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LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
KEY FEATURES
DESCRIPTION
ƒ Filter Free Operation
ƒ 12W +12W Output Power @
4Ω load: THD+N < 1%
ƒ High Efficiency > 85%
ƒ Full Audio Bandwidth: 20Hz to
20kHz
ƒ Low Distortion < 0.4% @ 30%
Max Power, 1kHz
ƒ High Signal-to-Noise Ratio:
90dB
ƒ Wide Supply Voltage Range
5.0V ~ 15V
ƒ 5mA Per Channel Typical
Quiescent Current
ƒ Turn ON/OFF POP Free
ƒ Standby / Mute Feature
ƒ Built-in Under Voltage Lockout
ƒ Thermal Protection
The part features on–board H-bridge
output stages with low RDSON. External
bootstrap capacitors are all that is
required to provide the gate drive to the
all-NFET output stage since on-board
bootstrap diodes are provided.
The LX1708 also features Mute and
Standby modes, POP-free turn-on and
turn-off, under-voltage lockout for both
input supplies, and multi-level overtemperature protection.
The LX1708 is offered in a small
thermally efficient footprint, low profile
surface mountable 32-pin Micro Lead
Quad Package (MLPQ) in 7mm x 7mm.
WWW . Microsemi .C OM
The LX1708 is a fully integrated
stereo class-D CMOS audio amplifier.
optimized
for
highly
efficient
operation and minimum system cost.
The stereo BTL (Bridge-tied-load)
configuration uses 3-level PWM
modulation. This allows eliminating
the LC filter to reduce the system cost
and simplify the system design. The
LX1708 outputs 15W into each of two
channels with better than 85%
efficiency. The entire signal path
from input to output is differential to
reject any sources of common-mode
noise or distortion.
APPLICATIONS
ƒ
ƒ
ƒ
ƒ
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
LCD TV
Car Navigation
MP3 Docking Stations
Portable Sound System
PRODUCT HIGHLIGHT
STBY
5V
TMON
ROSC
V5V
STBY
N.C.
STATUS
AVSS1
PVSS1N
OUT1N
OUT2N
BOOT2N
BOOT1N
PVDD1
PVDD
PVDD1
LX1708
BOOT1P
PVDD2
PVDD2
PVDD
BOOT2P
OUT1P
MUTE
N.C.
TCTRL
IN1P
OUT2P
VREF
PVSS1P
IN1N
AVSS2
PVSS2N
PVSS2P
IN2P IN2N
IN2P
IN1P
MUTE
LX1708
IN2N
IN1N
PACKAGE ORDER INFO
TA (°C)
LQ
Plastic MLPQ
32-Pin7mm x 7mm
RoHS Compliant / Pb-free
-40 to 85
LX1708ILQ
Note: Available in Tape & Reel. Append the letters “TR” to the
part number. (i.e. LX1708ILQ-TR)
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX1708
TM
®
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
PVDD1
PVDD1
BOOT1N
OUT1N
PVSS1N
31
30
29
28
27
26
25
1
24
TCTRL
IN1P
2
23
TMON
IN1N
3
22
AVSS2
N.C.
4
21
ROSC
N.C.
5
20
VREF
IN2N
6
19
AVSS1
IN2P
7
18
V5V
MUTE
8
17
STATUS
MSC
LX1708
XXXX
13
14
15
16
BOOT2N
OUT2N
PVSS2N
OUT2P
12
PVDD2
PVSS2P
11
PVDD2
10
BOOT2P
9
WWW . Microsemi .C OM
BOOT1P
32
STBY
XXXX =
date code /
lot code
THERMAL DATA
OUT1P
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
AVSS, except as noted. Currents are positive into, negative out of specified terminal.
