el5223 Intersil Corporation, el5223 Datasheet - Page 13

• Manufacturer Part Number: el5223
• Description: 12mhz 4-, 8-, 10- And 12-channel Rail-to-rail Input-output Buffers
• Manufacturer: Intersil Corporation

when sourcing, and
P
when sinking.
where:
If we set the two P
can solve for R
power dissipation curves provide a convenient way to see if
the device will overheat. The maximum safe power
dissipation can be found graphically, based on the package
type and the ambient temperature. By using the previous
equation, it is a simple matter to see if P
device's power derating curves.
Unused Buffers
It is recommended that any unused buffer have the input tied
to the ground plane.
Driving Capacitive Loads
The EL5123, EL5223, EL5323, and EL5423 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 10kΩ with just 1.5dB of peaking, and 100pF
with 6.4dB of peaking. If less peaking is desired in these
applications, a small series resistor (usually between 5Ω and
50Ω) 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.
DMAX
i = 1 to Total number of buffers
V
I
V
I
SMAX
LOAD
S
OUT
= Total supply voltage
=
i = Maximum output voltage of the application
i = Load current
= Maximum quiescent current per channel
Σi V
[
S
LOAD
×
I
SMAX
DMAX
i to avoid device overheat. The package
+
equations equal to each other, we
(
V
OUT
13
i V
–
S
- )
×
DMAX
EL5123, EL5223, EL5323, EL5423
I
LOAD
exceeds the
i
]
Power Supply Bypassing and Printed Circuit
Board Layout
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 supply pins
must be well bypassed to reduce the risk of oscillation. For
normal single supply operation, where the V
connected to ground, a 0.1µF ceramic capacitor should be
placed from V
should then be connected from V
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 to ground. A 4.7µF tantalum capacitor
S
+ pin to ground. One
S
- pin is
May 3, 2007
FN7176.2