HD6433044 Datasheet, PDF(638/867 Page) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

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HD6433044 Datasheet, PDF (638/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

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(8) Notes concerning mounting board developmentâhandling of VPP and mode MD2 pins

1. The standard 12 V high voltage is applied to the VPP and mode MD2 pins when erasing or

programming flash memory. The voltage at these pins also includes overshoot and noise, and

the following points should be noted to ensure that the 13 V maximum rated voltage is not

exceeded.

(a) Bypass capacitors should be inserted to eliminate overshoot and noise. These should be

positioned as close as possible to the chipâs VPP and mode MD2 pins.

1.0 ÂµF: Stabilizes fluctuations in the low-frequency components, such as power

supply ripple.

0.01 ÂµF: Bypasses high-frequency components such as induction noise.

(b) The VPP and mode MD2 pin wiring should be kept as short as possible to suppress

induction noise. When designing a new board, in particular, noise may be increased by

jumper wires, etc. In this case too, the power supply waveform should be monitored

and measures taken to prevent the maximum rating from being exceeded.

(c) The maximum rated voltage is based on the potential of the VSS pin. If the potential of

this pin oscillates due to current fluctuations, etc., the voltage of the VPP and mode

MD2 pins may reciprocally exceed the maximum rated voltage. Careful attention must

therefore be paid to stabilizing the reference potential.

Note: When the user systemâs 12 V power supply is connected, attention must be paid to

the current capacity. A power supply with a small current capacity will not be able to

handle fluctuations in the chipâs operating voltage, resulting in voltage drops and

rises or oscillation that may make it impossible to obtain the rated operating voltage.

If the power supply has a large current capacity, or if the 12 V voltage is turned on

abruptly by means of a switch, etc., caution is required since a voltage exceeding the

maximum rating may be generated due to the inductance component of the power

supply wiring or the power supply characteristics.

Before using the power supply, check the power supply waveform to ensure that the

above problems will not arise.

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