PVSS1P
Power Supply Voltage (PVDD) ................................................................... -0.3V to 16.5V
BOOTP/N - PVDD ......................................................................................... -0.3 to 16.5V
Bias Supply Voltage (V5V) ................................................................................. -0.3 to 6V
Input Pins (IN1P/N, IN2P/N ,TCTRL, STBY, MUTE) ......................-0.3V to V5V + 0.3V
Output Pins (VREF, STATUS, ROSC, TMON) .................................-0.3V to V5V + 0.3V
Maximum Operating Junction Temperature .............................................................. 150°C
Storage Temperature Range.........................................................................-65°C to 150°C
Package Peak Temp. for Solder Reflow (40 seconds maximum exposure) ... 260°C (+0 -5)
LQ PACKAGE
(Top View)
LQ
Plastic MLPQ 32-Pin 7mm x 7mm
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
Pb-free 100% Matte Tin Pin Finish
15.5°C/W
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
PACKAGE DATA
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
FUNCTIONAL PIN DESCRIPTION
Function
Pin
Number(s)
Description
PVSS1P
PVSS1N
PVSS2P
PVSS2N
Power
Ground
32
25
16
9
PVDD1
PVDD2
Power
Supply
28,29
12,13
V5V
Power
Supply
18
Analog Power Supply for the analog signal processing section.
AVSS1
AVSS2
Analog
Ground
19
22
Analog Ground for the analog signal processing section. Must be at the same potential
as PVSS, connect at one point to the power ground plane.
IN1N
IN1P
IN2N
IN2P
Analog
Input
3
2
6
7
Differential analog audio inputs for each channel. The common mode voltage will be
set by the LX1708 to around 2.25V.
OUT1N
OUT1P
OUT2N
OUT2P
Digital
Output
26
31
15
10
Differential high power audio outputs for each channel. Each output will swing
between PVDD and PVSS. These outputs are driven by an on-chip H-bridge output
driver which uses low RDSON NFETs.
BOOT1N
BOOT1P
BOOT2N
BOOT2P
Bootstrap
27
30
14
11
Bootstrap voltage pins which provide the high voltage needed to drive the upper NFET.
A bootstrap capacitor should be placed between the respective output and these pins.
VREF
Analog
Output
20
MUTE
CMOS
Input
8
Logic level control which mutes the audio signal when high.
STBY
CMOS
Input
1
Logic level control which places the chip into sleep mode when high.
STATUS
CMOS
Output
17
Digital monitoring pin which is used to flag internal fault states. This pin will be
synchronized with the internal clock to prevent glitches. See the STATUS flag list
(below) for a summary of which conditions will force this pin to go high.
ROSC
Analog
Input
21
Frequency control pin. A resistor between this pin and AVSS will set the oscillation
frequency for the Class-D modulator.
Power Ground for the two H-bridge output drivers, connect to power ground plane
Power Supply for the two H-bridge output drivers. Current draw will be up to 1.6A at 2
x 8W into 8Ω. These are peak currents when the part is run at maximum rated power
on both channels.
Typical 2.25V reference voltage which serves as an internal reference. An external
compensation capacitor of at least 1uF should be connected between this pin and
AVSS.
Test Pin
24
Test purpose only, Connect to AVSS1
TMON
Test Pin
23
Test purpose only, left open.
N.C.
No
connect
4,5
No Connect, pin is open
PACKAGE DATA
TCTRL
The STATUS pin will go high under any of the following conditions:
ƒ
STBY is high. This indicates that the chip is in “stand-by” mode.
ƒ
V5V is below the V5V UVLO threshold.
ƒ
PVDD is below the PVDD UVLO threshold.
ƒ
The die temperature is above about 140°C. This indicates that the part has gone in to gain foldback.
ƒ
A short circuit across the speaker has caused the output devices to shut off due to excessive temperature.
