LMX2355SLB National Semiconductor, LMX2355SLB Datasheet - Page 14

• Manufacturer Part Number: LMX2355SLB
• Description: PLLatinum Fractional N RF/ Integer N IF Dual Low Power Frequency Synthesizer
• Manufacturer: National Semiconductor

www.national.com
Programming Description
4.1.3 15-BIT PROGRAMMABLE REFERENCE DIVIDER RATIO (R COUNTER)
Notes: Divide ratio: 3 to 32,767 (Divide ratios less than 3 are prohibited).
RF_R_CNTR/IF_R_CNTR These bits select the divide ratio of the programmable reference dividers.
4.1.4 IF_CP_WORD
CP_GAIN_8 is used to toggle the IF charge pump current magnitude between 1X mode (100 µA typical) and 8X mode (800 µA
typical).
IF_PD_POL is set to one when IF VCO characteristics are positive. When IF VCO frequency decreases with increasing control
voltage IF_PD_POL should set to 0.
4.1.5 FoLD* Programming Truth Table
4.2 RF_R Register
If the Control Bits (CTL [1:0]) are 1 0, data is transferred from the 24-bit shift register into the RF_R register latch which sets the
RF PLL’s 15-bit R counter divide ratio. The divide ratio is programmed using the RF_R_CNTR word as shown in table 4.1.3. The
divide ratio must be
detailed in 4.2.2.
*FoLD - Fout/Lock Detect PROGRAMMING BITS
32,767
MSB
DLL_MODE
23
Divide
CP_GAIN_8
Ratio
3
4
•
CP_GAIN_8
IF_PD_POL
14
0
0
1
BIT
•
V2_EN
13
0
0
1
•
0 0 0
1 0 0
0 1 0
1 1 0
0 0 1
1 0 1
0 1 1
1 1 1
FoLD
3. The bits used to control the voltage doubler (V2_EN) and RF Charge Pump (RF_CP_WORD) are
(IF_R[17]–IF_R[18])
12
0
0
1
•
22 21
IF_PD_POL
RF_CP_WORD [4:0]
LOCATION
IF_R [18]
IF_R [17]
11
0
0
1
•
10
0
0
1
•
(IF_R[19]–IF_R[21])
(Continued)
IF_R_CNTR/RF_R_CNTR
9
0
0
1
•
IF Phase Detector
IF Charge Pump
Current Gain
FUNCTION
8
0
0
1
•
Polarity
17 16
14
RF_R_CNTR [14:0]
7
0
0
1
•
Fo/LD OUTPUT STATE
IF and RF Analog Lock Detect
IF Digital Lock Detect
RF Digital Lock Detect
IF and RF Digital Lock Detect
IF R counter
IF N counter
RF R counter
RF N counter
6
0
0
1
•
5
0
0
1
•
Negative
(IF_R[2]–IF_R[16])
1X
0
4
0
0
1
•
2 1
1
3
0
0
1
•
2
0
1
1
•
Positive
LSB
0
0
8X
1
1
1
0
1
•
0
1
0
1
•