Section 14 Power Supply Circuit; Overview; When Using Internal Power Supply Step-Down Circuit; Figure 14.1 Power Supply Connection When Internal Step-Down Circuit Is Used - Renesas H8/3847R Series Hardware Manual

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 pin. As a result, the current consumed when an external power supply is used
CC
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
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
made effective simply by adding this external circuit. In the external circuit interface, the external
power supply voltage connected to V
levels. For example, for port input/output levels, the V
and the V level is that for the low level. The LCD power supply and A/D converter analog
SS
power supply are not affected by the internal step-down circuit.
Step-down circuit
Internal
Internal
power
logic
supply

Figure 14.1 Power Supply Connection when Internal Step-Down Circuit is Used

Section 14 Power Supply Circuit

CC
and V , as shown in figure 14.1. The internal step-down circuit is
CC SS
and the GND potential connected to V
CC
V
CC
CV
CC
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
V
SS
or H8/38447)
Section 14 Power Supply Circuit
pin, and connect a capacitance of approximately 0.1
level is the reference for the high level,
CC
Rev. 6.00 Aug 04, 2006 page 461 of 680
are the reference
SS
REJ09B0145-0600