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DA6102

6-Channel High Efficiency PMIC for 2-Cell Systems

Datasheet

Revision 2.1

28-Apr-2017

39 of 82

9.9

Inductors, Output Capacitors, and Input Capacitors

Inductor Selection

More than any other component, selecting an inductor requires a balancing of trade-offs between

efficiency and solution size. However, there are two criteria which must be met for proper converter

operation. First, the inductor for each channel is first selected based on ripple current. A typical

guideline is to design for a peak to peak ripple current equal to 30 % to 50 % of nominal load current.





Iload

fsw

Vin

MIN







Lower inductor values will result in higher ripple content and lower efficiency, with the benefit of

requiring less board area. Once the inductor value is selected, confirm that the worst-case peak

inductor current is below the current limit threshold. Also consider that the Channel 3 inductor

selection will affect its compensation settings and overall loop stability.

The second criterion for inductor selection is current rating. The inductor must have an rms (or

average) current rating higher than the maximum load capability of the channel. More importantly,

the saturation current rating must be greater than the maximum peak current. Use the equation given

earlier for ILpeak to determine the maximum peak current requirement, using maximum load and

maximum input voltage.

Another important selection factor is the DCR of an inductor. DCR typically accounts for a large

percentage of power losses and should be considered carefully. Higher inductance values will

typically have a larger DCR for a given package size.

Output Capacitor Selection

The output capacitor filters the output ripple and provides the instantaneous current during load

transients. Larger capacitance values reduce output ripple and improve load response. The DA6102

is designed to work well with a very wide range of capacitance as indicated in Table 11. Within the

range shown, the required capacitance is determined by the transient and PCB area requirements.

At higher switching frequencies, less capacitance is required to achieve the same performance.

Since the minimum value for each channel is based on loop stability requirements, it is not

recommended to reduce the output capacitance below this value. As mentioned previously, the

Channel 3 output capacitor in combination with the inductor must be within range of the

compensation register FZ23_EFET (0x21).

Input Capacitor Selection

In a buck switching regulator, input current is pulsed via the high side FET with a high slew rate. This

current is the primary source of noise and radiated EMI in a buck switching regulator. Therefore, the

input capacitor is critical to providing a low impedance path for this current. Low ESR ceramic

capacitors must be used, with minimum recommended values given in Table 11. The input capacitor

for each channel must be placed as close as possible between the VINx and PGx pins, preferably

connected without vias. It is also good practice to use multiple values of capacitor, rather than one

large capacitor.

In addition to the input capacitors on each channel, at least one bypass capacitor of at least 10 µF

must also be placed at VBATT.

DA6102 Datasheet(PDF) 39 Page - Dialog Semiconductor

DA6102 Datasheet(HTML) 39 Page - Dialog Semiconductor

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