L6207 datasheet(8/53 Pages) STMICROELECTRONICS

8 / 53 page

AN1762 APPLICATION NOTE

8/53

Figure 7. Typical Application and Layout suggestions.

High current GND tracks (i.e. the tracks connected to the sensing resistors) must be connected directly to the

negative terminal of the bulk capacitor. A good quality, high-frequency bypass capacitor is also required (typi-

cally a 100nF÷200nF ceramic would suffice), since electrolytic capacitors show a poor high frequency perfor-

mance. Both bulk electrolytic and high frequency bypass capacitors have to be connected with short tracks to

VSA, VSB and GND. On the L6205, L6206, L6207 GND pins are the Logic GND, since only the quiescent current

flows through them. Logic GND and Power GND should be connected together in a

single point, the bulk ca-

pacitor, to keep noise in the Power GND from affecting Logic GND. Specific care should be paid layouting the

path from the

SENSE pins through the sensing resistors to the negative terminal of the bulk capacitor (Power

Ground). These tracks must be as short as possible in order to minimize parasitic inductances that can cause

dangerous voltage spikes on

SENSE and OUT pins (see the Voltage Ratings and Operating Range section);

for the same reason the capacitors on VSA, VSB and GND should be very close to the GND and supply pins.

Refer to the Sensing Resistors section for information on selecting the sense resistors. Traces that connect to

VSA, VSB, SENSEA, SENSEB, and the four OUT pins must be designed with adequate width, since high currents

are flowing through these traces, and layer changes should be avoided. Should a layer change prove neces-

sary, multiple and large via holes have to be used. A wide GND copper area can be used to improve power

dissipation for the device.

Figure 8 shows two typical situations that must be avoided. An important consideration about the location of the

bulk capacitors is the ability to absorb the inductive energy from the load, without allowing the supply voltage to

exceed the maximum rating. The diode shown in Figure 8 prevents the recirculation current from reaching the

capacitors and will result in a high voltage on the IC pins that can destroy the device. Having a switch or a power

connection that can disconnect the capacitors from the IC, while there is still current in the motor, will also result

in a high voltage transient since there is no capacitance to absorb the recirculation current.

VS = 8 ÷ 52 V

GND

SENSEA

SENSEB

VSA

VSB

VBOOT

OUT1B OUT2B

OUT1A OUT2A

RS1

RS2

L6205, L6206, L6207

Motors or

other loads

Logic

GND

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