APPLICATION NOTES

POWER SUPPLIES:

For the MSK 186 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 amplifiers as possible.

COMPENSATION:

For normal operation output compensation is not typically

required. However, if the MSK 186 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 for each ampli-

fier will provide stability. If driving large capacitive or inductive

loads, a snubber network will also enhance stability. Typically

3

Ω to 10Ω in series with 0.01µF is acceptable.

CURRENT LIMIT:

The MSK 186 offers accurate, user-selectable current limit.

Unlike typical designs that use a power resistor in series with

the output to sense load, the MSK 186 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

tion to select proper resistor value:

75,000

A low level control signal (0-633µA) can also be used to con-

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

the output current to it's maximum, typically 10A.

The amplifiers are equipped with thermal protection circuitry

that protects each 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

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 on page 5, safe operating

current decreases with an increase in temperature as well as an

increase 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:

For the MSK 186 this pin actually has a dual function. First,

when the pin is forced low, the output stage is disabled. Sec-

ond, 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

VR

pin. In noisy applications, a small value capacitor between

the E/S pin and VR may be required.

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

greater than 0.8V above VR. To once again enable the device,

the E/S pin must be brought at least 2.4 volts above VR or be

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 VR. Once shutdown has occurred this voltage will drop

to approximately 350mV above VR.

ENABLE/STATUS PIN:

-7.5K

Ω

and the E/S pin are referred. VR simply provides a reference

point accessible to the user that can be set to V-, ground, or

any reference of the user's choice. VR cannot be set below the

VR must be set at V-.

VR PIN

PRELIMINARY

Rev. B 11/06