AN4068 datasheet(45/63 Pages) STMICROELECTRONICS

tên linh kiện	AN4068

Giải thích chi tiết về linh kiện	ST7580 power line communication system-on-chip design guide

PDF	63 Pages

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nhà sản xuất	STMICROELECTRONICS [STMicroelectronics]

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45 / 63 page

AN4068

Design guidelines

Doc ID 022923 Rev 2

45/63

Equation 10

where TA is the ambient temperature (from -40 to +85 °C) and ZthJA is the junction to

ambient thermal impedance of the ST7580 IC, which is related to the length of the

transmission (tTX) and to the duty cycle d = tPKT / (tPKT + tIDLE), assuming a packet-

fragmented transmission as illustrated by Figure 36.

Figure 36.

Packet-fragmented transmission

When soldered to a proper dissipating area on the PCB as explained above, the ST7580 IC

is characterized by a steady-state thermal resistance RthJA of about 50 °C/W. The thermal

impedance curve obtained as the power dissipation step response is given in Figure 37.

Figure 37.

Measured ST7580 thermal impedance curve (typical)

It can be seen that the transient of ZthJA takes some thousand seconds, after which the

static value of 50 °C/W is reached. This means that during the transient phase (i.e. if the

transmission time tTX is some seconds or even less) the IC is able to dissipate a power that

is far higher than the one sustainable at steady-state.

)

(

Zth

)

(

⋅

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