HEAT SINKING

To select the correct heat sink for your application, refer to the

thermal model and governing equation below.

Thermal Model:

APPLICATION NOTES

CURRENT LIMIT

The MSK 106RH has an on-board current limit scheme

designed to limit the output drivers anytime output current

exceeds a predetermined limit. The following formula may

be used to determine the value of the current limit resis-

tance necessary to establish the desired current limit.

Current Limit Connection

3

0.7

___

See "Application Circuits" in this data sheet for additional

information on current limit connections.

POWER SUPPLY BYPASSING

Both the negative and the positive power supplies must be

effectively decoupled with a high and low frequency bypass

circuit to avoid power supply induced oscillation. An effec-

tive decoupling scheme consists of a 0.1 microfarad ceramic

capacitor in parallel with a 4.7 microfarad tantalum capacitor

from each power supply pin to ground.

It is also a good

practice with high power op-amps, such as the MSK 106RH,

to place a 30-50 microfarad capacitor with a low effective

series resistance, in parallel with the other two power supply

decoupling capacitors. This capacitor will eliminate any peak

output voltage clipping which may occur due to poor power

supply load regulation. All power supply decoupling capaci-

tors should be placed as close to the package power supply

pins as possible.

Governing Equation:

Where

= Junction Temperature

= Total Power Dissipation

R

θJC

= Junction to Case Thermal Resistance

R

θCS

= Case to Heat Sink Thermal Resistance

R

θSA

= Heat Sink to Ambient Thermal Resistance

= Case Temperature

= Ambient Temperature

= Sink Temperature

Example:

In our example the amplifier application requires the output to

drive a 10 volt peak sine wave across a 10 ohm load for 1 amp of

output current. For a worst case analysis we will treat the 1 amp

peak output current as a D.C. output current. The power supplies

are ±15 VDC.

1.) Find Power Dissipation

=(3.5 mA) X (30V) + (5V) X (1A)

=0.1W + 6W

=6.1W

4.) R

5.) Rearrange governing equation to solve for R

θSA:

R

= (125°C - 25°C) / 6.1W - (6.0°C/W) - (0.15°C/W)

= 10.2°C/W

The heat sink in this example must have a thermal resistance of

no more than 10.2°C/W to maintain a junction temperature of less

than +125°C.

Rev. D 1/05