zxcd1000 Zetex Semiconductors plc., zxcd1000 Datasheet - Page 4

• Manufacturer Part Number: zxcd1000
• Description: High Fidelity Class D Audio Amplifier Solution
• Manufacturer: Zetex Semiconductors plc.

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.
Figure 2.
Functional Block Diagram
ZXCD1000
Audio B
Audio A
V
CC
13
1
8
4
Oscillator & Ramp
Internal 5V5
Internal 9V
Generator
14
5
12
Buffers
Osc
16
3
6 7
4
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.
2
PWM
Comp A
PWM
Comp B
Pre-
Driver
Pre-
Driver
O/P
Driver
O/P
Driver
9
11
ISSUE 2 - APRIL 2002
10
15
Out A
Out B