PIC32MX440F256H-80I Datasheet, PDF (509/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

PIC32MX3XX/4XX
EQUATION 22-4: AVAILABLE SAMPLING
TIME, SEQUENTIAL
SAMPLING
TSMP
TSMP
= Trigger Pulse Interval (TSEQ) –
Conversion Time (TCONV)
= TSEQ – TCONV
Note: TSEQ is the trigger pulse interval time.
22.3.12 ACQUISITION TIME
CONSIDERATIONS
Different acquisition/conversion sequences provide dif-
ferent times for the sample-and-hold channel to acquire
the analog signal. The user must ensure the acquisition
time meets the sampling requirements.
When SSRC<2:0> (AD1CON1<7:5>) = 111, the con-
version trigger is under ADC clock control. The
SAMC<4:0> bits (AD1CON3<12:8>) select the number
of TAD clock cycles between the start of acquisition and
the start of conversion. This trigger option provides the
fastest conversion rates on multiple channels. After the
start of acquisition, the module will count a number of
TAD clocks specified by the SAMC bits.
22.3.13 TURNING THE ADC ON
When the ON bit (AD1CON1<15>) is ‘1’, the module is
in Active mode and is fully powered and functional.
When ON is ‘0’, the module is disabled. The digital and
analog portions of the circuit are turned off for maxi-
mum current savings.
In order to return to the Active mode from the Off mode,
the user must wait for the analog stages to stabilize.
For the stabilization time, refer to the Electrical
Characteristics section of the device data sheet.
Note:
Writing to ADC control bits other than ON
(AD1CON1<15>), SAMP (AD1CON1<1>),
and DONE (AD1CON1<0>) is not recom-
mended while the A/D converter is running.
22.3.14 INITIATING SAMPLING
22.3.14.1 Manual Mode
In manual sampling, a acquisition is started by writing a
‘1’ to the SAMP (AD1CON1<1>) bit. Software must
manually manage the start and end of the acquisition
period by setting SAMP and then clearing SAMP after
the desired acquisition period has elapsed.
22.3.14.2 Auto-Sample Mode
In Auto-Sample mode, the sampling process is started
by writing a ‘1’ to the ASAM (AD1CON1<2>) bit. In
Auto-Sample mode, the acquisition period is defined by
ADCS<7:0> (AD1CON3<7:0>). Acquisition is automat-
ically started after a conversion is completed. Auto-
Sample mode can be used with any trigger source
other than manual.
© 2008 Microchip Technology Inc.
Preliminary
DS61143E-page 507