R5F21324CNSP#U0 Renesas Electronics America, R5F21324CNSP#U0 Datasheet - Page 494

• Manufacturer Part Number: R5F21324CNSP#U0
• Description: MCU 1KB FLASH 16K ROM 20-LSSOP
• Manufacturer: Renesas Electronics America
• Series: R8C/3x/32Cr

Specifications of R5F21324CNSP#U0

• Core Processor: R8C
• Core Size: 16/32-Bit
• Speed: 20MHz
• Connectivity: I²C, LIN, SIO, SSU, UART/USART
• Peripherals: POR, PWM, Voltage Detect, WDT
• Number Of I /o: 15
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 4x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 20-LSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

R8C/32C Group
REJ09B0573-0100 Rev.1.00 Dec. 18, 2009
Page 465 of 573
27.9
Figure 27.10
To carry out A/D conversion properly, charging the internal capacitor C shown in Figure 27.10 has to be completed
within a specified period of time. T (sampling time) as the specified time. Let output impedance of sensor
equivalent circuit be R0, internal resistance of microcomputer be R, precision (error) of the A/D converter be X,
and the resolution of A/D converter be Y (Y is 1024 in the 10-bit mode, and 256 in the 8-bit mode).
Figure 27.10 shows Analog Input Pin and External Sensor Equivalent Circuit. When the difference between VIN
and VC becomes 0.1LSB, we find impedance R0 when voltage between pins VC changes from 0 to VIN-
(0.1/1024) VIN in time T. (0.1/1024) means that A/D precision drop due to insufficient capacitor charge is held to
0.1LSB at time of A/D conversion in the 10-bit mode. Actual error however is the value of absolute precision
added to 0.1LSB.
T = 0.75 µs when φAD = 20 MHz. Output impedance R0 for sufficiently charging capacitor C within time T is
determined as follows.
Thus, the allowable output impedance of the sensor equivalent circuit, making the precision (error) 0.1LSB or less,
is approximately 3.5 kΩ. maximum.
Output Impedance of Sensor under A/D Conversion
VC is generally
And when t = T,
Hence,
T = 0.75 µs, R = 10 kΩ, C = 6.0 pF, X = 0.1, and Y = 1024. Hence,
R0
Analog Input Pin and External Sensor Equivalent Circuit
=
R0
–
-------------------------------------------------- -
6.0
=
×
–
0.75
VC
10
-------------------
C
Sensor equivalent
circuit
VC
•
–
–
e
T
12
VIN
=
×
ln
–
--------------------------
C R0
10
•
VIN 1 e
X
--- -
Y
=
--------------------------T
C R0
(
ln
(
6 –
–
VIN
1
----------- -
1024
R



0.1
1
+
+
R
R0
–
–
R
)
–
X
--- - VIN
Y
T
10
)
–
=
×10
--------------------------
C R0
=
ln
(
X
--- -
Y
X
--- -
Y
3
1
=
≈
+
3.5
MCU
VIN 1
R
C (6.0 pF)
×10
)
R (10 kΩ)
t





3
–
X
--- -
Y


VC
27. A/D Converter