Copyright © 2007
Rev. 1.3, 2007-04-05
WWW . Microsemi .C OM
Name
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
Parameter
`
Symbol
FOSC
Temperature Stability
Supply Voltage
PVDD
UVLO
PVDD
UVLO Hysteresis
PVDD
+5V Supply
V5V
UVLO
V5V
UVLO Hysteresis
V5V
250
300
350
2
kHz
%
5
Start-up Voltage, Rising
12
15
4.5
4.9
500
4.5
Start-up Voltage , Rising
mV
5.5
4.25
V
4.50
250
V
mV
IQQ
For PVDD, STBY high
10
50
µA
Operating Current
IQQ
For PVDD, STBY low, Mute high
10
30
mA
Stand-By Current
IQQ5V5
For 5V5, STBY high
10
Operating Current
IQQ5V5
For 5V5, STBY low, Mute high
7
1
PSRR
For PVDD @ 1kHz
VREF
C bypass = 1µF
55
µA
15
mA
dB
2.25
V
GAIN
Stage Gain
G
Mute Gain
GMUTE
OFFSET
`
INPUT STAGE
Output DC Offset
VOFFSET
f = 1kHz; VMUTE = 0V
26
VMUTE = 5V
-40
Measured Differentially. Channel + to Channel -
40
mV
dB
Input Resistance
RIN
22
kΩ
Common Mode Voltage
VCM
2.25
V
220
mΩ
OUTPUT STAGE
MOSFET On Resistance
RDSON
IDS = 200mA
THERMAL
Thermal Recovery Temperature
TSD
150
TFB
140
TREC
110
ELECTRICALS
Thermal Shut Down Junction
Temperature
Thermal Gain Fold-back
Temperature
`
Varies with ROSC resistor value, value shown is
for default conditions.
Stand-By Current
`
`
Max
POWER SUPPLY
Reference Voltage
`
Typ
TA = -40°C to 85°C
Power Supply Rejection Ratio
`
Units
Min
OSCILLATOR
Oscillator Frequency
`
LX1708
Test Conditions
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ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C < TA < 85°C except where
otherwise noted and the following test conditions: PVDD = 12V, PVSS = AVSS = 0V, V5V = 5V, RROSC = 24.9kΩ
°C
MUTE / STBY
MUTE Threshold
MUTETH
STBY Threshold
STBYTH
Mute Mode
V5V 2
V
V5V 2
STBY To Output Enable
5
ms
Note 1: Not ATE Tested.
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
Parameter
`
Symbol
Test Conditions
Min
LX1708
Typ
Max
Units
AUDIO CHARACTERISTICS
Output Power Stereo
PO
Total Harmonic Distortion Stereo
THD+N
Power Efficiency
Channel Crosstalk
VXTALK
Audio Bandwidth
Stage Gain Stereo
Signal to Noise Ratio
Output Noise Floor
BW
THD+N < 1%
12
THD+N <10%
15
POUT = 50% of Maximum Power, FIN = 1kHz
with diodes
POUT = 50% of Maximum Power, FIN = 1kHz
No diodes
W
0.4
%
0.4
POUT = 1W, FIN = 20Hz~20kHz
0.6
POUT = Max, THD+N < 1%
85
POUT = 1W, FIN = 1kHz
-60
POUT = 1W, FIN = 20-20kHz
WWW . Microsemi .C OM
TYPICAL SYSTEM APPLICATION CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C < TA < 85°C except where
otherwise noted and the following conditions: PVDD = 12V, PVSS = AVSS = 0V, V5V = 5V, ROSC = 25kΩ, RL = 4Ω.
