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PDF DS89C387 Data sheet ( Hoja de datos )
| Número de pieza | DS89C387 | |
| Descripción | Twelve Channel CMOS Differential Line Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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May 1995
DS89C387
Twelve Channel CMOS Differential Line Driver
General Description
The DS89C387 is a high speed twelve channel CMOS differ-
ential driver that meets the requirements of TIA/EIA-422-B.
The DS89C387 features a low ICC specification of 1.5 mA
maximum, which makes it ideal for battery powered and
power conscious applications. The device replaces three
DS34C87s and offers a PC board space savings up to 30%.
The twelve channel driver is available in a SSOP package.
The device is ideal for wide parallel bus applications.
Each TRI-STATE® enable (EN) allows the driver outputs to
be active or in a HI-impedance off state. Each enable is com-
mon to only two drivers for flexibility and control. The drivers
may be disabled to turn off load current and to save power
when data is not being transmitted.
The driver’s input (DI) is compatible with both TTL and
CMOS signal levels.
Features
n Low power ICC: 1.5 mA maximum
n Meets TIA/EIA-422-B (RS-422)
n Guaranteed AC parameters:
— Maximum driver skew −3 ns
— Maximum transition time −10 ns
n Available in SSOP packaging:
— Requires 30% less PCB space than 3 DS34C87TMs
Connection Diagram
48L SSOP
DS89C387
Functional Diagram
1/6 of package
Truth Table
Enable
EN
L
H
H
Input
DI
X
H
L
DS012086-2
Outputs
DO DO*
ZZ
HL
LH
DS012086-1
Order Number DS89C387TMEA
See NS Package Number MS48A
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
© 1998 National Semiconductor Corporation DS012086
www.national.com
1 page  
Parameter Measurement Information (Continued)
Input pulse; f = 1 MHz, 50%, tr ≤ 6 ns, tf ≤ 6 ns
DS012086-7
FIGURE 4. Differential Rise and Fall Times
Typical Application
* RT is optional although highly recommended to reduce reflection.
FIGURE 5. Two-Wire Balanced System, RS-422
DS012086-8
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
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 tPHL
and tPLH measurements (see Figures 6, 7). Differential skew
is calculated from tPHLD and tPLHD measurements (see Fig-
ures 8, 9). Complementry skew is calculated from tPHL and
tPLH measurements (see Figures 10, 11).
(Circuit 1)
(Circuit 2)
DS012086-9
DS012086-10
FIGURE 6. Circuits for Measuring Single-Ended Propagation Delays (See Figure 7)
5 www.national.com
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| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet DS89C387.PDF ] | |
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