L6204D datasheet(8/12 Pages) STMICROELECTRONICS

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L6204

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APPLICATION INFORMATION

RECIRCULATION

During recirculation with the ENABLE input high, the voltage drop across the transistor is RDS(ON). IL for

voltages less than 0.7 V and is clamped at a voltage depending on the characteristics of the source-drain

diode for greater voltages. Although the device is protected against cross conduction, current spikes can

appear on the current sense pin due to charge/discharge phenomena in the intrinsic source drain capac-

itances. In the application this does not cause any problems because the voltage created across the sense

resistor is usually much less than the peak value, although a small RC filter can be added if necessary.

POWER DISSIPATION (each bridge)

In order to achieve the high performance provided by the L6204 some attention must be paid to ensure

that it has an adequate PCB area to dissipate the heat. The first stage of any thermal design is to calculate

the dissipated power in the appl ication, for this example the half step operation shown in figure 7 is con-

sidered.

RISE TIME Tr

When an arm of the half bridge is turned on current begins to flow in the inductive load until the maximum

current IL is reached after a time Tr.

The dissipated energy EOFF/ON is in this case :

EOFF/ON = [RDS(ON) · IL

2 · Tr] · 2/3

Figure 7.

ON TIME TON

During this time the energy dissipated is due to the ON resistance of the transistors EON and the commu-

tation ECOM. As two of the POWER DMOS transistors are ON EON is given by :

EON = IL

2 · RDS(ON) · 2 · TON

In the commutation the energy dissipated is :

ECOM = VS · IL · TCOM · fSWITCH · TON

Where :

TCOM = Commutation Time and it is assumed that ;

TCOM = TTURN-ON = TTURN-OFF = 100 ns

fSWITCH = Chopper frequency

Obsolete

Product(s)

- Obsolete

Product(s)

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