Setting Range Of Analog Power Supply And Other Pins; Notes On Board Design; Notes On Noise Countermeasures - Renesas H8S/2158 User Manual

Section 22 A/D Converter
22.8.3

Setting Range of Analog Power Supply and Other Pins

If conditions shown below are not met, the reliability of this LSI may be adversely affected.
•
Analog input voltage range
The voltage applied to analog input pin ANn during A/D conversion should be in the range
≤ ANn ≤ AV
AV
SS
• Digital input voltage range
The voltage applied to digital input pin CINn should be in the range AV
≤ CINn ≤ V
V
SS CC
• Relation between AV
For the relationship between AV
is not used, the AVCC and AVSS pins must on no account be left open.
• AVref pin reference voltage specification range
The reference voltage of the AVref pin should be in the range AV
• It is not recommended to use the D/A converter or A/D converter simultaneously with the USB
because the bus driver/receiver power supply pin DrVCC/DrVSS is shared with the analog
power supply pin AVCC/AVSS.
22.8.4

Notes on Board Design

In board design, digital circuitry and analog circuitry should be as mutually isolated as possible,
and layout in which digital circuit signal lines and analog circuit signal lines cross or are in close
proximity should be avoided as far as possible. Failure to do so may result in incorrect operation
of the analog circuitry due to inductance, adversely affecting A/D conversion values. Also, digital
circuitry must be isolated from the analog input signals (AN2 to AN7), analog reference voltage
(AV ), and analog power supply (AV
ref
(AV ) should be connected at one point to a stable digital ground (V
SS
22.8.5

Notes on Noise Countermeasures

A protection circuit connected to prevent damage due to an abnormal voltage such as an excessive
surge at the analog input pins (AN2 to AN7) and analog reference voltage (AV
connected between AVCC and AVSS as shown in figure 22.7. Also, the bypass capacitors
connected to AVCC and AVref, and the filter capacitors connected to AN7 to AN2 must be
connected to AVSS.
Rev. 3.00 Jan 25, 2006 page 712 of 872
REJ09B0286-0300
(n = 2 to 7).
ref
(n = 0 to 7).
, AV and V , V
CC SS CC
, AV
CC SS
) by the analog ground (AV
CC
SS
and V , V , set AV
CC SS SS
≤ CINn ≤ AV
SS
= V . If the A/D converter
SS
≤ AV
.
ref CC
). Also, the analog ground
SS
) on the board.
SS
) should be
ref
and
ref