MSK0004 datasheet(3/5 Pages) MSK

3 / 5 page

APPLICATION NOTES

Rev. - 8/02

HEAT SINKING

To determine if a heat sink is necessary for your appli-

cation and if so, what type, refer to the thermal model

and governing equation below.

Thermal Model:

Governing Equation:

TJ = PD X (RθJC + RθCS + RθSA) + TA

Where

= Junction Temperature

= Total Power Dissipation

RθJC = Junction to Case Thermal Resistance

RθCS = Case to Heat Sink Thermal Resistance

RθSA = Heat Sink to Ambient Thermal Resistance

= Case Temperature

= Ambient Temperature

= Sink Temperature

Example:

The example demonstrates a worst case analysis for

the op-amp output stage. This occurs when the output

voltage is 1/2 the power supply voltage. Under this con-

dition, maximum power transfer occurs and the output

is under maximum stress.

Conditions:

VCC=±40VDC

VO=±20Vp Sine Wave, Freq.=1KHz

RL=1KΩ

For a worst case analysis we treat the ±20Vp sine wave

as an 8 VDC output voltage.

1.) Find driver power dissipation

PD=(VCC-VO) (VO/RL)

=(40V-20V) (20V/1KΩ)

=400mW

2.) For conservative design, set TJ =+125°C.

3.) For this example, worst case TA =+100°C.

4.) RθJC = 16°C/W.

5.) RθCS=0.15°C/W for most thermal greases.

6.) Rearrange governing equation to solve for RθSA:

RθSA= ((TJ - TA) / PD) - (RθJC) - (RθCS)

= (125°C - 100°C)/0.4W - 16°C/W - 0.15°C/W

=62.5 - 16.15

=46.4°C/W

The heat sink in this example must have a thermal

resistance of no more than 46.4°C/W to maintain a junc-

tion temperature of less than +125°C.

TYPICAL APPLICATION CIRCUIT

REPLACING THE LH0004

The MSK 0004 is not an exact copy of the LM0004

but it is only slightly different. The MSK 0004 is inter-

nally compensated and is lower cost. Pins 1,5,6,7 and

10 are not connected internally in the MSK0004.

POWER SUPPLY BYPASSING

Both the negative and positive power supplies must

be effectively decoupled with a high and low frequency

bypass circuit to avoid power supply induced oscillation.

An effective deecoupling scheme consists of a 0.1

microfarad ceramic capacitor in parallel with a 4.7 mi-

crofarad tantalum capacitor from each power supply pin

to ground.

MSK0004 Datasheet(PDF) 3 Page - M.S. Kennedy Corporation

MSK0004 Datasheet(HTML) 3 Page - M.S. Kennedy Corporation

Html Pages

1 2 3 4 5

Datasheet Download

Link URL