DEMO MANUAL DC934A
HarDware setup
JP4,6,7:
I
2
C Address Selection. These are connected to the
CA0, CA1, CA2 pins. The demo software uses the global
I
2
C address, so these pins have no effect when used with
the QuikEval™ software. They can be used in prototyping
to set the I
2
C address of the LTC2607 – refer to the data
sheet for the mapping of CA0,1,2 levels to I
2
C addresses.
ANALOg CONNECTIONS
V
OUTA
, V
OUTB
:
LTC2607 Outputs
V
REF
: The V
REF
turret is connected directly to the reference
terminals of the LTC2607 and LTC2422 ADC. When one of
the onboard references is being used, the reference voltage
may be monitored at this point. An external reference may
also be applied to this turret after removing JP1.
grounding and Power Connections
Power (V
CC
):
Normally DC934A is powered by the DC590
controller. V
CC
can be supplied to this turret, however
the power supply on DC590 must be disabled! Refer to
DC590 Quick Start Guide for more details on this mode
of operation.
grounding:
Separate power and signal grounds are pro-
vided. Any large currents drawn from the DAC outputs
should be returned to power ground. Also, if an external
power supply is connected, power ground should be
used. Signal ground is connected to the exposed ground
planes at the top and bottom edges of the board, and to
the two turrets labeled GND. Use signal ground as the
reference point for measurements and connections to
external circuits.
experiments
The following experiments are intended to demonstrate
some of the outstanding features of the LTC2607. All can
be performed using the onboard LTC2422 to monitor
the DAC output voltage. The indicated output voltage will
typically agree with an HP3458A voltmeter to 5 digits. If
a DAC will be sinking or sourcing a significant current,
then the output voltage should be measured as close to
the DAC as possible.
Most of the data sheet specifications use a 4.096V refer-
ence, so this is the preferred reference to use for these
experiments. Using the 5V regulator as the source for V
CC
has the limitation that V
CC
may be slightly lower than V
REF
,
which may affect the full-scale error. Selecting the 5V ref-
erence as the source for V
CC
overcomes this, however the
total current that the LTC2607 can source will be limited
to approximately 5mA.
Using an external power supply is highly recommended for
these experiments, especially those that draw significant
current. Refer to the DC590 quick start guide for details.
RESOLUTION
The onboard LTC2422 ADC has an input resolution of
6μV. This will easily resolve a 1LSB (76μV for V
REF
= 5V,
62.5μV for V
REF
= 4.096V) change in the LTC2607 output.
Set the DAC output to a voltage close to mid-scale. Select
the FINE slider on the control panel with the mouse and
use the right and left arrow keys to step the output by
single LSBs. The change should be clearly visible in the
output graph. (It may be necessary to wait for the graph
to clear if a large step has just occurred.)
INTEgRAL NONLINEARITy
A rough measurement of INL can be taken using the onboard
ADC. Measure one of the LTC2607 outputs at code 256
and 65,535 and calculate the slope and intercept using a
spreadsheet. Next, take several readings at intermediate
points. The readings should not deviate from the calcu-
lated line by more than 64LSBs, and they will typically be
within 12LSBs.
LOAD REgULATION/DC OUTPUT IMPEDANCE
Select 5V REG for V
CC
source. Set one of the outputs to
mid-scale (code 32768). Source or sink 15mA from one
of the DAC outputs by pulling it to power ground or V
CC
with an appropriate value resistor. The voltage change
dc934af
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