DEMO MANUAL DC2073A LTC1799, LTC6900, LTC6905, LTC6905-XXX, LTC6906, LTC6907 LTC6908 SOT23 Silicon Oscillators DESCRIPTION DC2073A demo board features Linear Technology s SOT23 Design files for this circuit board are available at packaged silicon oscillators. The DC2073A demo board is DEMO MANUAL DC2073A QUICK START PROCEDURE Test Equipment: Verify Oscillator Accuracy 1. A single 3V power supply. The f accuracy of the resistor-set ICs (DC2073A-A, -B, OSC -C, -H, -I, -J or -K), can be verified by setting RSET to the 2. An oscilloscope with a bandwidth of at least 5x f . OSC exact value from the f equation shown in Table 2. For OSC (For example, if f = 100MHz then use a 500MHz OSC the DC2073A-A, -B, -C, -J, -K, RSET = RPOT + RSET2. oscilloscope). RSET1 and RSET2 are never installed on the same board. 3. A screwdriver to adjust the potentiometer. Connecting an ohmmeter across RPOT and RSET1 or RSET2 forces current into the IC set pin (Pin 3 or 4) and Basic Test Procedure: causes an error in the ohmmeter reading. The RS resistor + is in series with RPOT and equal to RSET1 or RSET2 and 1. Connect power supply to V and GND, turrets E4 and the equivalent RSET = RPOT + RS. E5. 2. Connect oscilloscope probe to OUT1 and GND. Procedure to Verify Oscillator Accuracy Note: The ground lead of an oscilloscope probe has a a. Calculate RSET for the desired frequency (RSET in Table 2). series inductance that can generate a resonant circuit b. Remove the power supply leads from DC2073A and con- with the probe s capacitance. Probe resonance adds + nect an ohmmeter from POT (E6) to V (DC2073A-A, transient peaks and ringing on a high speed wave- -B, -C, -J or -K) or GND (DC2073A-H or-I). form. Reliable probing of the high frequency LTC6905 and LTC6905-XXX (with corresponding demo boards C. Adjust RPOT for the exact value of RSET needed. DC2073A-A, -D, -E, -F or -G), must use a very short Note: If the potentiometer is turned near the fully clock- connection of the oscilloscope probe ground to the board wise or counter-clockwise position the RPOT adjustment GND (see probe tip picture in Figure1 Test Setup). may be too coarse for setting an exact RSET value. In 3. Set the JP1 jumper to the N divider position for the addition, for a frequency adjustment near the upper or desired frequency shown on Table2. lower f range, RSET may be greater or less than the OSC default DC2073A RPOT + RSET1 or RSET2 value, in this 4. Turn on supply. case the RSET1 or RSET2 resistor must be removed 5. The oscilloscope display shows a 3V squarewave and replaced with a lower or higher value. (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). dc2073af 2