LMX2541SQE3740E/NOPB National Semiconductor, LMX2541SQE3740E/NOPB Datasheet - Page 39

• Manufacturer Part Number: LMX2541SQE3740E/NOPB
• Description: IC PLL FREQ SYNTH W/VCO 36LLP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Clock/Frequency Synthesizer (RF)r

Specifications of LMX2541SQE3740E/NOPB

• Pll: Yes
• Input: Clock
• Output: Clock
• Number Of Circuits: 1
• Ratio - Input:output: 2:2
• Differential - Input:output: No/No
• Frequency - Max: 4GHz
• Divider/multiplier: Yes/No
• Voltage - Supply: 3.15 V ~ 3.45 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-LLP
• Frequency-max: 4GHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMX2541SQE3740ETR

2.1 REGISTER R7
Although Register 7 has no elective bits to program, it is very important to program this register because the action of doing so
with the bit sequence shown in the register map resets all the registers, including hidden registers with test bits that are not
disclosed. Register 7 should always be programmed first, because it will reset all other programming information. The register
reset occurs only after the LE signal has transitioned from low to high and back to low again.
2.1.1 REGISTER R13
This register needs to be programmed only in the event that the RFout pin is being used and VCO_DIV = 1.
VCO_DIV_OPT[2:0]
This word optimizes the RFout power level based on the VCO_DIV and VCO_GAIN words.
2.1.2 REGISTER R12
This register needs to be programmed as shown in the register map in the event that the internal VCO is being used. When using
external VCO mode, this register does not need to be programmed.
2.1.3 REGISTER R9
Program this register as shown in the register map.
2.1.4 REGISTER R8
AC_TEMP_COMP[4:0]
This word optimizes the VCO phase noise for possible temperature drift. When the VCO frequency is changed, the internal tuning
algorithm optimizes the phase noise for the current temperature. In fixed frequency applications, temperature drift may lead to sub-
optimal phase noise over time. In dynamic frequency applications, the re-tuning of the VCO frequency overcomes this problem
because the phase noise is re-optimized each time the VCO frequency is changed. The AC_TEMP_COMP word can be used to
optimize the VCO phase noise for temperature drift for these different scenarios. The following table indicates which values of this
word should be used for each scenario.
RFout Pin Disabled
RFout Pin Enabled
VCO_GAIN<13
VCO_GAIN>12
VCO_DIV>1
VCO_DIV=1
Condition
AND
OR
OR
AC_TEMP_COMP
All Other States
24
5
39
VCO_DIV_OPT
Dynamic Frequency
0
4
Application Type
Fixed Frequency
Invalid
programmed, since 0 is the default.
Register R13 Does Not need to be
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