SP339B Datasheet, PDF (15/23 Pages) Exar Corporation – TRANSCEIVER WITH INTERNAL TERMINATION

REV. 1.0.0
TEST CIRCUITS
SP339B
RS-232/RS-485/RS-422 TRANSCEIVER WITH INTERNAL TERMINATION
FIGURE 5. RS-485/422 RECEIVER TERMINATION RESISTANCE
R_TERM = 2 (V_A – V_B)
I_A – I_B
B
I_B
TERM = V_CC
±2V
R_TERM
Rx
-7V ≤ V_A, V_B ≤ +12V
I_A
A
Termination is enabled in RS-485/422 modes when the TERM pin is held high (V_CC).
FIGURE 6. RS-485/422 DIFFERENTIAL DRIVER OUTPUT VOLTAGE
Tx Input = 0V or V_CC
Tx
V_OD
Tx Enable = V_CC
B
R_L
2
V_CM
R_L
2
A
FIGURE 7. RS-485/422 DIFFERENTIAL DRIVER OUTPUT VOLTAGE OVER COMMON MODE
B
Tx Input = 0V or V_CC
Tx
375Ω
V_OD 60Ω
V_CM
375Ω
Tx Enable = V_CC
A
FIGURE 8. RS-485/422 DRIVER OUTPUT SHORT CIRCUIT CURRENT
B
Tx Input = 0V or V_CC
Tx
Tx Enable = 0V or V_CC
I_OSD
-7V to +12V _V
A
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