PIC18F4523-E/PT Microchip Technology, PIC18F4523-E/PT Datasheet - Page 30

• Manufacturer Part Number: PIC18F4523-E/PT
• Description: 32KB, Flash, 1536bytes-RAM, 36I/O, 8-bit Family,nanoWatt 44 TQFP 10x10x1mm TRAY
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F4523-E/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, HLVD, POR, PWM, WDT
• Number Of I /o: 36
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 13x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PIC18F2423/2523/4423/4523
2.1
For the A/D Converter to meet its specified accuracy,
the charge holding capacitor (C
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 2-3.
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 kΩ.
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 2-1:
EQUATION 2-2:
EQUATION 2-3:
DS39755C-page 30
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
=
=
) impedance varies over the device voltage
When the conversion is started, the
holding capacitor is disconnected from the
input pin.
Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient
T
) impedance directly affect the time
AMP
T
0.2 μs
(Temp – 25°C)(0.02 μs/°C)
(85°C – 25°C)(0.02 μs/°C)
1.2 μs
-(C
-(25 pF) (1 kΩ + 4 kΩ + 2.5 kΩ) ln(0.0004883) μs
1.56 μs
0.2 μs + 1.56 μs + 1.2 μs
2.96 μs
(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
/4096)) • (1 – e
+ R
HOLD
SS
SS
HOLD
+ R
+ R
) must be allowed
S
S
) ln(1/4095) μs
. The sampling
) ln(1/4096)
(-T
C
/C
HOLD
(R
IC
+ R
SS
+ R
S
To calculate the minimum acquisition time, Equation 2-1
may be used. This equation assumes that 1/2 LSb error
is used (4,096 steps for the A/D). The 1/2 LSb error is the
maximum error allowed for the A/D to meet its specified
resolution.
Example 2-3 shows the calculation of the minimum
required acquisition time, T
based on the application system assumptions shown in
Table 2-1:
TABLE 2-1:
))
)
Conversion Error
Temperature
C
V
HOLD
Rs
DD
COFF
= 0 ms.
T
ACQ
=
=
≤
=
=
© 2009 Microchip Technology Inc.
ASSUMPTIONS
85°C (system maximum)
ACQ
3V → Rss = 4 kΩ
. This calculation is
1/2 LSb
2.5 kΩ
25 pF