SPC5607BECLLR View Datasheet(PDF) - Freescale Semiconductor
Part Name
Description
MFG CO.
'SPC5607BECLLR' PDF : 92 Pages View PDF
3.5 Thermal characteristics
Electrical characteristics
3.5.1 External ballast resistor recommendations
External ballast resistor on VDD_BV pin helps in reducing the overall power dissipation inside the device. This resistor is
required only when maximum power consumption exceeds the limit imposed by package thermal characteristics.
As stated in Table 10 LQFP thermal characteristics, considering thermal resistance of LQFP144 as 48.3 °C/W, at ambient TA =
125 °C, the junction temp Tj will cross 150 °C if total power dissipation > (150 - 125)/48.3 = 517 mW. Therefore, total device
current IDDMAX at 125 °C/5.5V must not exceed 94.1 mA (i.e. PD/VDD). Assuming an average IDD(VDD_HV) of 15-20 mA
consumption typically during device RUN mode, the LV domain consumption IDD(VDD_BV) is thus limited to IDDMAX -
IDD(VDD_HV) i.e. 80 mA.
Therefore, respecting the maximum power allowed as explained in Section 3.5.2, “Package thermal characteristics, it is
recommended to use this resistor only in the 125 °C/5.5V operating corner as per the following guidelines:
• If IDD(VDD_BV) < 80 mA, then no resistor is required.
• If 80 mA < IDD(VDD_BV) < 90 mA, then 4 Ohm resistor can be used along with 14.7 µf decoupling.
• If IDD(VDD_BV) > 90 mA, then 8 Ohm resistor can be used along with 33 µf decoupling.
Using resistance in the range of 4-8 Ohm, the gain will be around 10-20% of total consumption on VDD_BV. For example, if 8
Ohm resistor is used, then power consumption when IDD(VDD_BV) is 110 mA is equivalent to power consumption when
IDD(VDD_BV) is 90 mA (approximately) when resistor not used.
3.5.2 Package thermal characteristics
Table 10. LQFP thermal characteristics1
Symbol
Value3
C
Parameter Conditions2 Pin count
Unit
Min
Typ
Max
RθJA
CC
D Thermal Single-layer
100
—
—
64
°C/W
resistance, board—1s
junction-to-
144
—
—
64
ambient
176
—
—
64
natural
convection4
Four-layer
100
—
board—2s2p 144
—
—
49.7
—
48.3
176
—
—
47.3
1 Thermal characteristics are targets based on simulation that are subject to change per device characterization.
2 VDD = 3.3 V ± 10% / 5.0 V ± 10%, TA = −40 to 125 °C.
3 All values need to be confirmed during device validation.
4 Junction-to-ambient thermal resistance determined per JEDEC JESD51-3 and JESD51-6. Thermal test board meets
JEDEC specification for this package. When Greek letters are not available, the symbols are typed as RthJA and RthJMA.
MPC5607B Microcontroller Data Sheet, Rev. 3
Freescale Semiconductor
17
Preliminary—Subject to Change Without Notice
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