L9803 datasheet(115/126 Pages) STMICROELECTRONICS

115 / 126 page

L9803

Electrical Characteristics

115/126

7.2

Power considerations

The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using the

following equation:

TJ = TA + (PD x θJA) (1)*

Where:

–TA is the Ambient Temperature in °C,

–

JA is the Package Junction-to-Ambient Thermal Resistance, in °C/W,

–PD is the sum of PINT and PI/O,

–PINT is the product of I1 and VB, plus the power dissipated by the power bridge,

expressed in Watts. This is the Chip Internal Power

–PI/O represents the Power Dissipation on Input and Output Pins; User Determined.

For most applications PI/O<<PINT and may be neglected. PI/O may be significant if the

device is configured to drive Darlington bases or sink LED Loads.

An approximate relationship between PD and TJ (if PI/O is neglected) is given by:

PD = K÷ (TJ + 273°C) (2)

Therefore:

K = PD x (TA + 273°C) + θJA x PD

2 (3)

Where:

–

K is a constant for the particular part, which may be determined from equation (3)

by measuring PD (at equilibrium) for a known TA. Using this value of K, the values

of PD and TJ may be obtained by solving equations (1) and (2) iteratively for any

value of TA.

(*) Maximum chip dissipation can directly be obtained from Tj (max), θJA and TA parameters.

Table 17.

Thermal Characteristics (VB=18V, TJ = 150°C, ILOAD = 2A)

Symbol

Description

Value

Unit

Dissipated Power

L9803 データシート(PDF) 115 Page - STMicroelectronics

L9803 データシート(HTML) 115 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

データシートダウンロード