MC68HC908LB8CPE Freescale Semiconductor, MC68HC908LB8CPE Datasheet - Page 56

• Manufacturer Part Number: MC68HC908LB8CPE
• Description: IC MCU 8K FLASH 8MHZ 20DIP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908LB8CPE

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Peripherals: LVR, POR, PWM
• Number Of I /o: 18
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 7x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Connectivity: -

Op Amp/Comparator Module
OACE — Op Amp/Comparator Enable Bit
4.7 Application Information
We make the following assumptions during the design of the operational amplifier.
We recommend the following.
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1. The signal amplified by the operational amplifier is sampled by the internal ADC.
2. Noise resulting from the operation of other circuitry within the MCU will appear at the output of the
1. An external 500pF capacitor should be added between the output of the operational amplifier
2. Care should be taken to ensure proper filtering at or around the operation bus speed in the
3. The maximum frequency of the signal to be amplified should be limited to 200kHz. This will ensure
4. Do not set the gain of the amplifier to less than 5 (except in the unity gain buffer).
5. Use the circuit component values suggested for the common amplfier configurations shown in the
Setting of the corresponding bit in the register enables the associated op amp/comparator and
connects it to the op amp/comparator pins.
0 = Comparator mode selected
1 = Op amp/comparator is connected to pins and powered on
0 = Op amp/comparator is disconnected from pins and powered off
circuit due to the amplification set by user.
(PTB7) and VSS. This capacitor will act as a filter to internal bus noise caused by the operation of
other digital circuitry in the MCU.
amplification circuit, to prevent noise from being amplified along with the desired signal.
that the filtering element will not affect the gain of the desired signal.
following figures
Enabling the op amp/comparator prevents PTB[5:7] from being used as
standard I/O. However, the PTB7 pin can be shared with AD6 and FAULT
if the ADC and PWM modules are also enabled.
Figure 4-4. Suggested Application Circuit for Unity Gain Buffer
Vin
(Figure
4-4,
Figure
MC68HC908LB8 Data Sheet, Rev. 1
+
–
VDD
4-5, and
Unity Gain Buffer
NOTE
Figure
4-6).
CL
500pF
RL
>20kΩ
Vout
Freescale Semiconductor