DS90LV047A_03 Datasheet, PDF (7/13 Pages) National Semiconductor (TI) – 3V LVDS Quad CMOS Differential Line Driver

Typical Application (Continued)
1. Open Input Pins. The DS90LV048A is a quad receiver
device, and if an application requires only 1, 2 or 3
receivers, the unused channel(s) inputs should be left
OPEN. Do not tie unused receiver inputs to ground or
any other voltages. The input is biased by internal high
value pull up and pull down resistors to set the output to
a HIGH state. This internal circuitry will guarantee a
HIGH, stable output state for open inputs.
2. Terminated Input. If the DS90LV047A driver is discon-
nected (cable unplugged), or if the DS90LV047A driver
is in a TRI-STATE or power-off condition, the receiver
output will again be in a HIGH state, even with the end of
cable 100Ω termination resistor across the input pins.
The unplugged cable can become a floating antenna
which can pick up noise. If the cable picks up more than
10mV of differential noise, the receiver may see the
noise as a valid signal and switch. To insure that any
noise is seen as common-mode and not differential, a
balanced interconnect should be used. Twisted pair
cable will offer better balance than flat ribbon cable.
3. Shorted Inputs. If a fault condition occurs that shorts
the receiver inputs together, thus resulting in a 0V differ-
ential input voltage, the receiver output will remain in a
HIGH state. Shorted input fail-safe is not supported
across the common-mode range of the device (GND to
2.4V). It is only supported with inputs shorted and no
external common-mode voltage applied.
External lower value pull up and pull down resistors (for a
stronger bias) may be used to boost fail-safe in the presence
of higher noise levels. The pull up and pull down resistors
should be in the 5kΩ to 15kΩ range to minimize loading and
waveform distortion to the driver. The common-mode bias
point should be set to approximately 1.2V (less than 1.75V)
to be compatible with the internal circuitry.
FIGURE 7. Driver Output Levels
10088709
Pin Descriptions
Pin No.
2, 3, 6, 7
10, 11, 14,
15
9, 12, 13,
16
1
Name
Description
D_IN Driver input pin, TTL/CMOS
compatible
D_OUT+ Non-inverting driver output pin,
LVDS levels
D_OUT− Inverting driver output pin, LVDS
levels
EN Driver enable pin: When EN is
low, the driver is disabled. When
EN is high and EN* is low or
open, the driver is enabled. If both
EN and EN* are open circuit, then
the driver is disabled.
Pin No.
8
4
5
Name
Description
EN* Driver enable pin: When EN* is
high, the driver is disabled. When
EN* is low or open and EN is
high, the driver is enabled. If both
EN and EN* are open circuit, then
the driver is disabled.
V_CC Power supply pin, +3.3V ± 0.3V
GND Ground pin
Ordering Information
Operating
Temperature
−40˚C to +85˚C
−40˚C to +85˚C
Package Type/
Number
SOP/M16A
TSSOP/MTC16
Order Number
DS90LV047ATM
DS90LV047ATMTC
7
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