Datasheet

Section 20 Power Supply Circuit
PSCKT00A_000020020200 Rev. 3.00 Sep. 10, 2007 Page 393 of 528
REJ09B0216-0300
Section 20 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.
20.1 Power Supply Connection of 5.0-V-Specification Microcontrollers
Connect the external power supply to the V
CC
pin, and connect a capacitor of approximately 0.1 µF
between V
CL
and V
SS
, as shown in figure 20.1. 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
CC
level is the reference for the high level, and the V
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
CL
V
SS
Internal
logic
Step-down circuit
Internal
power
supply
Stabilization
capacitor (approx. 0.1 µF)
V
CC
V
CC
= 4.5 to 5.5 V
Figure 20.1 Power Supply Connection of 5.0-V-Specification Microcontrollers