78Q8392L/A03 Low Power Ethernet Coaxial Transceiver November 2008 DESCRIPTION FEATURES The 78Q8392L/A03 Ethernet Transceiver is a Very low power consumption replacement for the SSI/TDK/Teridian Compliant with Ethernet II, IEEE 802.3 78Q8392L/A02 coax line transmitter/receiver. Only a 10Base5 and 10Base2 single resistor value change is required for Integrates all transceiver functions except upgrading an existing 78Q8392L/A02 design to the signal and power isolation 78Q8392L/A03. Innovative design minimizes external The device includes analog transmit and receive component count and power consumption buffers, a 10 MHz on-board oscillator, timing logic for jabber and heartbeat functions, output drivers Jabber timer function integrated on chip and bandgap reference, in addition to a current Externally selectable CED heartbeat allows reference and collision detector. operation with IEEE 802.3 compatible This transceiver provides the interface between the repeaters single-ended coaxial cable signals and the Squelch circuitry at all inputs rejects noise Manchester-encoded differential logic signals. Primary functional blocks include the receiver, Power-on reset and test modes transmitter, collision detection and jabber timer. This Advanced BiCMOS process IC may be used in either internal or external MAU environments. The 78Q8392L/A03 is available in lead-free 16-pin plastic and 28-pin PLCC packages. CONNECT DIAGRAM 510 5% 9V x 4 1 4 CD+ VEE COLLISION 5 VEE SIGNAL TO DTE 2 13 CD VEE 16 CDS 3 15 RX+ TXO 14 RXI DATA TO DTE 10 GND 6 RX 9 HBE 7 TX+ DATA FROM 12 78 RR- COAX DTE 8 TX- 11 RR+ Page: 1 of 14 2008 Teridian Semiconductor Corporation Rev 1.3 78Q8392L/A03 Low Power Ethernet Coaxial Transceiver The filter outputs a correctly shaped and band FUNCTIONAL DESCRIPTION limited signal to the transmit output driver, which The 78Q8392L/A03 incorporates six basic functions drives the transmission medium through a high of the Ethernet Transceiver, including receiving, impedance current source. When the transmitter is transmitting, collision signaling, collision detection, off, the capacitance of the transmit driver is isolated jabber timing, and the heartbeat function. Refer to from the transmission media by an external diode Figure 1 for a general system block diagram. with a low capacitance node. The shield of the transmission media serves as the ground return for RECEIVER FUNCTIONS the transmitter function. The receiver senses signals through the RXI input, A transmit squelch circuit, which consists of a pulse which minimizes reflections on the transmission threshold detector, a pulse width detector, and a media using a low capacitance, high resistance pulse duration timer, is used to suppress noise, as input buffer amplifier. The CDS ground input well as crosstalk on the AUI cable. The squelch attaches directly to the input buffer from the coaxial circuitry disables the transmit driver if the signal at shield to eliminate ground loop noise. TX+ or TX- is smaller than the pulse threshold. In addition to the input buffer, the receiver data path Pulse noise is rejected by a pulse width detector that consists of an equalizer, data slicer, receiver passes only pulses with durations greater than 20 squelch circuitry, and an output line driver. ns. The pulse duration timer disables the transmit driver if no pulses are received for two-bit periods The equalizer improves the cable-induced jitter the following valid pulses. At the end of a transmission, data slicer restores equalized received signals to the pulse duration timer disables the transmitter and fast transition signals with binary levels to drive the triggers the blanking timer, used to block dribble receiver line driver and the receiver line driver bits. drives the AUI cable through an isolation transformer that connects to the AUI interface. COLLISION DETECTION Noise on the transmission media is rejected by the A collision occurs when two or more transmitters receiver squelch circuitry, which determines valid simultaneously transmit on the transmission media. data via three criteria: Average DC level, pulse A collision is detected by comparing the average DC width and transition period. The DC voltage level is level of the transmission media to a collision detected and compared to a set level in the receiver threshold. The received signal at RXI is buffered and comparator circuit. The pulse width must be greater sent through a low pass filter, then compared in the than 20 ns to pass the narrow pulse filter the collision threshold circuit. If the average DC level transition timer outputs a true level on the RX Data exceeds a collision threshold, a 10 MHz signal is Valid line provided the time between transitions is output on the CD pins. less than about 200 ns. As long as a valid RXI signal COLLISION SIGNALING is detected, the output line driver remains enabled. The transition timer disables the line driver when When collision signaling is enabled (HBE pin is high there are no further transitions on the data medium, and the average DC level on RXI exceeds the and the RX+, RX- pins go to a zero differential collision threshold V ), a 10 MHz signal is sent from CD voltage state (Figure 3). the CD pins through an isolation transformer to the DTE. When the function is disabled, this output goes TRANSMITTER FUNCTIONS to a zero differential state. The 10 MHz signal output The transmitter data path consists of a transmit input from the CD pins indicates a collision on the buffer, pulse-shaping filter, transmit squelch transmission media, a heartbeat function, or that the circuitry and transmit output line driver. The transmitter is in jabber mode. self-biasing transmit input buffer receives data through an isolation transformer and translates the AUI differential analog signal to a square pulse suitable for driving the pulse shaping filter. Page: 2 of 14 2008 Teridian Semiconductor Corporation Rev 1.3