ZXCD50STEVAL Diodes Zetex, ZXCD50STEVAL Datasheet - Page 4

• Manufacturer Part Number: ZXCD50STEVAL
• Description: BOARD EVAL STEREO ANALOG CLASS D
• Manufacturer: Diodes Zetex
• Type: Amplifiers: Audio Class D Ampsr

Specifications of ZXCD50STEVAL

• Contents: Evaluation Board
• For Use With/related Products: ZXCD1000
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ZXCD50STEVAL CIRCUIT DESCRIPTION.
Propriety circuit design and high quality magnetics are
necessary to yield the excellent THD performance of
the solution. At the heart of the circuit is the Zetex
ZXCD1000 class D audio IC.
The ZXCD50STEVAL circuit diagram is shown in figure
4. The board features two class D channels, one master
and one slave. These channels are essentially the same
other than the triangle synchronisation facilitated by
Q1 on the master channel.
Each audio channel consists of an input phase splitter,
the ZXCD1000, an output bridge to drive the load - via
L-C filters, and an over-current protection circuit. Each
channel also features its own dropper voltage
regulator.
The voltage regulator (Q5/105, ZD1/101 etc.) is
necessary to drop higher supply voltages (25V on the
bridge for 50W) to a level suitable for the ZXCD1000
and input phase splitter (12V on the board).
The input phase splitter per channel, built around the
NE5532 dual op amp, is necessary to drive the Audio A
and Audio B channels on each ZXCD1000.
Each channel phase splitter features a mute transistor
(Q11/111) which is controlled via the circuit built
around Q12. This circuit provides a mute function with
an active low input. The mute function reduces the
effective output signal by 54dB.
The Output Bridges are built around the Zetex
ZXM64P035G and ZXM64N035G PMOS and NMOS
SOT223 transistors.
The circuit built around Q10 facilitates a slow start for
the bridge supply voltage This circuit performs
anti-pop for the solution.
R20/120 are over current sense resistors. The circuit
built around these (Q2/102, Q3/103 etc) enables an
over-current protection for the solution. In fault
conditions the circuit disables the triangle modulation
waveform to the channel and thus disables the output
bridge. Protection is given for speaker shorts and
speaker to ground shorts.
The ZXCD1000 outputs drive Output Bridge MOSFET’s,
with the PWM signal, which subsequently drives the
load via L-C filters. The purpose of the filters is to low
pass filter the high frequency switching PWM signal
from the bridge. Thus the lower frequency audio signal
is recovered and is available at the speaker outputs.
ZXCD50STEVAL
4
ZXCD50STEVAL CIRCUIT PERFORMANCE
The graph shown in fig 5 indicates the typical THD
performance of the solution. THD is shown from zero
up to full power.
Distortion is sub 1% all the way up to full power,
typically at 1W 1kHz distortion is 0.1%.
Figure 5.
WARNING - Appropriate safety precautions should be taken by
a competent person if the ZXCD100MOEVAL is to be connected
to any potentially hazardous equipment.
ISSUE 1 - JULY 2002