LMX2485E EVAL National Semiconductor, LMX2485E EVAL Datasheet - Page 32

• Manufacturer Part Number: LMX2485E EVAL
• Description: BOARD EVALUATION LMX2485E
• Manufacturer: National Semiconductor
• Series: PLLatinum™r

Specifications of LMX2485E EVAL

• Main Purpose: Timing, Frequency Synthesizer
• Utilized Ic / Part: LMX2485E
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -

www.national.com
2.5.3 RF_CPP -- RF PLL Charge Pump Polarity
2.5.4 IF_CPP -- IF PLL Charge Pump Polarity
For a positive phase detector polarity, which is normally the case, set this bit to 1. Otherwise set this bit for a negative phase
detector polarity.
2.5.5 OSC_OUT Oscillator Output Buffer Enable
2.5.6 OSC2X -- Oscillator Doubler Enable
When this bit is set to 0, the oscillator doubler is disabled and the TCXO frequency presented to the IF R and RF R counters is
equal to that of the input frequency of the OSCin pin. When this bit is set to 1, the TCXO frequency presented to the RF R counter
is doubled. Phase noise added by the doubler is negligible.
2.5.7 FM[1:0] -- Fractional Mode
Determines the order of the delta-sigma modulator. Higher order delta-sigma modulators reduce the spur levels closer to the carrier
by pushing this noise to higher frequency offsets from the carrier. In general, the order of the loop filter should be at least one
greater than the order of the delta-sigma modulator in order to allow for sufficient roll-off.
OSC2X
0
1
Frequency Presented to RF R Counter
OSC_OUT
RF_CPP
IF_CPP
FM
0
1
0
1
0
1
0
1
2
3
2 x f
f
OSCin
OSCin
32
Disable the delta-sigma modulator. Recommended for test use
Fractional PLL mode with a 2nd order delta-sigma modulator
Fractional PLL mode with a 4th order delta-sigma modulator
Fractional PLL mode with a 3rd order delta-sigma modulator
Frequency Presented to IF R Counter
Buffered output of OSCin pin
RF Charge Pump Polarity
Disabled (High Impedance)
IF Charge Pump Polarity
Positive (Default)
OSCout Pin
Function
Negative
Negative
Positive
only.
f
OSCin