DC1446A - Demo Manual

DEMO CIRCUIT 1446
DEMO CIRCUIT 1446 QUICK START GUIDE - LTC6909
QUICK START GUIDE
3 TO 8 OUTPUT MULTIPHASE OSCILLATOR WITH SSFM
LTC6909
3 TO 8 OUTPUT MULTIPHASE OSCILLATOR with SSFM
DESCRIPTION
Demonstration circuit 1446 features the LTC6909 multiple output oscillator with spread spectrum frequency
modulation (SSFM). The LTC®6909 is an easy to use
precision oscillator that can provide 1-, 2-, 3-, 4-, 5-, 6-,
7- or 8-phase synchronized outputs. The LTC6909
spread spectrum frequency modulation (SSFM), can be
enabled to improve electromagnetic compatibility (EMC)
performance. Eight separate outputs provide up to eight
rail-to-rail, 50% duty cycle clock signals. Using three
logic inputs, the outputs are configured for phase separation, ranging from 45° to 120° (three to eight phases).
The clock outputs can also be held low or configured for
Hi-Z. A single resistor (RSET) combined with the phase
configuration, sets the output frequency, based on the
following formula:
fOUT = (20MHz x 10k)/(RSET x PH)
where PH = 3, 4, 5, 6, 7 or 8
the fOUT range is 12.5kHz to 6.67MHz.
The PH0, PH1 and PH2 logic inputs define the LTC6909
multi-phase mode of operation and control its outputs as
follows:
PH2 PH1 PH0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
MODE
All Outputs Are Floating (Hi-Z)
All Outputs Are Held Low
3-Phase Mode (PH = 3)
4-Phase Mode (PH = 4)
5-Phase Mode (PH = 5)
6-Phase Mode (PH = 6)
7-Phase Mode (PH = 7)
8-Phase Mode (PH = 8)
A DC1446 contains an LTC6909 and test terminals for
the eight outputs. On board jumpers are provided to set
the LTC6909 phase inputs (PH0, PH1 and PH2) and the
SSFM modulation. The on board frequency setting resistor (RSET) is pre-loaded with a 100k surface mount resistor (in addition, two pin receptacles are provided for
using a leaded RSET resistor).
Design files for this circuit board are available.
Call the LTC factory.
LTC, LT are registered trademarks of Linear Technology Corporation.
QUICK START PROCEDURE
Demonstration circuit 1446 is easy to set up and test.
Refer to Figure 1 for the quick test setup and follow the
procedure below:
2. Set the power supply to 5V.
1. Place jumpers in the following positions:
4. With a 10x probe connected to OUT1 the oscilloscope
should show a 5V, 250kHz, squarewave (±4.5%).
3. Turn on the power supply.
JP3 (PH0) to V+, JP4 (PH1) to V+, JP1 (PH2) to V+ and
JP1 (MOD) to SSFM OFF.
1
DEMO CIRCUIT 1446 QUICK START GUIDE - LTC6909
3 TO 8 OUTPUT MULTIPHASE OSCILLATOR WITH SSFM
QUICK START SET-UP
Figure 1. Quick Test Setup
Single Power Supply
+
-
Oscilloscope
NOTE: The 6909 outputs (OUT1-OUT8) can drive 1k and 50pF loads. If a spectrum analyzer is used to measure the
spread spectrum bandwidth then use a high impedance probe to monitor the outputs (typically the input impedance
of a spectrum analyzer is 50 ohms).
DEMO CIRCUIT 1446 QUICK START GUIDE - LTC6909
3 TO 8 OUTPUT MULTIPHASE OSCILLATOR WITH SSFM
3
DEMO CIRCUIT 1446 QUICK START GUIDE - LTC6909
3 TO 8 OUTPUT MULTIPHASE OSCILLATOR WITH SSFM
DC1446 PARTS LIST
Item Qty
Reference
Part Description
Manufacturer / Part #
1
1
C1
CAP., X7R, 10uF, 10V, 20% 1206
AVX, 1206ZC106MAT2A
2
2
C5,C2
CAP., X7R, 0.1uF, 16V, 10% 0402
TDK, C1005X7R1C104K
3
2
C3,C6
CAP., X5R, 1uF, 6.3V, 10% 0402
TDK, C1005X5R0J105K
4
1
C4
CAP., C0G, 1000pF, 25V, 5% 0402
TDK, C1005C0G1E102J
5
2
E1,E2
JACK, BANANA
KEYSTONE, 575-4
6
10
E3-E12
TESTPOINT, TURRET, .094" pbf
MILL-MAX, 2501-2-00-80-00-00-07-0
7
3
JP1,JP3,JP4
3 PIN 0.079 SINGLE ROW HEADER
SAMTEC, TMM103-02-L-S
8
1
JP2
2X4, 0.079 DOUBLE ROW HEADER
SAMTEC, TMM104-02-L-D
9
4
xJP1-xJP4
SHUNT, .079" CENTER
SAMTEC, 2SN-BK-G
10
0
RSET(open)
Res.,
11
2
E13,E14
Pin, 0.057 hole
Mill-Max, 8427-0-15-15-30-84-04-0
12
1
U1
IC., LTC6909CMS, MSOP-16
Linear Tech., LTC6909CMS
13
4
(STAND-OFF)
STAND-OFF, NYLON 0.375"
KEYSTONE, 8832(SNAP ON)
0805
4
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