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dc2073af
DEMO MANUAL DC2073A
QUICK START PROCEDURE
Test Equipment:
1. A single 3V power supply.
2. An oscilloscope with a bandwidth of at least 5x f
OSC
.
(For example, if f
OSC
= 100MHz then use a 500MHz
oscilloscope).
3. A screwdriver to adjust the potentiometer.
Basic Test Procedure:
1. Connect power supply to V
+
and GND, turrets E4 and
E5.
2. Connect oscilloscope probe to OUT1 and GND.
Note: The ground lead of an oscilloscope probe has a
series inductance that can generate a resonant circuit
with the probe's capacitance. Probe resonance adds
transient peaks and ringing on a high speed wave-
form. Reliable probing of the high frequency LTC6905
and LTC6905-XXX (with corresponding demo boards
DC2073A-A, -D, -E, -F or -G), must use a very short
connection of the oscilloscope probe ground to the board
GND (see probe tip picture in Figure 1 Test Setup).
3. Set the JP1 jumper to the N divider position for the
desired frequency shown on Table2.
4. Turn on supply.
5. The oscilloscope display shows a 3V squarewave
(0V to 3V).
6. For the resistor-set ICs (DC2073A-A, -B, -C, -H, -I, -J
or -K) turn the RPOT potentiometer for the desired fre-
quency. (The frequency adjustment is very coarse when
the potentiometer is turned near the fully clockwise or
counter-clockwise position).
Verify Oscillator Accuracy
The f
OSC
accuracy of the resistor-set ICs (DC2073A-A, -B,
-C, -H, -I, -J or -K), can be verified by setting RSET to the
exact value from the f
OSC
equation shown in Table 2. For
the DC2073A-A, -B, -C, -J, -K, RSET = RPOT + RSET2.
RSET1 and RSET2 are never installed on the same board.
Connecting an ohmmeter across RPOT and RSET1 or
RSET2 forces current into the IC set pin (Pin 3 or 4) and
causes an error in the ohmmeter reading. The RS resistor
is in series with RPOT and equal to RSET1 or RSET2 and
the equivalent RSET = RPOT + RS.
Procedure to Verify Oscillator Accuracy
a. Calculate RSET for the desired frequency (RSET in Table 2).
b. Remove the power supply leads from DC2073A and con-
nect an ohmmeter from POT (E6) to V
+
(DC2073A-A,
-B, -C, -J or -K) or GND (DC2073A-H or-I).
C. Adjust RPOT for the exact value of RSET needed.
Note: If the potentiometer is turned near the fully clock-
wise or counter-clockwise position the RPOT adjustment
may be too coarse for setting an exact RSET value. In
addition, for a frequency adjustment near the upper or
lower f
OSC
range, RSET may be greater or less than the
default DC2073A RPOT + RSET1 or RSET2 value, in this
case the RSET1 or RSET2 resistor must be removed
and replaced with a lower or higher value.
