ZXLD1370EST16TC datasheet(21/36 Pages) DIODES

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ZXLD1370

Document number: DS32165 Rev. 4 - 2

21 of 36

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March 2011

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Applications Information (Continued)

Assuming that cumulatively the rise time and fall time can account for a maximum of 10% of the period, the maximum

frequency allowed in this condition is:

tPERIOD = 20*dt

f = 1/ tPERIOD = 515kHz

This frequency is within the recommended frequency range the device can handle, therefore the ZXMN6A09K is

recommended to be used with the ZXLD1370 for frequencies from 300kHz to 500kHz).

The recommended total gate charge for the MOSFET used in conjunction with the ZXLD1370 is less than 30nC.

Junction temperature estimation

Finally, the ZXLD1370 junction temperature can be estimated using the following equations:

Total supply current of ZXLD1370:

IQTOT ≈ IQ + f • QG

Where IQ = total quiescent current IQ-IN + IQ-AUX

Power consumed by ZXLD1370

PIC = VIN • (IQ + f • Qg)

Or in case of separate voltage supply, with VAUX < 15V

PIC = VIN • IQ-IN + Vaux • (IQ-AUX + f • Qg)

TJ =

TA + PIC • θJA =

TA + PIC • (θJC + θCA)

Where the total quiescent current IQTOT consists of the static supply current (IQ) and the current required to charge and

discharge the gate of the power MOSFET. Moreover the part of thermal resistance between case and ambient depends on

the PCB characteristics.

0.5

1.5

2.5

-40

-25

-10

2035506580

110

125

Ambient temperature (°C)

Figure 27. Power derating curve for ZXLD1370 mounted on test board according to JESD51

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