MC9RS08LA8 Datasheet, PDF (8/34 Pages) Freescale Semiconductor, Inc – MCU Block Diagram

Electrical Characteristics
1 _{Input must be current limited to the value specified. To determine the value of the required current-limiting resistor,}
calculate resistance values for positive (V_DD) and negative (V_SS) clamp voltages, then use the larger of the two
resistance values.
2 _{All functional non-supply pins are internally clamped to VSS and VDD except the RESET/VPP pin which is internally}
clamped to V_SS only.
3 _{Power supply must maintain regulation within operating VDD range during instantaneous and operating maximum}
current conditions. If positive injection current (V_In > V_DD) is greater than IDD, the injection current may flow out of VDD
and could result in external power supply going out of regulation. Ensure external VDD load will shunt current greater
than maximum injection current. This will be the greatest risk when the MCU is not consuming power. Examples are:
if no system clock is present, or if the clock rate is very low which would reduce overall power consumption.
3.3 Thermal Characteristics
This section provides information about operating temperature range, power dissipation, and package
thermal resistance. Power dissipation on I/O pins is usually small compared to the power dissipation in
on-chip logic and voltage regulator circuits and it is user-determined rather than being controlled by the
MCU design. In order to take P_I/O into account in power calculations, determine the difference between
actual pin voltage and V_SS or V_DD and multiply by the pin current for each I/O pin. Except in cases of
unusually high pin current (heavy loads), the difference between pin voltage and V_SS or V_DD will be very
small.
Table 4. Thermal Characteristics
Rating
Symbol
Operating temperature range (packaged)
T_A
Maximum junction temperature
Thermal resistance
Single layer board
Four layer board
T_JMAX
48-pin LQFP
48-pin QFN θ_JA
48-pin LQFP
48-pin QFN
Value
T_L to T_H
–40 to 85
105
71
84
49
28
Unit
°C
°C
°C/W
The average chip-junction temperature (TJ) in °C can be obtained from:
T_J = T_A + (P_D × θ_JA)
Eqn. 1
where:
T_A = Ambient temperature, °C
θ_JA = Package thermal resistance, junction-to-ambient, °C /W
P_D = P_int + P_I/O
P_int = I_DD × V_DD, Watts chip internal power
P_I/O = Power dissipation on input and output pins user determined
For most applications, P_I/O << P_int and can be neglected. An approximate relationship between PD and TJ
MC9RS08LA8 Series MCU Data Sheet, Rev. 1
8
Freescale Semiconductor