L6219DS-T View Datasheet(PDF) - Allegro MicroSystems

Part Name

Description

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L6219DS-T

Dual Full-Bridge PWM Motor Driver

Allegro MicroSystems 

L6219DS

Dual Full-Bridge PWM Motor Driver

Application Information

Current Sensing

To minimize current sensing inaccuracies caused by ground trace

IR drops, each current-sensing resistor should have a separate

return to the ground terminal of the device. For low-value sense

resistors, the IR drops in the PCB can be significant and should be

taken into account. The use of sockets should be avoided as their

contact resistance can cause variations in the effective value of RS.

Generally, larger values of RS reduce the aforementioned effects

but can result in excessive heating and power loss in the sense

resistor. The selected value of RS should not cause the absolute

maximum voltage rating of 1.5 V, for the SENSE terminal, to be

exceeded. The recommended value of RS is in the range of:

RS = 0.75 / ITRIP(max) ± 50% .

If desired, the reference input voltage can be filtered by placing

a capacitor from REFIN to ground. The ground return for this

capacitor as well as the bottom of any resistor divider used should

be independent of the high-current power-ground trace to avoid

changes in REFIN due to IR drops.

Thermal Considerations

For reliable operation, it is recommended that the maximum

junction temperature be kept below 110°C to 125°C. The junction

temperature can be measured best by attaching a thermocouple

to the power pins (6, 7, 18 and 19) of the device and measuring

the pin temperature, TTAB. The junction temperature can then be

approximated by using the formula:

TJ = TTAB + (2 × ILOAD × VF × RθJT) ,

where VF can be chosen from the electrical specification table

for the given level of ILOAD. The value for RθJT is approximately

6°C/W.

The power dissipation can be improved 20% to 30% by adding a

section of printed circuit board copper (typically 6 to 18 square

centimeters) connected to the power pins of the device.

The thermal performance in applications that run at high load

currents, high duty cycles, or both can be improved by adding

external diodes from each output to ground in parallel with the

internal diodes. Fast-recovery (≤200 ns) diodes should be used to

minimize switching losses.

Load Supply Terminal

The load supply terminal, VBB, should be decoupled with an

electrolytic capacitor (≥47μF is recommended), placed as close

to the device as is physically practical. To minimize the effect of

system ground IR drops on the logic and reference input signals,

the system ground should have a low-resistance return to the load

supply voltage.

Fixed Off-Time Selection

With increasing values of tOFF, switching losses decrease, low-

level load current regulation improves, EMI reduces, PWM

frequency decreases, and ripple current increases. The value of

tOFF can be chosen for optimization of these parameters. For

applications where audible noise is a concern, typical values of

tOFF should be chosen in the range of 15 to 35 μs.

Allegro MicroSystems, Inc.

7

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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