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LM53602, LM53603

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SNVSAR0 – NOVEMBER 2016

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Table 4. Recommended Output Capacitors

OUTPUT

VOLTAGE

NOMINAL OUTPUT CAPACITANCE

MINIMUM OUTPUT CAPACITANCE

PART NUMBER

(MANUFACTURER)

RATED

CAPACITANCE

MEASURED

RATED

CAPACITANCE

MEASURED

3.3 V

3 × 22 µF

63 µF

2 × 22 µF

42 µF

C3225X7R1C226M250AC (TDK)

5 V

3 × 22 µF

60 µF

2 × 22 µF

40 µF

C3225X7R1C226M250AC (TDK)

6 V

3 × 22 µF

59 µF

2 × 22 µF

39 µF

C3225X7R1C226M250AC (TDK)

3 × 22 µF

48 µF

2 × 22 µF

32 µF

C3225X7R1C226M250AC (TDK)

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Measured at 14 V and 25°C.

9.2.1.2.3

Input Capacitors

The ceramic input capacitors provide a low impedance source to the regulator in addition to supplying ripple

current and isolating switching noise from other circuits. Table 5 shows the nominal and minimum values of total

input capacitance recommenced for the LM53603. Also shown are the measured values of effective capacitance

for the indicated capacitor. In addition, small high frequency bypass capacitors connected directly between the

VIN and PGND pins are very helpful in reducing noise spikes and aid in reducing conducted EMI. TI

recommends that a small case size 10-nF ceramic capacitor be placed across the input, as close as possible to

the device (see Figure 47). Additional high frequency capacitors can be used to help manage conducted EMI or

voltage spike issues that may be encountered.

Table 5. Recommended Input Capacitors

NOMINAL INPUT CAPACITANCE

MINIMUM INPUT CAPACITANCE

PART NUMBER (MANUFACTURER)

RATED

CAPACITANCE

MEASURED

RATED

CAPACITANCE

MEASURED

3 x 10 µF

22.5 µF

2 × 10 µF

15 µF

CL32B106KBJNNNE (Samsung)

Many times it is desirable to use an electrolytic capacitor on the input, in parallel with the ceramics. This is

especially true if longs leads or traces are used to connect the input supply to the regulator. The moderate ESR

of this capacitor can help damp any ringing on the input supply caused by long power leads. The use of this

additional capacitor also helps with voltage dips caused by input supplies with unusually high impedance.

Most of the input switching current passes through the ceramic input capacitor(s). The approximate RMS value of

this current can be calculated from Equation 4 and should be checked against the manufacturers' maximum

ratings.

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9.2.1.2.4

Inductor

The LM53603 and LM53602 are optimized for a nominal inductance of 2.2 µH for the 5-V and 3.3-V versions.

This gives a ripple current that is approximately 20% to 30% of the full load current of 3 A. For output voltages

greater than 5 V, a proportionally larger inductor can be used. This keeps the ratio of inductor current slope to

internal compensating slope constant.

The most important inductor parameters are saturation current and parasitic resistance. Inductors with a

saturation current of between 5 A and 6 A are appropriate for most applications, when using the LM53603. For

the LM53602, inductors with a saturation current of between 4 A and 5 A are appropriate. Of course the inductor

parasitic resistance should be as low as possible to reduce losses at heavy loads. Table 6 gives a list of several

possible inductors that can be used with the LM53603.