DAC1401D125 3 © IDT 2012. All rights reserved.
Product data sheet Rev. 03 — 2 July 2012 19 of 25
Integrated Device Technology
DAC1401D125
Dual 14-bit DAC, up to 125 Msps
An external reference can also be used for applications requiring higher accuracy or
precise current adjustment. Due to the high input impedance of pin REFIO, applying an
external source disables the bandgap.
10.6 Gain control
Table 8 shows how to select the different gain control modes.
In Independent gain mode, both full-scale currents can be adjusted independently using
resistors R
A
on pin AVIRES and R
B
on pin BVIRES.
In Common gain mode, the full-scale current is adjusted with resistor R
A
on pin AVIRES
and divided by two in both DACs.
10.7 Analog outputs
See Figure 20 for the analog output circuit of one DAC. This circuit consists of a parallel
combination of PMOS current sources and associated switches for each segment.
Cascode source configuration enables the output impedance of the source to be
increased, thus improving the dynamic performance by reducing distortion.
The DAC1401D125 can be used either with:
• a differential output, coupled to a transformer (or operational amplifier) to reduce
even-order harmonics and noise
• or a single-ended output for applications requiring unipolar voltage.
The typical configuration is to use 1 V p-p level on each output IOUTAP/IOUTBP and
IOUTAN/IOUTBN but several combinations can be used as far as they respect the voltage
compliance range.
Table 8. Gain control
GAINCTRL Mode DAC A
full-scale control
DAC B
full-scale control
0 independent gain control AVIRES BVIRES
1 common gain control AVIRES AVIRES
Fig 20. Equivalent analog output circuit
001aai821
R
L
R
L
AGND AGND
IOUTAP/IOUTBP
IOUTAN/IOUTBN
