DF2148BTE20 Renesas Electronics America, DF2148BTE20 Datasheet - Page 654

• Manufacturer Part Number: DF2148BTE20
• Description: IC H8S MCU FLASH 128K 100-QFP
• Manufacturer: Renesas Electronics America
• Series: H8® H8S/2100r

Specifications of DF2148BTE20

• Core Processor: H8S/2000
• Core Size: 16-Bit
• Speed: 20MHz
• Connectivity: I²C, IrDA, SCI, X-Bus
• Peripherals: PWM, WDT
• Number Of I /o: 74
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: FLASH
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 75°C
• Package / Case: 100-TQFP, 100-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Other names: HD64F2148BTE20; HD64F2148BTE20

Section 21 A/D Converter
21.7
21.7.1
This LSI’s analog input (3-V version) is designed so that the conversion accuracy is guaranteed
for an input signal for which the signal source impedance is 5 k or less. This specification is
provided to enable the A/D converter’s sample-and-hold circuit input capacitance to be charged
within the sampling time; if the sensor output impedance exceeds 5 k , charging may be
insufficient and it may not be possible to guarantee the A/D conversion accuracy. However, if a
large capacitance is provided externally in single mode, the input load will essentially comprise
only the internal input resistance of 10 k , and the signal source impedance is ignored. However,
since a low-pass filter effect is obtained in this case, it may not be possible to follow an analog
signal with a large differential coefficient (e.g., voltage fluctuation ratio of 5 mV/µs or greater)
(see figure 21.7). When converting a high-speed analog signal or converting in scan mode, a low-
impedance buffer should be inserted. For details on the 5-V version, refer to section 28, Electrical
Characteristics.
21.7.2
Adding capacitance results in coupling with ground, and therefore noise in ground may adversely
affect the absolute accuracy. Be sure to make the connection to an electrically stable ground such
as AVss.
Care is also required to insure that filter circuits do not communicate with digital signals on the
mounting board, so acting as antennas.
Rev. 3.00 Mar 21, 2006 page 598 of 788
REJ09B0300-0300
Usage Notes
Permissible Signal Source Impedance
Influences on Absolute Accuracy
Sensor input
Sensor output
impedance
to 5 k
Low-pass
filter
C to 0.1 µF
Figure 21.7 Example of Analog Input Circuit
This LSI
C
15 pF
in
=
A/D converter equivalent circuit
10 k
20 pF