DAC34SH84 Datasheet, PDF (59/77 Pages) Texas Instruments – Quad-Channel, 16-Bit, 1.5 GSPS Digital-to-Analog Converter (DAC)

DAC34SH84
www.ti.com
SLAS808B – FEBRUARY 2012 – REVISED JULY 2012
OFFSET CORRECTION
Registers qmc_offsetA(12:0), qmc_offsetB(12:0), qmc_offsetC(12:0) and qmc_offsetD(12:0) can be used to
independently adjust the dc offsets of each channel. The offset values are in represented in 2s-complement
format with a range from –4096 to 4095.
The offset value adds a digital offset to the digital data before digital-to-analog conversion. Because the offset is
added directly to the data it may be necessary to back off the signal to prevent saturation. Both data and offset
values are LSB aligned.
qmc_offsetA
{–4096, –4095, ..., 4095}
16
A Data In
13
16
Σ
A Data Out
16
B Data In
qmc_offsetB
{–4096, –4095, ..., 4095}
16
Σ
13
B Data Out
qmc_offsetC
{–4096, –4095, ..., 4095}
16
C Data In
13
16
Σ
C Data Out
16
16
D Data In
Σ
D Data Out
13
qmc_offsetD
{–4096, –4095, ..., 4095}
B0165-03
Figure 76. Digital Offset Block Diagram
TEMPERATURE SENSOR
The DAC34SH84 incorporates a temperature sensor block which monitors the temperature by measuring the
voltage across 2 transistors. The voltage is converted to an 8-bit digital word using a successive-approximation
(SAR) analog to digital conversion process. The result is scaled, limited and formatted as a twos complement
value representing the temperature in degrees Celsius.
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.
Copyright © 2012, Texas Instruments Incorporated
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