EB-2100x
DDX All-Digital, High Efficiency
Evaluation Amplifier
FEATURES
DDX-2000/2100 CHIP SET
•
OPERATION 9 to 36 VDC
•
2x50W into 8Ω @ 1% THD
•
1x100W into 4Ω @ 1% THD
TYPICAL PERFORMANCE
•
0.07% THD+N (1W, 1kHz)
•
90 dB SNR (50Wrms, A-weighted)
•
88% EFFICIENCY
DIGITAL INPUT
•
S/PDIF COAX/OPTICAL
2
•
I S LOOP THROUGH
DIGITAL PREAMP FEATURES
•
VOLUME
•
BALANCE
•
ANTICLIPPING
•
AUTOMATIC MUTE
GENERAL DESCRIPTION
The EB-2100x is an evaluation amplifier that
showcases Apogee’s all-digital, high efficiency Direct
Digital Amplification (DDX®) technology. The board
features a DDX-2000 Controller and DDX-2100
Power Device which provide full digital audio
preamplifier functions and power amplification. The
board includes both coaxial and optical S/PDIF
interfaces, digital volume and balance controls and
local power regulation to operate from a single supply
voltage.
The EB-2100x is available in both a stereo 50W (EB-
2100S) and a mono 100W version (EB-2100M).
ORDERING INFO
EB-2100S – DDX stereo amplifier board
EB-2100M – DDX mono amplifier board
EB-2100x BLOCK DIAGRAM
V+
I
2
S Serial
PCM
S/PDIF
Receiver
PWM1
2
Coax or
Optical
Digital Audio
3
Volume
3
Mute
Reset
LP
Filter
DDX-2000
Controller
PWM2
2
+VL
DDX-2100
Power Device
LP
Filter
Left
Power Down
Right
Clock
129 Morgan Drive, Norwood MA 02062
1
voice: (781) 551-9450 fax: (781) 440-9528 email: sales@apogeeddx.com
Copyright Apogee Technology, Inc 2000 (All Rights Reserved)
Doc# 11010006-01
February 2002
_______________
DESIGN OVERVIEW
The EB-2100x is an all-digital amplifier
evaluation board that demonstrates Apogee’s
DDX-2000/2100 chip set solution. The board
features coaxial and optical S/PDIF digital
interfaces, volume and balance controls,
expansion headers for off-board processing, and
local power regulation enabling single supply
operation from 10 to 36VDC. The all-digital
amplifier board may be configured as either 2 x
50W into 8Ω or 1 x 100W into 4Ω.
__ EB-2100x
INL[1:2]
INR[1:2]
VL
PWRDN
TRI-STATE
OUTPL
Logic I/F
and Decode
Left
H-Bridge
OUTNL
FAULT
TWARN
Protection
Circuitry
OUTPR
Right
H-Bridge
OUTNR
Regulators
DDX-2000/2100 OVERVIEW
The DDX-2000 Controller is a 3.3V digital
integrated circuit that converts serial PCM digital
audio signals into Apogee's patented damped
ternary outputs.
The device supports two
modes of digital volume control, muting and anti-
clipping functions. A block diagram of the
device is shown in Figure 1.
ACE
MUTE
Figure 2 - DDX-2100 Block Diagram
SCHEMATIC DESCRIPTION
S/PDIF INPUT INTERFACE (FIG. 3A)
The EB-2100x accommodates either a coaxial
or an optical S/PDIF digital audio interface.
Either input may be selected by moving jumper
J2. Connect J2 pins 1-2 for coaxial or J2 pins 2-
3 for optical S/PDIF. A Crystal CS8415A digital
audio interface receiver is utilized to convert the
incoming S/PDIF signal to serial I
2
S used by the
DDX-2000. The receiver also recovers a 256*Fs
clock synchronized to the incoming signal which
is used as the master clock to the DDX-2000.
The design will support sample rates from below
32kHz to above 48kHz. The receiver PLL out-
of-lock signal is used to mute the amplifier’s
output when a valid S/PDIF signal is not present.
Zero ohm jumpers R6,R9,R10,R11,R42 are
provided to disconnect the outputs of the S/PDIF
receiver from the inputs to the DDX-2000 so that
external signals may be applied via the
expansion header J7 (see Fig. 3D).
DIGITAL SIGNAL PROCESSING (FIG. 3B)
The DDX-2000 converts serial I
2
S digital audio
signals into pulse-width-modulated digital
signals output at 8*Fs, according to Apogee’s
patented damped ternary architecture. Signals
from the S/PDIF receiver are applied as inputs
to the DDX processor and signals from the DDX
processor are applied to the inputs of the DDX
power stage.
