Si1000/1/2/3/4/5
5.2.2. Tracking Modes
Each ADC0 conversion must be preceded by a minimum tracking time in order for the converted result to
be accurate. The minimum tracking time is given in Table 4.9. The AD0TM bit in register ADC0CN controls
the ADC0 track-and-hold mode. In its default state when Burst Mode is disabled, the ADC0 input is contin-
uously tracked, except when a conversion is in progress. When the AD0TM bit is logic 1, ADC0 operates in
low-power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of 3 SAR
clocks (after the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in
low-power tracking mode, ADC0 tracks only when CNVSTR is low; conversion begins on the rising edge of
CNVSTR (see Figure 5.2). Tracking can also be disabled (shutdown) when the device is in low power
standby or sleep modes. Low-power track-and-hold mode is also useful when AMUX settings are fre-
quently changed, due to the settling time requirements described in “5.2.4. Settling Time Requirements” on
page 79.
A. ADC0 Timing for External Trigger Source
CNVSTR
(AD0CM[2:0]=100)
1
2 3 4 5 6 7 8 9 10 11 12 13 14
SAR Clocks
AD0TM=1
Low Power
or Convert
Low Power
Mode
Track
Convert
Convert
AD0TM=0
Track or Convert
Track
B. ADC0 Timing for Internal Trigger Source
Write '1' to AD0BUSY,
Timer 0, Timer 2,
Timer 1, Timer 3 Overflow
(AD0CM[2:0]=000, 001,010
011, 101)
1
1
2
3
4
4
5
5
6
6
7
7
8
8
9 10 11 12 13 14 15 16 17
SAR
Clocks
Low Power
or Convert
Track
Convert
Low Power Mode
AD0TM=1
2
3
9 10 11 12 13 14
SAR
Clocks
Track or
Convert
Convert
Track
AD0TM=0
Figure 5.2. 10-Bit ADC Track and Conversion Example Timing (BURSTEN = 0)
Rev. 1.0
77
SILICON [ SILICON ]
