Datasheet IL4622E, IL4685E (NVE) - 10

IL4622E / IL4685E Transceiver Operation
Receiver Features The receiver output “R” has tri-state capability via the active low RE input. Driver Features The driver features low propagation delay skew to maximize bit width and minimize EMI. Drivers have tri-state capability via the active-high DE input. True 3.3-volt Bus Operation IL46xx parts are guaranteed to provide the minimum RS-485 / RS-422 differential voltages with a 3.0-volt bus supply, providing true 3.3-volt bus operation with ample design margins. Deterministic Power Up and Brownout Detection IL46xx parts have circuitry to disable the transceiver bus until the driver-side voltage (VDD2B, normally provided by the DC-DC convertor) reaches approximately 2.5 volts on power-up. The transceiver is disabled when the voltage drops below approximately 2.3 volts on power-down. This brownout circuitry ensures the transceiver does not “crash” the bus on power up, power down, or brownout, and eliminates the need for external power supply monitors. In addition, a patented refresh circuit maintains the correct transceiver output state with respect to data input (DC correctness). The refresh circuit ensures the bus outputs will follow the Function Table shown on Page 1 after power up. Hot Plug Operation Deterministic power-up allows IL46xx nodes to “hot plug” into the bus, since the bus driver will be in a high-impedance state until the DC-DC convertor output is enough for the bus driver to operate. Unpowered Nodes The bus driver reverts to high impedance when VDD2 is not present, so that unpowered nodes do not disturb bus operation. Full Fail-Safe The receiver is full fail-safe, meaning it guarantees a forces a logic high state on “R” if the “A” and “B” bus inputs are unconnected, shorted together, or connected to a terminated bus with all the transmitters disabled (terminated/undriven). Thermal Shutdown Internal DC-DC convertor thermal management circuitry gradually limits the output voltage and power output to approximately 250 mW as the junction temperature increases to avoid thermal overload (see Figure 10). In addition, the bus driver is disabled when the driver die temperature exceeds approximately 150 °C, and re-enabled when the die temperature drops below approximately 135°C. The receiver and DC-DC convertor sections continue to operate during thermal shutdown.
Internal Connections
Ground Connections There are two pins for each ground connection: pin 2 is internally connected to pin 8 and pin 15 is internally connected to pin 9. Power Connections The controller-side DC-DC convertor and transceiver functions have separate power connections, VDD1A and VDD1B respectively, which should be connected externally for normal operation. The bus-side DC-DC convertor and transceiver functions have separate power connections (VDD2A and VDD2B) in the IL4685. The bus-side DC-DC convertor and transceiver functions are internally connected in the IL4622. Bus Connections The IL4685 has a half-duplex transceiver generally used with RS-485. Bus input “A” is internally connected to “Y” and “B” connected to “Z.” The IL4622 has full-duplex connections for RS-422 busses. For a half duplex RS-485 network with the IL4622, “A” can be externally connected to “Y,” and “B” connected to “Z.” 10 NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344 (952) 829-9217 www.nve.com YouTube.com/NveCorporation iso-apps@ www.nve.com