SLLSFS0 April 2024 THVD4421
PRODUCTION DATA
THVD4421 has 2 termination resistors of nominal 120Ω, one across R1/R2 and another across R3/R4 in RS-485 mode. Both termination resistors are enabled or disabled using pins as described in Table 7-2. Both the termination resistors can be enabled or disabled independent of the state of driver or receiver. Termination is OFF in RS-232 loopback, RS-232 2T2R, RS-485 loopback, unpowered and thermal shutdown modes.
Signal state | Device mode | Function | Comments |
---|---|---|---|
TERM_TX = VIO | Full duplex mode | 120Ω enabled between R1 and R2 | Termination between R1/R2 is disabled by default |
TERM_TX = GND or floating | Full duplex mode | 120Ω disabled between R1 and R2 | |
TERM_RX = VIO | Full duplex mode | 120Ω enabled between R3 and R4 | Termination between R3/R4 is disabled by default |
TERM_RX = GND or floating | Full duplex mode | 120Ω disabled between R3 and R4 | |
TERM_RX = X, TERM_TX = VIO | Half duplex mode | 120Ω enabled between R1 and R2 | In half duplex mode, TERM_RX is don't care and TERM_TX has higher priority |
TERM_RX = X, TERM_TX = GND | Half duplex mode | 120Ω disabled between R1 and R2 |
On-chip 120Ω termination resistor is designed to have minimum variation with temperature and across common mode voltage on bus pins. Also, the termination block offers a resistive load to the bus, and does not alter the magnitude or phase of the bus signals from DC to 20Mbps signaling.