Cirrus Logic CRD42L51 User Manual

Reference Design for CS42L51
CRD42L51
Features
! Ultra Small Layout ! Single AAA Battery Source ! 1/8” Stereo Input Allows up to 2 Vrms Signals ! On-Board MIC ! 1/8” Stereo Headphone Output Jack ! S/PDIF Input (CS8416 Receiver) ! Flexible User Interface
2 Pushbuttons Enable, Disable and
Navigate between Reset, Standby, Input Source and Effects Options
2 Pushbuttons Adjust Volume and Effects
CRD42L51 Actual Size
Description
The CRD42L51 evaluation board provides a quick and easy evaluation of select features in the CS42L51 Low Power, Stereo CODEC. Four pushbuttons and sixteen LED’s comprise the user interface, allowing manipula­tion of the CS42L51’s registers and control clock/data routing between the CODEC, crystal oscillator, and S/PDIF Receiver.
Two 1/8” stereo jacks provide analog input and output connections, and a S/PDIF optical receiver provides a digital input connection. An on-board microphone dem­onstrates the high dynamic range of the CS42L51’s Programmable Gain Amplifier (PGA) and MIC pre­amplifier.
Power is derived from a single AAA battery boosted up to 3.3 V for the interface and control logic, then regulat­ed down to 1.8 V for the CS42L51 ’s anal og/digital co re and headphone supply.
The CRD42L51 highlights the ultra small layout re­quired for the CS42L51. Required components include only a few small ceramic capacitors and resistors.
ORDERING INFORMATION
CRD42L51 Reference Design
Push Buttons
Microcontroller
Optical
Input Jack
CS8416
12.2880 MHz Oscillator
LED Selection
Indicators
I²C Control/Reset
Clocks/Data
Master Clock
+3.3 V +1.8 V
CS42L51
Step Up DC-DC
Converter w/
Linear Reg.
1/8" Stereo Headphone Jack
AAA
Battery Clip
1/8" Stereo Line Input Jack
Omni-directional Microphone
http://www.cirrus.com
Copyright © Cirrus Logic, Inc. 2005
(All Rights Reserved)
DECEMBER '05
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TABLE OF CONTENTS
1. QUICK-START GUIDE ........................................................................................................................... 3
2. FUNCTION & LEVEL DETAILS ............................................................................................................ 4
3. SYSTEM OVERVIEW ............................................................................................................................. 5
3.1 Power (U2) ..................................................................................................................................... 5
3.2 Microcontroller (U5) ........................................................................................................................ 5
3.3 CS42L51 Audio CODEC (U1) ........................................................................................................ 5
3.4 CS8416 Digital Audio Receiver (U4) .............................................................................................. 5
3.5 Oscillator (Y1) ................................................................................................................................. 5
3.6 Analog Input ................................................................................................................................... 5
3.7 Analog Outputs ............................................................................................................................... 5
3.8 Switch & Pushbutton ...................................................................................................................... 6
3.9 LEDs ............................................................................................................................................... 6
3.10 Error Indicators ........................................... ... ... .... ... ... ... .... ........................................................... 6
3.11 Layout .................. ... .... ... ... ....................................... ... ... .... ... ........................................................ 6
4. SYSTEM CONNECTIONS & INTERFACE ............................................................................................. 7
5. CRD42L51 SCHEMATICS ..................................................................................................................... 9
6. CRD42L51 LAYOUT ........................................................................................................................... 13
7. REVISION HISTORY ............................................................................................................................ 19
LIST OF FIGURES
Figure 1. Block Diagram............................................................................................................................... 8
Figure 2. CS42L51 and Analog I/O (Schematic Sheet 1) .................................................................... ... .... .9
Figure 3. S/PDIF Input (Schematic Sheet 2).............................................................................................. 10
Figure 4. Microcontroller, Pushbuttons and LED Indicators (Schematic Sheet 3) ..................................... 11
Figure 5. DC-DC Converter and AAA Battery Clip (Schematic Sheet 4)................................................... 12
Figure 6. Silk Screen Top........................... ... ... ... .... ... ... ... ....................................... ... .... ... ... ...................... 13
Figure 7. Silk Screen Bottom ..................................................... ... .... ... ... ... ... .... ......................................... 14
Figure 8. Top-Side Layer ........................................................................................................................... 15
Figure 9. Internal Layer (Ground Plane) ................................................. ... ... ............................................. 16
Figure 10. Internal Layer (Power Plane).................................................................................................... 17
Figure 11. Bottom-Side Layer.................................................................................................................... 18
CRD42L51
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1. QUICK-START GUIDE

