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Linear Technology DC1846A Demo Manual

Ltc6947 ultralow noise and spurious fractional-n synthesizer
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DESCRIPTION
Demonstration circuit 1846A features the
Ultralow Noise and Spurious Fractional-N Synthesizer.
DC1846A provides 50Ω SMA connectors for the reference
frequency (REF+) and the two single-ended RF outputs
(RF+ and RF–).
 
 
 
Frequency 
reference input, 
SMA 
Ribbon 
cable 
connection 
to DC590 
3.3 V DC supply, 
banana jacks 
 
DEMO MANUAL DC1846A
Ultralow Noise and Spurious
Fractional-N Synthesizer
LTC
6947, an
A DC590 USB serial controller board is used for SPI com-
®
munication with the LTC6947, controlled by the supplied
FracNWizard™ software.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
FracNWizard is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Active loop filter op‐
amp DC supply, turret 
Figure 1. DC1846A Connections
LTC6947
U3 (VCO) DC 
supply, turret 
U4 (VCO or VCXO) 
DC supply, turret 
5 V DC supply, 
banana jacks
Differential 
output of VCO 
buffer, SMA 
Enable (pin 2) 
of U4 (VCO or 
VCXO), turret 
External VCO 
input, SMA 
 
dc1846af
1

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Summary of Contents for Linear Technology DC1846A

  • Page 1 Design files for this circuit board are available at (RF+ and RF–). http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and FracNWizard is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
  • Page 2 DEMO MANUAL DC1846A QUICK START PROCEDURE Connect the DC590 to one of your computer’s USB ports The DC1846A is easy to set up to evaluate the performance with the included USB cable. of the LTC6947. Follow the procedure below. The DC590 and FracNWizard application are required to FracNWizard Installation control the DC1846A through a personal computer (PC).

  • Page 3: Quick Start Procedure

    Figure 1 and the Typical DC1846A Requirements and Characteristics table). DC1846A Configuration 4. Connect the DC590 to the DC1846A with the provided 1. Connect a 100MHz reference frequency source (at J2) ribbon cable. and signal analyzers to RF+ and/or RF– (at J6 and/or 5.

  • Page 4: Troubleshooting

    Connect the C26 and C28 external VCO output to J5. Use CPGAIN to tune the external device. *These are the default installation options. For the DC1846A-A, U3 is populated with CVCO55CC-2328-2536 from Crystek dc1846af...
  • Page 5 VCO) and R15 = 0Ω, tune voltage of the depopulate R14 and populated VCO (U3 or U4), up to 24V applied to V+OA turret TYPICAL DC1846A REQUIREMENTS AND CHARACTERISTICS PARAMETER INPUT OR OUTPUT PHYSICAL LOCATION DETAILS 3.3V Power Supply Input J9 and J10 banana jacks Low noise and spur-free 3.3V,...

  • Page 6: Parts List

    DEMO MANUAL DC1846A PARTS LIST ITEM REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER CI1_A, C3_F2, C3_F3, CP_A, C14 CAP, 0603 CI1_P, C5, C12, C13, C18, C31 CAP, 0603 1.0µF 10% 10V X7R TAIYO YUDEN, LMK107B7105KA-T CI2_P, CI2_A CAP, 1206 CP_P CAP, 0603 47nF 10% 50V X7R...

  • Page 7: Schematic Diagram

    DEMO MANUAL DC1846A SCHEMATIC DIAGRAM dc1846af...
  • Page 8 DEMO MANUAL DC1846A SCHEMATIC DIAGRAM Note: The buffers shown on sheet 2 of 2 of the schematic are used to protect the LTC6947 when connected to the DC590 before the LTC6947 is powered up. There is no need for such circuitry if the SPI bus is not powered before powering up the LTC6947. The EEPROM is for identification and is not needed to program the LTC6947.

  • Page 9: Layout Top Layer

    Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
  • Page 10 Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods.

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