%
3
dB
High
VIN = 200mVRMS, F = 20Hz~20kHz
26
Low
VIN = 2VRMS, FIN = 20Hz~20khz
-40
SNR
FIN = 1kHz @ 20Hz-20kHz non A-weighted
90
dB
VN
Input short, non A-weighted @ 20Hz-20kHz
200
µVRMS
ELECTRICALS
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
SIMPLIFIED BLOCK DIAGRAM
PVSS1P
MUTE
VREF
BOOT1P
+
IN1P
+
PWM
-
IN1N
-
NFET
H-BRIDGE
OUT1P
BOOT1N
WWW . Microsemi .C OM
PVDD1
OUT1N
VREF
PVSS1N
MUTE
MUTE
PVDD
ROSC
OSC
V5V
VREF
CONTROL BLOCK
-UVLO
-De-Pop
Mute
-Thermal
STBY
MUTE
TCTRL
STATUS
TMON
AVSS2
AVSS1
PVDD2
PVSS2P
MUTE
VREF
BOOT2P
+
IN2P
+
PWM
-
IN2N
-
NFET
H-BRIDGE
OUT2P
BOOT2N
OUT2N
PVSS2N
MUTE
Figure 1 – Simplified Block Diagram
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
BLOCK DIAGRAM
VREF
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
TEST SYSTEM SET-UP
WWW . Microsemi .C OM
8 TO 4 OHM SPEAKER LOAD
OR SPEAKER SIMULATOR
+5V
+/- 0.5V
POWER
SUPPLY
TB2
LOW PASS FILTER
AVSS
+
TB4
V5V
OUT1P
OUT1N
J1
LOW PASS FILTER
IN1P
CHA
AUDIO
ANALYZER
OUTPUT CHB
TB1
PVDD
IN1N
LX1708
J2
PVSS
LOW PASS FILTER
CHA
+5V
TO
+15V
POWER
SUPPLY
AUDIO
ANALYZER
INPUT
CHB
TB3
IN2P
OUT2N
IN2N
OUT2P
LOW PASS FILTER
LX1708 EVALUATION BOARD
8 TO 4 OHM SPEAKER LOAD
OR SPEAKER SIMULATOR
Figure 2 – System Test Set-up Diagram
Note: Speaker Load is simulated with 8Ω resistor in series with 66µH inductor for 8Ω speaker
and 4Ω resistor in series with 33µH inductor for 4Ω speaker
APPLICATIONS
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
APPLICATION CIRCUITS
+VIN
VIN
CR1
1N5817
C1
47µF 25V
RTN
R9 470
C23
4.7nF
TB1
WWW . Microsemi .C OM
TEST PURPOSE
R8 470
TP4
RT-P
C24
2.2nF
CR2
1N5817
OUTR+
+5V
OUTR-
+5V
TP2
1P
C2
22µF 6.3V
RTN
TP3
1N
TEST PURPOSE
TB1
VIN
VIN
TP1
GND
R6 470
C4 0.47µF
INRJP1
HEADER 1
C5 0.47µF
INL-
C6 0.47µF
INL+
MUTE
JP2
HEADER 2
J2
+5V
M
L
RCA Jack
U1
Part
LX1708
STATUS
R1 24.9K
C11 1µF
C12 1µF
TP6 STATUS
+5V
N
+5V
Header
3x2
C14
1µF
TP7
GND
C15
1µF
C13 1µF
C16 1µF
VIN
R10
124K
C22
2.2nF
OUT1N
PVSS1N
TCTRL
TMON
AVSS2
ROSC
VREF
AVSS1
V5V
PVSS2N
STBY
IN1P
IN1N
N/C
N/C
IN2N
IN2P
C3 0.47µF
INR+
OUT2N
RCA Jack
PVSS2P
OUT2P
BOOT2P
PVDD2
PVDD2
BOOT2N
SW1
SLEEP
C21
4.7nF
C9
1µF
PVSS1P
OUT1P
BOOT1P
PVDD1
PVDD1
BOOT1N
C8
1µF
+5V
TP5
RT-N
C10 1µF
C7 1µF
J1
R7 470
TP8
2P
TEST PURPOSE
TP10
LEFT-N
VIN
TP9
2N
R2 470
C17
4.7nF
R3 470
C18
2.2nF
R11
75K
CR8
1N5817
OUTLOUTL+
TEST PURPOSE
R4 470
C19
4.7nF
APPLICATIONS
CR7
1N5817
TP1
LEFT-P
R5 470
C20
2.2nF
Note 1: CR1, CR2, CR7, CR8 can be used for lower distortion performance.
