APPLICATION NOTES

POWER SUPPLIES:

The MSK 181 maximum total supply voltage is specified as

60V. However, dual and unbalanced power supply operation is

permissible as long as total supply voltage does not exceed

60V.

POWER SUPPLY BYPASSING:

Power supply terminals must be effectively decoupled with a

high and low frequency bypass circuit to avoid power supply

induced oscillation. An effective decoupling scheme consists

of a 0.1µF ceramic capacitor in parallel with a 10µF tantalum

capacitor for each power supply pin to ground. In addition, it is

recommended that a 0.01µF capacitor be placed between ±Vcc

as close to the MSK 181 as possible.

COMPENSATION:

For normal operation output compensation is not typically

required. However, if the MSK 181 is intended to be driven into

current limit the user may find that an R/C network is required.

A snubber network from the output to ground will provide sta-

bility. If driving large capacitive or inductive loads, a snubber

network will also enhance stability. Typically 3Ω to 10Ω in se-

ries with 0.01µF is acceptable.

CURRENT LIMIT:

The MSK 181 offers accurate, user-selectable current limit.

Unlike typical designs that use a power resistor in series with

the output to sense load, the MSK 181 senses the load indi-

rectly and therefore does not require a resistor to handle the full

output current. Current limit is selected by controlling the input

The easiest method is to use a resistor or potentiometer con-

tion to select proper resistor value:

71,250

A low level control signal (0-330µA) can also be used to con-

trol the current level digitally. If the pin is left open, the current

sets the output current to it's maximum, typically 5A.

The MSK 181 is equipped with thermal protection circuitry

that protects the amplifier from damage caused by excessive

junction temperature. The output is disabled when the junction

temperature reaches approximately 160°C. After the junction

temperature cools to approximately 140°C, the output is again

enabled. The thermal protection may cycle on and off depend-

ing on the output load and signal conditions; this may have an

undesirable effect on the load.

It should be noted that even though this internal protection

circuitry does protect against overload conditions, it does not

take the place of proper heat sinking. For reliable operation,

junction temperature should be limited to 150°C, maximum.

TYPICAL CONNECTION DIAGRAM

PRELIMINARY Rev. C 8/01

3

SAFE OPERATING AREA:

The safe operating area curve is a graphical representation of

the power handling capability of the amplifier under various

conditions. Power dissipation of the device is equal to the prod-

uct of the voltage across the output transistor times the output

current. As can be seen in the curve, safe operating current

decreases with an increase in temperature as well as an in-

crease in the voltage across the output transistor. Therefore,

for maximum amplifier performance it is important to keep case

temperature as low as possible and to keep ±Vcc as close to

the output rail as achievable.

THERMAL PROTECTION:

This pin actually has a dual function. First, when the pin is

forced low, the output stage is disabled. Second, it can be

monitored to determine if the device is in thermal shutdown.

These functions can be used on the same device with either

single or dual supplies. For normal operation, the E/S pin must

be left open or pulled at least 2.4 volts above the negative rail.

In noisy applications, a small value capacitor between the E/S

pin and -Vcc may be required.

ENABLE/STATUS PIN:

To disable the output, the user must pull the E/S pin low, no

greater than 0.8V above -Vcc. To once again enable the de-

vice, the E/S pin must be brought at least 2.4 volts above -Vcc

or disconnected. It should be noted that when the E/S pin is

high, the internal thermal shutdown is still active.

If the E/S pin is used to monitor thermal shutdown, during

normal operation the voltage on the E/S pin is typically 3.5V

above -Vcc. Once shutdown has occurred this voltage will drop

to approximately 350mV above -Vcc.

-13.75KΩ

Rcc=