SP505AN Datasheet, PDF (26/30 Pages) Sipex Corporation – Multi-Protocol Serial Transceivers

A
C
V_OC
Figure 45. V.28 Driver Open Circuit Voltage
A
3kΩ
V_T
C
6.3.1.4 Generator polarities
The driver's single-ended output A shall be:
a) greater than point C (V_OUT > 0V) when the
signal condition 0 is transmitted for data
circuits, or ON for control circuits; and
b) less than point C (V_OUT < 0V) when the signal
condition 1 is transmitted for data circuits, or
OFF for control circuits.
6.3.3.5 Receiver maximum shunt capacitance
The total effective shunt capacitance shall be
less than 2500pF at point A with respect to
ground. This is measured by applying a 14V_P
signal with 0V offset at 9.6kbps with 50% duty
cycle through a 1.2kΩ resistor. The rise time
measured from -3V to +3V at point A to point C
(t₁) and the fall time measured from +3V to -3V
at point A to point C (t₂) is measured and recorded.
Then replace the receiver with a 3kΩ resistor in
parallel with a 2500pF capacitor and apply
the same signal through the 1.2kΩ resistor.
The new rise time (t₃) is recorded and compared
to t₁ and t₂. The times t₁ and t₂ shall be less than
or equal to t₃.
Figure 46. V.28 Driver Terminated Voltage
A
3kΩ
2500pF Oscilloscope
C
A
1.2kΩ
9600bps, 14.0V_p-p
V_L
Square Wave
C
Figure 48. V.28 Receiver Effective Shunt Capacitance
Figure 47. V.28 Transition Time
SP505/6/7APN/03
SP505, SP506, SP507 Application Note
26
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