Datasheet

Section 26 Electrical Characteristics
Rev. 4.00 Sep 27, 2006 page 910 of 1130
REJ09B0327-0400
26.6.7 Usage Note
(1) The F-ZTAT and mask ROM versions have been confirmed as fully meeting the reference
values for electrical characteristics shown in this manual. However, actual performance
figures, operating margins, noise margins, and other properties may vary due to differences in
the manufacturing process, on-chip ROM, layout patterns, etc.
When system evaluation testing is carried out using the F-ZTAT version, the same evaluation
tests should also be conducted for the mask ROM version when changing over to that version.
(2) On-chip power supply step-down circuit
The following products incorporate an internal power supply step-down circuit, which
automatically drops down the internal power supply voltage to the optimum internal voltage
level: the F-ZTAT A-mask versions of the H8S/2144 (HD64F2144A) and the mask ROM
versions of the H8S/2144, and H8S/2143 (HD6432144S and HD6432143S).
The voltage-stabilization capacitor (0.47 µF one or two connected in series) must be connected
between the VCL (internal power supply step-down) and VSS pins.
Figure 26.3 shows the connection of the external capacitors.
For the 5- or 4-V version, do not connect the VCL pin in a product incorporating an internal
step-down circuit to the V
CC
power supply. (Connect the VCC1 pin to the V
CC
power supply as
usual.)
For the 3-V version, connect both the VCL and VCC1 pins to the system power supply.
When changing from the F-ZTAT versions not incorporating an internal step-down circuit to
the mask ROM versions incorporating an internal step-down circuit, the VCL pin has the same
pin location as the VCC2 pin.
Therefore, note that the circuit patterns differ between these two types of products.