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 28 of 43
NXP Semiconductors
DAC1405D750
Dual 14-bit DAC, up to 750 Msps; 4 and 8 interpolating
10.9 DAC transfer function
The full-scale output current for each DAC is the sum of the two complementary current
outputs:
(3)
The output current depends on the digital input data:
(4)
(5)
The setting applied to CODING (register 00h[2]; see Table 9 “
Register allocation map”)
defines whether the DAC1405D750 operates with a binary input or a two’s complement
input.
Table 38
shows the output current as a function of the input data, when I
O(fs)
= 20 mA.
10.10 Full-scale current
10.10.1 Regulation
The DAC1405D750 reference circuitry integrates an internal bandgap reference voltage
which delivers a 1.29 V reference to the GAPOUT pin. It is recommended to decouple pin
GAPOUT using a 100 nF capacitor.
The reference current is generated via an external resistor of 953  (1 %) connected to
pin VIRES. A control amplifier sets the appropriate full-scale output current (I
O(fs)
) for both
DACs (see Figure 11
).
Table 38. DAC transfer function
Data I13 to I0 and Q13 to Q0 IOUTP (mA) IOUTN (mA)
Binary Two’s complement
0 00 0000 0000 0000 10 0000 0000 0000 0 20
... ... ... ... ...
8192 10 0000 0000 0000 00 0000 0000 0000 10 10
... ... ... ... ...
16383 11 1111 1111 1111 01 1111 1111 1111 20 0
I
Ofs
I
IOUTP
I
IOUTN
+=
I
IOUTP
I
Ofs
DATA
16383
----------------


=
I
IOUTN
I
Ofs
16383 DATA–
16383
-------------------------------------


=