Datasheet

LMX2541SQ2060E, LMX2541SQ2380E
LMX2541SQ2690E, LMX2541SQ3030E
LMX2541SQ3320E, LMX2541SQ3740E
SNOSB31I –JULY 2009–REVISED FEBRUARY 2013 www.ti.com
RFOUT RFoutEN Pin RFout Pin State
2 Don't Care Enabled
Low Disabled
1 or 3
High Enabled
DIVGAIN[3:0], VCOGAIN[3:0], and OUTTERM[3:0] - Power Controls for RFout
These three words may be programmed in a value from 0 to 15 and work in conjunction to control the output
power level of the RFout pin. Increasing any of these values increases the output power at the expense of higher
current consumption of the buffer. Although there may be more than one way to get the same output power,
some combinations may have lower current. The typical performance characteristics show these trade-offs. The
default setting for all these bits is 12. The value of VCO_DIV determines which two of these three words have an
impact.
VCO_DIV Bits that Impact Power
1 (Bypass) OUTTERM, VCOGAIN
>1 (Not Bypass) OUTTERM, DIVGAIN
Register R5
This register controls the fastlock mode which enables a wider loop bandwidth when the device is changing
frequencies.
FL_TOC[13:0] -- Time Out Counter for FastLock
When the value of this word is 3 or less, FastLock time out counter is disabled, and the FLout pin can be used
for general purpose I/O. When this value is 4 or greater, the time out counter is engaged for the amount of phase
detector cycles shown in the table below.
TOC Value FLout Pin State Fastlock Engagement Time
0 High Impedance Disabled
1 Low Always Engaged
2 Low Disabled
3 High Disabled
Engaged for
4 Low
4 × 2 Phase Detector Cycles
. . .
Engaged for
16383 Low
16383 × 2 Phase Detector Cycles
When this count is active, the FLout Pin is grounded, the FastLock current is engaged, and the resistors R3 and
R4 are also potentially changed. The table below summarizes the bits that control various values in and out of
FastLock.
FastLock State FLout Charge Pump Current R3_LF Value R4_LF Value
Not Engaged High Impedance CPG R3_LF R4_LF
Engaged Grounded FL_CPG FL_R3_LF FL_R4_LF
FL_R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3 During Fastlock
FL_R3_LF Value R3 Resistor During Fastlock (kΩ)
0 Low ( 200 Ω )
1 1
2 2
3 4
4 16
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Product Folder Links: LMX2541SQ2060E LMX2541SQ2380E LMX2541SQ2690E LMX2541SQ3030E
LMX2541SQ3320E LMX2541SQ3740E