LAPIS Semiconductor ML610471, User Manual, Page: 214 / 281

ML610471/472/473/Q471/Q472/Q473 User's Manual
Chapter 17 RC Oscillation Type A/D Converter
17-9
In Table 17-1, mode No.7 is mode where external clocks to be input to the IN1 pin is used for measurement with the RC
oscillator circuit stopped.
As shown in Table 17-1, the oscillator circuit, RCOSC1, is so specified that they cannot operate concurrently in order to
prevent interference in oscillation from occurring when they oscillate concurrently.
The relationship between an oscillation frequency f
RCCLK
and an RC constant is expressed by the following equation:
1
f
RCCLK
= t
RCCLK
= k
RCCLK
•R•C
where t
RCCLK
is the period of the oscillator clock, k
RCCLK
the proportional constant, and R x C the product of capacitances
CS, CT, (CS+CVR) and (CT+CVR) and resistances RS and RT. The value of k
RCCLK
slightly changes depending on the
value of the supply voltage VDD, RI, R, or C.
Table 17-2 lists the typical k
RCCLK
values.
Table 17-2 Typical Values of the Proportional Constant k
RCCLK
of RC Oscillator Circuits
V
DD
(V) CS1(pF) CVR1(pF) RS1, RT1 (k Ω ) k
RCCLK
(Typ.)
3 560 820 10 1.26
560 820 100 1.24
3 560 820 15 1.25
560 820 105 1.24
1.5 560 820 15 1.26
560 820 105 1.22
Note:
Out of the Port 3 and Port 4 pins, pins that are to be used for the RC-ADC function must be configured as secondary
function input or output using the mode register (P3MOD0, P4MOD0, P4MOD1) of the corresponding port.
The P44 to P47 pins of Port 4 cannot be used as their primary functions in oscillation mode No. 5, 6 or 7.
Figures 17-2 show the oscillator circuit configurations, the modes of oscillation for each configuration, and the OM3–0
bit settings.
OM3 OM2 OM1 OM0 oscillation mode
0 1 0 1
Oscillates with the reference
resistor RS1 and CS1
0 1 1 0
Oscillates with the sensor
RT1 and CS1
Figure 17-2 When RCOSC1 Is Used for Measurement with One Resistive Sensor
CS1
RS1
RT1
IN1
CS1
RS1
RT1
CVR1