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AS1324

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

Higher value, low cost ceramic capacitors are available in very small case sizes, and their high ripple current, high volt-

age rating, and low ESR make them ideal for switching regulator applications. Because the AS1324 control loop is not

dependant on the output capacitor ESR for stable operation, ceramic capacitors can be used to achieve very low out-

put ripple and accommodate small circuit size.

At light loads, the converter operates in powersave mode and the output voltage ripple is in direct relation to the output

capacitor and inductor value used. Larger output capacitor and inductor values minimize the voltage ripple in power-

save mode and tighten DC output accuracy in powersave mode.

Input Capacitor Selection

age transients while minimizing the interference with other circuits caused by high input voltage spikes, a low ESR

input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given as:

for design because even significant deviations only provide negligible affects.

The input capacitor can be increased without any limit for better input voltage filtering. Take care when using small

ceramic input capacitors. When a small ceramic capacitor is used at the input, and the power is being supplied through

pin. This ringing can then couple to the output and be mistaken as loop instability, or could even damage the part by

exceeding the maximum ratings.

Ceramic Input and Output Capacitors

These dielectrics have the best temperature and voltage characteristics for a given value and size. Y5V and Z5U

dielectric capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequen-

cies and therefore should not be used.

Because ceramic capacitors lose a lot of their initial capacitance at their maximum rated voltage, it is recommended

that either a higher input capacity or a capacitance with a higher rated voltage is used.

Feedback Resistor Selection

cuitry allows for remote voltage sensing and adjustment.

Table 6. Recommended Input and Output Capacitor

Part Number

C

TC Code

Rated Voltage

Dimensions (L/W/T)

Manufacturer

JMK212BJ226MG-T

22µF

X5R

6.3V

0805

Taiyo Yuden

www.t-yuden.com

GRM188R60J106ME47

10µF

X5R

6.3V

0603

Murata

www.murata.com

GRM21BR71A475KA73

4.7µF

X7R

10V

0805

(EQ 6)

I

RMS

I

MAX

V

OUT

V

IN

V

OUT

–

()

×

V

IN

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×

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