DSPIC30F6015 Microchip Technology Inc., DSPIC30F6015 Datasheet - Page 144

• Manufacturer Part Number: DSPIC30F6015
• Description: High-performance, 16-bit Digital Signal Controllers
• Manufacturer: Microchip Technology Inc.

dsPIC30F6010A/6015
20.8
The analog input model of the 10-bit A/D converter is
shown in Figure 20-3. The total sampling time for the
A/D is a function of the internal amplifier settling time,
device V
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (C
to fully charge to the voltage level on the analog input
pin. The analog output source impedance (R
interconnect impedance (R
pling switch (R
the time required to charge the capacitor C
combined impedance must therefore be small enough
to fully charge the holding capacitor within the chosen
sample time. To minimize the effects of pin leakage
currents on the accuracy of the A/D converter, the max-
imum recommended source impedance, R
conversion rates up to 500 ksps and a maximum of
500
analog input channel is selected (changed), this sam-
pling function must be completed prior to starting the
conversion. The internal holding capacitor will be in a
discharged state prior to each sample operation.
FIGURE 20-3:
DS70150C-page 142
for conversion rates up to 1 Msps. After the
DD
A/D Acquisition Requirements
and the holding capacitor charge time.
Note: C
SS
) impedance combine to directly affect
Legend: C
VA
PIN
Rs
A/D CONVERTER ANALOG INPUT MODEL
value depends on device package and is not tested. Effect of C
V
I leakage
R
R
C
ANx
PIN
T
IC
SS
HOLD
IC
C
PIN
), and the internal sam-
HOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
= interconnect resistance
= sampling switch resistance
= sample/hold capacitance (from DAC)
various junctions
) must be allowed
S
V
, is 5 k for
DD
HOLD
V
V
T
T
S
= 0.6V
= 0.6V
), the
. The
R
I leakage
IC
500 nA
250
The user must allow at least 1 T
time, T
ple to be acquired. This sample time may be controlled
manually in software by setting/clearing the SAMP bit,
or it may be automatically controlled by the A/D con-
verter. In an automatic configuration, the user must
allow enough time between conversion triggers so that
the minimum sample time can be satisfied. Refer to
Section 24.0 “Electrical Characteristics” for T
sample time requirements.
SAMP
Sampling
Switch
R
, between conversions to allow each sam-
SS
PIN
R
negligible if Rs
SS
V
SS
C
= DAC capacitance
= 4.4 pF
HOLD
3 k
© 2007 Microchip Technology Inc.
AD
5 k .
period of sampling
AD
and