HD64F36049 datasheet(433/562 Pages) RENESAS

433 / 562 page

Section 21 Power Supply Circuit

Rev. 3.00 Mar. 15, 2006 Page 401 of 526

REJ09B0060-0300

Section 21 Power Supply Circuit

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, 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.

21.1

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 between V

CL and VSS, as shown in figure 21.1. 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 A/D converter analog power supply is not affected by the

internal step-down circuit.

VCL

VSS

Internal

logic

Step-down circuit

Internal

power

supply

Stabilization

capacitance

(approx. 0.1

µF)

VCC

VCC = 3.0 to 5.5 V

Figure 21.1 Power Supply Connection when Internal Step-Down Circuit is Used

HD64F36049 Datasheet(PDF) 433 Page - Renesas Technology Corp