bq20z40-R1

SLUS993A

– DECEMBER 2009 – REVISED MARCH 2011

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THERMAL INFORMATION

bq20z40-R1

THERMAL METRIC(1)

TSSOP (PW)

QFN (RSM)

UNITS

20 PINS

32 PINS

θJA, High K

Junction-to-ambient thermal

89.5

37.4

resistance(2)

θJC (top)

Junction-to-case(top) thermal

23.4

30.6

resistance(3)

θJB

Junction-to-board thermal

41.0

7.7

resistance(4)

°C/W

ψJT

Junction-to-top characterization

0.9

0.4

parameter(5)

ψJB

Junction-to-board characterization

40.5

7.5

parameter(6)

θJC (bottom)

Junction-to-case(bottom) thermal

n/a

2.6

resistance(7)

(1)

For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

(2)

The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as

specified in JESD51-7, in an environment described in JESD51-2a.

(3)

The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific

JEDEC-standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.

(4)

The junction-to-board thermal resistance is obtained by simulating in an environment with a ring cold plate fixture to control the PCB

temperature, as described in JESD51-8.

(5)

The junction-to-top characterization parameter,

ψJT, estimates the junction temperature of a device in a real system and is extracted

from the simulation data for obtaining

θJA, using a procedure described in JESD51-2a (sections 6 and 7).

(6)

The junction-to-board characterization parameter,

ψJB, estimates the junction temperature of a device in a real system and is extracted

from the simulation data for obtaining

θJA , using a procedure described in JESD51-2a (sections 6 and 7).

(7)

The junction-to-case (bottom) thermal resistance is obtained by simulating a cold plate test on the exposed (power) pad. No specific

JEDEC standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.

2

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