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CS8416 S/PDIF decoder

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Introduction

Circuit
description

Schematics
diagram

Assembling

Component
view

Printed
Circuit Board

Settings

Photos

Parts

Links

End

Updates

Introduction

For transferring of digital audio between components is usually used S/PDIF
(electrical) and TOSLINK (optical) interface for commercial use or AES3 for
professional use. S/PDIF decoder module is intended for converting this
interface to I2S interface, which is standardly used on audio DACs. I already
built S/PDIF decoder with DIR9001 circuit, but in our country is available
CS8416. I had troubles with resetting of this circuit in past, but now I was
succesful and circuit works perfectly. CS8416 in comparison with DIR9001 support
192kHz sample frequency. It has 4 inputs instead of one. In direct comparison
with older circuits CS8413/14 it has lower jitter when we use PDUR=1 settings
(122ps instead 150ps). DIR9001 has jitter about 50ps.

Circuit description

In supply section after bridge rectifier and smoothing capacitor I use
LOW-DROP voltage regulators IC3, IC4 LE33CZ and IC5 LE50CZ. I used separated
voltages 3.3V for analog and digital part. For inputs and outputs I choosed +5V
because I needed them for optical receiver too. I used supply transformer with
9V on secondary winding. We can use more, but regulators will be hot.

CS8416 circuit may work in hardware or software mode. I choosed hardware mode
with R9 resistor connected to the ground. In this mode are functions of this
chip limited and settings of parameters is made with resistors 47k connected to
the ground or VL. It is not necessary connect external microprocessor to this
chip.

Optical receiver is TORX173 from Toshiba and his output goes to the RXP1
input of decoder. Electrical input with impedance 75R is galvanically isolated
with pulse transformer TR1 and connected to the RXP0 input. Inputs RXP2 and RXP3
are wired to the special connectors JP7 and JP8 and is possible connect to them
another S/PDIF sources like USB soundcard with S/PDIF output. Negative terminal
RXN of symmetrical input is connected through C15 to the ground. CS8416 has
bult-in RS485 receiver, that we don't need to use external and we can directly
connect S/PDIF signal with +/- 1V levels or TTL.

On the FILT pin are connected PLL filter components. Their values are from
datasheet and they allow right detection of signal with 32-192kHz sample
frequency. Clocks and other signals are synchronized to S/PDIF input signal.

Circuit CS8416 must be resetted after power-on with external reset circuit. I
choosed circuit IC2 MCP130T-475I/TT with internal pull-up resistor, because it
is not part of IC1. Circuit IC2 works that, that after power-on holds RESET
signal on the ground until voltage is not above 4.75 volts. After that it still
holds them for about 350ms. Next signal goes to the logical one thanks to
internal pull-up resistor. When voltage goes down under threshold value, that
reset circuit drops RESET signal down.

Output signals GND, SCK, LRCK, BCK, DATA and +5V goes to six pin connector,
which is dedicated for connection of DAC. POWER LED signaling presence of power
voltage. ERROR LED lights when S/PDIF signal is not present or there are
detected error. In difference to DIR9001 decoder lights when S/PDIF signal is
right detected, but sound is not played. For _AUDIO LED was not space on the
board. Next circuit includes few blocking capacitors and many setting jumpers
with resistors which are described later.

Schematics diagram

schematics 1.1
in Eagle 5

schematics
1.0 in Eagle 5

schematics 1.0
in PNG

Assembling

We must place components on board from smaller to bigger. We can begin with
IC1. I soldered two end pins for good fixing of circuit on the right place. I
applied fluid flux on all pins for easier soldering. Next I solder all pins with
soldering iron and pipe tin. Some of pins can be shorted together. I used solder
wick for superfluous tin. I checked visually PCB with bright lamp. Next I
continued with placing of SMD resistors, capacitors, transistor and IC2. Next I
continued from upper side with wire-wraps and all other components. When we
doesn't need optical input, we doesn't place OX1, C12 and L1. When we don't want
electrical input, we don't place X1, R1 and TR1.

Component view

Printed circuit board

Printed circuit board is designed with only one side and two wire
connections. It allows to create him in amateur conditions. Dimension of PCB,
connectors and holes are identical to DIR9001 decoder, that we can replace one
with another. PCB is a little complicated, but I had not troubles with
assembling. Signal and power trails was designed with emphasis on low
interference and influence specially on analog part which is important for low
jitter.

