Datasheet
2010 - 2015 Microchip Technology Inc. DS00001692C-page 43
USB251xB/xBi
6.2.1 PACKAGE THERMAL SPECIFICATIONS
Thermal parameters are measured or estimated for devices with the exposed pad soldered to thermal vias in a multi-
layer 2S2P PCB per JESD51. Thermal resistance is measured from the die to the ambient air. The values provided are
based on the package body, die size, maximum power consumption, 85°C ambient temperature, and 125°C junction
temperature of the die.
Use the following formulas to calculate the junction temperature:
T
J
= P x
JA
+ T
A
T
J
= P x
JT
+ T
T
T
J
= P x
JC
+ T
C
Max Power Supported = (T
J Max. Spec.
x T
Amb.
)/
JA
Symbol
USB2512B/12Bi USB2513B/13Bi
USB2514B/14Bi
(°C/W)
Velocity (meters/s)
JA
40.1 0
35.0 1
JT
0.5 0
0.7 1
JC
6.3 0
6.3 1
TABLE 6-9: LEGEND
Symbol Description
T
J
Junction temperature
P Power dissipated
JA
Junction-to-ambient-temperature
JC
Junction-to-top-of-package
JT
Junction-to-bottom-of-case
T
A
Ambient temperature
T
C
Temperature of the bottom of the case
T
T
Temperature of the top of the case