DC861 QUICK START GUIDE
6
D . A 4:1 Analog M U X 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-M UX’D, SW 1-D-O N , SW 2-O FF, 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.
Note: The daisy chain flat ribon cable shorts the m aster board’
s OUT A and B to the slave board’
s OUT A and B.
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, and #3 digit to 2 and #1 digit to 1.
7. Press the SEN D switch repeatedly and the display will show in sequence:
a. on the master display 01 then 02 then on the slave display 10 and 05 (LTC6912-1) or
b. on the master display 01 then 02 then on the slave display 08 and 04 (LTC6912-2).
The oscilloscope display should show in sequence:
a. 0.1Vp-p, 1kH z sine, 0.2Vp-p, 1kH z sinewave, 1.0Vp-p, 1kH z sinewave and 0.5Vp-p (for an LTC6912-1) or
b. 0.1Vp-p, 1kH z sine, 0.2Vp-p, 1kH z sinewave, 0.8Vp-p, 1kH z sinewave and 0.4Vp-p (for an LTC6912-2).
AD D ITIO N AL BO AR D FU N CTIO N S
N ote A
: For the lowest analog noise and distortion tests, set SW 1 to D-O FF after pressing the SEN D sw.
W hen SW -1 is set to D-O FF, the board’s digital circuits are disconnected and the LTC6912 is a fixed gain
amplifier (dual or single depending if the J6 junper is in DUAL or M UX’D position). The amplifier’s gain
is the last setting before the SEN D sw is pressed.
N ote B.
For an optional external serial control of the LTC6912, remove the jumper wires of J1 from 1-2, 4-5 and
7-8 and connect jumper wires to 2-3, 5-6 and 8-9 (see DC861 schematic). The external SPI control
inputs are the CLK, DN and CS/LD miniature turrets under connector J4 (on the lower left corner of
DC861).
N ote C.
The VSLV miniature turret under the J4 connector is for monitoring the digital 5V voltage of the slave
board in a daisy chain connection. The +5V miniature turret under the J4 connector is for monitoring
the DC861 5V switching regulator that provides power to the board’s digital circuits.