LMS1487ECM National Semiconductor, LMS1487ECM Datasheet - Page 11

• Manufacturer Part Number: LMS1487ECM
• Description: RS422/485 5V BUS XCVR 15KV, 1487
• Manufacturer: National Semiconductor

Specifications of LMS1487ECM

• No. Of Drivers: 1
• Driver Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Svhc: No SVHC (15-Dec-2010)
• Operating Temperature Max: 85°C
• Operating Temperature Min: -40°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Information
POWER LINE NOISE FILTERING
A factor to consider in designing power and ground is noise
filtering. A noise filtering circuit is designed to prevent noise
generated by the integrated circuit (IC) as well as noise
entering the IC from other devices. A common filtering
method is to place by-pass capacitors (C
power and ground lines.
Placing a by-pass capacitor (C
the proper location solves many power supply noise prob-
lems. Choosing the correct capacitor value is based upon
the desired noise filtering range. Since capacitors are not
bp
) with the correct value at
FIGURE 11. Placement of by-pass Capacitors, C
bp
) between the
11
ideal, they may act more like inductors or resistors over a
specific frequency range. Thus, many times two by-pass
capacitors may be used to filter a wider bandwidth of noise.
It is highly recommended to place a larger capacitor, such as
10µF, between the power supply pin and ground to filter out
low frequencies and a 0.1µF to filter out high frequencies.
By-pass capacitors must be mounted as close as possible to
the IC to be effective. Longs leads produce higher imped-
ance at higher frequencies due to stray inductance. Thus,
this will reduce the by-pass capacitor’s effectiveness. Sur-
face mounted chip capacitors are the best solution because
they have lower inductance.
20085622
bp
www.national.com