HD6473887 Datasheet, PDF (389/523 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

Section 14 Power Supply Circuit
14.1 Overview
The H8/3887 Series incorporates 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 1.5 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 1.8 V or above can be held down
to virtually the same low level as when used at approximately 1.5 V. 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 the 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 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.
Notes: 1. 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.
2. When the internal power supply step-down circuit is used, operating frequency fosc
when V_CC = 2.2 to 5.5 V is 0.4 MHz to 2 MHz. Otherwise, fosc is 0.4 MHz to 1 MHz.
3. The LCD power supply and A/D converter analog power supply are not affected by
internal step-down processing.
VCC
Step-down circuit
CVCC
Internal ^Internal
logic ^power
supply
Stabilization
capacitance
(approx. 0.1 µF)
VSS
Figure 14-1 Power Supply Connection when Internal Step-Down Circuit Is Used
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