CRD-42L51 Cirrus Logic Inc, CRD-42L51 Datasheet - Page 5

• Manufacturer Part Number: CRD-42L51
• Description: Audio Modules & Development Tools Ref Bd Low-volt Stereo CODEC
• Manufacturer: Cirrus Logic Inc

Specifications of CRD-42L51

• Product: Audio Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DS679RD1
3. SYSTEM OVERVIEW
The CRD42L51 reference design provides a quick and general overview of the features in the CS42L51 CODEC
and provides a reference of an ultra small layout design. Line, MIC and S/PDIF sources are accomodated, and a
microcontroller automatically configures the board and the CODEC’s internal registers for straightforward opera-
tion.
The CRD42L51 schematic-set has been partitioned into four pages and is shown in
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Power (U2)
Power is supplied to the board through a single AAA battery. A DC-DC Converter boosts the battery’s volt-
age to 3.3 V which is then regulated down to 1.8 V. The CS42L51 is powered from 1.8 V, demonstrating its
internal ground-centered amplifier’s ability to deliver ample power into headphone loads even at low supply
voltages. The interface logic between the CS8416, oscillator and CS42L51 operates at 3.3 V.
Microcontroller (U5)
The microcontroller controls digital signal routing between the CS42L51, CS8416 and oscillator in response
to user input via four pushbuttons. It automatically initializes the board to predefined settings once power is
applied.
CS42L51 Audio CODEC (U1)
A complete description of the CS42L51
The CS42L51 is automatically configured by the microcontroller to the default settings following a power-on
condition and later modified based on user input via four pushbuttons. See
each functional mode and the associated configuration setting for the CS42L51.
CS8416 Digital Audio Receiver (U4)
A complete description of the CS8416 receiver
interface are included in the CS8416 data sheet.
The CS8416 converts the input S/PDIF data stream from the optical connector into PCM data for the
CS42L51. The S/PDIF input may be mixed with the Line or MIC input. In this case, the CODEC clock source
comes from the CS8416. Should the S/PDIF source become unavailable, causing a Receiver Error, the mi-
crocontroller will automatically switch the system master clock to the oscillator for uninterrupted operation
of the Line or MIC input.
Oscillator (Y1)
The on-board oscillator provides the system master clock when the digital audio receiver is powered down
or when a Receiver Error occurs. Selections are automatically determined based on user input and system
status.
Analog Input
An 1/8” jack supplies the line-level analog inputs through an AC-coupled passive filter. Voltage dividers be-
fore the inputs to the CS42L51 allow up to 2 Vrms signals (NOTE: To amplify smaller signals, enable the
Automatic Level Control (ALC). The CS42L51 applies up to +12 dB analog gain, as needed, using the ALC
together with the integrated Programmable Gain Amplifier (PGA)). A surface-mount microphone connects
to one of the inputs of the CS42L51 and is mux’d with the Line input. Either the Line or MIC input may be
mixed with the S/PDIF input.
Analog Outputs
An 1/8” jack outputs the signal from the CS42L51’s ground-centered headphone amplifier. The load stabi-
lizer circuitry made up of a resistor/capacitor pair allow the amplifier to drive headphone in addition to line-
level loads.
(Figure 2 on page
(Figure 3 on page
9) is included in the CS42L51 product data sheet.
10) and a discussion of the digital audio
Figures 2
Section 2
through 5.
for a description of
CRD42L51
5