Datasheet

LMX2541SQ2060E, LMX2541SQ2380E
LMX2541SQ2690E, LMX2541SQ3030E
LMX2541SQ3320E, LMX2541SQ3740E
www.ti.com SNOSB31I –JULY 2009–REVISED FEBRUARY 2013
General Programming Information
The LMX2541 is programmed using several 32-bit registers used to control the LMX2541 operation. A 32-bit shift
register is used as a temporary register to indirectly program the on-chip registers. The shift register consists of a
data field and an address field. The last 4 register bits, CTRL[3:0] form the address field, which is used to
decode the internal register address. The remaining 28 bits form the data field DATA[27:0]. While LE is low,
serial data is clocked into the shift register upon the rising edge of clock (data is programmed MSB first). When
LE goes high, data is transferred from the data field into the selected register bank. For initial device
programming the register programming sequence must be done in the order as shown in the register map. The
action of programming register R7 and bringing LE low resets all the registers to default values, including hidden
registers. The programming of register R0 is also special for the device when operating in full chip mode
because the action of programming either one of these registers activates the VCO calibration.
In addition to changing the values of various words, the programming of certain registers triggers certain events
as described in the table below:
Configurations
Programming Event Event Triggered Where it Has an Significance
Impact
Resets all registers,
Action of This needs to be the first programming step for all configurations. If
including hidden
programming register All register R7 is ever programmed again, all programming information
ones, to a default
R7 and bring LE low will be reset to the default state.
state
The VCO calibration tunes the VCO to the correct frequency band
Action of
and optimizes the phase noise. It is necessary whenever the
programming register Activates the VCO Only in Full Chip
internal VCO frequency is changed. Also, if the temperature drifts
R0 and bringing LE calibration Mode
considerably, then this calibration can better optimize the phase
low
noise.
Only when the RFout
Action of
Synchronizes the pin ins enabled and
programming register Consult the Functional Description for more details.
VCO Divider the VCO divider is set
R4
to 4 or 5
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Product Folder Links: LMX2541SQ2060E LMX2541SQ2380E LMX2541SQ2690E LMX2541SQ3030E
LMX2541SQ3320E LMX2541SQ3740E