R5F21257SYFP#U0 Renesas Electronics America, R5F21257SYFP#U0 Datasheet - Page 414
![MCU 2KB FLASH 48K 52-LQFP](/photos/28/61/286101/52-lqfp_sml.jpg)
R5F21257SYFP#U0
Manufacturer Part Number
R5F21257SYFP#U0
Description
MCU 2KB FLASH 48K 52-LQFP
Manufacturer
Renesas Electronics America
Series
R8C/2x/25r
Specifications of R5F21257SYFP#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
48KB (48K x 8)
Program Memory Type
FLASH
Ram Size
2.5K x 8
Voltage - Supply (vcc/vdd)
2.2 V ~ 5.5 V
Data Converters
A/D 12x10b
Oscillator Type
Internal
Operating Temperature
-20°C ~ 105°C
Package / Case
52-LQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
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R8C/24 Group, R8C/25 Group
Rev.3.00
REJ09B0244-0300
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 the 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
Feb 29, 2008
VC is generally
And when t = T,
Hence,
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
=
R0
–
-------------------------------------------------- -
6.0
=
×
Page 395 of 485
–
0.25
10
VC
-------------------
C
Sensor equivalent
circuit
VC
•
–
–
e
12
T
=
×
VIN
NOTE:
ln
–
--------------------------
C R0
10
1. The capacity of the terminal is assumed to be 4.5 pF.
•
VIN 1 e
X
--- -
Y
=
--------------------------T
C R0
(
ln
(
6 –
–
VIN
1
----------- -
1024
R
0.1
1
+
+
R
–
–
R
R0
–
)
X
--- - VIN
Y
T
2.8
)
–
=
--------------------------
C R0
=
×10
ln
(
X
--- -
Y
X
--- -
Y
3
1
=
≈
+
VIN 1
1.7
R
MCU
)
×10
t
C (6.0 pF)
R (2.8 kΩ)
3
–
X
--- -
Y
VC
18. A/D Converter
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