THERMAL PROTECTION

A thermalprotection circuit has been included that

will disable the device if the junction temperature

reaches 150

°C. When the temperature has fallen

to a safe level the device restarts under the con-

trol of the input and enable signals.

APPLICATION INFORMATION

RECIRCULATION

During recirculationwith the ENALBE input high,

for voltages less than 0.6V and is clamped at a

voltages depending on the characteristics of the

source-drain diode for greater voltages. Although

the device is protected against cross conduction.

POWER DISSIPATION each bridge

In order to achieve the high performance provided

by the L9925 some attention must be paid t en-

sure that it has an adequate PCB area to dissi-

pate the heat. The forst stage of any thermal de-

sign is to calculate the dissipated power in the

application, for this example the half step opera-

tion shown in Fig. 6 is considered.

When an arm of the half bridge is turned on cur-

rent begins to flow in the inductive load until the

2

3

During this time the energy dissipated is due to

2

In the commutation the energy dissipated is:

Where:

≤ 20µs

For this example it is assumed that the energy

dissipated in this part of the cycle takes the same

form as that shown for the rise time:

2

3

QUIESCENT ENERGY

The last contribution of the energy dissipation is

due to the quiescrent supply current and is given

by:

TOTAL ENERGY PER CYCLE

+(2

=

T

T = Period

D99AT435

Figure 6.

L9925

7/9