IEEE 1394

Circuit Protection of IEEE 1394 port

Design Notes:

Protection Application:
IEEE 1394 uses a low-voltage differential signaling system operating between 1.20V to 2.00V, with a maximum data rate of 400 Mbps (1394a) to 1,600 Mbps (1394b). At these data rates, the capacitance of the suppressor needs to be minimized. The signal lines to be protected against ESD include TPA+, TPA-, TPB+ and TPB-. The 30VDC power bus should be protected against ESD and overcurrent events.
Solution Description:
As shown at the left, a multilayer varistor is used on the power bus for ESD protection, and a PTC is used for resettable overcurrent protection. For the data lines, discrete PulseGuard® suppressors can be used for board layout flexibility, or to reduce part count, a single PulseGuard array can be used.
Companion Solutions:
Other solutions within the Littelfuse portfolio exist in addition to these recommendations. For example, leaded PTCs can be substituted for the SMD versions, or a TVS diode can be substituted for the MLV.
Regulatory Issues:
The IEC 61000-4-2 will be the most appropriate standard that applies for this port. It supplies a test method for verifying that the end product is not susceptible to ESD events.
Unique Features:
Does not apply.
Application Warnings:
It is recommended that only resettable protection devices like PTCs be used on hot-plug ports like 1394.