PIC18F23K20-E/SP Microchip Technology, PIC18F23K20-E/SP Datasheet - Page 275

• Manufacturer Part Number: PIC18F23K20-E/SP
• Description: 8 KB Enh Flash, 768 RAM, 25 I/O Pb Free, Nanowatt XLP 28 SPDIP .300in TUBE
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F23K20-E/SP

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, HLVD, POR, PWM, WDT
• Number Of I /o: 24
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 28-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

19.3
For the ADC to meet its specified accuracy, the charge
holding capacitor (C
charge to the input channel voltage level. The Analog
Input model is shown in Figure 19-5. The source
impedance (R
impedance directly affect the time required to charge the
capacitor C
varies over the device voltage (V
The maximum recommended impedance for analog
sources is 10 k. As the source impedance is
decreased, the acquisition time may be decreased.
After the analog input channel is selected (or changed),
EQUATION 19-1:
 2010 Microchip Technology Inc.
Note 1: The reference voltage (V
The value for T
Solving for T
Therefore:
Assumptions:
2: The charge holding capacitor (C
3: The maximum recommended impedance for analog sources is 10 k. This is required to meet the pin
A/D Acquisition Requirements
HOLD
leakage specification.
T
V
S
V
V
ACQ
T
) and the internal sampling switch (R
T
APPLIE D
. The sampling switch (R
ACQ
APPLIE D
APPLI ED
C
C
=
=
=
=
=
:
C
HOLD
=
=
=
–
ACQUISITION TIME EXAMPLE
Temperature
–
5µs
7.45µs
can be approximated with the following equations:
1.20
13.5pF 1k
C
Amplifier Settling Time
T
5µs








) must be allowed to fully
AMP
1
HOLD
1 e
+
1 e
µs
–
+
–
1.20µs
–
----------- -
2047

+
T

R
C
DD
1
–
--------- -
–
-------- -
T
RC
RC
T
Tc
IC

+
C
), see Figure 19-5.
C








+
+

+
+
REF

=
T
Temperature - 25°C
R
700

SS
=
=
=

COFF
) has no effect on the equation, since it cancels itself out.
SS
50°C- 25°C
50°C and external impedance of 10k
) impedance
V
V
V

+
HOLD
CHOL D
CHOL D
APPL IED
+
R
S
10k
+
 ln(1/2047)
) is discharged after each conversion.
SS
Hold Capacitor Charging Time

)
 0.05 




ln(0.0004885)
1
–
 0.05µs/°C

----------- -
2047
s/
1
an A/D acquisition must be done before the conversion
can be started. To calculate the minimum acquisition
time, Equation 19-1 may be used. This equation
assumes that 1/2 LSb error is used (1024 steps for the
ADC). The 1/2 LSb error is the maximum error allowed
for the ADC to meet its specified resolution.
°C
PIC18F2XK20/4XK20




;[2] V
;combining [1] and [2]
;[1] V


CHOLD
CHOLD

3.0V V
+
charged to within 1/2 lsb
charge response to V
Temperature Coefficient
DD
DS41303G-page 275
APPLIED