DS89C387TMEA National Semiconductor, DS89C387TMEA Datasheet - Page 5

• Manufacturer Part Number: DS89C387TMEA
• Description: RS422/485 Line Driver IC
• Manufacturer: National Semiconductor

Specifications of DS89C387TMEA

• Device Type: Line
• No. Of Drivers: 1
• Driver Case Style: SSOP
• No. Of Pins: 48
• Mounting Type: Surface Mount
• No. Of Driver/receivers: 12/0
• Peak Reflow Compatible (260 C): No
• Supply Voltage: 5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Parameter Measurement Information
Input pulse; f = 1 MHz, 50%, t
Typical Application
* R
Application Information
SKEW
Skew may be thought of in a lot of different ways, the next
few paragraphs should clarify what is represented by “Skew”
in the datasheet and how it is determined. Skew, as used in
this databook, is the absolute value of a mathematical differ-
ence between two propagation delays. This is commonly ac-
cepted throughout the semiconductor industry. However,
there is no standardized method of measuring propagation
delay, from which skew is calculated, of differential line driv-
ers. Elucidating, the voltage level, at which propagation de-
lays are measured, on both input and output waveforms are
T
is optional although highly recommended to reduce reflection.
FIGURE 6. Circuits for Measuring Single-Ended Propagation Delays (See Figure 7 )
r
(Circuit 1)
6 ns, t
f
6 ns
DS012086-9
FIGURE 5. Two-Wire Balanced System, RS-422
FIGURE 4. Differential Rise and Fall Times
(Continued)
5
not always consistant. Therefore, skew calculated in this
datasheet, may not be calculated the same as skew defined
in another. This is important to remember whenever making
a skew comparison.
Skew may be calculated for the DS89C387, from many dif-
ferent propagation delay measurements. They may be clas-
sified into three categories, single-ended, differential, and
complementry. Single-ended skew is calculated from t
and t
is calculated from t
ures 8, 9 ). Complementry skew is calculated from t
t
PLH
measurements (see Figures 10, 11 ).
PLH
measurements (see Figures 6, 7 ). Differential skew
PHLD
DS012086-7
(Circuit 2)
and t
PLHD
DS012086-10
DS012086-8
measurements (see Fig-
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PHL
and
PHL