Datasheet

DAC1405D750 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 5 — 31 January 2012 32 of 43
NXP Semiconductors
DAC1405D750
Dual 14-bit DAC, up to 750 Msps; 4 and 8 interpolating
10.13 Auxiliary DACs
The DAC1405D750 integrates 2 auxiliary DACs that can be used to compensate for any
offset between the DAC and the next stage in the transmission path.
Both auxiliary DACs have a resolution of 10-bit and are current sources (referenced to
ground).
(6)
The output current depends on the auxiliary DAC data:
(7)
(8)
Table 42
shows the output current as a function of the auxiliary DAC data.
10.14 Output configuration
10.14.1 Basic output configuration
The use of a differentially-coupled transformer output provides optimum distortion
performance (see Figure 13
). In addition, it helps to match the impedance and provides
electrical isolation.
Table 42. Auxiliary DAC transfer function
Default settings are shown highlighted.
Data AUX[9:0] (binary) I
AUXP
(mA) I
AUXN
(mA)
0 00 0000 0000 0 2.2
... ... ... ...
512 10 0000 0000 1.1 1.1
... ... ... ...
1023 11 1111 1111 2.2 0
I
OAUX
I
AUXP
I
AUXN
+=
AUXP I
OAUX
AUX 9:0
1023
-------------------------


=
AUXN I
OAUX
(1023 A– UX 9:0
1023
---------------------------------------------


=
Fig 13. 1 V
o(p-p)
differential output with transformer
001aaj817
50 Ω
50 Ω
50 Ω
IOUTnP/IOUTnN; V
o(cm)
= 2.8 V; V
o(dif)(p-p)
= 1 V
IOUTnP
IOUTnN
0 mA to 20 mA
2:1
0 mA to 20 mA
V
DDA(3V3)
V
DDA(3V3)