PIC18F87J72-I/PT Microchip Technology, PIC18F87J72-I/PT Datasheet - Page 278

• Manufacturer Part Number: PIC18F87J72-I/PT
• Description: IC PIC MCU 8BIT 14KB FLSH 80TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F87J72-I/PT

• Program Memory Type: FLASH
• Program Memory Size: 128KB (64K x 16)
• Package / Case: 80-TQFP
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, LVD, POR, PWM, WDT
• Number Of I /o: 51
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 3.6 V
• Data Converters: A/D 12x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART, SPI, I2C
• Maximum Clock Frequency: 8 MHz
• Number Of Programmable I/os: 51
• Number Of Timers: 4
• Operating Supply Voltage: 2 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 14
• Controller Family/series: PIC18F
• No. Of I/o's: 51
• Ram Memory Size: 3923Byte
• Cpu Speed: 48MHz
• No. Of Timers: 4
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

PIC18F87J72 FAMILY
21.1
For the A/D Converter to meet its specified accuracy,
the Charge Holding Capacitor (C
allowed to fully charge to the input channel voltage
level. The analog input model is shown in Figure 21-2.
The source impedance (R
switch (R
required to charge the capacitor, C
switch (R
(V
at the analog input (due to pin leakage current). The
maximum recommended impedance for analog
sources is 2.5 k. After the analog input channel is
selected (changed), the channel must be sampled for
at least the minimum acquisition time before starting a
conversion.
EQUATION 21-1:
EQUATION 21-2:
EQUATION 21-3:
DS39979A-page 278
T
V
or
T
T
T
T
Temperature coefficient is only required for temperatures > 25C. Below 25C, T
T
T
ACQ
DD
Note:
C
ACQ
AMP
COFF
C
ACQ
HOLD
). The source impedance affects the offset voltage
=
=
A/D Acquisition Requirements
SS
=
=
=
=
=
SS
=
=
When the conversion is started, the
holding capacitor is disconnected from the
input pin.
) impedance varies over the device voltage
Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient
T
) impedance directly affect the time
AMP
T
0.2 s
(Temp – 25C)(0.02 s/C)
(85C – 25C)(0.02 s/C)
1.2 s
-(C
-(25 pF) (1 k + 2 k + 2.5 k) ln(0.0004883) s
1.05 s
0.2 s + 1 s + 1.2 s
2.4 s
(V
-(C
AMP
HOLD
+ T
REF
HOLD
+ T
C
– (V
ACQUISITION TIME
A/D MINIMUM CHARGING TIME
CALCULATING THE MINIMUM REQUIRED ACQUISITION TIME
+ T
)(R
C
)(R
+ T
S
REF
COFF
IC
IC
) and the internal sampling
+ R
COFF
/2048)) • (1 – e
+ R
SS
SS
HOLD
+ R
+ R
HOLD
S
S
) ln(1/2048) s
. The sampling
) ln(1/2048)
) must be
(-T
C
/C
HOLD
Preliminary
(R
IC
+ R
SS
+ R
S
To
Equation 21-1 may be used. This equation assumes
that 1/2 LSb error is used (1,024 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 21-3 shows the calculation of the minimum
required acquisition time, T
based
assumptions:
))
C
Rs
Conversion Error
V
Temperature
)
HOLD
DD
calculate
on
COFF
the
= 0 ms.
the
=
=

=
=
following
minimum
 2010 Microchip Technology Inc.
25 pF
2.5 k
1/2 LSb
3V  Rss = 2 k
85C (system max.)
ACQ
. This calculation is
application
acquisition
system
time,