A low-cost microcontroller with an ADC is used
to implement the volume and balance controls.
The amplifier’s volume and balance levels are
SCLK
SDATA
LRCLK
SERIAL
INTERFACE
ANTI-
CLIPPING
PWM
GENERATION
OUTL[1:2]
VMODE
VCLK/UP
VDATA/DN
VOLUME/
GAIN
SYSTEM
CLOCKING
OUTR[1:2]
XI XO LPIN LPOUT
Figure 1 - DDX-2000 Functional Diagram
The DDX-2100 Power Device is a dual channel
H-Bridge that can deliver over 50 watts per
channel of audio output power. The DDX-2100
includes; a logic interface, integrated bridge
drivers, high efficiency MOSFET outputs and
protection circuitry. Two logic level signals per
channel are used to control high-speed
MOSFET switches to connect the speaker load
to the input supply or to ground in a bridge
configuration, according to Apogee's patented
damped ternary PWM. The DDX-2100 includes
over-current and thermal protection, and under-
voltage lockout with automatic recovery. A
thermal warning status is also provided.
2
Details are subject to change without notice.
_______________
adjusted using two potentiometers. The DC
voltage set by the potentiometers is read by the
microcontroller that interfaces to the volume
serial port of the DDX-2000. The DDX-2000 has
independent volume control registers that have
an adjustment range from –82.5dB to +12.0dB in
0.75dB increments.
A 0dB switch setting is
included to signal the microcontroller to set the
volume level for both channels to be unity gain.
This setting is particularly useful for audio
measurements.
The EB-2100x permits three separate methods
for clocking the DDX-2000. The default is via
the 256*Fs recovered clock output from the
S/PDIF receiver IC. The second is via the
expansion header J7 used to apply an external
clock source to synchronize, for example,
multiple DDX-2000 ICs to the same clock. Zero-
ohm jumper R35 is installed to pass either of
these clock sources to the DDX-2000 master
clock input. The last method is asynchronous
from an external crystal.
The DDX-2000
contains a crystal oscillator which may be used
for single sample-rate applications. Oscillator
circuit Y1, C30, C37, R24, R26 may be
populated and jumper R35 removed for
applications where a 256*Fs clock source is not
convenient. The DDX-2000 tolerates a sample
rate mismatch of +/-0.2% about the crystal
frequency without performance degradation.
The crystal footprint is a surface mount Epson
MA-506.
There
are
additional
provisions
for
demonstrating DDX-2000 functionality.
The
GCEN flag is used to disable the anticlipping
function and is controlled by DIP rocker switch
SW1. Jumper R29 is provided to change the
2
serial port mode on the DDX-2000 from I S to
left-justified to accommodate an external set of
signals. Jumpers R13, R14, R30 are provided
for test modes and must not be changed. A
channel reverse flag is provided which inverts
LRCLK causing left channel data to be output on
the right channel and vice versa. This function
is intended to be used for multiple amplifiers
configured as mono when used in a
multichannel audio demonstration.
POWER OUTPUT (FIG. 3C)
The DDX-2100 provides power amplification by
translating logic level PWM signals into power
level signals. These power level signals are
applied to a passive two-pole lowpass filter to
reconstruct the audio signal providing power to
__ EB-2100x
the load. The output filter functions to attenuate
unwanted high frequency signals from reaching
the load. A filter design for 8Ω loads is shown in
the Fig. 3C schematic for reference.
The DDX-2100 is designed for stereo operation
as either two independent full-bridges or for
mono operation as one full-bridge with twice the
current capability, enabling higher output power.
The EB-2100x is designed to demonstrate both
configurations via component substitutions. The
schematic notes in Fig. 3C detail component
changes to convert from stereo to mono
operation. Evaluation boards configured as
either stereo or mono may be ordered with the
appropriate part number designations. Jumpers
R19, R22, R25, R33 are used to configure PWM
inputs for stereo operation. Jumpers R17, R23,
R27, R36 are used to configure PWM inputs for
mono operation. Jumpers JP1 and JP3 parallel
the output bridges enabling higher output
current. Jumpers JP2 and JP4 parallel the
output filter sections to a 4Ω load. Capacitor
C29 is the differential capacitor required for the
4Ω filter only.
In applications where only mono 100W /
4Ω operation is desired, e.g. subwoofer, the
output filter may be simplified.
