38C3 datasheet(175/224 Pages) RENESAS

175 / 224 page

3-30

APPENDIX

38C3 Group User’s Manual

3.3 Notes on use

3.3.5 Notes on A-D converter

(1)

Analog input pin

s Make the signal source impedance for analog input low, or equip an analog input pin with an

external capacitor of 0.01

µF to 1 µF. Further, be sure to verify the operation of application

products on the user side.

q Reason

An analog input pin includes the capacitor for analog voltage comparison. Accordingly, when

signals from signal source with high impedance are input to an analog input pin, charge and

discharge noise generates. This may cause the A-D conversion precision to be worse.

(2)

A-D converter power source pin

The AVSS pin is A-D converter power source pin. Regardless of using the A-D conversion function

or not, connect it as following :

• AVSS : Connect to the VSS line.

q Reason

If the AVSS pin is opened, the microcomputer may have a failure because of noise or others.

(3)

Clock frequency during A-D conversion

The comparator consists of a capacity coupling, and a charge of the capacity will be lost if the clock

frequency is too low. Thus, make sure the following during an A-D conversion.

• f(XIN) is 500 kHz or more.

• Use clock divided by main clock (f(XIN)) as internal system clock.

• Do not execute the STP instruction and WIT instruction.

3.3.6 Notes on reset circuit

(1)

Reset input voltage control

Make sure that the reset input voltage is 0.5 V or less for Vcc of 2.5 V (Note).

Perform switch to the high-speed mode when power source voltage is within 4.0 to 5.5 V.

Note: M version of mask ROM version is 2.2 V.

(2)

Countermeasure when RESET signal rise time is long

In case where the RESET signal rise time is long, connect a ceramic capacitor or others across the

RESET pin and the VSS pin. And use a 1000 pF or more capacitor for high frequency use. When

connecting the capacitor, note the following :

• Make the length of the wiring which is connected to a capacitor as short as possible.

• Be sure to verify the operation of application products on the user side.

q Reason

If the several nanosecond or several ten nanosecond impulse noise enters the RESET pin, it may

cause a microcomputer failure.

38C3 Datasheet(PDF) 175 Page - Renesas Technology Corp

38C3 Datasheet(HTML) 175 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL