 |
Motore di ricerca datesheet componenti elettronici |
|
|
Motore di ricerca datesheet componenti elettronici |
|
ML4664 Scheda tecnica(PDF) 9 Page - Micro Linear Corporation |
|
||||||||||||||||||||||||||||||
ML4664 Scheda tecnica(HTML) 9 Page - Micro Linear Corporation |
|
|
9 / 16 page  9 ML4664/ML4669 SYSTEM DESCRIPTION OPTICAL TRANSMISSION The optical transmit function consists of detecting the presence of data from the TP inputs TPINP and TPINN and driving that data onto the fiber optic LED transmitter. A positive signal on the TPINP lead relative to the TPINN lead will result in no current, hence the fiber optic LED is in a low light condition. When TPINP is more negative than TPINN, the ML4664/ML4669 will sink current into the chip and the fiber optic LED will light up. Before data will be transmitted onto the fiber optic cable it must exceed the squelch requirements. The TP inputs, squelch circuit serves the function of preventing any noise from being transmitted onto the fiber. FIBER OPTIC LED DRIVER The output stage of the transmitter is a current mode switch which develops the output light by sinking current through the LED into the OPOUT pin. Once the current requirement for the LED is determined, the RTSETOP resistor is selected. The following equation is used to select the correct RTSETOP resistor: RTSETOP= 52mA IOUT ´115W (1) The ML4664/ML4669 optical transmitter (in the PLCC package only) is capable of driving up to 100mA maximum which requires resistor RSTETOP to equal 60 W. (This option is only available with the PLCC package) The transmitter enters the idle state when it detects start of idle on TPINP and TPINN input pins. After detecting the start of idle the transmitter switches to a 1MHz output idle signal. The output current is switched through the OPOUT pin during the on cycle and the OPVCC pin during the off cycle. Since the sum of the current in these two pins is constant, OPVCC should be connected as close as possible to the VCC connection for the LED. TP SQUELCH The twisted pair receive data is transformer coupled and low pass filtered before it is fed into the input pins TPINP and TPINN. The input is differential with the common mode voltage internally set. At the start of packet reception from the twisted pair link, no more than 5 bits are received from the twisted pair cable and not transmitted. The first bit sent at the optical transmitter may contain phase violations or invalid data, but all subsequent bits are valid. The TP squelch will reject the following signals on the TPINP and TPINN inputs: 1. All signals that produce a peak magnitude less than 300mV (450mV typical). 2. All continuous sinusoidal signals of amplitude less than 6.2VP–P and frequency less than 2MHz. 3. All single sinusoidal cycles of amplitude less than 6.2VP–P and either polarity, where the frequency is between 2MHz and 15MHz. For a period of 4 BT before and after this single cycle, the signal will conform to (1) above. 4. All sinusoidal cycles gated by a 100ns pulse gate of amplitude less than 6.2VP–P and either polarity, where the sinusoidal frequency is between 2MHz and 30MHz. The off time of the pulse gate on the sinusoidal signal shall be at least 400ns. The first three receive squelch criteria are required to conform to the 10BASE-T standard. The fourth receive squelch criteria exceeds the 10BASE-T requirements and enhances performance. The fourth squelch criteria prevents a false unsquelch caused by cross talk or noise typically found coupling from the phone lines onto the receive twisted pair. After the TP inputs are unsquelched, the detection threshold is lowered to 225mV. Upon passing the TP squelch requirements the receive data passes to the LED Driver. The addition of jitter through the TP to OP path is no more than ±1.5ns. While in the unsquelch state, the TP squelch circuit looks for the start of idle signal at the end of the packet. When start of idle is detected, TP squelch is turned on again. The proper start of idle occurs when the input signal remains above 300mV for 160ns. LINK TEST FUNCTION Transmission — Whenever data is not being delivered to the twisted pair link, the idle signal is applied. The idle signal is a sequence of Link Pulses separated by a 16ms period of silence. The idle signal starts with a period of silence after a packet transmission ends. The link test pulse is a single high pulse with the same amplitude requirements as the data signal. Reception — The transceiver monitors the receive twisted pair input for packet and link pulse activity. If neither a packet nor a link test pulse is received for 50 to 150ms, the transceiver enters the Link Test Fail state and inhibits transmission and reception. Link pulses received with the wrong polarity will be ignored and cause the chip to go into link test fail. When a packet, or five consecutive link test pulses is received from the twisted pair input, the transceiver will exit the Link Test Fail state upon transmit and receive data being idle, and re-enable transmission and reception. |
Codice articolo simile - ML4664 |
|
Descrizione simile - ML4664 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEETIT.COM |
| Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
Italian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