Figure 3 – Typical Application
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
FUNCTIONAL DESCRIPTION
The LX1708 drives each output between PVDD and
PVSS using an all-NFET, bootstrapped, H-bridge driver for
each channel. High efficiency is obtained by forcing all
transistors to operate either completely on or completely off
as required for a true class-D amplifier. The entire signal
path from input to output is differential to reject any sources
of common-mode noise or distortion. Even the triangle
wave operates differentially. Filterless class-D modulation
operates such that with no input signal, the outputs switch
at the programmed clock frequency and are in-phase with
each other. Because the two signals are identical, the
differential signal to the speaker is zero. As a direct result,
there is no requirement for a low-pass LC filter to present
high impedance at the modulation frequency. This allows a
cheaper and simpler audio amplifier to be designed. As the
input signal goes positive, the duty cycle to the positive
output increases while the duty cycle of the negative output
decreases. This produces a net positive current flow into
the load. A negative signal reduces the positive output duty
cycles and increases the negative output duty cycle. The
differential signal actually appears at twice the modulation
frequency and alternates between +PVDD, 0, and –PVDD
which allows the parasitic inductance of the load to
effectively filter the switching signal so that only the audio
band portion remains.
Because each speaker is driven by an in-phase signal, the
common mode voltage to the speaker switches at the full
PVDD amplitude at the clock frequency. This is a possible
source of EMI radiation. Typically, a ferrite bead is placed
with a small common-mode filter capacitor to reduce EMI
generation by filtering the edges of the output signals.
NOISE-FREE TURN-ON AND OFF
Copyright © 2007
Rev. 1.3, 2007-04-05
AC-COUPLING AND BOOTSTRAP CAPACITORS
Input AC-coupling capacitors should be used to block
any input DC and low frequency components below the
desired low frequency corner. Since the input resistance to
the LX1708 is 25kΩ, a 20Hz low frequency corner can be
achieved with a 0.33µF AC-coupling capacitor. 1µF
bootstrap capacitors are required at each output to supply
the gate drive voltage for the upper level NFET in each
half-bridge.
THERMAL OVERLOAD PROTECTION
The LX1708 protects itself by monitoring its operating
temperature in two different ways. A general thermal
protection scheme monitors the overall die temperature.
Above 140°C, the amplifier gain is reduced by 6dB so that
the audio signal is still amplified, but the on-chip power
dissipation is halved. When the die temperature goes
below 110°C, the amplifier gain is restored. Above 150°C,
the LX1708 forces all outputs to PVSS so that no power is
dissipated until the chip cools down to 110°C.
A dynamic thermal protection scheme operates by
placing temperature sensors near each of the output
devices. When a differential temperature rise of about
60°C occurs above the core die temperature, the outputs
are disabled to protect the part. This provides short circuit
protection for differential shorts across the output. Shorts
to PVDD and ground (PVSS) are not protected.
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
APPLICATIONS
Noise-free turn-on and off is accomplished by carefully
sequencing the signal path when the amplifier is enabled or
disabled. Prior to turn-on, the outputs are initially both at
PVSS so there is no differential signal. The internal error
amplifier is held in a reset condition so that the internal
loop compensation components are “ready to go”. When
the outputs begin to toggle, the audio signal path is muted
for about 1.6ms. Following that time, the internal mute
signal is de-asserted and the audio input signal is allowed
to drive the pulse-width–modulator which then adjusts the
output duty cycle as necessary to drive the speaker. At
turn-off, the internal mute signal is asserted to silence the
input audio signal. The outputs continue switching in this
muted condition for about 0.6ms prior to being pulled low.
Once the outputs are forced low, the error amplifier is reset
so that the part is ready to begin a new power-up sequence.
This scheme basically limits the pop noise at turn-on or off
to be no larger than the differential offset voltage of the
error amplifier.
