9

FN6104.4

March 15, 2007

Output Drive Capability

The ISL59110 does not have internal short circuit protection

circuitry. If the output is shorted indefinitely, the power

dissipation could easily overheat the die or the current could

eventually compromise metal integrity. Maximum reliability is

maintained if the output current never exceeds ±40mA. This

limit is set by the design of the internal metal interconnect.

Note that in transient applications, the part is robust.

Short circuit protection can be provided externally with a

back match resistor in series with the output placed close as

possible to the output pin. In video applications this would be

a 75

Ω resistor and would provide adequate short circuit

protection to the device. Care should still be taken not to

stress the device with a short at the output.

Power Dissipation

With the high output drive capability of the ISL59110, 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 an application to determine if load conditions

or package types need to be modified to assure operation of

the amplifier in a safe operating area.

The maximum power dissipation allowed in a package is

determined according to Equation 1:

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 load, or:

for sourcing:

for sinking:

Where:

overheat.

Power Supply Bypassing Printed Circuit Board

Layout

As with any modern operational amplifier, a good printed

circuit board layout is necessary for optimum performance.

Lead lengths should be as short as possible. The power

supply pin must be well bypassed to reduce the risk of

oscillation. For normal single supply operation, a single

4.7µF tantalum capacitor in parallel with a 0.1µF ceramic

Printed Circuit Board Layout

For good AC performance, parasitic capacitance should be

kept to a minimum. Use of wire wound resistors should be

avoided because of their additional series inductance. Use

of sockets should also be avoided if possible. Sockets add

parasitic inductance and capacitance that can result in

compromised performance.

PD

MAX

T

JMAX

T

AMAX

–

Θ

JA

---------------------------------------------

=

(EQ. 1)

PD

MAX

V

S

I

SMAX

V

S

V

OUT

–

()

+

×

V

OUT

R

L

----------------

×

=

(EQ. 2)

PD

MAX

V

S

I

SMAX

V

OUT

V

S

–

()

+

×

I

LOAD

×

=

(EQ. 3)

ISL59110