CIRCUIT DESCRIPTION

L6204 is a dual full bridge IC designed to drive

DC motors, stepper motors and other inductive

loads. Each bridge has 4 power DMOS transistor

Ω and the relative protection and

control circuitry. (see fig. 3)

The 4 half bridges can be controlled independently

by means of the 4 inputs IN!, IN2, IN3, IN4 and 2

enable inputs ENABLE1 and ENABLE2.

External connections are provided so that sensing

resistors can be added for constant current chop-

per applications.

LOGIC DRIVE (*)

INPUTS

OUTPUT MOSFETS

EN1=EN2=H

IN1

IN3

IN2

IN4

L

L

H

H

L

H

L

H

Sink 1, Sink 2

Sink 1, Source 2

Source 1, Sink 2

Source 1, Source 2

EN1=EN2=L

X

X

All transistor turned

OFF

L = Low

H = High

X = Don’t care

(*) True table for the two full bridges

CROSS CONDUCTION

Although the device guarantees the absence of

cross-conduction, the presence of the intrinsic di-

odes in the POWER DMOS structure causes the

generation of current spikes on the sensing termi-

nals. This is due to charge-discharge phenomena

in the capacitors C1 & C2 associated with the

drain source junctions (fig. 1). When the output

switches from high to low, a current spike is gen-

erated associated with the capacitor C1. On the

low-to-high transition a spike of the same polarity

is generated by C2, preceded by a spike of the

opposite polarity due to the charging of the input

capacity of the lower POWER DMOS transistor

(see fig. 2).

TRANSISTOR OPERATION

ON STATE

When one of the POWER DMOS transistors is ON

Ω at

a junction temperature of 25

°C.

In this condition the dissipated power is given by :

can provide high currents with low power dissipa-

tion.

OFF STATE

When one of the POWER DMOS transistor is

power dissipation during this period is given by :

TRANSITIONS

Like all MOS power transistors the DMOS

POWER transistors have as intrinsic diode be-

tween their source and drain that can operate as

a fast freewheeling diode in switched mode appli-

cations. During recirculation with the ENABLE in-

put high, the voltage drop across the transistor is

ode voltage it is clamped to its characteristic.

When the ENABLE input is low, the POWER

MOS is OFF and the diode carries all of the recir-

culation current. The power dissipated in the tran-

sitional times in the cycle depends upon the volt-

age and current waveforms in the application.

BOOTSTRAP CAPACITORS

To ensure the correct driving of high side drivers

Figure 2: Current Typical Spikes on the Sensing Pin

Figure 1: Intrinsic Structures in the POWER

MOS Transistors

L6204

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