AM26LS30

9

MOTOROLA ANALOG IC DEVICE DATA

Operating Temperature Range

The maximum ambient operating temperature, listed as

+85

°C, is actually a function of the system use (i.e.,

specifically how many drivers within a package are used) and

at what current levels they are operating. The maximum

power which may be dissipated within the package is

determined by:

P

Dmax +

T

Jmax *

T

A

RqJA

where R

θJA = package thermal resistance which is typically:

67

°C/W for the DIP (PC) package,

120

°C/W for the SOIC (D) package,

TJmax = max. allowable junction temperature (150°C)

TA = ambient air temperature near the IC package.

1) Differential Mode Power Dissipation

For the differential mode, the power dissipated within the

package is calculated from:

PD = [(VCC – VOD)  IO] (each driver) + (VCC  IB)

where:

VCC = the supply voltage

where:

VOD = is taken from Figure 6 for the known

where:

where:

IB = the internal bias current (Figure 7)

As indicated in the equation, the first term (in brackets) must

be calculated and summed for each of the two drivers, while

the last term is common to the entire package. Note that the

term (VCC –VOD) is constant for a given value of IO and does

not vary with VCC. For an application involving the following

conditions:

TA = +85°C, IO = –60 mA (each driver), VCC = 5.25 V, the

suitability of the package types is calculated as follows.

The power dissipated is:

PD = [3.0 V  60 mA  2] + (5.25 V  18 mA)

PD = 454 mW

The junction temperature calculates to:

TJ = 85°C + (0.454 W  67°C/W) = 115°C for the

TJ = 85°C + (0.454 W  120°C/W) = 139°C for the

Since the maximum allowable junction temperature is not

exceeded in any of the above cases, either package can be

used in this application.

2) Single–Ended Mode Power Dissipation

For the single–ended mode, the power dissipated within

the package is calculated from:

PD = (IB+  VCC) + (IB–  VEE) +

[(IO  (VCC – VOH)](each driver)

The above equation assumes IO has the same magnitude

for both output states, and makes use of the fact that the

absolute value of the graphs of Figures 10 and 11 are nearly

identical. IB+ and IB– are obtained from the right half of

Figures 12 and 13, and (VCC – VOH) can be obtained from

Figure 10. Note that the term (VCC – VOH) is constant for a

given value of IO and does not vary with VCC. For an

application involving the following conditions:

TA = +85°C, IO = –60 mA (each driver), VCC = 5.25 V,

VEE = –5.25 V, the suitability of the package types is

calculated as follows.

The power dissipated is:

PD = (24 mA  5.25 V) + (–3.0 mA  –5.25 V) +

PD = 490 mW

The junction temperature calculates to:

TJ = 85°C + (0.490 W  67°C/W) = 118°C for the

TJ = 85°C + (0.490 W  120°C/W) = 144°C for the

Since the maximum allowable junction temperature is not

exceeded in any of the above cases, either package can be

used in this application.