H838532H datasheet(409/508 Pages) RENESAS

409 / 508 page

Section 14 Power Supply Circuit

Rev. 1.00 May 30, 2008 Page 389 of 484

REJ09B0436-0100

Section 14 Power Supply Circuit

14.1

Overview

This LSI 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 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 0.33

µF between CV

CC and VSS, 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 VSS are the reference levels. For

example, for port input/output levels, the V

CC level is the reference for the high level, and the VSS

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 current.

CVCC

VSS

Internal

logic

Step-down circuit

Internal

power

supply

Stabilization capacitance

(approximately 0.33 µF)

VCC

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

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