ZXLD1356Q

Document number: DS37077 Rev. 2 - 2

20 of 28

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October 2015

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ZXLD1356Q

Q

A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in series with the supply source impedance and

lowers overall efficiency. This capacitor has to supply the relatively high peak current to the coil and smooth the current ripple on the input

supply.

When the input voltage is close to the output voltage, the input current increases which places more demand on the input capacitor. The

minimum value of 2.2µF may need to be increased to 4.7µF; higher values will improve performance at lower input voltages, especially when the

source impedance is high. The input capacitor should be placed as close as possible to the IC.

For maximum stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric is recommended. Capacitors with Y5V

dielectric are not suitable for decoupling in this application and should NOT be used.

A suitable capacitor would be NACEW100M1006.3x8TR13F (NIC Components).

The following web sites are useful when finding alternatives:

www.murata.com

www.niccomp.com

www.kemet.com

Inductor Selection

Recommended inductor values for the ZXLD1356Q are in the range 68 µH to 220 µH.

Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in

increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range.

(see graphs on Pages 10-16). The inductor should be mounted as close to the device as possible with low resistance connections to the LX and

The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean

output current.

Suitable coils for use with the ZXLD1356Q may be selected from the MSS range manufactured by Coilcraft, or the NPIS range manufactured by

NIC components. The following websites may be useful in finding suitable components.

www.coilcraft.com

www.niccomp.com

www.wuerth-elektronik.de

The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the specified limits over the supply voltage

and load current range.

Figures 3 and 4 (following) can be used to select a recommended inductor based on maintaining the ZXLD1356Q case temperature below

+60°C for the different package types. For detailed performance characteristics for the inductor values 68, 100, 150 and 220µH, see graphs on

Pages 10-16.