LMX2433TM National Semiconductor, LMX2433TM Datasheet - Page 42
![no-image](/images/manufacturer_photos/0/4/469/national_semiconductor_sml.jpg)
LMX2433TM
Manufacturer Part Number
LMX2433TM
Description
PLLatinum Dual High Frequency Synthesizer for RF Personal Communications
Manufacturer
National Semiconductor
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
www.national.com
Reg
R2
2.0 Programming Description
2.5.4 RF_PD - RF Synthesizer Powerdown (R1[23])
The RF_PD bit is used to switch the RF PLL between a powered up and powered down mode.
Furthermore, the RF_PD bit operates in conjuction with the RF_CPT bit to set a synchronous or an asynchronous powerdown
mode. Refer to Section 2.4.4 for more details on how to program the RF_CPT bit.
2.6 R2 REGISTER
The R2 Register contains the RF_TOC control word. The RF_TOC is used to setup the RF syhnthesizer’s Fastlock circuitry. The
RF_TOC is a 12-bit binary counter programmable from 0 to 4095.
2.6.1 RF_TOC[0:11] - RF Synthesizer Timeout Counter (R2[14:3])
The FLoutRF pin can be configured as a general purpose CMOS TRI-STATE output or as a Fastlock output by programming the
RF_TOC appropriately. When the RF_TOC is programmed from 0 to 3, Automatic Fastlock is disabled, and the FLoutRF pin is
either configured as a general purpose CMOS TRI-STATE output or Manual Fastlock is enabled. When the RF_TOC is
programmed to 0, the FLoutRF pin will be in TRI-STATE (high impedance) mode. The charge pump current is then the value
specified by RF_CPG (R0[19]). When the RF_TOC is programmed to 1, the FLoutRF pin is pulled to a LOW state. The charge
pump current is then set to a HIGH gain state (RF_CPG bit = 1). This condition is known as the Manual Fastlock. When the
RF_TOC is programmed to 2, the FLout_RF pin will again be pulled to a LOW state, but this time the charge pump current is the
value specified by RF_CPG (R0[19]). When the RF_TOC is programmed to 3, the FLoutRF pin is pulled to a HIGH state. Again,
the charge pump current is the value specified by RF_CPG (R0[19]). When the RF_TOC is programmed from 4 to 4095, Fastlock
is enabled and the FLoutRF pin is pulled to a LOW state. Fastlock will time-out after the specified number of PFD events. At this
time, the FLoutRF pin will switch to TRI-STATE (high impedance) mode. The value programmed into RF_TOC represents the
number of PFD events that the RF synthesizer will spend in the Fastlock state. Note that any write to the RF_TOC requires a PFD
event on the RF synthesizer to latch the contents. This means that writes to the RF_TOC take effect synchronously with the next
PFD event.
RF_TOC[11:0]
23
0
4095
22
0
…
0
1
2
3
4
Control Bit
RF_PD
21
0
20
0
19
0
Automatic Fastlock
Automatic Fastlock
FastLock Mode
Manual Fastlock
18
Register Location
Disabled
Disabled
Disabled
0
Enabled
Enabled
Enabled
…
17
0
R1[23]
16
0
15
0
DATA[20:0] FIELD
14
(Continued)
RF Powerdown
Fastlock Period
[PFD Events]
13
Description
4095
N/A
N/A
N/A
N/A
…
4
12
42
11
10
General Purpose.
High Impedance State
General Purpose.
Logic LOW State
General Purpose.
Logic LOW State
General Purpose.
Logic HIGH State
FastLock.
Logic LOW State.
Switches to High
Impedance after 4 PFD
events
FastLock.
Logic LOW State.
Switches to High
Impedance after 4095
PFD events
RF PLL Active
RF_TOC[11:0]
Functionality/ State
9
FLoutRF Pin
8
0
…
7
Function
6
RF PLL Powerdown
5
I
controlled by R0[19]
I
I
controlled by R0[19]
I
controlled by R0[19]
I
Switches to 1 mA after
4 PFD events
I
Switches to 1 mA after
4095 PFD events
CPoutRF
CPoutRF
CPoutRF
CPoutRF
CPoutRF
CPoutRF
I
CPoutRF
4
1
magnitude
= 4 mA
magnitude
magnitude
= 4 mA
= 4 mA
3
Magnitude
…
2
0
ADDRESS
FIELD
[2:0]
1
1
0
0