TL2575HV-33-Q1

TL2575HV-05-Q1

SLVSAH9 – SEPTEMBER 2010

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APPLICATION INFORMATION

addition, since most electrolytic capacitors have decreasing capacitances and increasing ESR as temperature

drops, adding a ceramic or solid tantalum capacitor in parallel increases the stability in cold temperatures.

To extend the capacitor operating lifetime, the capacitor RMS ripple current rating should be:

where

For both loop stability and filtering of ripple voltage, an output capacitor also is required, again in close proximity

to the regulator. For best performance, low-ESR aluminum electrolytics are recommended, although standard

aluminum electrolytics may be adequate for some applications. Based on the following equation:

Output ripple of 50 mV to 150 mV typically can be achieved with capacitor values of 220 mF to 680 mF. Larger

standard electrolytic capacitors may be used. Alternatively, higher-grade capacitors such as high frequency, low

inductance, or low ESR can be used.

•

At cold temperatures, the ESR of the electrolytic capacitors can rise dramatically (typically 3× nominal value

at –25°C). Because solid tantalum capacitors have significantly better ESR specifications at cold

temperatures, they should be used at operating temperature lower than –25°C. As an alternative, tantalums

also can be paralleled to aluminum electrolytics and should contribute 10% to 20% to the total capacitance.

•

susceptible to this occurrence.

•

The capacitor’s ripple current rating of 52 kHz should be at least 50% higher than the peak-to-peak inductor

ripple current.

Catch Diode

As with other external components, the catch diode should be placed close to the output to minimize unwanted

noise. Schottky diodes have fast switching speeds and low forward voltage drops and, thus, offer the best

fast-recovery, or ultra-fast-recovery diode is used in place of a Schottky, it should have a soft recovery (versus

abrupt turn-off characteristics) to avoid the chance of causing instability and EMI. Standard 50-/60-Hz diodes,

such as the 1N4001 or 1N5400 series, are not suitable.

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