Datasheet

D[15:0]P/N
FRAMEP/N
SYNCP/N
T0528-01
DATACLKP/N (DDR)
Sync
Option #1
Sync
Option #2
Pattern 0
[15:0]
Pattern 1
[15:0]
Pattern 2
[15:0]
Pattern 3
[15:0]
Pattern 4
[15:0]
Pattern 5
[15:0]
Pattern 6
[15:0]
Pattern 7
[15:0]
Start cycle again with optional rising edge of FRAME or SYNC
DAC3484
www.ti.com SLAS749C –MARCH 2011–REVISED AUGUST 2012
The sampling is controlled by the serial interface signals SDENB and SCLK. If the temperature sensor is enabled
(tsense_sleep = “0” in register config26) a conversion takes place each time the serial port is written or read. The
data is only read and sent out by the digital block when the temperature sensor is read in tempdata(7:0) in
config6. The conversion uses the first eight clocks of the serial clock as the capture and conversion clock, the
data is valid on the falling eighth SCLK. The data is then clocked out of the chip on the rising edge of the ninth
SCLK. No other clocks to the chip are necessary for the temperature sensor operation. As a result the
temperature sensor is enabled even when the device is in sleep mode.
In order for the process described above to operate properly, the serial port read from config6 must be done with
an SCLK period of at least 1 μs. If this is not satisfied the temperature sensor accuracy is greatly reduced.
DATA PATTERN CHECKER
The DAC3484 incorporates a simple pattern checker test in order to determine errors in the data interface. The
main cause of failures is setup/hold timing issues. The test mode is enabled by asserting iotest_ena in register
config1. In test mode the analog outputs are deactivated regardless of the state of TXENABLE or sif_texnable in
register config3.
The data pattern key used for the test is 8 words long and is specified by the contents of iotest_pattern[0:7] in
registers config37 through config44. The data pattern key can be modified by changing the contents of these
registers.
The first word in the test frame is determined by a rising edge transition in FRAME or SYNC, depending on the
syncsel_fifoin(4:0) setting in config32. At this transition, the pattern0 word should be input to the data pins.
Patterns 1 through 7 should follow sequentially on each edge of DATACLK (rising and falling). The sequence
should be repeated until the pattern checker test is disabled by setting iotest_ena back to “0”. It is not necessary
to have a rising FRAME or SYNC edge aligned with every pattern0 word, just the first one to mark the beginning
of the series.
Figure 79. IO Pattern Checker Data Transmission Format
The test mode determines if the 16-bit LVDS data D[15:0]P/N of all the patterns were received correctly by
comparing the received data against the data pattern key. If any of the 16-bit data D[15:0]P/N were received
incorrectly, the corresponding bits in iotest_results(15:0) in register config4 will be set to “1” to indicate bit error
location. Furthermore, the error condition will trigger the alarm_from_iotest bit in register config5 to indicate a
general error in the data interface. When data pattern checker mode is enabled, this alarm in register config5, bit
7 is the only valid alarm. Other alarms in register config5 are not valid and can be disregarded.
For instance, pattern0 is programmed to the default of 0x7A7A. If the received Pattern 0 is 0x7A7B, then bit 0 in
iotest_results(15:0) will be set to “1” to indicate an error in bit 0 location. The alarm_from_iotest will also be set to
“1” to report the data transfer error. The user can then narrow down the error from the bit location information
and implement the fix accordingly.
Copyright © 2011–2012, Texas Instruments Incorporated Submit Documentation Feedback 67
Product Folder Links: DAC3484