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| 78Q8392L Low Power Ethernet Coaxial Transceiver February 1998 DESCRIPTION The 78Q8392L Ethernet Transceiver is a low power BiCMOS coax line transmitter/receiver. The device includes analog transmit and receive buffers, a 10 MHz on-board oscillator, timing logic for jabber and heartbeat functions, output drivers and bandgap reference, in addition to a current reference and collision detector. This transceiver provides the interface between the single-ended coaxial cable signals and the Manchester-encoded differential logic signals. Primary functional blocks include the receiver, transmitter, collision detection and jabber timer. This IC may be used in either internal or external MAU environments. The 78Q8392L is available in 16-pin plastic and 28pin PLCC packages. FEATURES * * * * * * Very low power consumption Compliant with Ethernet II, IEEE 802.3 10Base5 and 10Base2 Integrates all transceiver functions except signal and power isolation Innovative design minimizes external components count and power consumption Jabber timer function integrated on chip Externally selectable CED heartbeat allows operation with IEEE 802.3 compatible repeaters Squelch circuitry at all inputs rejects noise Power-on reset and test modes Advanced BiCMOS process * * * CONNECT DIAGRAM 510 5% x4 1 COLLISION SIGNAL TO DTE CD+ VEE VEE 2 CD- VEE CDS 3 DATA TO DTE RX+ TXO RXI 6 RX- GND 4 5 13 16 15 14 10 -9V 7 DATA FROM DTE HBE TX+ RR- 9 78 8 TX- 12 COAX RR+ 11 78Q8392L Low Power Ethernet Coaxial Transceiver FUNCTIONAL DESCRIPTION The 78Q8392L incorporates six basic functions of the Ethernet Transceiver, including receiving, transmitting, collision signaling, collision detection, jabber timing, and the heartbeat function. Refer to Figure 1 for a general system block diagram. RECEIVER FUNCTIONS The receiver senses signals through the RXI input, which minimizes reflections on the transmission media using a low capacitance, high resistance input buffer amplifier. The CDS ground input attaches directly to the input buffer from the coaxial shield to eliminate ground loop noise. In addition to the input buffer, the receiver data path consists of an equalizer, data slicer, receiver squelch circuitry, and an output line driver. The equalizer improves the cable-induced jitter; the data slicer restores equalized received signals to fast transition signals with binary levels to drive the receiver line driver; and the receiver line driver drives the AUI cable through an isolation transformer that connects to the AUI interface. Noise on the transmission media is rejected by the receiver squelch circuitry, which determines valid data via three criteria: Average DC level, pulse width and transition period. The DC voltage level is detected and compared to a set level in the receiver comparator circuit. The pulse width must be greater than 20 ns to pass the narrow pulse filter; the transition timer outputs a true level on the RX Data Valid line provided the time between transitions is less than about 200 ns. As long as a valid RXI signal is detected, the output line driver remains enabled. The transition timer disables the line driver when there are no further transitions on the data medium, and the RX+, RX- pins go to a zero differential voltage state (Figure 3). TRANSMITTER FUNCTIONS The transmitter data path consists of a transmit input buffer, pulse-shaping filter, transmit squelch circuitry and transmit output line driver. The self-biasing transmit input buffer receives data through an isolation transformer and translates the AUI differential analog signal to square pulse suitable for driving the pulse shaping filter. The filter outputs a correctly shaped and bandlimited signal to the transmit output driver, which drives the transmission medium through a high impedance current source. When the transmitter is off, the capacitance of the transmit driver is isolated from the transmission media by an external diode with a low capacitance node. The shield of the transmission