APPLICATION NOTES

POWER SUPPLIES:

For the MSK 182/183/184/185 maximum total supply volt-

age 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 182 or MSK 183 is intended to

be driven into current limit the user may find that an R/C net-

work is required. A snubber network from the output to ground

for each amplifier will provide stability. If driving large capaci-

tive or inductive loads, a snubber network will also enhance

stability. Typically 3

Ω to 10Ω in series with 0.01µF is accept-

able.

CURRENT LIMIT:

The MSK 182 and MSK 183 offer accurate, user-selectable

current limit. Unlike typical designs that use a power resistor in

series with the output to sense load, the MSK 182 and MSK

183 sense the load indirectly and therefore do not require a

resistor to handle the full output current. Current limit is se-

The easiest method is to use a resistor or potentiometer

equation 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. Such is

the case with the MSK 184 or the MSK 185.

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

Rev. I 3/04

4

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 6, 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 182 and MSK 183 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.

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 device,

the E/S pin must be brought at least 2.4 volts above -Vcc 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 -Vcc. Once shutdown has occurred this voltage will drop

to approximately 350mV above -Vcc. This function is not avail-

able on the MSK 184 or the MSK 185.

ENABLE/STATUS PIN:

-13.75K

Ω

Rcc=

The MSK 185 is a hermetically sealed, hi-reliability, pin simi-

lar replacement for the APEX PA26. The supply voltage input

tion on the MSK 185. Therefore, any external circuitry con-

nected to pins 3,4,9 & 10 will not degrade the performance of

the MSK 185.

The MSK 185 also provides 4-40 isolated mounting studs in

place of the mounting holes of the PA26.

These mounting

studs, which are brazed to the package bottom, offer excellent

heat sink mounting performance while decreasing the potential

amplifier/package damage sometimes experienced with mount-

ing holes.

APEX PA26 REPLACEMENT: