Section 14 Power Supply Circuit
Rev. 6.00 Aug 04, 2006 page 461 of 680
REJ09B0145-0600
Section 14 Power Supply Circuit
14.1
Overview
H8/3847R Group, H8/38347 Group and H8/38447 Group incorporate an internal power supply
step-down circuit. Use of this circuit enables the internal power supply to be fixed at a constant
level of approximately 3.0 V to 3.2 V, independently of the voltage of the power supply connected
to the external V
CC
pin. As a result, the current consumed when an external power supply is used
at 3.0 V or above can be held down to virtually the same low level as when used at approximately
3.0 V. If the external power supply is 3.0 V or below, the internal voltage will be practically the
same as the external voltage. It is, of course, also possible to use the same level of external power
supply voltage and internal power supply voltage without using the internal power supply step-
down circuit.
14.2
When Using Internal Power Supply Step-Down Circuit
Connect the external power supply to the V
CC
pin, and connect a capacitance of approximately 0.1
µF, in the case of the H8/3847R, or approximately 0.33 µF, in the case of the H8/38347 or
H8/38447, between CV
CC
and V
SS
, as shown in figure 14.1. The internal step-down circuit is
made effective simply by adding this external circuit. In the external circuit interface, the external
power supply voltage connected to V
CC
and the GND potential connected to V
SS
are the reference
levels. For example, for port input/output levels, the V
CC
level is the reference for the high level,
and the V
SS
level is that for the low level. The LCD power supply and A/D converter analog
power supply are not affected by the internal step-down circuit.
CV
CC
V
SS
Internal
logic
Step-down circuit
Internal
power
supply
Stabilization capacitance
(approximately 0.1 µF, in the case of the H8/3847R,
or approximately 0.33 µF, in the case of the H8/38347
or H8/38447)
V
CC
Figure 14.1 Power Supply Connection when Internal Step-Down Circuit is Used
Содержание H8/38342
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