60
SLVSDC2B – FEBRUARY 2016 – REVISED AUGUST 2016
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Copyright © 2016, Texas Instruments Incorporated
Table 6. ADC Divider Ratios (continued)
CHANNEL #
SIGNAL
TYPE
AUTO-SEQUENCED
DIVIDER RATIO
BUFFERED
22
GPIO0
Voltage
No
3
Yes
23
Unused
Voltage
No
3
Yes
24
GPIO2
Voltage
No
3
Yes
25
GPIO3
Voltage
No
3
Yes
26
GPIO4
Voltage
No
3
Yes
27
GPIO5
Voltage
No
3
Yes
28
GPIO6
Voltage
No
3
Yes
29
GPIO7
Voltage
No
3
Yes
30
GPIO8
Voltage
No
3
Yes
31
BUSPOWERZ
Voltage
No
3
Yes
9.3.16.2 ADC Operating Modes
The ADC is configured into one of three modes: single channel readout, round-robin automatic readout and one
time automatic readout.
9.3.16.3 Single Channel Readout
In Single Channel Readout mode, the ADC reads a single channel only. Once the channel is selected by
firmware, a conversion takes place followed by an interrupt back to the digital core.
shows the timing
diagram for a conversion starting with an ADC enable. When the ADC is disabled and then enabled, there is an
enable time T_ADC_EN (programmable) before sampling occurs. Sampling of the input signal then occurs for
time T_SAMPLE (programmable) and the conversion process takes time T_CONVERT (12 clock cycles). After
time T_CONVERT, the output data is available for read and an Interrupt is sent to the digital core for time
T_INTA (2 clock cycles).
In Single Channel Readout mode, the ADC can be configured to continuously convert that channel.
shows the ADC repeated conversion process. In this case, once the interrupt time has passed after a conversion,
a new sample and conversion occurs.
9.3.16.4 Round-Robin Automatic Readout
When this mode is enabled, the ADC state machine will read from channel 0 to channel 11 and place the
converted data into registers. The host interface can request to read from the registers at any time. During
Round-Robin Automatic Readout, the channel averaging must be set to 1 sample.
When the TPS65981 is running a Round Robin Readout, it will take approximately 696
μ
s (11 channels × 63.33
μ
s conversion) to fully convert all channels. Since the conversion is continuous, when a channel is converted, it
will overwrite the previous result. Therefore, when all channels are read, any given value may be 649
μ
s out of
sync with any other value.
9.3.16.5 One Time Automatic Readout
The One Time Automatic Readout mode is identical to the Round-Robin Automatic Readout except the
conversion process halts after the final channel is converted. Once all 11 channels are converted, an interrupt
occurs to the digital core.
