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What is the maximum total current over all applicable ports on the MCU?

Latest Updated:03/01/2005

Question:

(I/O Port)  What is the maximum total current over all applicable ports on the MCU ? [2005/03/01]

Answer:

It depends on the MCU. At peak, the maximum total current is the sum of "H" ("L") total peak output current (ΣIOH(peak), ΣIOL(peak)). At steady-state current, the maximum total current is the sum of "H" ("L") total average output current (ΣIOH(avg), ΣIOL(avg)). Please calculate maximum total current based on the specifications of the MCU you are using.
For the ratings described above, refer to the "Electrical Characteristics" and "Recommended Operating Conditions" of each group User's Manual and Data Sheet. The following is an example for the 3803 Group.

Peak Current Value

The peak value is the sum of "H" ("L") total peak output current (ΣIOH(peak), ΣIOL(peak)).
Accordingly, the maximum amount of source current for all ports on the MCU is 160mA (80mA + 80mA);
the sum of ["H" total peak output current of ports P00-P07, P10-P17, P20-P27, P30, P31, P34-P37] and ["H" total peak output current of ports P40-P47, P50-P57, P60-P67].
In the same manner, the maximum amount of sink current for all ports on the MCU is 240mA (80mA + 80mA + 80mA); the sum of "L" total peak output current.

Steady Current Flow Value
The steady current value is the sum of "H" total average output current (ΣIOH(avg)) and the sum of "L" total output average current (ΣIOL(avg)).
Accordingly, the maximum amount of source current for all ports on the MCU is 80mA (40mA + 40mA);
the sum of ["H" total output average current of ports P00-P07, P10-P17, P20-P27, P30,P31, P34-P37] and ["H" total output average current of ports P40-P47, P50-P57, P60-P67].
In the same manner, the maximum amount of sink current for all ports on the MCU is 120mA (40mA + 40mA + 40mA); the sum of "L" total output average current.

Therefore, set the value in the above conditions so that the absolute maximum rating of power dissipation (Pd) is not exceeded.
Power Dissipation (Pd)
Pd = Vcc × Icc + Σ{( - IOH) × (Vcc - VOH)}+Σ(IOL × VOL)
Example using actual values
"H" output ports (3), IOH = -5mA for each port, VOH = 4.8V (from typical characteristics graph)
"L" output ports (3), IOL = 10mA for each port, VOL = 0.2V (from typical characteristics graph)
When Vcc = 5.0V and Icc = 7.5mA; Pd = 5.0 × 7.5 + 3 × (5 × 0.2) + 3 × (10 × 0.2) = 37.5+3+6 = 46.5mW

(#105175)

Suitable Products
3803H
3803L
3823
3850A
3858
38D2
38D5
7544
7545
7546
7547
7548
7549