HD64F3670 Datasheet, PDF (231/323 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

Section 15 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.
15.1 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 V_SS, as shown in figure 15.1. 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 V_SS are the reference levels. For
example, for port input/output levels, the V level is the reference for the high level, and the V
CC
SS
level is that for the low level. The A/D converter analog power supply is not affected by the
internal step-down circuit.
V_CC
V_CC = 3.0 to 5.5 V
Step-down circuit
V_CL
Internal
logic
Internal
power
supply
Stabilization
capacitance
(approx. 0.1 µF)
V_SS
Figure 15.1 Power Supply Connection when Internal Step-Down Circuit is Used
PSCKT00A_000020020300
Rev. 2.0, 03/02, page 207 of 298