PIC16F74-I/P Microchip Technology, PIC16F74-I/P Datasheet - Page 408

• Manufacturer Part Number: PIC16F74-I/P
• Description: IC MCU FLASH 4KX14 A/D 40DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F74-I/P

• Core Size: 8-Bit
• Program Memory Size: 7KB (4K x 14)
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Core Processor: PIC
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Number Of I /o: 33
• Program Memory Type: FLASH
• Ram Size: 192 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Controller Family/series: PIC16F
• No. Of I/o's: 33
• Ram Memory Size: 192Byte
• Cpu Speed: 20MHz
• No. Of Timers: 3
• Package: 40PDIP
• Device Core: PIC
• Family Name: PIC16
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 5 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 33
• Interface Type: I2C/SPI/USART
• On-chip Adc: 8-chx8-bit
• Number Of Timers: 3
• Processor Series: PIC16F
• Core: PIC
• Data Ram Size: 192 B
• Maximum Clock Frequency: 20 MHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: ICE2000, DM163022
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 444-1001 - DEMO BOARD FOR PICMICRO MCU
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

PICmicro MID-RANGE MCU FAMILY
22.3
DS31022A-page 22-6
A/D Acquisition Requirements
For the A/D converter to meet its specified accuracy, the charge holding capacitor (C
be allowed to fully charge to the input channel voltage level. The analog input model is shown in
Figure
directly affect the time required to charge the capacitor C
ance varies over the device voltage (V
impedance for analog sources is 10 k . After the analog input channel is selected (changed)
this acquisition must be done before the conversion can be started.
To calculate the minimum acquisition time,
that 1/2 LSb error is used (512 steps for the A/D). The 1/2 LSb error is the maximum error allowed
for the A/D to meet its specified resolution.
Equation 22-1:Acquisition Time
Equation 22-2:A/D Minimum Charging Time
Example 22-1
lation is based on the following system assumptions.
Rs
Conversion Error
V
Temperature
V
Example 22-1:
T
V
or
Tc
T
T
T
T
DD
HOLD
ACQ
ACQ
ACQ
C
ACQ
HOLD
=
22-3. The source impedance (R
=
=
=
=
=
=
=
Amplifier Settling Time +
Holding Capacitor Charging Time +
Temperature Coefficient
T
T
5 s + Tc + [(Temp - 25 C)(0.05 s/ C)]
-C
-51.2 pF (1 k + 7 k + 10 k ) ln(0.0020)
-51.2 pF (18 k ) ln(0.0020)
-0.921 s (-6.2146)
5.724 s
5 s + 5.724 s + [(50 C - 25 C)(0.05 s/ C)]
10.724 s + 1.25 s
11.974 s
(V
-(51.2 pF)(1 k + R
shows the calculation of the minimum required acquisition time T
AMP
AMP
HOLD
REF
Calculating the Minimum Required Acquisition Time
+ T
+ T
- (V
(R
=
=
=
=
C
C
IC
REF
+ T
+ T
+ R
/512)) • (1 - e
COFF
COFF
10 k
1/2 LSb
5V
50 C (system max.)
0V @ time = 0
SS
+ R
SS
Rss = 7 k
+ R
S
) ln(1/512)
S
DD
) and the internal sampling switch (R
S
) ln(1/511)
(-Tc/C
Equation 22-1
), see
HOLD
Figure
(R
IC
HOLD
(see graph in
+ R
22-3. The maximum recommended
may be used. This equation assumes
SS
. The sampling switch (R
+ R
S
))
1997 Microchip Technology Inc.
)
Figure
22-3)
ACQ
SS
) impedance
. This calcu-
HOLD
SS
) imped-
) must