CS

SCLK

DOUT

DIN

1

16

TM_BUSY

1

16

1

16

InvalidData

Command:

SelectChannelTSENSE

InvalidData

Command:

SelectChannelAIN0

NoWritetothe

ControlRegister

ConversionResultfor

TemperatureMeasurement

WaitingforConfiguration

IntegratingandConverting

forT

SENSE

ConvertingforChannelAIN0

t

ACQ

CS

SCLK

DOUT

DIN

1

16

InvalidData

InvalidData

Command:

SelectChannelAIN3

Command:

SelectChannelAIN5

ConversionResultfor

ChannelAIN3

Command:

SelectChannelAIN1

Command:

SelectChannelAINx

ConversionResultfor

ChannelAIN5

ConvertingforChannelAIN3

WaitingforConfiguration

ConvertingforChannelAIN5

ConvertingforChannelAIN1

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 TSENSE 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, tACQ

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)

20

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