R5F2121AJFP#U0 Renesas Electronics America, R5F2121AJFP#U0 Datasheet - Page 391

• Manufacturer Part Number: R5F2121AJFP#U0
• Description: MCU FLASH 96K 5K CMOS 48-LQFP
• Manufacturer: Renesas Electronics America
• Series: R8C/2x/21r

Specifications of R5F2121AJFP#U0

• Core Processor: R8C
• Core Size: 16/32-Bit
• Speed: 20MHz
• Connectivity: I²C, LIN, SIO, SSU, UART/USART
• Peripherals: POR, Voltage Detect, WDT
• Number Of I /o: 41
• Program Memory Size: 96KB (96K x 8)
• Program Memory Type: FLASH
• Ram Size: 5K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 48-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

R8C/20 Group, R8C/21 Group
Rev.2.00 Aug 27, 2008
REJ09B0250-0200
18.6
Figure 18.11
To carry out A/D conversion properly, charging the internal capacitor C shown in Figure 18.11 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 18.11 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.
When f(XIN) = 10 MHz, T = 0.25 µs in the A/D conversion mode without sample & hold. 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 1.7 kΩ maximum.
Output Impedance of Sensor Under A/D Conversion
VC is generally VC = VIN 1 - e
And when t = T, VC = VIN -
Hence, R0 = -
T = 0.25 µs, R = 2.8 kΩ, C = 6.0 pF, X = 0.1, and Y = 1024. Hence,
R0 = -
Analog Input Pin and External Sensor Equivalent Circuit
6.0 × 10
0.25 × 10
C 1n
-12
Page 373 of 458
-
e
T
C(R0 + R)
-
NOTE:
1n
C(R0 + R)
X
Y
-6
Sensor equivalent circuit
1024
1. The capacity of the terminal is assumed to be 4.5 pF
0.1
1
-R
1
VIN
- 2.8 × 10
T
X
Y
T
= 1n
VIN = VIN 1 -
=
-
C(R0 + R)
X
Y
X
Y
R0
1
3
~ ~
1.7 × 10
t
X
Y
MCU
3
R(2.8kΩ)
C(6.0pF)
VC
18. A/D Converter