Datasheet

CS
SCLK
DOUT
DIN
1
16
TM_BUSY
1
16
1
16
InvalidData
Command:
SelectChannelT
SENSE
InvalidData
Command:
SelectChannelAIN0
NoWritetothe
ControlRegister
ConversionResultfor
TemperatureMeasurement
WaitingforConfiguration
IntegratingandConverting
forT
SENSE
ConvertingforChannelAIN0
t
ACQ
CS
SCLK
DOUT
DIN
1 16
InvalidData InvalidData
Command:
SelectChannelAIN3
Command:
SelectChannelAIN5
ConversionResultfor
ChannelAIN3
Command:
SelectChannelAIN1
Command:
SelectChannelAINx
ConversionResultfor
ChannelAIN5
ConvertingforChannelAIN3WaitingforConfiguration ConvertingforChannelAIN5 ConvertingforChannelAIN1
1
16
1 16 1
16
ADS8028
SBAS549B –MAY 2011–REVISED MARCH 2012 www.ti.com
Internal Temperature Sensor Channel
The internal temperature sensor can be selected for conversion by writing a '1' to the T
SENSE
bit in the Control
Register. On the next CS falling edge, the TM_BUSY pin goes high and remains high throughout the temperature
sensor conversion process. When the TM_BUSY pin goes high, 16 clocks are required to execute one valid read
or write cycle: to read the previous conversion result and to program the next conversion settings. However, any
subsequent read or write operations are ignored until TM_BUSY goes low; CS is ignored, the Control Register is
not updated, and DOUT returns all '1's.
The ADS8028 takes 100 μs (max) to measure and convert the temperature channel. A TM_BUSY signal falling
edge can be used to initiate a read operation in order to read the temperature conversion result. However, t
ACQ
must be allowed to elapse between the TM_BUSY falling edge and the subsequent CS falling edge to ensure
that the subsequent conversion has sufficient acquisition time. Figure 34 shows the temperature sensor
conversion sequence.
After TM_BUSY goes high, the temperature conversion can be aborted by writing a '1' to the STANDBY bit in the
first write operation. The device aborts the ongoing conversion and enters STANDBY mode on the 16th SCLK
falling edge.
Figure 34. Serial Interface Timing Diagram for the Temperature Sensor Conversion
MODES OF OPERATION
Channel Scanning
The ADS8028 offers different modes of operation that can be selected by programming the Control Register.
Channel-scanning modes enable any of the nine channels to be selected for conversion and also allow the
selected channels to be repeatedly converted. Low-power modes allow power consumption and throughput rate
ratio to be optimized.
Single or Multiple Channels: One Conversion
The ADS8028 can be configured to convert any of the nine channels by writing a '1' to the Control Register bit
associated with the desired channel. After power-up, a valid write operation must be executed on the Control
Register to select the desired channel. In this mode, the REPEAT bit in the Control Register should be set to '0'.
The selected channel is converted in the second frame and the conversion result can be clocked out in the third
frame. During the second frame, the Control Register can be written to select the channel to be converted in the
third frame. Figure 35 shows a diagram of this configuration.
Figure 35. Configuring a Conversion and Read with the ADS8028
(One Channel Selected for Conversion, REPEAT = 0)
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