DC861 QUICK START GUIDE
5
B. 2:1 Analog M U X
1. Connect a DC861 board as shown in Figure 5.
(J2-Dual, J6-M UX’D, SW 1-D-O N , SW 2-O FF, SW 3-EN BL).
2. Set the power supply to ±5V and turn it on.
3. Turn on the sinewave generator and set it to a 1Vp-p, 1kH z sinewave
(refer to Tables 1 or 2 for the nominal PG A A and B input impedance).
4. Connect one oscilloscope channel to an output (in a M UX operation O UT A and B are shorted).
5. Use the SELECT and UP and DO W N switches to set the gain to one (0dB) for PG A A and two (6dB) for PG A B
and press the SEN D switch to send the data to the LTC6912.
6. Pressing the SEN D switch repeatedly will show on the LED display an 01 or an 02 (the 2:1 M UX gain switches
from one to two) and the output between O UT A or O UT B (the oscilloscope display should alternately show a
1Vp-p and a 2Vp-p, 1kH z sinewave (the 2:1 M UX switches between amplifier gains one and two).
C. Q U AD PG A (D aisy Chain O peration of tw o D C861)
Note: In a daisy chain m ode, the PGA settings are set in hex and on SEND the settings are shown in decim al.
1. Connect two DC861 boards as shown in Figure 7.
(jumpers and switches on master and slave boards, J2-Dual, J6-DUAL, SW 1-D-O N , SW 3-EN BL).
2. O n the master board set SW 2 to O N and on the slave board set SW 2 to O FF.
3. Set the power supply to ±5V and turn it on.
4. Turn on the sinewave generator and set it to a 0.1V p-p (100mV), 1kH z sinewave
(refer to Tables 1 or 2 for the nominal PG A A and B input impedance).
5. The 4-digit display on the slave board should be blank and the gain settings for all four PG As shown in hex digits on
the master board’s 4-digit LED display.
6. Use the SELECT and UP and DO W N switches to set on the master’s display the gains in hex of the four PG As
as follows: #1 digit to 4, #2 digit to 3, #3 digit to 2 and #1 digit to 1.
Note: Before the SEND sw is pressed, the m aster display shows the PGA gain from left to right in the sam e sequence of the
16-bit SPI word (the setting for the slave PGA B is sent first then the setting for the slave PGA A, then the setting for the
m aster PGA B and last the setting for the m aster PGA A).
7. Press the SEN D switch to send the data to the LTC6912 on the master and slave boards.
8. The master and slave display and oscilloscope display should show:
a. M aster display digits #1 and 2, PG A B gain=02 and on oscilloscope channel #2 a 0.2Vp-p, 1kH z sinewave.
b. M aster display digits #3 and 4, PG A A gain=01 and on oscilloscope channel #1 a 0.1Vp-p, 1kH z sinewave.
c. Slave display digits #1 and 2, PG A B gain=10 (LTC6912-1) or PG A B gain=08 (LTC6912-2) and on
oscilloscope channel #4 a 1.0Vp-p, 1kH z sinewave (LTC6912-1) or a 0.8Vp-p, 1kH z sinewave (LTC6912-2).
d. Slave display digits #3 and 4, PG A A gain=05 (LTC6912-1) or PG A B gain=04 (LTC6912-2) and on
oscilloscope channel #3 a 0.5Vp-p, 1kH z sinewave (LTC6912-1) or a 0.5Vp-p, 1kH z sinewave (LTC6912-2).
(See Figure 7 example).