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PDF ZXCD1000 Data sheet ( Hoja de datos )
| Número de pieza | ZXCD1000 | |
| Descripción | HIGH FIDELITY CLASS D AUDIO AMPLIFIER SOLUTION | |
| Fabricantes | Zetex Semiconductors | |
| Logotipo |  |
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ZXCD1000
HIGH FIDELITY CLASS D AUDIO AMPLIFIER SOLUTION
DESCRIPTION
The ZXCD1000 provides complete control and
modulation functions at the heart of a high efficiency
high performance Class D switching audio amplifier
solution. In combination with Zetex HDMOS MOSFET
devices, the ZXCD1000 provides a high performance
audio amplifier with all the inherent benefits of Class D.
The ZXCD1000 solution uses proprietary circuit design
to realise the true benefits of Class D without the
traditional drawback of poor distortion performance.
The combination of circuit design, magnetic
component choice and layout are essential to realising
these benefits.
The ZXCD1000 reference designs give output powers
up to 100W rms with typical open loop (no feedback)
distortion of less than 0.2% THD + N over the entire
audio frequency range at 90% full output power. This
gives an extremely linear system. The addition of a
minimum amount of feedback (10dB) further reduces
distortion figures to give < 0.1 % THD + N typical at
1kHz.
From an acoustic point of view, even more important
than the figures above, is that the residual distortion is
almost totally free of any crossover artifacts. This
allows the ZXCD1000 to be used in true hi-fi
applications. This lack of crossover distortion, sets the
ZXCD1000 solutions quite apart from most other
presently available low cost solutions, which in general
suffer from severe crossover distortion problems.
FEATURES
• >90% efficiency
• 4 / 8 Ω drive capability
• Noise Floor -115dB for solution
• Flat response 20Hz - 20kHz
• High gate drive capability ( 2200pF)
• Very low THD + N 0.2% typical full 90% power, full
band ( for the solution)
Distortion v Power
8Ω open loop at 1kHz.
• Complete absence of crossover artifacts
• OSC output available for sync in multi-channel
applications
10W
5W
1W
• Available in a 16 pin exposed pad QSOP package
APPLICATIONS
• DVD Players
• Automotive audio systems
• Home Theatre
• Multimedia
• Wireless speakers
• Portable audio
• Sub woofer systems
• Public Address system
Output Power
The plot shows Distortion v Power into an 8Ω load at
1kHz. This plot clearly demonstrates the unequalled
performance of the Zetex solution. Typical distortion of
0.05% at 1W can be seen with better than 0.15% at 10W.
Truly world class performance.
ISSUE 2 - APRIL 2002
1
1 page  
ZXCD1000
Audio A/B
Triangle A/B
Audio A/B
O/P
PWM Comparator
Audio A/B
Triangle A/B
Figure 3a.
O/P
Comparator O/P
(Duty Cycle = 50%)
Figure 3b.
Audio A/B
Triangle A/B
Triangle A/B
Comparator O/P
(Duty Cycle = 75%)
Figure 3c.
Comparator O/P
(Duty Cycle = 25%)
Figure 3d.
Figures 3a,3b,3c and 3d
The audio input Pulse Width Modulates the comparator output.
With no audio input signal applied, the AudioA/B
inputs are biased at the mid-point of the triangular
wave, and the duty cycle at the output of the
comparators is nominally 50%. As the AudioA/B signal
ascends towards the peak level, the crossing points
with the (higher frequency) triangular wave also
ascend. The comparator monitoring these signals
exhibits a corresponding increase in output duty cycle.
Similarly, as the AudioA/B signal descends, the duty
cycle is correspondingly reduced. Thus the audio input
Pulse Width Modulates the comparator outputs. This
principle is illustrated in Figures 3a, b, c and d. The
comparator outputs are buffered and used to drive the
OutA and OutB outputs. These in turn drive the speaker
load (with the audio information contained in the PWM
signal) via the off chip output bridge and single stage
L-C filter network.
