IEC 60958-4-4:2016 pdf download – Digital audio interface – Part 4-4: Professional applications – Physical and electrical parameters.
3.1 unit interval UI shortest nominal time interval in the coding scheme Note 1 to entry: There are 1 28 UI in a sample frame. See Annex A. Note 2 to entry: This note applies to the French language only. 3.2 interface jitter deviation in timing of interface data transitions (zero crossings) when measured with respect to an ideal clock 3.3 intrinsic jitter output interface jitter of a device that is either free-running or synchronized to a jitter-free reference 3.4 jitter gain ratio of the amplitude of jitter at the synchronization input of a device to the resultant jitter at the output of the device Note 1 to entry: This definition excludes the effect of intrinsic jitter. Note 2 to entry: The ratio is expressed in decibels. 3.5 frame rate frequency at which frames are transmitted 4 Common features All interfaces shall be subject to the common jitter requirements in accordance with Clause 5. Other parameters shall comply with the transmission type specified. The interface should use the balanced transmission format specified in Annex B. The interface may use the format specified in Annex C or one of the alternative transmission formats to be specified in a future edition (see Annex D). 5 Jitter 5.1 Output interface jitter 5.1 .1 General Jitter at the output of a device shall be measured as the sum of the jitter intrinsic to the device and jitter being passed through from the timing reference of the device. 5.1 .2 Intrinsic jitter The peak value of the intrinsic jitter at the output of the interface, measured at all the transition zero crossings shall be less than 0,025 UI when measured with the intrinsic-jitter measurement filter. The following aspects have to be considered.
B.1 .2 Equalisation Equalization may be used at the receiver. There shall be no equalization before transmission. The frequency range used to qualify the interface electrical parameters is dependent on the maximum data rate supported. The upper frequency is 1 28 times the maximum frame rate (about 6 MHz for 48 kHz). B.1 .3 Cable The interconnecting cable shall be balanced with a nominal characteristic impedance of 1 1 0 Ω at frequencies from 1 00 kHz to 1 28 times the maximum frame rate. The cable shall be one of the following types: • shielded (screened) cable; • unshielded (unscreened) twisted pair (UTP) structured wiring (Category 5 or better, see ISO/IEC 1 1 801 ); see item e) below. • shielded (screened) twisted pair (STP) structured wiring (see ISO/IEC 1 1 801 ). The same cable type shall be used throughout any single interface connection, including patch leads. The following additional considerations have to be taken into account.
a) Holding closer tolerances for the characteristic impedance of the cable, and for the driving and terminating impedances, can increase the cable lengths for reliable transmission and for higher data rates. b) Closer tolerances for the balance of the driving impedance, the terminating impedance, and for the cable itself can reduce both electromagnetic susceptibility and emissions. c) Using cable having lower loss at higher frequencies can improve the reliability of transmission for greater distances and higher data rates. d) Care should be taken concerning the design of the interface to provide adequate balance on the twisted pair within the Category 5 cable. Using RJ45 connectors, conventionally wired, current practice favours the use of pins 4 and 5 for signals using this balanced interface (separating them from ATM signals on the same cable, for example). Pins 3 and 6 are the preferred second pair. For full protection, the interface may have to withstand power voltages specified to support network equipment, and the use of transformers and blocking capacitors on the balanced interface is strongly recommended. e) The UTP cable has been shown to offer transmission up to 400 m overall unequalised, or 800 m equalised, at 48 kHz frame rate. (See AES preprint 3783.) B.2 Line driver characteristics B.2.1 Output impedance The line driver shall have a balanced output with an internal impedance of 1 1 0 Ω with a tolerance of 20 %, at frequencies from 0,1 MHz to 1 28 times the maximum frame rate when measured at the output terminals. B.2.2 Signal amplitude The signal amplitude shall lie between 2 V and 7 V peak-to-peak, when measured across a 1 1 0 Ω resistor connected to the output terminals, without any interconnecting cable present. NOTE A typical value is 4 V ± 1 0 %.