Copyright © Cirrus Logic, Inc. 2005
(All Rights Reserved)
http://www.cirrus.com
Reference Design for CS42L51
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 manipula-
tion 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 dem-
onstrates the high dynamic range of the CS42L51’s
Programmable Gain Amplifier (PGA) and MIC pre-
amplifier.
Power is derived from a single AAA battery boosted up
to 3.3 V for the interface an d contro l lo gic, then reg ulat-
ed down to 1. 8 V fo r the CS42 L51’s an alog/d igital core
and headphone supply.
The CRD42L51 highlights the ultra small layout re-
quired for the CS42L51. Required components include
only a few small ceramic capacitors and resistors.
ORDERING INFORMATION
CRD42L51 Reference Design
LED Selection
Indicators Battery Clip
CS42L51
Microcontroller 1/8" Stereo Line
Input Jack
Omni-directional
Microphone
1/8" Stereo
Headphone Jack
Optical
Input Jack
Push Buttons AAA
I²C Control/Reset
Clocks/Data
+3.3 V
12.2880 MHz
Oscillator
+1.8 V
Step Up DC-DC
Converter w/
Linear Reg.
Master Clock
CS8416
DECEMBER '05
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CRD42L51
2DS679RD1
CRD42L51
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
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CRD42L51
1. QUICK-START GUIDE
Pushbutton
Control Key Press Description
SELECT
<
(only) Left/Up Navigation - Shifts the focus between functions. A blinking LED indicates which func-
tion has received focus.
>
(only) Right/Down Navigation - Shifts the focus between functions. A blinking LED indicates which
function has received focus.
< AND >
(simultaneously) 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.
ADJUST
-
(only) Decreases the volume level of the function that is in-focus.
Increases the threshold level of the ALC/Limiter when either is in-focus.
+
(only) Increases the volume level of the function that is in-focus.
Decreases the threshold level of the ALC/Limiter when either is in-focus.
- AND +
(simultaneously) Enables/Disables confirmation/error beeps.
3
45
6
2
1
7
3. Switch the power
switch to the ON po-
sition. (NOTE: 1 AAA
battery, installed on the
back side, is required.)
The Reset Function will
activate. No selections or
adjustments can be
made while Reset is on.
4. Push both SELECT buttons simulta-
neously to turn off the Reset function.
The board will enter Standby for a moment and
then automatically activate the Line function.
5. Use any one of the SELECT buttons to navigate
between and shift the focus to select functions.
To turn selected functions on or off, push both SELECT but-
tons simultaneously. The assocated LED will turn on or off.
6. Use any one of the AD-
JUST buttons to control
the volume/ threshold
level of each Source/Ef-
fects that receives focus.
The Level Meter will briefl
y
display a pre-defined gradien
t
that represents the volume
/
threshold level in dBs. The op-
timal/default level flashes for a
few seconds.
2. Connect the desired inter-
face. Apply up to 2 Vrms to the Line
Input. For smaller signals, enable the
ALC function for automatic level con-
trol (up to +12 dB analog gain). For dig-
ital source, connect optical cable to
S/PDIF Input
1. Begin by connecting 16 Ω
or 32 Ω headphones.
7. Speak into the microphone or activate the exter-
nal S/PDIF or Line pl ayer to begin eval uation.
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2. FUNCTION & LEVEL DETAILS
Function State/LED
Illumination Description
Reset ON CS42L51, CS8416, optical receiver, oscillator held in reset and disabled.
OFF CS42L51, oscillator out of reset. CS8416 and optical receiver controlled by S/PDIF function. The Line function
is enabled automatically.
Standby 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.
Line ON Stereo Line Input selected, unmuted; MIC powered down.
OFF Stereo Line Input muted.
MIC ON Mono MIC selected, powered up, unmuted; Line disabled.
OFF MIC muted.
S/PDIF ON S/PDIF Input selected, unmuted; CS8416 and optical receiver powered up. (Line or MIC mixed with S/PDIF if
enabled.)
OFF S/PDIF Input muted; CS8416 and optical receiver powered down.
Bass 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.
Treble 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.
Limiter ON Limiter enabled, attack rate set to 0x02, release rate set to 0x3D.
OFF Limiter disabled.