WWW . Microsemi .C OM
FILTERLESS CLASS-D MODULATION
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
APPLICATION NOTE/PCB DESIGN GUIDELINE
The value of ROSC selects the switching frequency;
smaller values increase the switching frequency. See
Figure 4, Typical Switching Frequency vs. ROSC. The
recommended range of ROSC is between 17.5KΩ and
42.5KΩ
Sw itching Frequency vs ROSC
SW FREQ (kHz)
450
400
350
300
250
200
150
17.5
22.5
27.5
32.5
37.5
42.5
ROSC (kOhm s)
Figure 4 – Typical Switching Frequency vs. ROSC
BOOTSTRAP CAPACITORS
C8, C9, C14, and C15 are bootstrap capacitors for
internal NMOSFETs gate drive voltage, they work together
with internal diodes to provide sufficient gate drive voltage
for upper MOSFETS. Those capacitors should be placed as
close to the IC as possible.
BYPASSING CAPACITORS
C7, C10, C11, C12, C13, and C16 are bypassing
capacitors for input supplies and internal reference voltage
(VREF), nominal value is 1µF. These capacitors should be
placed as close to the IC as possible, to guarantee low ripple
and noise.
PCB DESIGN GUIDELINES
Component placement for the LX1708 should be done
such that low-level inputs to the LX1708 are routed away
from the high frequency switching outputs. Special care
should be given to the bypass and bootstrap capacitors.
Capacitors (C7, C10, C13, C16, C8, C9, C14, and C15 in
the application schematic), should be placed as close to the
IC as possible. If workable, they should be mounted on the
same layer as the IC, with a direct connection to the IC on
that layer. It is best not to use vias to establish the critical
connection of these components to the LX1708. Bypass
capacitors for V5V input, as well as VREF (C11 and C12
in the application schematic), should be mounted close to
the IC as well.
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OSCILLATOR
One of the key efforts in implementing the MLP
package on a pc board is the design of the land pattern.
The MLP has a rectangular exposed thermal pad on the
bottom surface of the package body. Electrical and
mechanical connection between the component and the pc
board is made by screen printing solder paste on the pc
board and then reflowing the paste after placement. To
guarantee reliable solder joints it is essential to properly
design the land pattern to the MLP terminal pattern,
exposed thermal pad, and thermal pad vias. There are two
basic designs for PCB land pads for the MLP: Copper
Defined style (also known as Non Solder Mask Defined
(NSMD)) and the Solder Mask Defined style (SMD). The
industry has had some debate on the merits of both styles
and although Microsemi recommends the Copper Defined
style land pad (NSMD). Both styles are acceptable for use
with the MLP package. NSMD pads are recommended
over SMD pads due to the tighter tolerance on copper
etching than solder masking. NSMD by definition also
provides a larger copper pad area and allows the solder to
anchor to the edges of the copper pads thus providing
improved solder joint reliability.
APPLICATIONS
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
APPLICATION NOTE/PCB DESIGN GUIDELINE (CONTINUED)
The construction of the Exposed Pad MLP enables
enhanced thermal and electrical characteristics. In order to
take full advantage of this feature the exposed pad must be
physically connected to the PCB substrate with solder. The
exposed pad is internally connected to the die substrate, so
it is very important that the PCB substrate potential be
connected to the same potential as AVSS.
The PCB thermal pad dimensions should be greater than
the dimensions of the MLPQ thermal pad whenever
possible; however adequate clearance must be met to
prevent solder bridging to the outer pads. A minimum
clearance of 0.2mm is recommended. If this clearance
cannot be met, then the PCB thermal pad should be reduced
in area.
7.55 [0.297]
5.10 [0.201] MAX.
CL
Ø0.30 [Ø0.012]
OPTIONAL 16 PLS.
1.20 [0.047]
TYP.
CL 5.10 [0.201] MAX.
7.55 [0.297]
1.20 [0.047]
TYP.
0.98 [0.038] MAX.
TYP. 32 PLS.
THERMAL PAD VIA DESIGN
0.65 [0.026]
TYP. 28 PLS.
There are two types of on-board thermal pad designs:
one using thermal vias to sink the heat to an inner layer
utilizing a copper plane. Based on the JEDEC Specification
(JESD 51-5) the thermal vias should be designed similar to
Figure 5, with the following specifications:
0.43 [0.017] MAX.