media serves as the ground return for the transmitter function. A transmit squelch circuit, which consists of a pulse threshold detector, a pulse width detector, and a pulse duration timer, is used to suppress noise, as well as crosstalk on the AUI cable. The squelch circuitry disables the transmit driver if the signal at TX+ or TX- is smaller than the pulse threshold. Pulse noise is rejected by a pulse width detector that passes only pulses with durations greater than 20 ns. The pulse duration timer disables the transmit driver if no pulses are received for two-bit periods following valid pulses. At the end of a transmission, the pulse duration timer disables the transmitter and triggers the blanking timer, used to block "dribble" bits. COLLISION DETECTION A collision occurs when two or more transmitters simultaneously transmit on the transmission media. A collision is detected by comparing the average DC level of the transmission media to a collision threshold. The received signal at RXI is buffered and sent through a low pass filter, then compared in the collision threshold circuit. If the average DC level exceeds a collision threshold, a 10 MHz signal is output on the CD pins. COLLISION SIGNALING When collision signaling is enabled, a 10 MHz signal is sent from the CD pins through an isolation transformer to the DTE. When the function is disabled, this output goes to a zero differential state. The 10 MHz output from the CD pins indicates a collision on the transmission media, a heartbeat function, or that the transmitter is in jabber mode. 2 78Q8392L Low Power Ethernet Coaxial Transceiver JABBER FUNCTION When valid data on the TX pins detected, the jabber timer is started. If there is valid data for more than 20 ns, a latch is set which disables the transmitter output and enables the 10 MHz output on the CD pins. The latch is reset within 0.5 seconds after the valid data is removed from the transmitter input (TX). This action resets the jabber timer and disables the 10 MHz CD output. The TX inputs must remain inactive during the 0.5 second reset period. HEARTBEAT FUNCTION The 10 MHz CD outputs are enabled for about 1 s at approximately 1.1 s after the end of each transmission. The heartbeat signal tells the DTE that the circuit is functioning. This is implemented by starting the heartbeat timer when the valid data signal indicates the end of a transmission. This function is disabled when HBE pin is tied to VEE. DATA MEDIA RXI RECEIVER INPUT BUFFER EQUALIZER SLICER RX+ RX- CDS NARROW PULSE FILTER RX DATA VALID TRANSITION PERIOD TAMER ENABLE SQUELCH COMPARATOR LP FILTER SQUELSH THRESHOLD COLLISION COMPARATOR TRANSMIT OUTPUT DRIVER TXO COLLISION THRESHOLD PULSE SHAPING FILTER BUFFERED TX SLICER TRANSMIT INPUT BUFFER TX+ TX- TX DISABLE CONTROL LOGIC TX ON JABBER TIMER TX DATA VALID TRANSITION PERIOD TIMER NARROW PULSE FILTER TX > -250 mV TX < -250 mV COMPARATOR BLANKING TIMER END TRANSMIT HEART BEAT TIMER TX DISABLE TRANSITION END TIMER 10 MHz OSC CD ON SIGNAL PRESET DETECT ENABLE CD+ CD- BANDGAP REFERENCE AND CURRENT REFERENCE RR+ RR- FIGURE 1: 78Q8392L General System Block Diagram 3 78Q8392L Low Power Ethernet Coaxial Transceiver PIN DESCRIPTION NAME CD+*/CDTYPE O DESCRIPTION Collision Output. Balanced differential line driver outputs from the collision detect circuitry. The 10 MHz signal from the internal oscillator is transferred to these outputs in the event of collision, excessive transmission (jabber), or during CD Heartbeat condition. These outputs are open emitters; pulldown resistors to VEE are required. When operating into a 78 transmission line, these resistors should be 510. In Cheapernet applications, where the 78 drop cable is not used, higher resistor values (up to 1.5k) may be used to save power. Receive Output. Balanced differential line driver outputs from the Receiver. These outputs also require 510 pulldown resistors. Transmit Input. Balanced differential line receiver inputs to the Transmitter. The common mode voltage for these inputs is determined internally