ISSUE 2 - APRIL 2002

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 VCC 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 (Cosc) and on chip resistor. The triangular

waveform must be externally AC coupled back into the

ZXCD1000 at the TriangleA and TriangleB inputs.

AC 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.

ZXCD1000

4

Oscillator & Ramp

Generator

Internal 5V5

Internal 9V

PWM

Comp A

PWM

Comp B

Pre-

Driver

Pre-

Driver

O/P

Driver

O/P

Driver

Audio A

Audio B

Out A

Out B

1

2

3

45

6 7

8

9

10

11

12

13

14

15

16

Osc

Buffers

Figure 2.

Functional Block Diagram