Datasheet
VccPLL1
VccPLL2
OSCin
OSCin*
RFout
Vtune
CPout
LMX2541
Microcontroller
VccCP1
VccCP2
VccRFout
C1_LF
R2_LF
VregRFout
VccVCO
VccDig
VregVCO
VrefVCO
100 pF
51:
C2_LF
FLout
+3.3V
VccFRAC
VregFRAC
VccDiv
VccOSCin
VccBias
Bypass
4.7:
1 PF
18:
Ferrite
Ferrite
ExtVCOin
+3.3V
Ferrite
+3.3V
+3.3V
0.1 PF
+3.3V
Ferrite
0.1 PF
+3.3V
Ferrite
0.1 PF
+3.3V
Ferrite
0.1 PF
+3.3V
Ferrite
0.1 PF
+3.3V
+3.3V
+3.3V
0.1 PF
0.1 PF
18:
18:
To
Circuit
C4_LF
R4_LF
C3_LF
R2pLF
R3_LF
51:
1 PF
0.1 PF
4.7:
DATA
CLK
LE
CE
Ftest/LD
RFoutEN
LMX2541SQ2060E, LMX2541SQ2380E
LMX2541SQ2690E, LMX2541SQ3030E
LMX2541SQ3320E, LMX2541SQ3740E
SNOSB31I –JULY 2009–REVISED FEBRUARY 2013
www.ti.com
Figure 31. External VCO Mode, Single-Ended OSCin, RFout Pin not Used
For both of the able connection diagrams, L1, L2, and Lmid should be left open, but the pads should be placed
on these pins for optimal solderability. The GND pins should have separate vias to ground and the GND DAP
also needs to be grounded with 9 vias. The VccVCO, VccRFout, and VccDiv pins can be shorted to the power
plane, but need to be connected. For the other Vcc pins, ferrite beads and bypass capacitors may be added in
order to improve spurious performance. VregVCO and VrefVCO need to be connected even if the internal VCO
is not being used. The VregRFout pin only needs to be connected if the RFout pin is being used. When a block is
not used, it is always still necessary to connect the corresponding Vcc pin, but the bypassing is not necessary,
as shown in the above diagram for the external VCO mode.
OSCin/OSCin* Connections
For single-ended operation, the signal is driven into the OSCin pin. The OSCin* pin is terminated the same as
the OSCin pin. This is a typical case if the device is driven by a TCXO. For both single-ended and differential
operation, the input is AC coupled because the OSCin/OSCin* pins self-bias to an optimal DC operating point.
Better performance for both phase noise and fractional spurs is obtained for signals with a higher slew rate, such
as a square wave. This is especially important for lower frequency signals, since slower frequency sine waves
have lower slew rates. Fractional spurs are typically about four dB better when running in differential mode as
opposed to single-ended mode.
50 Submit Documentation Feedback Copyright © 2009–2013, Texas Instruments Incorporated
Product Folder Links: LMX2541SQ2060E LMX2541SQ2380E LMX2541SQ2690E LMX2541SQ3030E
LMX2541SQ3320E LMX2541SQ3740E