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t /
CRD42L51
4. Push both SELECT buttons simulta­neously to turn off the Reset function.
The board will enter Standby for a moment and then automatically activate the Line function.
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3. Switch the power switch to the ON po­sition.
battery, installed on the back side, is required.) The Reset Function will activate. No selections or adjustments can be made while Reset is on.
(NOTE: 1 AAA
1. Begin by connecting 16 or 32 headphones.
7. Speak into the microphone or activate the exter­nal S/PDIF or Line player to begin evaluation.
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4
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5. Use any one of the SELECT buttons to navigate between and shift the focus to select functions.
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To turn selected functions on or off, push both SELECT but­tons simultaneously. The assocated LED will turn on or off.
6. Use any one of the AD­JUST buttons to control the volume/ threshold level of each Source/Ef­fects that receives focus.
The Level Meter will briefl display a pre-defined gradien that represents the volume threshold level in dBs. The op­timal/default level flashes for a few seconds.
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2. Connect the desired inter­face. Apply up to 2 Vrms to the Line
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Input. For smaller signals, enable the ALC function for automatic level con­trol (up to +12 dB analog gain). For dig­ital source, connect optical cable to S/PDIF Input
Pushbutton
Control Key Press Description
<
(only)
SELECT
ADJUST
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>
(only)
< AND >
(simultaneously)
-
(only)
+
(only)
- AND +
(simultaneously)
Left/Up Navigation - Shifts the focus between functions. A blinking LED indicates which func-
tion has received focus. Right/Down Navigation - Shifts the focus between functions. A blinking LED indicates which
function has received focus. Enables/Disables the function that is in-focus. When the selected function is enabled AND
in-focus, the associated LED blinks ON, periodically, with a longer duty cycle.
Decreases the volume level of the function that is in-focus. Increases the threshold level of the ALC/Limiter when either is in-focus.
Increases the volume level of the function that is in-focus. Decreases the threshold level of the ALC/Limiter when either is in-focus.
Enables/Disables confirmation/error beeps.

2. FUNCTION & LEVEL DETAILS

State/LED
Function
Reset
Standby
Line
MIC
S/PDIF
Bass
Treble
Limiter
ALC
Illumination Description
ON CS42L51, CS8416, optical receiver, oscillator held in reset and disabled.
OFF
ON CS8416, optical receiver, oscillator held in reset and disabled; CS42L51 soft powered down.
OFF All devices out of reset; CS42L51 powered up, register settings restored.
ON Stereo Line Input selected, unmuted; MIC powered down.
OFF Stereo Line Input muted.
ON Mono MIC selected, powered up, unmuted; Line disabled.
OFF MIC muted.
ON
OFF S/PDIF Input muted; CS8416 and optical receiver powered down.
ON Tone Control enabled, Bass corner frequency set to 200 Hz, Treble corner frequency set to 7 kHz.
OFF Tone Control (Bass and Treble) disabled.
ON Tone Control enabled, Bass corner frequency set to 200 Hz, Treble corner frequency set to 7 kHz.
OFF Tone Control (Bass and Treble) disabled.
ON Limiter enabled, attack rate set to 0x02, release rate set to 0x3D.
OFF Limiter disabled.
ON ALC enabled, attack rate set to 0x02, release rate set to 0x3D.
OFF ALC disabled.
CS42L51, oscillator out of reset. CS8416 and optical receiver controlled by S/PDIF function. The Line function is enabled automatically.
S/PDIF Input selected, unmuted; CS8416 and optical receiver powered up. (Line or MIC mixed with S/PDIF if enabled.)
CRD42L51
Level Meter
(LED Luminosity)
LED12_ON +6.0 +44.0 +12.0 -18.0 -24.0 LED12_75% +4.0 +42.5 +10.5 - - LED12_50% +2.0 +41.0 - - - LED12_25% +0.0 +39.5 +9.0 - -
LED13_ON -1.5 +38.0 +7.5 -12.0 -18.0 LED13_75% -3.0 +36.5 +6.0 - - LED13_50% -4.5 +35.0 - - - LED13_25% -6.0 (default) +33.5 +4.5 - -
LED14_ON -7.5 +32.0 (default) +3.0 -9.0 -12.0 LED14_75% -9.0 +30.5 +1.5 - - LED14_50% -11.0 +29.0 - - - LED14_25% -13.0 +27.5 +0.0 (default) - -
LED15_ON -16.0 +26.0 -1.5 -6.0 (default) -9.0 (default) LED15_75% -19.0 +24.5 -3.0 - - LED15_50% -22.0 +23.0 - - - LED15_25% -26.0 +21.5 -4.5 - -
LED16_ON -30.0 +20.0 -6.0 -3.0 -6.0 LED16_75% -35.0 +18.5 -7.5 - - LED16_50% -40.0 +17.0 - - - LED16_25% -45.0 +15.5 -9.0 - - LED16_OFF -51.5 +14.0 -10.5 +0.0 -3.0
Line/SPDIF MIC Bass/Treble MAX MIN/Cushion
Level (dB) ALC/Limiter Threshold (dB)
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CRD42L51

