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MTD492 の電気的特性と機能

MTD492のメーカーはMysonです、この部品の機能は「Coaxial Transceiver Interface」です。


製品の詳細 ( Datasheet PDF )

部品番号 MTD492
部品説明 Coaxial Transceiver Interface
メーカ Myson
ロゴ Myson ロゴ 




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MTD492 Datasheet, MTD492 PDF,ピン配置, 機能
MYSON
TECHNOLOGY
MTD492
Coaxial Transceiver Interface
FEATURES
Compatible with IEEE 802.3 10Base5 (Ethernet) and 10Base2 (Cheapernet).
• Internal AUI squelch circuitry for noise rejection.
• Transmission IDL detection at end of packet and dribble bit rejection window.
• Reception dribble bit rejection window.
• Reception and transmission mode collision detection.
• Extended collision detection to turn off receiving path.
• CD heartbeat externally controllable.
• Advanced low-power, high-performance CMOS technology.
• ESD protection greater than 2000 Volts.
16-pin PDIP and 28-pin PLCC packages.
GENERAL DESCRIPTION
The MTD492 transceiver integrates the coaxial cable interface functions of the Medium Attachment Unit
(MAU) in Ethernet or Cheapernet LAN applications. In an Ethernet 10Base5 network, MTD492 is mounted
on the thick Ethernet coaxial cable and connects to a station through an AUI cable. For Cheapernet
applications, MTD492 is connected to the Cheapernet coaxial cable through a BNC connector and is
usually mounted on the LAN adapter in a station.
BLOCK DIAGRAM
COAX
FXI
GND
125 XMT
10K
VEE
RECV
CDS
TXO
HIGH PASS
EQUALIZATION
LOW PASS
FILTER
LOW PASS
FILTER
COM
-
+
AUI
DRIVER
CARRIER
SENSE
AUI
DRIVER
RX+
RX-
CD+
CD-
TX+
LOW PASS
FILTER
- COLLISION
+
WAVEFORM
SHAPING
+
-
TX-
DC/AC
SQUELCH
10MHz CLK WATCH DOG
VEE
OSC
TIMER 26ms
RR+
1K
RR-
REFERENCE
CIRCUIT
TRANSMIT
STATE
MACHINE
HBE
JABBER RESET XMTSQ
TIMER 0.4sec
RECEIVE
STATE
MACHINE
This datasheet contains new product information. Myson Technology reserves the rights to modify the product specification without notice. No
liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
MTD492 Revision 3.5 01/07/1997
1/8

1 Page





MTD492 pdf, ピン配列
MYSON
TECHNOLOGY
MTD492
RX+,RX- O
TXO
GND
VEE
O
3,6 4,12 Reception Data Output. A balanced differential output drives the
data
recovered from the network to the MCC. These outputs are also open
sources, and pull-down resistors of 510to VEE are required. These
pins are biased at -2V during idle time. When an extended period of
collision condition happens, the receiving path is disabled. Any
interruption of collision will re-enable the receiving path.
15 28 Transmission Output. Should be connected to the coaxial cable via
either one (Cheapernet) or 2 serial isolation diodes (Ethernet).
10 17 Positive Supply Pin(Ground). Should be connected to the COAX
shield.
4,5, 5, 6, 7, Negative Power Supply. -9 Volts. A 0.1µF decoupling capacitor
13 8, 9, 10, must be connected across GND and VEE as close to the device as
11, 20, possible.
21, 22,
23, 24,
25
3.0 FUNCTIONAL DESCRIPTIONS
3.1. Transmission Path
The transmission data is input from TX+/- pins differentially. In general, this differential signal is coupled
through an AUI isolation transformer. In the MAU design, it is preferable that an equivalent 78 Ohm load be
placed across these 2 pins for proper loading for the signal source. Improper load termination may cause
excess undershoot at the end of the packet, which causes the dribble bit to be transmitted erroneously.
The transmission signal is first checked against the on-chip DC/AC squelch condition. If the signal is
greater than the squelch threshold (-175 to -300 mV) and the width is wider than 17 nsec, the squelch is
turned off. The squelch remains off until the DC squelch condition is not met or an end-of-packet IDL is
detected (at the end of the packet, data remains at 1 for longer than 175 nsec). Once IDL is detected,
MTD492 provides a 0.8 usec rejection window that prevents dribble bit transmission at the AUI interface.
When the squelch is off, the transmission path is enabled and data is fed into a waveform shaping circuit
followed by the transmission output buffer. The waveform shaping function controls the output rise/fall time
between 20nsec and 30 nsec, and minimizes the mismatch between the rise/fall time. MTD492 provides a
current source output that should be connected to the coaxial cable through at least one isolation diode.
When data is high, the output current is virtually zero (there is approximately less than 1mA output in this
state to maintain the linearity of the output buffer); when data is low, the output current peaks at around 80
mA. This provides an approximate 2V peak to peak swing on a 25 Ohm load. Due to the nature of
Manchester code, the average output DC current is half of the peak - 40 mA, i.e. 1V DC average on the
cable 25 Ohm load.
3.2. Reception Path
The signal on the coaxial cable is first buffered. The DC average of the signal is extracted by a low pass
filter. When the DC average exceeds the carrier sense threshold (Vcs), the reception data path is turned
on. The signal goes through a high pass filter for equalization of high frequency loss on the cable and then
is compared with its center value. The comparator output is amplified by the AUI driver to provide adequate
driving for the RX+/- output.
The end of the packet is determined by 2 conditions. If the received data is high longer than 175nsec or the
DC average does not meet the carrier sense threshold, the reception data path is turned off. MTD492 then
appends the IDL pulse to the end of the packet. A rejection window of 1 usec that blocks the data reception
path is also turned on.
MTD492 Revision 3.5 01/07/1997
3/8


