10

If the capacitor is increased above 1µF, stability is generally

improved and short pulses of current will cause a smaller

of the amplifier is however degraded as its bandwidth is

decreased. At capacitor values around 10µF, a subtle

interaction with internal DC gain boost circuitry will decrease

the phase margin and may give rise to some overshoot in

the response. The amplifier will remain stable though.

RESPONSE TO HIGH CURRENT SPIKES

This limit level, which is roughly the same for sourcing and

sinking, is included to maintain reliable operation of the part.

It does not necessarily prevent a large temperature rise if the

current is maintained. (In this case the whole chip may be

shut down by the thermal trip to protect functionality.) If the

display occasionally demands current pulses higher than

this limit, the reservoir capacitor will provide the excess and

the amplifier will top the reservoir capacitor back up once the

pulse has stopped. This will happen on the µs time scale in

practical systems and for pulses 2 or 3 times the current

next line is processed.

Power Dissipation

With the high-output drive capability of the EL5224, EL5324,

and EL5424 buffer, it is possible to exceed the 125°C

“absolute-maximum junction temperature” under certain load

current conditions. Therefore, it is important to calculate the

maximum junction temperature for the application to

determine if load conditions need to be modified for the

buffer to remain in the safe operating area.

The maximum power dissipation allowed in a package is

determined according to:

where:

•

The maximum power dissipation actually produced by an IC

is the total quiescent supply current times the total power

supply voltage, plus the power in the IC due to the loads, or:

when sourcing, and:

when sinking.

where:

• i = 1 to total number of buffers

package 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

device's power derating curves.

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

are connected to ground, two 0.1µF ceramic capacitors

4.7µF tantalum capacitor should then be connected from

used for multiple devices. This same capacitor combination

should be placed at each supply pin to ground if split

must be shorted in the PCB layout.

Important Note: The metal plane used for heat sinking of

the device is electrically connected to the negative

to ground, the thermal pad can be connected to ground.

Otherwise, the thermal pad must be isolated from any

other power planes.

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EL5224, EL5324, EL5424