L9945 datasheet(16/151 Pages) STMICROELECTRONICS

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4.4

Thermal behavior

The table below contains the temperature ranges and the thermal resistance information. The device functionality

is lifetime guaranteed up to 150 °C (junction temperature). If the junction temperature crosses TOT_OFF,

overtemperature is detected. Status of the overtemperature comparator can be monitored reading OT_STATE bit

via SPI. The external microcontroller can either read the temperature measured by the Temperature ADC or

monitor OT_STATE bit: in case of overtemperature, L9945 must be disabled via external input.

Note:

VVPS_UV < VVPS < 60 V, all supplies are independent; 4.5 V < VDD5 < 5.5 V; 3.0 V < VIO < 5.5 V, unless

otherwise noted.

Table 5. Thermal behavior

Symbol

Parameter description

Comment

Min.

Max.

Unit

Temperature ranges

Tj_op

Operating / Lifetime (junction)

Lifetime guaranteed

-40

150

°C

Tstg

Storage temperature

-55 °C is allowed for a maximum of 15h

-40

+150

°C

Tj_fct

Functional (junction)

Transient condition

150 TOT_OFF

TOT_OFF Over temperature comparator threshold

165

190

°C

tOff_prot

Comparator reaction time including

analogue deglitching filter

100

900

Thermal resistance

Rth_j_c Thermal resistance (junction to case)

Values are according to Jedec JESD51-2,-5,-7 at natural

convection on FR4 2s2p board (see Figure 9)

2.4

°C/W

Rth_j_a Thermal resistance (junction to ambient)

°C/W

Figure 9. Sketch of a 2s2p PCB with thermal vias

GADG2702170724PS

2s2p PCB + vias

ΘJ-A (2s2p)

Note:

In "2s2p", the "s" suffix stands for "Signal" and the number before indicates how many PCB layers are dedicated

to signal wires. The "p" suffix stands for "Power" and the number before indicates how many PCB layers are

dedicated to power planes.

The graph below shows the thermal impedance of the package.

L9945

Thermal behavior

DS12275 - Rev 8

page 16/151

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