ALC ON ALC enabled, attack rate set to 0x02, release rate set to 0x3D.
OFF ALC disabled.
Level Meter
(LED Luminosity)
Level (dB) ALC/Limiter Threshold (dB)
Line/SPDIF MIC Bass/Treble MAX MIN/Cushion
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
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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 re fe re nc e of an ul tr a sm all 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 opera -
tion.
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 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.
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 CS42L5 1 (Figure 2 on page 9) is included in the CS42L51 product data sh eet.
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 ma y 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.
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 Err or occurs. Selectio ns are au tomatically de termined based on user inp ut and syste m
status.
3.6 Analog Input
An 1/8” jack supplies the line-level analog inputs through an AC-c oupled 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 app lies up to +12 dB analog gain, a s needed, using th e 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 stabi-
lizer circuitry made up of a resistor/capacitor pair allow the amplifier to drive headphone in addition to line-
level loads.
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CRD42L51
3.8 Switch & Pushbutton
The POWER switch engages the AAA battery when switched to the ON position. Power is applied to the
board and th e microcon troller initia lizes. The SEL ECT pu shbutton switches allow the u ser 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 deco de). When the selected function receives focu s, the
Level Meter LEDs are illuminated for a brief moment, reflecting the volume/threshold level, and flash when
the adjustment re aches the default level.
3.10 Error Indicators
Low Battery: When the battery voltage level in the AAA battery drops 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.
Receiver Error: If the S/PDIF function is enabled and the CS8416 loses its PLL lock (triggered 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 perfor mance results. Its inte-
grated ground-centered amplifier eliminates the need for bulky DC-blocking capacitors and only requires
two tiny ceramic capacitors for the charge pump. Additional compone nts inc l ud e lo ad- sta b iliz at ion cir cuit ry
and power supply decoupling. See the CS42L51 data sheet for further details.
Figure 1 on pag e 8 provides an over view of the connections to the CS42L5 1. Figure 6 on page 13 and Fig-
ure 7 on page 14 show the component placement. Figure 8 on page 15 shows the top layout; Figure 9 on
page 16 and Fi gure 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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CRD42L51
4. SYSTEM CONNECTIONS & INTERFACE
Connector/
Interface Reference
Designator Input/Output Description
AAA BT1 Input Battery Power Supply.
< SELECT S3 Input Pushbutton for navigating to the left or upwards. On/Off (function enable/dis-
able) control when pushed simultaneously with SEL ECT >.
SELECT > S4 Input Pushbutton for navigating to the right or downwards. On/Off (function
enable/disable) control when pushed simultaneously with < SELECT.
- ADJUST S1 Input Pushbutton for decreasing volume levels and increasing threshold levels.
On/Off (beep enable/disable) control when pushed simultaneously with
ADJUST +.
ADJUST + S2 Input Pushbutton for increasing volume levels and decreasing threshold levels.
On/Off (beep enable/disable) control when pushed simultaneously with
ADJUST +.
Line Input J1 Input 1/8” jack for analog input signal to CS42L51. Up to 2 Vrms signals allowed.
MIC MK1 Input Microphone for analog input signal to CS42L51.
Headphone J2 Output Headphone or Line-level jack for analog outputs.
S/PDIF IN OPT1 Input CS8416 digital audio input via optical cable.
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CRD42L51
CRD42L51 BLOCK DIAGRAM
Figure 1. Block Diagram
LED Selection
Indicators Battery Clip
CS42L51
Microcontroller 1/8" Stereo Line
Input Jack
Omni-directional
Microphone
1/8" Stereo
Headphone Jack
Optical
Input Jack
Push Buttons AAA
I²C Control/Reset
Clocks/Data
+3.3 V
12.2880 MHz
Oscillator
+1.8 V
Step Up DC-DC
Converter w/
Linear Reg.
Master Clock
CS8416
Figure 3 on pag e 10
Figure 4 on page 11
Figure 2 on page 9
Figure 5 on page 12
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CRD42L51
7. REVISION HISTORY
Release Changes
RD1 Initial Release
Contacting Cirrus Logic Support
For all product questions and inquiries contact a Cirrus Logic Sales Representative.
To find the one neare st to you go to www.cirrus.com/corporate/contacts/sales.cfm
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