Cirrus Logic CDB44800 - Manual (Page 3)

CDB44800
DS632DB2 3
1. SYSTEM OVERVIEW
The CDB44800 demonstration board is an excellent means for evaluating the CS44800 eight-
channel Class-D PWM modulator. It incorporates a digital audio interface, four full-bridge and 4
half-bridge configurations, and power supply rejection (PSR) circuitry, all on a two-layer board.
The CDB44800 schematic set is shown in Figures 4 through 12 and the board layout is shown
in Figures 13 through 15.
1.1 CS44800 PWM Modulator
A complete description of the CS44800 is included in the CS44800 product data sheet.
The CS44800 converts linear PCM data to pulse width modulated (PWM) output. It uses an
SRC to minimize jitter effects, resulting in high-quality sound output.
All supply voltages (VDX, VLS, VLC, and VDP) can be set using J30, J31, J32, and J28. A
push button is provided for immediate muting of the PWMOUTxxx outputs. PCM data and
clocks are input from either the CS8416 or J24 (PCM Input). J25 provides the SYS_CLK and
J21 provides the PS_SYNC output clocks for system development.
1.2 CS4461 PSR Feedback ADC
A complete description of the CS4461 is included in the CS4461 product data sheet.
The CS4461 is connected to the CS44800 to provide power supply rejection (PSR) for the
VP supply voltage connected to J17. Resistors R41 and R42 should be scaled for the supply
voltage used. See the CS4461 data sheet for equations to determine the resistor values.
The board comes initially populated with resistor values set for VP = 40 V.
1.3 TDA8939 Power Stage
A complete description of the Philips TDA8939 is included in the TDA8939 product data
sheet.
The TDA8939 is a high-voltage PWM amplifier power stage. It integrates two half-bridge driv-
ers and fault protection. With VP set to 40 V and R
load
= 8
Ω, the TDA8939 can produce up
to 65 W when set as a full-bridged output. With VP set to 40 V and R
load
= 4
Ω, the TDA8939
can produce up to 35 W when set as a half-bridged output.
The supply voltage is set through J17 (VP) and should be between 20 V and 50 V. LEDs
D1 - D6 (DIAG) indicate a fault condition with the corresponding power stage. These signals
are OR’ed and input to GPIO0 pin on the CS44800. Speaker outputs are available from J1 -
J16. Care should be taken to not connect the full bridge black speaker connectors to ground
as these outputs are driven. The half bridge black speaker connectors can be connected di-
rectly to ground as these outputs are tied to ground on the board.
1.4 CS8416 Digital Audio Receiver
The operation of the CS8416 receiver and a discussion of the digital audio interface are in-
cluded in the CS8416 data sheet.