R5F21132FP#U0 Renesas Electronics America, R5F21132FP#U0 Datasheet - Page 148

• Manufacturer Part Number: R5F21132FP#U0
• Description: IC R8C MCU FLASH 8K 32LQFP
• Manufacturer: Renesas Electronics America
• Series: M16C™ M16C/R8C/Tiny/13r

Specifications of R5F21132FP#U0

• Core Processor: R8C
• Core Size: 16-Bit
• Speed: 20MHz
• Connectivity: SIO, UART/USART
• Peripherals: LED, POR, Voltage Detect, WDT
• Number Of I /o: 22
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 32-LQFP
• For Use With: R0K521134S000BE - KIT EVAL STARTER FOR R8C/13R0E521134EPB00 - KIT EMULATOR PROBE FOR PC7501R0E521134CPE00 - EMULATOR COMPACT R8C/13
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

R8C/13 Group
Rev.1.20
REJ09B0111-0120
14.7 Output Impedance of Sensor under A/D Conversion
To carry out A/D conversion properly, charging the internal capacitor C shown in Figure 14.11 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, microcomputer’s internal resistance be R, precision
(error) of the A/D converter be X, and the A/D converter’s resolution be Y (Y is 1024 in the 10-bit mode,
and 256 in the 8-bit mode).
Figure 14.11 shows analog input pin and external sensor equivalent circuit. When the difference
between VIN and VC becomes 0.1 LSB, 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 0.1 LSB at time of A/D conversion in the 10-bit mode. Actual
error however is the value of absolute precision added to 0.1 LSB. When f(X
in the A/D conversion mode with sample & hold. Output impedance R0 for sufficiently charging capaci-
tor C within time T is determined as follows.
Thus, the allowable output impedance of the sensor circuit capable of thoroughly driving the A/D
converter turns out to be approximately 7.3 k .
Jan 27, 2006
R0 = –
VC is generally VC = VIN {1 – e
And when t = T,
Hence, R0 = –
T = 0.25 s, R = 2.8 k , C = 1.5 pF, X = 0.1, and Y = 1024 . Hence,
6.0 X 10
page 135 of 205
0.25 X 10
e
–
C • ln
–12
–
VC=VIN –
C (R0 +R)
• ln
C (R0 + R)
T
1
–6
1
X
Y
1024
0.1
– R
T
Y
X
T = ln
–
– 2.8 X 10
=
C (R0 + R)
VIN = VIN(1 –
1
Y
X
Y
X
14.7 Output Impedance of Sensor under A/D Conversion
3
t
}
7.3 X 10
Y
X
)
3
IN
) = 10 MHz, T = 0.25 µs