Datasheet

LTC2755
20
2755f
Grounding
As with any high resolution converter, clean grounding is
important. A low impedance analog ground plane and star
grounding techniques should be used. I
OUT2X
must be tied
to the star ground with as low a resistance as possible.
When it is not possible to locate star ground close to
I
OUT2
, a low resistance trace should be used to route this
pin to star ground. This minimizes the voltage drop from
this pin to ground caused by the code dependent current
fl owing to ground. When the resistance of this circuit
board trace becomes greater than 1, a force/sense am-
plifi er confi guration should be used to drive this pin (see
APPLICATIONS INFORMATION
Figure 2). This preserves the excellent accuracy (1LSB
INL and DNL) of the LTC2755-16.
Layout
Figures 3, 4, 5, and 6 show the layout for the LTC2755
evaluation board, DC1112. This shows how to route
the digital signals around the device without interfering
with the reference and output op amps. Complete demo
board documentation is available in the DC1112 quick
start guide.
–
+
–
+
1/2 LT1469
1/2 LT1469
DAC A
LTC2755-16
V
REF
5V
2
1
3
59
60
61
64
63
1
62
I
OUT1A
15pF
I
OUT2A
R
FBA
R
VOSA
REFA
R
COM1
R
IN1
R
OFSA
V
OUTA
2
58
–
+
6
1
23
I
OUT2
2
3
*SCHOTTKY BARRIER DIODE
ZETEX*
BAT54S
LT1001
2755 F02
1000pF
ALTERNATE AMPLIFIER FOR OPTIMUM SETTLING TIME PERFORMANCE
6
1
23
2,14, 34, 46
–
+
LT1468
3
ZETEX
BAT54S
2
200
200Ω
I
OUT2
150pF
3
2
DAC B
DAC C
DAC D
–
+
–
+
–
+
Figure 2. Optional Circuits for Driving I
OUT2
from GND with a Force/Sense Amplifi er.