PCB 1.1
in PDF

PCB 1.1
in Eagle5

PCB
1.0 in PNG

PCB 1.0
in PDF

PCB 1.0 in
Eagle5

Settings

Jumpers JP1 (RXSEL0) and JP2 (RXSEL1) are designated for choose of one input
from the four RXP0-RXP3 inputs. Output data format is selected with jumpers
JP3 SFSEL0 and JP4 SFSEL1. It is necessary to choose same format that supports
our DAC. RMCK frequency or system clock (SCK) we select with jumper JP5 to same
value that is supported by our DAC. If DAC doesn't use this signal we can
select any of them. PDUR (Phase Detector Update Rate) we select with JP6.
Circuit CS8416 has built-in pull-down resistor on this pin, that we short jumper
only for PDUR=1. This setting is suitable for sample frequency to 96kHz because
it guarantee lower jitter. It is not supported for 192kHz sample frequency. When
we want to use this frequency, we must pull out jumper. Detailed description and
tests are in linked application note.

Settings table

Digital input selection RXP0-RXP3

JP2 RXSEL1

JP1 RXSEL0

Used input

0

0

RXP0 - electrical

0

1

RXP1 - optical

1

0

RXP2 - external

1

1

RXP3 - external

Data output format selection

JP4 SFSEL1

JP3 SFSEL0

Data output format

0

0

24-bit, left-justified

0

1

24-bit, I2S

1

0

24-bit, right-justified

1

1

Direct AES3

System clock selection RMCK (SCK)

JP5 RMCK

RMCK frequency

0

256*fs

1

128*fs

Phase Detector Update Rate selection

JP6 PDUR

PDUR

0

Normal

1

Higher

Photos

Parts

Most of components we can get in our local store, for example GM Electronic
or GES Electronic. Circuit CS8416 i bought at MES Praha company and pulse
transformer PE-65612 i bought on EBay.

Partlist

name

value and type

quantity

R1

75R SMD1206

1x

R2

3k SMD0805

1x

R3-R4

1k2 SMD1206

2x

R5-R8

33R SMD1206

4x

R9-R17

47k SMD1206

9x

C1

4700uF/25V elektrolytic

1x

C2-C5

10uF/10V SMD tantal size B

4x

C6-C14

100nF SMD1206 ceramic

9x

C15-C17

10nF SMD1206 ceramic

3x

C18-C19

1nF SMD0805 ceramic

2x

C20

22nF SMD0805 ceramic

1x

L1

47uH axial

1x

L2

ferrite bead

1x

IC1

CS8416 28SOIC

1x

IC2

MCP130T-475I/TT SOT23

1x

IC3-IC4

LE33CZ

2x

IC5

LE50CZ

1x

Q1

transistor BC846BSMD SOT23

1x

LED1

LED green 2mA 3mm

1x

LED2

LED red 2mA 3mm

1x

B1

bridge rectifier 1.5A/100V

1x

OX1

TORX173 toshiba - PCB version 1.0

1x

OX1

TORX177 Toshiba, GP1FAV50RK0F Sharp - pcb version 1.1

1x

SV1

jumper ribbon 6 pins

1x

JP1-JP5

JP2E 3 pin jumper ribbon

5x

JP6-JP8

JP1E 2 pin jumper ribbon

3x

TR1

LL1572 or S22083 or PE-65612 or DA102C

1x

X1

cinch female to PCB TOBU3

1x

X2

frame terminal AK300/2

1x

Links

http://www.cirrus.com/en/pubs/proDatasheet/CS8416_F3.pdf
CS8416 datasheet

http://www.cirrus.com/en/pubs/appNote/AN339REV1.pdf
AN339 CS8416 Delivers Performance Gains Over CS8413/14

http://www.mespraha.cz/ Shop which
has CS8416 in Czech republic

http://cz.farnell.com/ Shop which has
CS8416 and DA102C transformer in Czech republic

End

Board works perfectly on first connection. This S/PDIF decoder we can use
like alternative to DIR9001 based decoder maybe because it will be easily
available in your country or when you want to use 192kHz sample frequency.

Updates

February 26 2011 - Board was succesfully tested on playing of
192kHz/24bit samples, but only with electrical input. Old optical receiver is
slow. Because optical receiver TORX173 was discontinued that PCB was corrected
for use of new receiver TORX177 from TOSHIBA or GP1FAV50RK0F from SHARP. These
new receivers are about two times faster. Every manufacturer have mount pins
on another place, that I designed part with holes for both types. TOSHIBA use
two bigger holes and SHARP use three smaller holes. Board and schematics are
now in version 1.1.

February 26 2011 - There was changed connection of R16 resistor. Now LED
ERROR doesn't light when there is decoded silence. Error reporting is now
identical to DIR9001 based decoder.

February 26 2011 - In to the partlist was added pulse transformer DA102C
from Murata.

March 29 2011 - Update of PCB to version 1.1a because I2S connector was
moved for 0.635mm.

©2010 - 2011 pavouk[at]pavouk.org