and must not be externally established. Signals meeting Transmitter squelch requirements are waveshaped and output at TXO. Heartbeat Enable. This input enables CD Heartbeat when grounded or left opened, disables it when connected to VEE. External Resistor. A fixed 1 k 1% resistor connected between these pins establishes internal operating currents. Receive Input. Connects directly to the coaxial cable. Signals meeting Receiver squelch requirements are equalized for inter-symbol distortion, amplified, and output at RX+ and RX- pin. Transmit Output. Connects via an isolation diode to the coaxial cable. Collision Detect Sense. Ground sense connection for the collision detect circuit. This pin should be connected separately to the shield to avoid ground drops from altering the receive mode collision threshold. Positive Supply Pin. Negative Supply Pins. These pins should be connected to a large metal frame area on the PC board to handle heat dissipation, and bypassed to the GND pin with a 0.1 F capacitor as close to the package as possible. RX+*/RXTX+*/TX- O I HBE RR+/RRRXI I I I TXO CDS O I GND VEE S S *IEEE names for CD = CI, RX = DI, TX = DO Notes: Pin type: I-input; O-output; S-power supply 4 78Q8392L Low Power Ethernet Coaxial Transceiver ELECTRICAL SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings indicate limits beyond which permanent damage may occur. Continuous operation at these limits is not recommended; operations should be limited to those conditions specified under recommended operating characteristics. PARAMETER Supply Voltage Input Voltage Storage Temperature Soldering (Reflow or Dip) Package power dissipation DC OPERATING CHARACTERISTICS 0C T (ambient) +70C, VEE = -9V 5% PARAMETER IEE1 IEE2 IRXI ITDC ITAC VCD VOD VOC VOB VTS CX RRXI RTXO Supply current out of VEE pin - non-transmitting Supply current out of VEE pin - transmitting Receive input bias current (RXI) Transmit output dc current level (TXO) Transmit output ac current level (TXO) Collision threshold (Receive mode) Differential output voltage (RX, CD) Common mode output voltage (RX, CD) Differential output voltage imbalance (RX, CD) Transmitter squelch threshold (TX) Input capacitance (RXI) Shunt resistance - non-transmitting (RXI) Shunt resistance - transmitting (TXO) See Note 3 See Note 4 See Notes 4 & 5 See Note 9 See Notes 3 & 7 See Note 3, 6 & 7 See Notes 3, 7 & 8 -340 -260 1.2 See Note 3 See Note 4 100 200 150 -2 37 28 -1.58 550 -3.0 -2.5 -1.52 41 CONDITION MIN NOM 6 50 MAX 8 65 +25 45 ITDC -1.404 1200 -2.0 40 -200 UNIT mA mA A mA mA V mV V mV mV pF k k RATING -10V 0 to VEE -65 to 150C 235C for 10 sec 1.0 watts @ 25C 5 78Q8392L Low Power Ethernet Coaxial Transceiver DC OPERATING CHARACTERISTICS (continued) NOTES 1. Currents into device pins are positive, currents out of device pins are negative. If not specified, voltages are referenced to ground. 2. All typicals are for VEE = -9V, Ta = 25C. 3. -8.55V > VEE > -9.45V. 4. The voltage on TXO is -4V < V(TXO) < 0.0V. 5. The AC current measurement is referenced to the DC current level. 6. Operating or idle state. 7. Test load as shown in Figure 2. 8. Device measurement taken in idle state. 9. This threshold can be determined by monitoring the CD output with a DC level in RXI. GND + VOC 510 5% 50 H 1% VEE 78 1% + VOB + VOD = VCOM RX+ or CD+ ETHERNET XCVR RXor CD- 510 5% VEE FIGURE 2: Test Load for CD or RX 6 78Q8392L Low Power Ethernet Coaxial Transceiver AC OPERATING CHARACTERISTICS 0C < T(ambient) < +70C, VEE = 9V 5% PARAMETER tRON Receiver startup delay (RXI to RX) tRd Receiver propagation delay (RXI to RX) tRr Differential outputs rise time (RX , CD) tRf Differential outputs fall time (RX , CD) tRJ Receiver & cable total jitter tTST tTd tTr tTf tTM tTON tTOFF tCON tCOFF fCD tCP tHON tHW tJA tJR tRO Transmitter startup delay (TX to TXO) Transmitter propagation delay (TX to TXO) Transmitter rise time - 10% to 90% (TXO) Transmitter fall time90% to 10% (TXO) tTr and tTf mismatch Transmit turn-on pulse width at VTS (TX) Transmit turn-off pulse width at