3Pages


MTD492 電子部品, 半導体
MYSON
TECHNOLOGY
MTD492
5.0 ELECTRICAL CHARACTERISTICS (under operating conditions) (Note 1)
OPERATING CONDITIONS
DC Supply Voltage (VEE)
Operating Temperature
8.55-9.45V
0o to 70oC
Parameter
Recommended Supply Voltage
Supply Current (all VEE pins) Non-transmission
Transmission
Receiver Input Bias Current (RXI)
Transmission Output DC Current (TXO)
Transmission Output AC Current (TXO)
Collision Threshold (Reception Mode)
Carrier Sense Threshold (RXI)
Differential Output Voltage (RX+,CD+)
DC Common Mode Output Voltage (RX+)
DC Common Mode Output Voltage (CD+) (Note 2)
Idle State Differential Offset Voltage(RX+,CD+)
Transmission Squelch Threshold(TX+) (Note 3)
Input Capacitance (RXI)
Shunt Resistance - Non-transmission
Shunt Resistance - Transmission
Symbol
VEE
IEEidle
IEExmt
Irxi
Itdc
Itac
Vcd
Vcs
Vod
Vocrx
Voccd
Vob
Vts
Cx
Rrxi
Rtxo
Min
-8.55
-
-
-2
37
+28
-1.45
-0.38
+500
-1.0
VEE
-
-175
-
100
10
Typ
-9.0
-25
-70
-
41
-
-1.53
-0.45
-
-2.0
VEE
0
-225
1.5
-
-
Max
-9.45
-35
-80
+25
45
Itdc
-1.62
-0.52
+1500
-3.0
VEE
+40
-300
-
-
-
Unit
V
mA
mA
µA
mA
mA
V
V
mV
V
V
mV
mV
pF
k
k
Notes: 1. Testing is done under the testing load defined in Figure 6.
2. During an idle condition, Voc is pulled down to VEE to minimize the power dissipation across the
load resistors connected to CD+pins.
3. Tested under continuous 5MHz waveform that represents the preamble.
6.0 SWITCHING CHARACTERISTICS (under operating conditions) (Note 1)
Parameter
Symbol Min Typ Max Unit
Reception Start-up Delay (RXI to RX+)
Tron
- 2.5 5 bits
Reception Propagation Delay (RXI to RX+)
Trd - 35 50 ns
Differential Output Rise Time (RX+,CD+)
Trr - 4 7 ns
Differential Output Fall Time (RX+,CD+)
Trf - 4 7 ns
Receiver and Cable Total Jitter
Trj
- +2 -
ns
Transmission Start-up Delay
Ttst - 1 2 bits
Transmission Propagation Delay
Ttd - 25 50 ns
Transmission Rise Time (10%-90%) (TXO)
Ttr
20 25 30
ns
Transmission Fall Time (10%-90%) (TXO)
Ttf
20 25 30
ns
Ttr and Trf Mismatch
Ttm - +0.5 +3.0 ns
Transmission Skew(TXO)
Tts
- +0.5 +2
ns
Transmission Turn-on Pulse Width at Vts(TX+) (Note 4) Tton
10 20 40
ns
Transmission Turn-off Delay
Ttoff 130 200 260 ns
Transmission IDL Detection Time (Note 5)
Ttidl 130 170 200 ns
Collision Turn-on Delay
Tcon
-
7 13 bits
Collision Turn-off Delay
Tcoff
-
- 20 bits
MTD492 Revision 3.5 01/07/1997
6/8

6 Page



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共有リンク

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部品番号部品説明メーカ
MTD492

Coaxial Transceiver Interface

Myson
Myson
MTD49x

(MTDxxx) Coaxial Transceiver Interface

Myson
Myson


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