Switching; Gamma Resistor Strings; Output Load Sockets - Analog Devices EVAL-ADD8504 Quick Start Manual

EVAL-ADD8504/ADD8505/ADD8506

SWITCHING

The ADD8504/ADD8505/ADD8506 evaluation board can be
switched by driving the A/B pin of Block 1 with a 0 V to 5 V
clock. A 5 V input on the A/B pin selects GAMMA A; a 0 V
input selects GAMMA B. The user can also switch manually
using hardware Switch SW1. Switch Position A selects
GAMMA A (RA1 to RA7), and switch Position B selects
GAMMA B (RB1 to RB7), see Figure 3.

GAMMA RESISTOR STRINGS

The ADD8504/ADD8505/ADD8506 evaluation board includes
two external gamma resistor strings consisting of seven resistors
each to produce the necessary tap point voltages. This board has
been preconfigured (refer to the Factory Settings section for
details) as follows: GAMMA A consists of Resistor RA1 to
Resistor RA7, and GAMMA B consists of Resistor RB1 to
Resistor RB7 (see Figure 3).
The user can change the resistor values to produce the desired
voltages. Included with the ADD8504/ADD8505/ADD8506
evaluation board kit is the gamma voltage calculator that allows
the user to specify the desired voltages and automatically calcu-
late the necessary resistor values. In addition, the calculator
allows the user to specify resistances and calculate voltages. The
gamma voltage calculator expedites the evaluation process. It is
located on the ADD8504/ADD8505/ADD8506 evaluation board
kit CD labeled ADD8504-05-06 Gamma Voltage Calculator.xls.
Figure 3. Gamma Resistor String Schematic

OUTPUT LOAD SOCKETS

Sockets are provided on the evaluation board for a series
resistance and capacitive load to ground for each of the six
gamma buffer outputs. The sockets are labeled RLOAD1 to
RLOAD6 and CLOAD1 to CLOAD6; they are located in Block 4
on the evaluation board (see Figure 4). These loads are optional
and are for customer evaluation purposes only. If no load is
desired, neither resistor nor capacitor should be added.
As shipped from the factory, all six output load resistors are
jumpered (0 Ω resistors). All six output load capacitors are 1 nF.
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VCC
RA1
INA1
RA2
INA2
RA3
INA3
GAMMA A
RA4
(VCOM+)
INA4
RA5
INA5
RA6
INA6
RA7
RB1
INB1
GND
RB2
INB2
RB3
INB3
GAMMA B
RB4
INB4
(VCOM–)
RB5
INB5
RB6
INB6
RB7