TYP. 32 PLS.
ALL DIMENSIONS IN MM [ IN ].
Figure 5 – Recommended Land Pad with Vias for 7x7mm
LQ package
Via Barrel diameter: 0.3mm
Min. Via Barrel plating: 0.025mm
Center to center spacing: 1.2mm
For the LX1708 7x7mm MLPQ package, there will be
enough space for 16 vias. This method is recommended
for use on a multilayer board, and will give the best
thermal performance. Thermal vias may be used on a two
layer board as well, with reduced performance.
Another method is the no via thermal pad, which uses
only the copper pad as a heat sink, and relies on the PCB
substrate material for thermal conduction. This type of
thermal pad is good for a two layer board; however thermal
performance will not be as good as the thermal via method
on a multilayer board.
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
WWW . Microsemi .C OM
EXPOSED PAD PCB DESIGN
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
THD+N VS. OUTPUT POWER
THD+N VS. OUTPUT POWER
WWW . Microsemi .C OM
12V, 8 Ohm Load with External Diodes
100
100
50
50
20
20
10
10
5
5
2
2
1
1
0.5
0.5
%
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
0.01
0.005
0.005
0.002
0.001
0.002
60m
100m
200m
500m
1
2
5
10
0.001
20
60m
100m
200m
500m
W
1
2
5
10
20
W
THD VS. POWER SUPPLY
THD+N VS. OUTPUT POWER
12V, 4 Ohm Load, No External Diodes
12V, 4 Ohm Load, With External Diodes
100
100
50
50
20
20
10
10
5
5
2
2
1
1
0.5
0.5
%
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
0.01
0.005
0.005
0.002
0.002
0.001
60m
100m
200m
500m
1
2
5
10
0.001
20
60m
100m
200m
500m
W
1
2
5
10
20
10
20
W
THD+N VS. FREQUENCY
THD+N VS. FREQUENCY
12V, 8 Ohm Load, No External Diodes
12V, 8 Ohm Load, with External Diodes
100
50
50
20
20
10
10
5
5
2
2
CHARTS
100
1
1
0.5
0.5
%
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
0.01
0.005
0.005
0.002
0.002
0.001
0.001
60m
100m
200m
500m
1
2
5
10
20
Copyright © 2007
Rev. 1.3, 2007-04-05
60m
100m
200m
500m
1
2
5
W
W
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 12
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
THD+N VS. FREQUENCY
THD+N VS. FREQUENCY
100
12V, 4 Ohm Load, With External Diodes
100
50
50
20
20
10
10
5
5
2
2
1
WWW . Microsemi .C OM
12V, 4 Ohm Load, No External Diodes
1
0.5
0.5
%
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
0.01
0.005
0.005
0.002
0.002
0.001
20
50
100
200
500
1k
2k
5k
10k
0.001
20
20k
50
100
200
500
Hz
THD VS. POWER SUPPLY
2k
5k
10k
20k
THD VS. POWER SUPPLY
8 Ohm Load, 6V, 9V, 12V, 15V
100
1k
Hz
4 Ohm Load, 6V, 9V, 12V, 15V
100
50
50
20
6V
10
20
15V
6V
10
5
5
2
2
1
1
0.5
0.5
%
15V
%
0.2
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
0.01
0.005
0.005
0.002
0.002
0.001
60m
100m
200m
500m
1
2
5
10
0.001
20
60m
W
200m
500m
1
2
5
10
20
50
W
OUTPUT POWER BANDWIDTH @ 1% THD
OUTPUT POWER BANDWIDTH @ 1% THD
12V, 8 Ohm Load
20
100m
12V, 4 Ohm Load
30
20
10
10
7
6
8
5
6
4
5
W
3
4
CHARTS
W
3
2
2
1
1
800m
700m
600m
20
600m
50
