Datasheet

Ch 3 Data
Auto/0000h
Ch 0 Data
Aux (TS Enable)
Ch 3 Data
Sel Temp Sensor
Ch 0 Data Temp Data
Ch 3
Sample
Ch 0
Sample
Ch 3
Sample
Ch 0
Sample
Temperature
Sample
Ch 0
Ch 3 Ch 0 Temp Sensor Ch 3
SCLK
DOUT
DIN
Selected
Channel
Auto Scan
Deselect Temp
Sensor
Auto/0000h
Auto ScanTemp Sensor
CS
ADS8634
ADS8638
SBAS541A –MAY 2011– REVISED AUGUST 2011 www.ti.com
DEVICE TEMPARATURE READ
The ADS8634/8 feature an internal temperature sensor. The device temperature can be read at any time during
any scan. It is essential to enable (power-up) the internal temperature at least one cycle before selecting the
temperature sensor for the device temperature measurement. The temperature sensor must be deselected after
temperature measurement. The device resumes the channel sequence from where it left the scan after
deselection of the temperature sensor. Do not disable (power-down) the temperature sensor before it is
deselected. Figure 88 illustrates a typical command sequence for device temperature measurement during an
auto scan.
Figure 88. Reading Temperature During Auto Scan (Channels 0 and 3 are selected for auto sequence)
SPI INTERFACE
The ADS8634/8 employ a four-wire SPI-compatible interface. Apart from the interface, CS and SCLK also
perform an ADC control function.
The data frame is synchronized with the CS falling edge. A low level on CS releases the DOUT pin from
three-state and the ADC conversion results are output on the DOUT line. Data bits are clocked out on the falling
edges of SCLK. The ADS8634/8 sample the analog input signal on the falling edge of CS and conversion is
performed using SCLK.
DOUT is the serial data output line. Depending on register settings,the ADC conversion results are output along
with the selected channel address or register data on the DOUT pin. The data output frame always consists of 16
bits. The SDO line goes to three-state after all the 16-bits of data frame are output or after CS goes high.
DIN is a serial data input line. It is used to program various registers for either device configuration or for
dynamic changes applicable on the next immediate CS falling edge.
34 Submit Documentation Feedback Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): ADS8634 ADS8638