The ramp amplitude is approximately 1V. The AudioA,
AudioB, TriangleA and TriangleB inputs are internally
biased to a DC voltage of approximately VCC/5. The
mid - point DC level of the OscA and OscB triangular
outputs is around 2V. The triangular wave at the Cosc
pin traverses between about 2.7Vand 3.8V and the dist
pin exhibits a roughly square wave from about 1.4V to
2V. (The above voltages may vary in practice and are
included for guidance only).
ISSUE 2 - APRIL 2002
5
5 Page 
ZXCD1000
Class D 50W Mono Bridge Tied Load (BTL)
Solution with Feedback – Circuit Description
With the addition of feedback (hence closed loop
solution) it is possible to obtain even better THD
performance. A schematic diagram for this is shown in
Figure 9. Again proprietary circuit and special
magnetic design is necessary to yield the high THD
performance and deviation from this could
significantly reduce performance.
Much of the circuitry is the same as described for the
open loop solution. The main differences being a
consequence of using the feedback circuitry. The audio
input is ac coupled and applied to an op-amp (1/2 of U3)
configured as a non–inverting amplifier with a gain of
approximately 4. Feedback is applied differentially
from the bridge outputs via the other half of U3
op-amp. A portion of the single ended output from this
op-amp is subtracted from the output of the
non-inverting op-amp output above. Overall negative
feedback is applied due to the polarity and connection
of the signals involved.
The audio signal from the above circuitry is applied to a
phase splitter as was done for the open loop solution.
This is built around the other 5532 dual op-amp (U2).
One of these op-amps is configured as a voltage
follower and the other as a X1 inverting amplifier. This
produces in phase and inverted signals for application
to the ZXCD1000 Audio A and Audio B inputs
respectively.
The output circuitry downstream of the ZXCD1000 is as
described for the open loop solution. In order to
support the 50W output power of this solution a 25V
rail is required for a 4⍀ load. The MOSFETs used are
SOT223 packaged (ZXM64N035G and ZXM64P035).
Higher Power Solutions
With some modifications the applications solutions
can be extended to give output power up to 100W. The
main differences being the supply voltage, the TO220
MOSFETs, and the output magnetics. The magnetics
for 100W are necessarily larger than required for
25/50W in order to handle the higher load currents. For
100W operation the supply voltage to the circuit is
nominally 35V with a 4⍀ load. However the maximum
supply voltage to the ZXCD1000 class D controller IC is
18V, hence a voltage dropper is required. This could be
done, for example, as in the open loop solution
described previously. A 100W circuit is shown on
figure 10. This features a 35V bridge supply TO220
MOSFETs (ZXM64N035L3 and ZXM64P035L3) and
also proposed protection circuits for over current and
over temperature and an alternative anti pop circuit.
Further information on this 100W reference design can
be obtained through Zetex applications.
The ZXCD1000 class D controller IC is inherently
capable of driving even higher power solutions, with
the appropriate external circuitry. However as stated
above the maximum supply voltage to the ZXCD1000
class D controller IC is 18V and the higher supply
voltages must therefore be dropped. Also due
consideration must be given to the ZXCD1000 output
drive levels and the characteristics of the bridge
MOSFET’s. The latter must be sufficiently enhanced by
the OutA and OutB outputs to ensure the filter and load
network is driven properly. If the gate drive of the
ZXCD1000 is too low for the chosen MOSFET then the
OUTA and OUTB signal must be buffered using an
appropriate MOSFET driver circuit. Additionally,
suitable magnetics are essential to achieve good THD
performance.
Package details
Further information on this design is available through
Zetex applications.
The ZXCD1000 is available in a 16 pin exposed pad
QSOP package. The exposed pad on the underside of
the package should be soldered down to an area of
copper on the PCB, to function as a heatsink. The PCB
should have plated through vias to the underside of the
board, again connecting to an area of copper.
ISSUE 2 - APRIL 2002
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ZXCD1000.PDF ] | |
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