LMP92066_15 Datasheet, PDF (46/62 Pages) Texas Instruments – LMP92066 Dual Temperature-Controlled DAC with Integrated EEPROM and Output ON/OFF Control

LMP92066
SNAS634A – MARCH 2014 – REVISED APRIL 2015
www.ti.com
Typical Applications (continued)
3. Check the slope of the pBUF(T). Record the sign of the slope, and from here on consider a positive slope
function cG(T). The design variable set in this step is the POL bit. pBUFF(T) is a monotonically increasing
function, therefore:
POL  0
cG(T)  pBUFF(T)
(9)
4. Discretize the continuous cG(T) along its temperature domain, thus creating the sequence G(k). Maintain the
full precision of the G(k) values. Note the full precision cG(T) at T = 24°C — this is the full precision BASE
value, fpBASE, still in voltage domain.
G(0)  cG( 28GC)  2.2499
G(1)  cG( 24GC)  2.2508
G(2)  cG( 20GC)  2.2508
F
G(13)  cG(24GC)  2.2747  fpBASE
F
G(39)  cG(128GC)  2.4667
5. Apply difference operation to the G(k) sequence, and obtain new sequence fpDEL(k). These are now the full
precision increments of the target function with each 4°C interval.
fpDEL(0)  G(1) G(0)  0.9528 K10 ³
fpDEL(1)  G(2) G(1)  1.1846 K10 ³
fpDEL(2)  G(3) G(2)  1.3891K10 ³
F
fpDEL(38)  G(39) G(38)  16.9789 K10 ³
6. Convert the full precision voltages of fpDEL(k) and fpBASE to a numeric, quantized domain. This reverses
the DAC action.
BASE
round
§
¨©
fpBASE u
5
4096
·
¸¹
1863₁₀
747₁₆
011101000111₂
DEL(0)
§
round _¨©
fpDEL(0)
5
u
4096
·
¸¹
1₁₀
1₁₆
0001₂
p
DEL(38)
§
round _¨©
fpDEL(38)
5
u
4096
·
¸¹
14₁₀
E₁₆
1110₂
7. Usually BYP bit is reset, BYP=0. However, in cases where it is desirable to bypass the LUT and ALU, and
have the DACx output produce voltage equivalent of the BASE value, set BYP = 1.
8. Repeat steps 1 to 6 to obtain POL, BYP, BASE, DELx values for the second channel.
9. Now have BYP, POL, BASE, and DEL(0..38) values ready to be programmed into the LUT.
NOTE
The device has to be in the L2 Access Level before commencing the WRITE access of
BYP, POL, BASE, DELx values. The register WRITE operation immediately affects the
operation of the device. However, operating memory is volatile, and BURN operation is
required to commit the LUT coefficients to non-volatile memory, EEPROM.
46
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