DAC7562T Datasheet, PDF (42/60 Pages) Texas Instruments – Internal Reference

DAC7562T, DAC7563T, DAC8162T
DAC8163T, DAC8562T, DAC8563T
SLASE61A – SEPTEMBER 2015 – REVISED OCTOBER 2015
www.ti.com
Typical Applications (continued)
V_OUT
=
R_G
2
´
æ
ççè
V_DAC - V_REF
R _SET
ö
÷÷ø
(5)
When configured for current mode, the XTR300 routes the internal output of its current copy circuitry to the SET
pin. This provides feedback for the internal OPA driver based on 1 / 10th of the output current, resulting in a
voltage-to-current transfer function. Generating bipolar current outputs from the single-ended DAC output
voltage, VDAC, requires the application of an offset to the XTR300 SET pin. Connect the R_SET resistor from the
SET pin to V_REF to apply the offset and obtain the transfer function shown in Equation 6.
I_OUT
=
10 ´
æ
ççè
V_DAC
R
- V_REF
SET
ö
÷÷ø
(6)
The desired output ranges for VDAC and V_REF voltages determine the R_SET and R_G resistor values, calculated
using Equation 7 and Equation 8. The system design requires a V_DAC voltage range of 0.04 V to 4.96 V in order
to operate the DAC8563T in the specified linear output range from codes 512 to 65 024.
R_SET
=
10 ´
æ
ççè
V _DAC - V_REF
I_OUT
ö
÷÷ø
=
10
´
æ
çè
4.96 V - 2.5
0.024 A
V
ö
÷ø
=
1025
Ω
(7)
R_G
=
2 ´ V_{OUT_MAX} ´ R _SET
V_DAC - V_REF
=
2 ´10 V ´1020 Ω
4.96 V - 2.5 V
= 8292 Ω
(8)
I_MON and IA_OUT accomplish load monitoring. The sizing of R_IMON and R_IA determine the monitoring output voltage
across the resistors. Size the resistors according to Equation 9 and Equation 10 and the expected output load
current I_DRV.
R_IMON
=
10 ´ V_IMON
I_DRV
(9)
R_IA =
10 ´ V_IA
I_IA
(10)
For more detailed information about the design procedure of this circuit and how to isolate it, see Two-Channel
Source/Sink Combined Voltage & Current Output, Isolated, EMC/EMI Tested Reference Design (TIDU434).
42
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