
RL and valley voltages, and the charge and discharge
currents are proportional to the supply voltage. This
keeps the frequency relatively constant while keeping
the slope of the PWM ramp proportional to the voltage
on the VDD pin. For operating frequencies other than
333kHz, the frequency can be approximated by the
following equation:
Frequency =
VIN
1
(0.577)( RPWM )(CPWM ) + 320ns
R12
P+
10
Ω
Q1
OUT+
R11
N+
10
Ω
Q2
MULTI CHANNEL REQUIREMENTS AND FREQUENCY
SYNCHRONIZATION
- 3451 . 1 $
resistors, which improves (decreases) the THD+N
from 0.1% to 0.05% with a slight impact on efficiency
of approximately 2%. The recommended gate resistor
1 6!
OSCILLATOR CONFIGURATION
The oscillator is programmed by the external timing
components RPWM and CPWM. For a nominal
frequency of 333kHz, RPWM and CPWM should be
set to 49.9kOhms and 100pF respectively. Note that
in order to keep the slope of the PWM ramp voltage
proportional to the supply voltage, both the ramp peak
Copyright  2000
Rev. 1.1, 2000-12-01
For applications that require more than a single
channel, the oscillators of multiple LX1710/1711
controllers can be configured for synchronous
operation. One unit, the master, is programmed for
the desired frequency with the RPWM and CPWM as
usual. Additional units will be slave units, and their
oscillators will be disabled by leaving the RPWM pin
disconnected. The CLOCK pin and the CPWM pin of
the slave units should be tied to the CLOCK pin and
the CPWM pin of the master unit respectively. In this
configuration, the CLOCK pins of the slave units begin
receiving instead of transmitting clock pulses. Also,
the CPWM pins quit driving the PWM capacitor in the
slave units. Note that for optimum performance, all
slave units should be located within a few inches of the
master unit.
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 14
LXE1710 EVALUATION BOARD
USER GUIDE
PCB LAYOUT RECOMMENDATIONS
Like most analog circuits, component placement,
signal routing, and power/ground isolation can affect
the overall performance of the design. The layout
should utilize individual ground traces/planes for the
audio amplifier whenever possible. The audio input
and controller ground, FET ground, and output filter
ground are routed using a “star” connection in the
LXE1710 evaluation board. See PCB layer views.
The power to the controller IC should be routed using
separate traces that do not carry high current pulses
Copyright  2000
Rev. 1.1, 2000-12-01
from the switching circuit. In general, minimizing the
high frequency, high power currents from flowing
through the same copper as the audio signal
references are recommended. Signal traces that
could be sensitive to noise should be node to node
connections (no “shared” traces). Stray capacitance at
the controller pins RPWM, EAOUT, EAIN, and FAOUT
can affect the circuit performance and components
associated with these pins should be placed as close
to the controller IC as possible.
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 15
LXE1710 EVALUATION BOARD
USER GUIDE
PRINTED CIRCUIT BOARD LAYOUT
CN1: RCA Jack
Audio In
J3: Optional Connections
Audio In +, Audio In -
Silkscreen Layer
J1: Sleep Jumper
Copyright  2000
Rev. 1.1, 2000-12-01
J2: Mute Jumper
TB1: Power Supply Terminal Block
+V, GND
TB2: Audio Output Terminal Block
+ OUT, - OUT
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 16
LXE1710 EVALUATION BOARD
USER GUIDE
PRINTED CIRCUIT BOARD
Bottom Layer
Top Layer
Copyright  2000
Rev. 1.1, 2000-12-01
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 17
LXE1710 EVALUATION BOARD
USER GUIDE
BILL OF MATERIALS
Line
Item
1
2
3
4
5
6
7
8
9
Part Description
Controller
N-Channel MOSFET
P-Channel MOSFET
Printed Circuit Board
Inductor, 15uH
Phono Jacks, 90° Nickel Plated, Wht
Strip Line Plugs, Straight, Single Row .100"
Shorting Jumpers, Open Top, Black
Terminal Block 2 pos 5mm
Manufacturer & Part #
LX1710
FDS6612A
FDS4953
SGE2758
RL622-150K
161-4214
CA-S36-24B-44
151-8030
301-021-1000
Line
Item
Part Description
1
Capacitor, COG, 18pF, 50V, 5%
2
Capacitor, COG, 150pF, 50V, 5%
3
4
Capacitor, COG, 220pF, 50V, 5%
Capacitor, X7R, 330pF, 50V, 10%
5
Capacitor, X7R, .47uF, 16V, 20%
6
Capacitor, X7R, 1uF, 50V, 10%
7
Capacitor, COG, 100pF, 50V, 5%
8
9
Capacitor Tant 0.1uF 35V 20%
Capacitor Tant 2.2uF 25V 20%
10
Capacitor, Tant, 4.7uF, 16V, 20%
11
12
13
14
Capacitor Stacked MF 0.1uF 50V 5%
Capacitor Stacked MF 0.47uF 50V 5%
Capacitor Stacked MF 0.68uF 50V 5%
Capacitor, Elect 220uF, 25V, 20%
Reference
Designators
Qty
U1
Q2, Q4
Q1, Q3
REV.X
L1, L2
CN1
J1, J2
J1
TB1, TB2
1
2
2
1
2
1
2
1
2
Case
Reference
Designators
Qty
1206
C5
1
1206
C4
1
1206
1206
C6, C7
C26
2
1
1206
C3, C14
2
1206
C1, C2
2
0805
C16
1
3216
3216
C9
C13
1
1
3216
C10, C11
2
TH
TH
TH
NT
C8, C12, C22
C18, C19
C20, C21
C17
3
2
2
1
Case
Reference
Designators
Qty
1206
1206
0805
0805
0805
0805
0805
R2
R3, R4
R6, R10, R11, R12
R8, R9
R5
R7
R1
1
2
4
2
1
1
1
2512
R13
1
2512
RS1
1
Case
SSOP 28
SO-8
SO-8
TH
TH
TH
TH
TH
Part Description
1206N180J500NT
12065C180JAT2A
1206N151J500NT
12065C151JAT2A
12065C221JAT2A
ECU-V1H331KBM
1206B474M160NT
1206YC474MAT2A
1206B105K500NT
12065C105KAT2A
0805N101J500NT
08055C101JAT2A
TAJA104M035R
! T491A225M025AS
! T491A475M016AS
TAJA475M016R
ECQ-V1H104JL
ECQ-V1H474JL
ECQ-V1H684JL
" RV-25V221MH10-R
Line
Item
Part Description
1
2
3
4
5
6
7
Resistor, 10K, 5%, 1/4W
Resistor, 24.3K, 1%, 1/4W
Resistor, 10 Ohm, 5%, 1/8W
Resistor, 10K, 5%, 1/8W
Resistor, 34.8K, 1%, 1/8W
Resistor,20K, 5%, 1/8W
Resistor, 56.2K, 1%, 1/8W
8
Resistor, 15 Ohm 5% 1W
9
Resistor, Low Value Flat .0374
Copyright  2000
Rev. 1.1, 2000-12-01
Part Description
# CR32J103T
# CR32F2432T
# CR J100T
# CR21J103T
# CR21F3482T
# CR J203T
# CR21F5622T
$ RM73B3A150J
% ! MCR100JZHJ150
% LR2010-01-R0374-F
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 18