PAM2301 datasheet(9/13 Pages) DIODES

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PAM2301

Document number: DS36384 Rev. 3 - 2

9 of 13

www.diodes.com

February 2018

PAM2301

Application Information

The basic PAM2301 application circuit is shown on Page 1. External component selection is determined by the load requirement, selecting L first

and then CIN and COUT.

Inductor Selection

For most applications, the value of the inductor will fall in the range of 1μH to 4.7μH. Its value is chosen based on the desired ripple current.

Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher VIN or VOUT also increases the ripple

current as shown in Equation 1. A reasonable starting point for setting ripple current is ΔIL = 320mA (40% of 800mA).

  



















OUT

Equation 1

The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation.

Thus, a 1120mA rated inductor should be enough for most applications (800mA + 320mA). For better efficiency, choose a low DC-resistance

inductor.

CIN and COUT Selection

In continuous mode, the source current of the top MOSFET is a square wave of duty cycle VOUT/VIN. To prevent large voltage transients, a low

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









required

OUT

OMAX

RMS





This formula has a maximum at VIN = 2VOUT, where IRMS =IOUT/2. This simple worst-case condition is commonly used for design because even

significant deviations do not offer much relief. Note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life.

This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. Consult the

manufacturer if there is any question.

The selection of COUT is driven by the required effective series resistance (ESR).

Typically, once the ESR requirement for COUT has been met, the RMS current rating generally far exceeds the IRIPPLE (P-P) requirement. The

output ripple VOUT is determined by:





















ESR

OUT

Where f = operating frequency, COUT = output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is

highest at maximum input voltage since ΔIL increases with input voltage.

Using Ceramic Input and Output Capacitors

Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and

low ESR make them ideal for switching regulator applications. Using ceramic capacitors can achieve very low output ripple and small circuit size.

When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best

temperature and voltage characteristics of all the ceramics for a given value and size.

Setting the Output Voltage

The internal reference is 0.6V (Typical). The output voltage is calculated as below:

The output voltage is given by Table 1.

Table 1: Resistor selection for output voltage setting.

1.2V

100k

1.5V

150k

100k

1.8V

200k

100k

2.5V

380k

120k

3.3V

540k

120k



















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