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[ADM7154] doubt on thermal resistance for SOIC package

Hi to all,

on ADM7154 datasheet it's reported thermal resistance for SOIC-8 package (junction-to-ambient) as 36,9 °C/W "in worst case".
What does "worst case" exactly mean?
Reading datasheet (Thermal data) I understand thermal resistance has been measured with 4-layer PCB with soldered exposed pad.

Vin = 5.0V, Vout = 3.3V, Imax = 0.2A -> Pd= 340mW on 2 layer PCB.
Can I use SOIC-8 without soldered exposed pad? What would be thermal resistance in this condition?
Taking a look to other LDO on same package (but without exposed ground pad), highest thermal resistance I've found is 69 °C/W (LT1129); can I get this thermal resistance as reference value for not soldered exposed pad?

[edited by: Killertechno at 10:34 AM (GMT 0) on 30 Oct 2019]
  • Hi Killertechno,

    The value of theta_JA is highly dependent on the copper size area that dissipates the heat of the device. The value of theta_JA on table 5 which your are referring to (36.9°C/W) is based on a standard JEDEC board. You may refer to Table 7 on page 18 of 23. There are several copper sizes (in sq. mm) given on the table. There are also plots that follow on pages 19 and 20 showing the junction temperature vs power dissipation at various copper sizes for ADM7154 SOIC package.

    Best Regards,