VTS (TX) Collision turn-on delay Collision turn-off delay Collision frequency (CD) Collision pulse width (CD) CD Heartbeat delay (TX to CD) CD Heartbeat duration (CD) Jabber activation delay (TX to TXO off and CD) Jabber reset unjab time (TX to TXO and CD) Receive Off Pulse Width (RX+ to RX-) 8.5 40 0.6 0.6 20 250 200 500 1.0 1.0 10 CONDITION MIN NOM 400 10 4 4 2 100 35 20 20 25 25 0.5 8 140 20 160 700 MAX 500 50 5 5 4 200 50 30 30 2 30 180 900 2000 11.5 60 1.6 1.5 60 650 UNIT ns ns ns ns ns ns ns ns ns ns ns ns ns ns MHz ns s s ms ms ns 7 78Q8392L Low Power Ethernet Coaxial Transceiver ELECTRICAL SPECIFICATIONS (continued) TRANSMIT SPECIFICATIONS The first bit transmitted from TXO may have data and phase violations. The second through last bit reproduce the TX signal with less than or equal to the specified jitter. There is no logical signal inversion between Tx and TXO output. A low level from TX+ to TX- results in more current flowing from the coaxial cable into the TXO pin. At the end of transmission, when the transmitter changes from the enabled state to the idle state, no spurious pulses are generated, i.e., the transition on TXO proceeds monotonically to zero current. RXI 50% RECEIVE SPECIFICATIONS The first bit sent from RX may have data and phase violations. The second through last bit reproduce the received signal with less than or equal to the specified jitter. There is no logical signal inversion between the RXI input and the RX output. A high level at RXI produces a positive differential voltage from RX+ to RX-. tRON tRd tRO 50% 90% 10% 1st BIT tRf tRr RX FIGURE 3: Receiver Timing TX 50% VTS tTON tTd tTST VTS tTOFF TXO 90% 10% 90% 50% 10% tTF tTr FIGURE 4: Transmitter Timing 8 78Q8392L Low Power Ethernet Coaxial Transceiver INPUT STEP FUNCTION R = 1K RXI 78Q8392L COLLISION DETECTOR CD OUTPUT C = 150 pF RC NETWORK SIMULATES WORST CASE CABLE STEP RESPONSE VCD (MIN) VCD (MAX) RXI tCON CD tCOFF 1 fCD tCP FIGURE 5: Collision Timing TX tHON CD tHW FIGURE 6: Heartbeat Timing TX tJA TXO tJR CD FIGURE 7: Jabber Timing 9 78Q8392L Low Power Ethernet Coaxial Transceiver R = 1K INPUT SIGNAL WITH 30 NSEC RISE AND FALL TIMES C = 36 pF RXI 78Q8392L RECEIVER RX OUTPUT RC NETWORK SIMULATES WORST CASE CABLE JITTER tRJ Input jitter <= 1 nsec RX Output jitter <= 7 nsec Difference <= 6 nsec FIGURE 8: Receive Jitter Timing TRANSMIT OUTPUT (TXO) 25 FIGURE 9: Test Loads TXO 10 78Q8392L Low Power Ethernet Coaxial Transceiver 1:1 39 1% 10 MHz 39 1% VTS TX+ 78Q8392L TX- GND FIGURE 10: Test Circuit for TX Input 11 78Q8392L Low Power Ethernet Coaxial Transceiver PACKAGE PIN DESIGNATIONS (Top View) CAUTION: Use handling procedures necessary for a static sensitive component. CDS RX+ TXO CD+ CD- CD+ CDRX+ VEE VEE RXTX+ TX- 1 2 3 4 5 6 7 8 78Q8392L 16 15 14 13 12 11 10 9 CDS VEE 5 6 7 8 9 10 11 4 3 2 1 28 27 N/C 26 25 24 VEE VEE VEE VEE VEE VEE RR- TXO VEE RXI VEE RRRR+ GND HBE RXI 23 22 21 20 19 18 RR+ VEE VEE VEE VEE VEE 78Q8392L 12 RX- 13 TX+ 14 TX- 15 HBE 16 GND 17 GND 16-Pin DIP 28-Pin PLCC ORDERING INFORMATION PART DESCRIPTION 78Q8392L 78Q8392L 16-Pin Plastic DIP 28-Pin Plastic PLCC ORDER NUMBER 78Q8392L-CP 78Q8392L-28CH PACKAGE MARK 78Q8392L-CP 78Q8392L-28CH No responsibility is assumed by TDK Semiconductor Corporation for use of this product nor for any infringements of patents and trademarks or other rights of third parties resulting from its use. No license is granted under any patents, patent rights or trademarks of TDK Semiconductor Corporation and the company reserves the right to make changes in specifications at any time without notice. Accordingly, the reader is cautioned to verify that you are referencing the most current data sheet before placing orders. To do so, see our web site at http://www.tsc.tdk.com or contact your local TDK Semiconductor representative. TDK Semiconductor Corp., 2642 Michelle Dr., Tustin, CA 92780, (714) 508-8800, FAX (714) 508-8877, http://www.tsc.tdk.com (c)TDK Semiconductor Corporation 02/03/98 - rev.B 12 |
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