Section 14 Power Supply Circuit; Overview - Hitachi H8/3827R Series Hardware Manual

14.1

Overview

The H8/3827R Series 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 1.5 V,
independently of the voltage of the power supply connected to the external V
the current consumed when an external power supply is used at 1.8 V or above can be held down
to virtually the same low level as when used at approximately 1.5 V. 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 the Internal Power Supply Step-Down Circuit
Connect the external power supply to the V
µF between CV
and V
CC
effective simply by adding this external circuit.
Notes: 1. In the external circuit interface, the external power supply voltage connected to V
and the GND potential connected to V
input/output levels, the V
is that for the low level.
2. When the internal power supply step-down circuit is used, operating frequency f
MHz to 4 MHz when V
to 5.5 V.
3. The LCD power supply and A/D converter analog power supply are not affected by
internal step-down processing.
Figure 14.1 Power Supply Connection when Internal Step-Down Circuit Is Used

Section 14 Power Supply Circuit

, as shown in figure 14.1. The internal step-down circuit is made
SS
level is the reference for the high level, and the V
CC
= 1.8 V to 5.5 V, and 1 MHz to 10 MHz when V
CC
Step-down circuit
Internal
Internal
power
logic
supply
pin, and connect a capacitance of approximately 0.1
CC
are the reference levels. For example, for port
SS
V
CC
CV
CC
Stabilization
capacitance
(approx. 0.1µF)
V
SS
pin. As a result,
CC
CC
level
SS
is 1
osc
= 2.7 V
CC
353