Datasheet

Section 25 Electrical Characteristics
Rev. 4.00 Jun 06, 2006 page 758 of 1004
REJ09B0301-0400
25.3.7 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 version of the H8S/2138 (HD64F2138A) and the mask ROM
versions of the H8S/2138 and H8S/2137 (HD6432138S, HD6432138SW, HD6432137S, and
HD6432137SW).
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 V
SS
pins.
Figure 25.3 shows the connection of the external capacitors.
For the 5- or 4-V version whose power supply (V
CC
) voltage exceeds 3.6 V, 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 whose power
supply (V
CC
) voltage is 3.6 V or lower, 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 F-ZTAT A-mask versions or 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.