ML610Q409-NNNTBZ03A7 Rohm Semiconductor, ML610Q409-NNNTBZ03A7 Datasheet - Page 304

• Manufacturer Part Number: ML610Q409-NNNTBZ03A7
• Description: MCU 8BIT 16K FLASH 4CH 100-TQFP
• Manufacturer: Rohm Semiconductor
• Series: -r

Specifications of ML610Q409-NNNTBZ03A7

• Core Processor: nX-U8/100
• Core Size: 8-Bit
• Speed: 2MHz
• Connectivity: SSP, UART/USART
• Peripherals: LCD, Melody Driver, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: -
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 1.25 V ~ 3.6 V
• Data Converters: A/D 2x16b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 70°C
• Package / Case: 100-TFQFP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Chapter 21 RC Oscillation Type A/D Converter
21.3.3 Example of Use of RC Oscillation Type A/D Converter
This section describes the method of performing A/D conversion for sensor values in Counter A and B reference modes
by taking temperature measurement by a thermistor as an example.
Figure 21-8 shows the circuit configuration of 1-thermistor RC oscillator circuit using RCOSC0.
Figure 21-9 shows the temperature characteristics of the thermistor resistance RT0.
RT0 is expressed as a function of temperature T by the following equation:
Figure 21-10 shows the ideal characteristics of A/D conversion with the assumption that RT0 is an analog quantity. In
the ideal characteristics, the A/D conversion value nT0 will purely depend on RT0 only. Assuming that nT0 is
proportional to RT0, let proportional constant be K, then nT0 has the following relationship with temperature T:
Therefore, temperature T can be expressed as a digital value by performing the conversion processing that accords with
the characteristics shown in Figure 21-9 for nT0 by software.
To convert from an RT0 value to a digital value, the ratio is used between a) the oscillation frequency by the thermistor
connected to the RT0 pin and the capacitor connected to the CS0 pin and b) the oscillation frequency by the reference
resistor (which ideally should have no temperature characteristics) connected to the RS0 pin and the capacitor connected
to the CS0 pin. This is for making the conditions other than resistance equal to eliminate the error factor in oscillation
characteristics.
As shown in Figures 21-9 and 21-11, the RT0 value depends on temperature T and the RS0 value is assumed to be
constant regardless of temperature T. It is ideal if the characteristics of the oscillation frequency f
using these resistances will be like the solid lines in Figures 21-12 and 21-13; however, in reality, it would appear that
they will be like the dotted lines due to error factors such as IC temperature characteristics.
Since the condition of f
almost the same; therefore, errors can almost be eliminated by using the ratio between f
RT0
nT0
Figure 21-9 Temperature Characteristics of
=
=
Figure 21-8 Configuration of 1-Thermistor RC Oscillator Circuit Using RCOSC0
f (T)
K•RT0
Thermistor Characteristics
RCCLK
RT0 = f(T)
=
Reference resistor
(RT0) and that of f
Thermistor RT0
K•f (T)
Temperature T
CS0
... Expression A
RCCLK
21-14
(RS0) are the same except for the resistances, the error ratios are
RT0
RS0
CS0
IN0
(Ideal characteristics when nT0 is proportional to
Figure 21-10 A/D Conversion
RT0)
RCCLK
nT0 = K•RT0
(RT0) and f
= K•f(T)
OSC
to temperature T
RT0
RCCLK
(RS0).