PIC16F84A-20/P Microchip Technology, PIC16F84A-20/P Datasheet - Page 440

• Manufacturer Part Number: PIC16F84A-20/P
• Description: IC MCU FLASH 1KX14 EE 18DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F84A-20/P

• Program Memory Type: FLASH
• Program Memory Size: 1.75KB (1K x 14)
• Package / Case: 18-DIP (0.300", 7.62mm)
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Peripherals: POR, WDT
• Number Of I /o: 13
• Eeprom Size: 64 x 8
• Ram Size: 68 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 68 B
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 13
• Number Of Timers: 1
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 70 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: ICE2000
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: I3-DB16F84A - BOARD DAUGHTER ICEPIC3DVA16XP180 - ADAPTER DEVICE FOR MPLAB-ICEAC164010 - MODULE SKT PROMATEII DIP/SOIC
• Data Converters: -
• Connectivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PICmicro MID-RANGE MCU FAMILY
23.14
DS31023A-page 23-18
Design Tips
Question 1:
Answer 1:
1.
2.
3.
Question 2:
Answer 2:
After the holding capacitor is disconnected from the input channel, typically 100 ns after the GO
bit is set, the input channel may be changed.
Question 3:
Answer 3:
A very good reference for understanding A/D conversions is the “Analog-Digital Conversion
Handbook” third edition, published by Prentice Hall (ISBN 0-13-03-2848-0).
Make sure you are meeting all of the timing specifications. If you are turning the module
off and on, there is a minimum delay you must wait before taking a sample. If you are
changing input channels, there is a minimum delay you must wait for this as well, and
finally there is T
ADCON0 and should be between 1.6 and 6 s. If T
fully converted before the conversion is terminated, and if T
on the sampling capacitor can droop before the conversion is complete. These timing
specifications are provided in the
data sheet for device specific information.
Often the source impedance of the analog signal is high (greater than 1k ohms) so the
current drawn from the source to charge the sample capacitor can affect accuracy. If the
input signal does not change too quickly, try putting a 0.1 F capacitor on the analog input.
This capacitor will charge to the analog voltage being sampled and supply the instanta-
neous current needed to charge the 120 pF internal holding capacitor.
Finally, straight from the data book: “In systems where the device frequency is low, use of
the A/D clock derived from the device oscillator is preferred...this reduces, to a large
extent, the effects of digital switching noise.” and “In systems where the device will enter
SLEEP mode after start of A/D conversion, the RC clock source selection is required.This
method gives the highest accuracy.”
I find that the Analog to Digital Converter result is not always accurate.
What can I do to improve accuracy?
After starting an A/D conversion may I change the input channel (for my
next conversion)?
Do you know of a good reference on A/D’s?
AD
, which is the time selected for each bit conversion. This is selected in
Preliminary
“Electrical Specifications”
AD
is too short, the result may not be
AD
is made too long the voltage
1997 Microchip Technology Inc.
section. See the device