L6201 datasheet(12/20 Pages) STMICROELECTRONICS

12 / 20 page

Quiescent Energy

The last contribution to the energy dissipation is

due to the quiescent supply current and is given by:

EQUIESCENT = IQUIESCENT

⋅ Vs ⋅ T

Total Energy Per Cycle

ETOT = EOFF/ON + ELD + ECOM +

+ EON/OFF + EQUIESCENT

The Total Power Dissipation PDIS is simply :

PDIS = ETOT/T

Tr = Rise time

TLD = Load drive time

Tf = Fall time

Td = Dead time

T = Period

T = Tr + TLD + Tf + Td

DC Motor Speed Control

Since the I.C. integrates a full H-Bridge in a single

package it is idealy suited for controlling DC mo-

tors. When used for DC motor control it performs

the power stage required for both speed and di-

rection control. The device can be combined with

a current regulator like the L6506 to implement a

transconductance amplifier for speed control, as

shown in figure 17. In this particular configuration

only half of the L6506 is used and the other half

of the device may be used to control a second

motor.

The L6506 senses the voltage across the sense

resistor RS to monitor the motor current: it com-

pares the sensed voltage both to control the

speed and during the brake of the motor.

Between the sense resistor and each sense input

of the L6506 a resistor is recommended; if the

connections between the outputs of the L6506

and the inputs of the L6203 need a long path, a

resistor must be added between each input of the

L6203 and ground.

A snubber network made by the series of R and C

must be foreseen very near to the output pins of

the I.C.; one diode (BYW98) is connected be-

tween each power output pin and ground as well.

The following formulas can be used to calculate

the snubber values:

≅ VS/lp

C = lp/(dV/dt) where:

VS is the maximum Supply Voltage foreseen on

the application;

Ip is the peak of the load current;

dv/dt is the limited rise time of the output voltage

(200V/

µs is generally used).

If the Power Supply Cannot Sink Current, a suit-

able large capacitor must be used and connected

near the supply pin of the L6203. Sometimes a

capacitor at pin 17 of the L6506 let the application

better work. For motor current up to 2A max., the

L6202 can be used in a similar circuit configura-

tion for which a typical Supply Voltage of 24V is

recommended.

Figure 17: Bidirectional DC Motor Control

L6201 - L6202 - L6203

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