EL5421C Elantec Semiconductor, Inc. (acquired by Intersil), EL5421C Datasheet - Page 12

• Manufacturer Part Number: EL5421C
• Description: Quad 12MHz Rail-to-rail I/o Buffer
• Manufacturer: Elantec Semiconductor, Inc. (acquired by Intersil)

EL5421C
Quad 12MHz Rail-to-Rail Input-Output Buffer
Driving Capacitive Loads
The EL5421C can drive a wide range of capacitive
loads. As load capacitance increases, however, the -3dB
bandwidth of the device will decrease and the peaking
increase. The buffers drive 10pF loads in parallel with
10 kΩ with just 1.5dB of peaking, and 100pF with 6.4dB
of peaking. If less peaking is desired in these applica-
tions, a small series resistor (usually between 5 Ω and 50
Ω) can be placed in series with the output. However, this
will obviously reduce the gain slightly. Another method
of reducing peaking is to add a "snubber" circuit at the
output. A snubber is a shunt load consisting of a resistor
in series with a capacitor. Values of 150Ω and 10nF are
typical. The advantage of a snubber is that it does not
draw any DC load current or reduce the gain
12
Power Supply Bypassing and Printed Circuit
Board Layout
The EL5421C can provide gain at high frequency. As
with any high-frequency device, good printed circuit
board layout is necessary for optimum performance.
Ground plane construction is highly recommended, lead
lengths should be as short as possible and the power sup-
ply pins must be well bypassed to reduce the risk of
oscillation. For normal single supply operation, where
the V
capacitor should be placed from V
4.7µF tantalum capacitor should then be connected in
parallel, placed in the region of the buffer. One 4.7µF
capacitor may be used for multiple devices. This same
capacitor combination should be placed at each supply
pin to ground if split supplies are to be used.
S
- pin is connected to ground, a 0.1 µF ceramic
S
+ to pin to V
S
- pin. A