QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1397
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LTC2656
DESCRIPTION
Demonstration circuit 1397 features the LTC2656
Octal 16 bit DAC. This device establishes a new
board-density benchmark for 16 bit DACs and ad-
vances performance standards for output drive,
crosstalk and load regulation in single supply,
voltage-output multiple DACs.
DC1397 has many features for evaluating the per-
formance of the LTC2656. Onboard 2.5 volt and
1.25 volt precision references are provided.
Another feature of this board is the onboard
LTC2428 20 bit ADC for monitoring DAC output
voltage. The 16ppm total error of this device is
adequate for taking meaningful measurements of
various LTC2656 parameters.
Design files for this circuit board are available.
Call the LTC factory.
Table 1. LTC2656 Performance Summary
PARAMETER CONDITION VALUE
Resolution 16 BITS
Monotonicity Vcc = 5V, Vref = 4.096V 16 BITS
Differential Nonlinearity Vcc = 5V, Vref = 4.096V +/-1 LSB
Integral Nonlinearity Vcc = 5V, Vref = 4.096V +/-12 LSB Typical
Load Regulation Vcc = Vref = 5V, Midscale
Iout = +/- 15 mA
2 LSB/mA Max
DC Crosstalk Due to load current change on any other channel 3.5 µV/mA
Demoboard
Type
LTC2656 Variation Full Scale
A L 2.5V
B H 4.096V
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QUICK START PROCEDURE
Connect DC1397 to a DC590 USB serial con-
troller using the supplied 14 conductor ribbon
cable. Connect DC590 to a host PC with a stan-
dard USB A/B cable. Run the evaluation soft-
ware supplied with DC590 or download it from
www.linear.com. The correct control panel will be
loaded automatically. Click the COLLECT button
to begin outputting codes to the DACs and read-
ing back the resulting output voltage for each
DAC.
Complete software documentation is available
from the Help menu item, as features may be
added periodically.
HARDWARE SET-UP
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JUMPERS
JP1 – Vref Select. Either a 2.5 volt internal or
1.25 volt on-board reference can be selected. To
apply an external reference through the Vref Tur-
ret, set jumper to EXT.
JP2 – Power Up Mode. The LTC2656 can be set
to either power up in Mid Scale or Zero Scale.
JP3 – ADC Disable. Set to ON for normal opera-
tion, with the onboard ADC enabled. For very
sensitive noise measurements, the ADC may be
disabled. The software will then display a posi-
tive full-scale reading.
ANALOG CONNECTIONS
DAC outputs – The eight DAC outputs from the
LTC2656 are brought out to turrets labeled DAC
A through DAC H. These may be connected to
external instruments or other circuitry.
NOTE:
DAC outputs are not in alphabetical order
on the circuit board.
Vref – The Vref turret is connected directly to the
reference terminals of the LTC2656 and
LTC2428 ADC. When one of the onboard refer-
ence is being used, the reference voltage may
be monitored at this point. An external reference
may also be applied to this turret after removing
JP2.
GROUNDING AND POWER CONNECTIONS
Power (Vcc) – Normally DC1397 is powered by
the DC590 controller. Vcc 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 opera-
tion.
Grounding – Separate power and signal grounds
are provided. Any large currents drawn from the
DAC outputs should be returned to power
ground. Also, if an external power supply is con-
nected, 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.
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