L6219L-S24-R datasheet(6/9 Pages) UTC

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L6219

LINEAR INTEGRATED CIRCUIT

UNISONIC TECHNOLOGIES CO., LTD

6 of 9

www.unisonic.com.tw

QW-R109-005.D



APPLI CAT I ON I N FORM AT I ON (Cont .)

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

×I

LOAD

×V

×Rθ

JT)

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.

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