
2009 Microchip Technology Inc.
DS41341E-page 101
PIC16F72X/PIC16LF72X
TABLE 9-1:
ADC CLOCK PERIOD (TAD) VS. DEVICE OPERATING FREQUENCIES
FIGURE 9-2:
ANALOG-TO-DIGITAL CONVERSION TAD CYCLES
ADC Clock Period (TAD)
Device Frequency (FOSC)
ADC
Clock Source
ADCS<2:0>
20 MHz
16 MHz
8 MHz
4 MHz
1 MHz
Fosc/2
000
100 ns(2)
125 ns(2)
250 ns(2)
500 ns(2)
2.0
μs
Fosc/4
100
200 ns(2)
250 ns(2)
500 ns(2)
1.0
μs4.0 μs
Fosc/8
001
400 ns(2)
0.5
μs(2)
1.0
μs2.0 μs
8.0
μs(3)
Fosc/16
101
800 ns
1.0
μs2.0 μs4.0 μs
16.0
μs(3)
Fosc/32
010
1.6
μs2.0 μs4.0 μs
8.0
μs(3)
32.0
μs(3)
Fosc/64
110
3.2
μs4.0 μs
8.0
μs(3)
16.0
μs(3)
64.0
μs(3)
FRC
x11
1.0-6.0
μs(1,4) 1.0-6.0 μs(1,4) 1.0-6.0 μs(1,4) 1.0-6.0 μs(1,4) 1.0-6.0 μs(1,4)
Legend: Shaded cells are outside of recommended range.
Note 1:
The FRC source has a typical TAD time of 1.6
μs for VDD.
2:
These values violate the minimum required TAD time.
3:
For faster conversion times, the selection of another clock source is recommended.
4:
When the device frequency is greater than 1 MHz, the FRC clock source is only recommended if the
conversion will be performed during Sleep.
TAD1
TAD2
TAD3
TAD4
TAD5
TAD6
TAD7
TAD8
TAD9
Set GO/DONE bit
Holding Capacitor is Disconnected from Analog Input (typically 100 ns)
b7
b6
b5
b4
b3
b2
b1
b0
Tcy to TAD
Conversion Starts
ADRES register is loaded,
GO/DONE bit is cleared,
ADIF bit is set,
Holding capacitor is connected to analog input
TAD0