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 lay ou t de sign. Line, MIC and S/PDIF sources are accomodated, and a microcontroller automatically configures the board and the CODEC’s internal registers for straightforward opera­tion.
The CRD42L51 schematic-set has been partitioned into four pages and is shown in Figures 2 through 5.

3.1 Power (U2)

Power is supplied to the board through a single AAA battery. A DC-DC Converter boosts the battery’s volt­age to 3.3 V which is then regulated down to 1.8 V. The CS42L51 is powered fro m 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.

3.2 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.

3.3 CS42L51 Audio CODEC (U1)

A complete description of the CS42L51 (Figure 2 on page 9) is included in the CS42L51 product d ata sheet. 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 Section 2 for a description of each functional mode and the associated configuration setting for the CS42L51.

3.4 CS8416 Digital Audio Receiver (U4)

A complete description of the CS8416 receiver (Figure 3 on page 10) and a discussion of the digital audio 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 mi­crocontroller will automatically switch the system master clock to the oscillator for uninterrupted operation of the Line or MIC input.

3.5 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 de termined ba sed on user input an d system status.

3.6 Analog Input

An 1/8” jack supplies the line-level analog inputs through an AC-coupled passive filter. Voltage dividers be­fore 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 ne eded, 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.

3.7 Analog Outputs

An 1/8” jack outputs the signal from the CS42L51’s ground-centered headphone amplifier. The load stabi­lizer circuitry made up of a resistor/capacitor pair allow the amplifier to drive headphone in addition to line­level loads.
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3.8 Switch & Pushbutton

The POWER switch engages the AAA battery when switched to the ON position. Power is applied to the board and the microcontroller initializes. T he SELECT push button switches allow the user to navig ate back and forth between the FUNCTION options. When both SELECT buttons are pushed simultaneously, the state of the function that receives focus (indicated by a blinking LED) is toggled. The ADJUST buttons allow the user to apply gain, attenuation and move the threshold levels of the ALC and Limiter (the level of each is shown in the Level Meter LED’s). When both ADJUST buttons are pushed simultaneously, the state of the CS42L51’s internal beep generator is toggled.

3.9 LEDs

The FUNCTION LEDs provide a visual indication of which functions are presently ON (constant illumination) or OFF (no illumination) and which has received focus (periodic illumination). The Level Meter LEDs provide a visual indication of the Line, MIC, S/PDIF, Bass and Treble volume levels as well as the Limiter and ALC threshold levels (see Section 2 for LED luminosity decode). When the selected function re ceives focus, the Level Meter LEDs are illuminated for a brief moment, reflecting the volume/threshold level, and flash when the adjustment reaches the default level.

3.10 Error Indicators

Low Battery: When the battery voltage level in the AAA battery d rops below approximately 0.96 V, this LED
will illuminate. Operation will continue until the level drops to approximately 0.70 V; but after a power cycle, the DC-DC converter will only start up when the level is at least 1.1 V.
CRD42L51
Receiver Error: If the S/PDIF function is enabled and the CS8416 loses its PLL lock (trigg ered by unpluggin
the cable from the optical connector, OPT1, or turning off the S/PDIF audio source), this LED will illuminate. If the Line or MIC function is presently enabled, the CRD will automatically switch from the CS8416’s master clock to the on-board oscillator and configure the CS42L51 accordingly for uninterrupted operation of the Line or MIC input.

3.11 Layout

The CS42L51 requires only a minimal set of components to achieve specified performance results. Its inte­grated ground-centered amplifie r eliminates the need for bulky DC-blocking capacitors and only requires two tiny ceramic capacitors for the charge pump. Additional components include load-stabilization circuitry and power supply decoupling. See the CS42L51 data sheet for further details.
Figure 1 on page 8 provides an overview of the connections to the CS42L5 1. Figure 6 on page 13 and Fig­ure 7 on page 14 show the component placement. Figure 8 on page 15 shows the top layout; Figure 9 on page 16 and Figure 10 on page 17 show the inner layers, and Figure 11 on page 18 shows the bottom lay-
out. The decoupling capacitors are located as close to the CS42L51 as possible. Extensive use of ground plane fill in the reference design yields large reductions in radiated noise.
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