PIC16C63A Microchip Technology, PIC16C63A Datasheet - Page 78

• Manufacturer Part Number: PIC16C63A
• Description: 28/40-Pin 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

PIC16C63A/65B/73B/74B
10.1
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 10-4. The source
impedance (R
impedance directly affect the time required to charge
the capacitor C
impedance varies over the device voltage (V
source impedance affects the offset voltage at the ana-
log input (due to pin leakage current). The maximum
recommended 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.
FIGURE 10-4: ANALOG INPUT MODEL
DS30605A-page 78
A/D Acquisition Requirements
S
) and the internal sampling switch (R
HOLD
Legend C
VA
. The sampling switch (R
Rs
V
I leakage
R
SS
C
T
PIN
IC
HOLD
ANx
C
5 pF
HOLD
PIN
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
various junctions
) must be allowed
V
DD
DD
). The
V
V
T
T
SS
SS
= 0.6V
= 0.6V
)
)
I leakage
500 nA
To calculate the minimum acquisition time, T
the
(DS33023). This equation calculates the acquisition
time to within 1/2 LSb error (512 steps for the A/D). The
1/2 LSb error is the maximum error allowed for the A/D
to meet its specified accuracy.
R
Note:
IC
PICmicro
1k
V
SS R
DD
Sampling
Switch
When the conversion is started, the hold-
ing capacitor is disconnected from the
input pin.
6V
5V
4V
3V
2V
SS
Mid-Range
Sampling Switch
5 6 7 8 9 10 11
V
SS
C
= DAC capacitance
= 51.2 pF
( k )
HOLD
1998 Microchip Technology Inc.
Reference
ACQ
Manual,
, see