H8SSLASH2224 datasheet(889/1071 Pages) RENESAS

889 / 1071 page

Section 25 Power Supply Circuit

Rev. 5.00 Aug 08, 2006 page 803 of 982

REJ09B0054-0500

Section 25 Power Supply Circuit

25.1

Overview

The H8S/2258 Group, H8S/2238B, and H8S/2236B 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, independently of the voltage of the power supply connected to the external

VCC 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.

The H8S/2239 Group, H8S/2238R, H8S/2236R, H8S/2237 Group, and H8S/2227 Group do not

have an on-chip internal power supply voltage step-down circuit.

An external power supply should be connected to the VCC and CVCC pins.

25.2

Power Supply Connection for H8S/2258 Group, H8S/2238B, and

H8S/2236B (On-Chip Internal Power Supply Step-Down Circuit)

Connect the external power supply to the VCC pin, and connect a capacitance of approximately 0.1

µF between CVCC and VSS, as shown in figure 25.1. The internal step-down circuit is made

effective simply by adding this external circuit. Permanent damage on the chip may result if the

absolute maximum rating of CVCC 4.3 V is exceeded. Must not connect the external power supply

to the CVCC pin.

Notes: 1. In the external circuit interface, the external power supply voltage connected to VCC

and the GND potential connected to VSS are the reference levels. For example, for port

input/output levels, the VCC level is the reference for the high level, and the VSS level is

that for the low level.

2. The A/D converter and D/A converter analog power supply are not affected by internal

step-down processing.

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