MCP652 datasheet(25/62 Pages) MICROCHIP

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DS20002146D-page 25

MCP651/1S/2/3/4/5/9

4.3.0.3

Power Dissipation

Since the output short circuit current (ISC) is specified

at ±100 mA (typical), these op amps are capable of

both delivering and dissipating significant power. Two

common loads, and their impact on the op amp’s power

dissipation, will be discussed.

Figure 4-7 shows a resistive load (RL) with a DC output

voltage (VOUT). VL is RL’s ground point, VSS is usually

ground (0V) and IOUT is the output current. The input

currents are assumed to be negligible.

FIGURE 4-7:

Diagram for Resistive Load

Power Calculations.

The DC currents are:

EQUATION 4-1:

The DC op amp power is:

EQUATION 4-2:

The maximum op amp power, for resistive loads at DC,

occurs when VOUT is halfway between VDD and VL or

halfway between VSS and VL:

EQUATION 4-3:

Figure 4-7 shows a capacitive load (CL), which is

driven by a sine wave with DC offset. The capacitive

load causes the op amp to output higher currents at

higher frequencies. Because the output rectifies IOUT,

the op amp’s dissipated power increases (even though

the capacitor does not dissipate power).

FIGURE 4-8:

Diagram for Capacitive Load

Power Calculations.

The output voltage is assumed to be:

EQUATION 4-4:

The op amp’s currents are:

EQUATION 4-5:

The op amp’s instantaneous power, average power

and peak power are:

EQUATION 4-6:

The power dissipated in a package depends on the

powers dissipated by each op amp in that package:

MCP65X

VDD

VOUT

IDD

ISS

IOUT

VSS

OUT

–

--------------------------

max 0 I

OUT





–

min 0 I

OUT





Where:

IQ = Quiescent supply current for one

op amp (mA/amplifier)

VOUT = A DC value (V)

DD VDD

OUT

–

 I

SS VSS

OUT

–



max P



DD VDD

–



max

–





------------------------------------------------------------------

MCP65X

VDD

VOUT

IDD

ISS

IOUT

VSS

OUT

t



sin

Where:

VDC = DC offset (V)

VAC = Peak output swing (VPK)

 = Radian frequency (2 f) (rad/s)

OUT

-----------------



ACCL

t



cos

max 0 I

OUT





–

min 0 I

OUT





Where:

IQ = Quiescent supply current for one

op amp (mA/amplifier)

DD VDD

OUT

–

 I

SS VSS

OUT

–



ave P



–

 I

AC fCL



------------------------





max P



–

 I

AC fCL



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