TS2576CM5 datasheet(6/7 Pages) TSC

6 / 7 page

TS2576

6-7

2003/12 rev. A

Grounding

To maintain output voltage stability, the power ground

connections must be low-impedance. For the 5-lead

TO-220 and TO-263 style package, both the tab and pin

3 are ground and rather connection may be used.

Thermal Characteristics

The output ripple voltage is due mainly to the inductor

sawtooth ripple current multiplied by the ESR of the

output capacitor. The output ripple voltage of a switching

power supply will contain a sawtooth ripple voltage at the

switcher frequency, typically about 1% of the output

voltages, and may also contain short voltage spokes of

the sawtooth waveform.

Due to the fast switching action, and the parasitic

inductance of the output filter capacitor, there is voltage

spikes presenting at the peaks of the sawtooth

waveform.

Cautions

must

taken

for

stray

capacitance. Wiring inductance, and even the scope

probes used for transients evaluation. To minimize these

voltage spikes, shortening the lead length and PCB

traces is always the first thought. Further more, an

additional small LC filter (30µH & 100µF) (as shown in

Figure 3) will possibly provide a 10X reduction in output

ripple voltage and transients.

Heatsink and Thermal Consideration

Although the TS2576 requires only a small heatsink for

most cases, the following thermal consideration is

important for all operation. With the package thermal

resistances Өja and Өjc , total power dissipation can be

estimated as follows:

PD= (Vin x Iq) + (Vout / Vin) (Iout x Vsat);

When no heatsink is used, the junction temperature rise

can be determined by the following:

∆TJ = PD x Өja

With the ambient temperature, the actual junction

temperature will be:

Tj = ∆Tj + Ta

If the actual operating junction temperature is out of the

safe operating junction temperature (typically 125

oC),

then a heatsink is required. When using a heatsink, the

junction temperature rise will be reduced by the

following :

∆Tj= PD x (Өjc + Ө interface + Ө heatsink );

Also one can see from the above, it is important to

choose an heatsink with adequate size and thermal

resistance, such that to maintain the regulator’s junction

temperature below the maximum operating temperature.

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