ZXCD1000
ZXCD1000 Class D controller IC
A functional block diagram of the ZXCD1000 is shown
in Figure 2. The on chip series regulators drop the
external V
CC
supply (12V-18V) to the approximate 9V
(9VA/9VB) and 5.5V (5V5) supplies required by the
internal circuitry.
A triangular waveform is generated on chip and is
brought out at the OscA and OscB outputs. The
frequency of this is set (to ~200kHz) by an external
capacitor (C
osc
) and on chip resistor. The triangular
waveform must be externally AC coupled back into the
ZXCD1000 at the TriangleA and TriangleB inputs. AC
Triangle B
coupling ensures symmetrical operation resulting in
minimal system DC offsets. TriangleA is connected to
one of the inputs of a comparator and TriangleB is
connected to one of the inputs of a second comparator.
The other inputs of these two comparators are
connected to the AudioA and AudioB inputs, which are
anti-phase signals externally derived from the audio
input. The triangular wave is an order higher in
frequency than the audio input (max 20kHz). The
outputs of the comparators toggle every time the
TriangleA/B and the (relatively slow) AudioA/B signals
cross.
Triangle A
Osc A
4
5
3
Osc B
Cosc
Dist
6 7
2
Oscillator & Ramp
Generator
Osc
Buffers
Audio A
1
Audio B
8
V
CC
Internal 5V5
Pre-
Driver
PWM
Comp A
Pre-
Driver
PWM
Comp B
O/P
Driver
Out A
15
Out B
10
O/P
Driver
13
Internal 9V
Gnd
Figure 2.
Functional Block Diagram
Gnd2
9VA
9VB
5V5
14
12
16
9
11
ISSUE 1 - MARCH 2001
4
ETC [ ETC ]