100
200
500
1k
2k
5k
10k
20k
Hz
Copyright © 2007
Rev. 1.3, 2007-04-05
20
50
100
200
500
1k
2k
5k
10k
20k
Hz
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 13
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
PSRR @ 8 OHM
CHANNEL CROSSTALK @ 8 OHM
Channel Crosstalk @ 8 ohm
+0
+0
-10
-10
-20
-20
-30
-30
-40
-40
dB
dBr
WWW . Microsemi .C OM
PSRR @ 8 ohm
-50
-50
-60
-60
-70
-70
-80
-80
-90
-90
-100
20
-100
20
50
100
200
500
1k
2k
5k
10k
20k
50
100
200
500
SIGNAL TO NOISE RATIO @ 8 OHM
2k
5k
10k
20k
NOISE FLOOR @ 8 OHM
SNR @ 8 ohm
+0
1k
Hz
Hz
Noise Floor @ 8 ohm
+0
-10
-10
-20
-20
-30
-30
-40
-40
dBV
dBr
-50
-50
-60
-70
-60
-80
-70
-90
-80
-100
-90
-110
-100
20
50
100
200
500
1k
2k
5k
10k
20k
-120
20
50
100
200
Hz
500
1k
2k
5k
10k
20k
Hz
PVDD CURRENT VS. OUTPUT POWER
EFFICIENCY
12V, 4 Ohm Load + 33µH
12V, 4 Ohm Load + 33µH
100%
3.0
95%
2.5
90%
85%
2.0
80%
75%
1.5
CHARTS
70%
1.0
65%
60%
0.5
55%
0.0
50%
0
5
10
15
20
25
30
Ou t p u t P o we r - 2 C h a n ne l s T o t a l ( Wa t t s R M S )
Copyright © 2007
Rev. 1.3, 2007-04-05
0
5
10
15
20
25
30
Ou t p ut P owe r - 2 C ha nn e l s T ot a l ( Wa t t s R M S )
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 14
LX1708
®
TM
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
IQQ VS. FREQUENCY
GAIN @ 8 OHM
WWW . Microsemi .C OM
GAIN @ 8 ohm
40
+30
35
+28
+26
30
+24
+22
+20
+18
20
dBr
IQQ (mA)
25
+16
+14
15
+12
+10
10
+8
+6
5
+4
0
150k
+2
250k
350k
450k
550k
650k
750k
850k
950k 1,050k 1,150k
SW Freq. (Hz)
+0
20
50
100
200
500
1k
2k
5k
10k
20k
50k 80k
Hz
CHARTS
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 15
LX1708
15+15W Stereo Filterless Class-D Amplifier
®
TM
P RODUCTION D ATA S HEET
PACKAGE DIMENSIONS
WWW . Microsemi .C OM
LQ
32-Pin MLPQ Plastic (7x7mm EP)
D
E2
b
L
D2
E
e
MILLIMETERS
MIN
MAX
0.80
1.00
0
0.05
0.25 REF
0.23
0.38
7.00 BSC
5.00
5.25
7.00 BSC
5.00
5.25
0.65 BSC
0.45
0.65
INCHES
MIN
MAX
0.031
0.039
0
0.002
0.010
0.009
0.015
0.276 BSC
0.197
0.207
0.276 BSC
0.197
0.207
0.026
0.018
0.026
Note:
A
A1
Dim
A
A1
A3
b
D
D2
E
E2
e
L
1. Dimensions do not include mold flash or protrusions; these
shall not exceed 0.155mm (.006”) on any side. Lead
dimension shall not include solder coverage.
A3
MECHANICALS
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 16
LX1708
TM
®
15+15W Stereo Filterless Class-D Amplifier
P RODUCTION D ATA S HEET
NOTES
WWW . Microsemi .C OM
NOTES
PRODUCTION DATA – Information contained in this document is proprietary to
Microsemi and is current as of publication date. This document may not be modified in
any way without the express written consent of Microsemi. Product processing does not
necessarily include testing of all parameters. Microsemi reserves the right to change the
configuration and performance of the product and to discontinue product at any time.
Copyright © 2007
Rev. 1.3, 2007-04-05
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 17