Two filter
sections may be employed in lieu of sections in
parallel. Inductors may be ½ the value with
twice the current rating. Capacitors are double
the value and resistors are ½ the value at twice
the power rating.
Snubbers are employed to protect the output
MOSFETs from inductive transients.
Peak
voltage on the DDX-2100 output and power pins
must not exceed 40V. Output snubbers for the
stereo implementation are R15,C23 and
R31,C40 and the snubber for the mono
implementation is R21,C32.
Input protection is provided for the amplifier by
diode D1. D1 will protect from overvoltage and
reverse power applications by shunting the
power supply.
A thermal warning indicator is activated by the
DDX-2100 when its junction temperature
exceeds +130
o
C. The thermal warning output is
used to force the power LED to change color
from green to red forecasting the potential of an
overtemperature shutdown.
3
Details are subject to change without notice.
_______________
HEADERS / REGULATORS (FIG. 3D)
The EB-2100x features local power regulation to
facilitate operation from a unipolar +10 to +36
VDC supply. Alternatively, auxiliary power may
be applied at J8 (removing bead L7) separating
logic and output power supplies. Output from
the onboard +5V regulator is available on the J6
test header. Output from the onboard +3.3V
regulator is available on the J7 expansion
header. There is capability available to power
external circuits from either the +5V or the +3.3V
supplies or a combination not to exceed a total
current of 0.33A.
Expansion header J7 is provided to monitor or
apply input signals to the DDX-2000. Jumper
R42 may be removed to pass serial data
provided by an external processor. Test header
J6 is provided to monitor signals output from the
DDX-2000. Signals INLC, INLD, INRC, INRD
are driven low by the DDX-2000 and are used
for test purposes only. DIP switch SW1 is used
for control functions:
POS1 reverses data
channels when open, normal when closed;
POS2 sets unity gain for test when closed,
normal when open; POS3 forces the DDX-2100
into low power mode when closed, normal when
open; POS4 disables the anticlipping function
when closed, normal when open.
Supervisor U8 is used for power-on-reset,
power-off sequencing, and as a convenient
means of commanded reset via pushbutton.
__ EB-2100x
state duty rating of 50W RMS per channel with
both channels driven into 8Ω.
The DDX-2100 surface mount package includes
an exposed thermal pad on the top of the device
to provide a direct thermal path from the
integrated circuit to the heat sink. For continuous
duty rated applications, careful consideration
must be made to the overall thermal design.
Performance Measurements
Typical performance measurements for the
evaluation board are shown in Figs 4 through
11.
Class D amplifiers produce measurable
switching distortion outside the audio bandwidth.
Apogee's DDX amplifier uses a patented PWM
modulation scheme that significantly reduces the
size of these products compared to typical Class
D designs. However, in order to obtain accurate
performance measurements in the audio
bandwidth (i.e., 20Hz to 20kHz) additional
filtering is required.
The Typical Performance data in was taken
using a brick wall filter with a break frequency of
22kHz. This type of filter is often provided as
part of audio measurement systems.
OPERATING INSTRUCTIONS
Refer to Fig. 12 evaluation amplifier assembly
drawing. Attach a regulated power supply at J3
set between +10V and +36VDC. At +36V, the
power supply must be capable of delivering 4A
minimum for two channels. Attach a digital
audio input source at either the coaxial or optical
S/PDIF connectors. Select the digital input
source via J2. Connect 8 Ohm speakers to J4
(left speaker) and J5 (right speaker). Configure
SW1 as POS1 closed, POS2,3,4 open. Note,
the speaker outputs are bridged. Do not ground
any speaker connections, e.g. through an
oscilloscope.
Apply power, digital source
material
and
enjoy!
ADDITIONAL INFORMATION
Bill of Materials
A bill of materials for the evaluation board is
provided in Table 1 for reference.
Note
equivalent
components
from
alternate
manufacturers may be substituted. No warranty
of system performance is implied by Apogee
through use of the reference bill of materials.
Power Dissipation/Heat Sink Requirements
The DDX-2100 is a high efficiency dual channel
design intended for audio applications needs up
to 50 Watts RMS per channel. The power
dissipation of the device will depend primarily on
the supply voltage, load impedance, and output
modulation level. The thermal performance of
the evaluation board is consistent with a steady-
4
Details are subject to change without notice.
________________
__ EB-2100x
FIG. 3A - DDX EVAL AMPLIFIER SCHEMATIC: S/PDIF INPUT INTERFACE
5
Details are subject to change without notice.
京公网安备 11010802033920号
EEWORLD
