17位LVTTL至GTLP可调节边沿速率通用总线，提供缓冲时钟输出收发器 17-BIT LVTTL-TO-GTLP ADJUSTABLE-EDGE-RATE UNIVERSAL BUS TRANSCEIVER WITH BUFFERED CLOCK OUTPUTS
The SN74GTLPH1616 is a high-drive, 17-bit UBT transceiver that provides LVTTL-to-GTLP and GTLP-to-LVTTL signal-level translation. It allows for transparent, latched, clocked, or clock-enabled modes of data transfer. Additionally, it provides for a copy of CLKAB at GTLP signal levels CLKOUT and conversion of a GTLP clock to LVTTL logic levels CLKIN. The device provides a high-speed interface between cards operating at LVTTL logic levels and a backplane operating at GTLP signal levels. High-speed about three times faster than standard TTL or LVTTL backplane operation is a direct result of GTLP"s reduced output swing <1 V, reduced input threshold levels, improved differential input, OEC circuitry, and -OPC circuitry. Improved GTLP OEC and TI-OPC circuits minimize bus-settling time and have been designed and tested using several backplane models. The high drive allows incident-wave switching in heavily loaded backplanes with equivalent load impedance down to 11 .
GTLP is the Texas Instruments TI derivative of the Gunning Transceiver Logic GTL JEDEC standard JESD 8-3. The ac specification of the SN74GTLPH1616 is given only at the preferred higher noise margin GTLP, but the user has the flexibility of using this device at either GTLV TT = 1.2 V and VREF = 0.8 V or GTLP VTT = 1.5 V and VREF = 1 V signal levels.
Normally, the B port operates at GTLP signal levels. The A-port and control inputs operate at LVTTL logic levels but are 5-V tolerant and are compatible with TTL and 5-V CMOS inputs. VREF is the reference input voltage for the B port.
This device is fully specified for live-insertion applications using Ioff, power-up 3-state, and BIAS VCC. The Ioff circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down. The power-up 3-state circuitry places the outputs in the high-impedance state during power up and power down, which prevents driver conflict. The BIAS VCC circuitry precharges and preconditions the B-port input/output connections, preventing disturbance of active data on the backplane during card insertion or removal, and permits true live-insertion capability.
This GTLP device features TI-OPC circuitry, which actively limits the overshoot caused by improperly terminated backplanes, unevenly distributed cards, or empty slots during low-to-high signal transitions. This improves signal integrity, which allows adequate noise margin to be maintained at higher frequencies.
High-drive GTLP backplane interface devices feature adjustable edge-rate control ERC\\\\. Changing the ERC\ input voltage between GND and VCC adjusts the B-port output rise and fall times.This allows the designer to optimize system data-transfer rate and signal integrity to the backplane load.
Active bus-hold circuitry is provided to hold unused or undriven LVTTL data inputs at a valid logic state. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended.
When VCC is between 0 and 1.5 V, the device is in the high-impedance state during power up or power down. However, to ensure the high-impedance state above 1.5 V, the output-enable OE\\\\ input should be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
