Re-Calibration After Power Up

TRF3762

c. Set DB<30:18> of register 2 to the desired frequency. For example: 2200MHz would be 0100010011000

(2200).

d. Set DB31of register 2 to 1 to start the calibration. The VCO calibration runs for 5ms. During the cal

procedure it will not be possible to program register 2 and 3. At the end of the calibration, bit DB31 of

register 2 resets to 0.

e. Subsequent frequency programming requires DB31 to be set to 0.

Register 3

• Completion of the frequency set up, on initial calibration, cannot proceed until 5ms has elapsed, due to full

calibration, then it will require that the A and B values, the prescalar ratio, be known. See Synthesizing a

Selected Frequency section below for calculation. Reference Table 3.

a. The first 4 bits of the 32-bit code sent to the chip are set DB <3:0> to 0010; which is the address of

register 3.

b. DB<5:4> sets the prescalar ratio, 8/9, 16/17, 32/33, 64/65. For example: if 16/17 are required, set the

register bits DB<5:4> to 01.

c. DB<11:6> sets the A value for the N counter. For example: if A is 4, set DB<11:6> as follows: 000100 (4).

d. DB<24:12> sets the B value for the N counter. For example: if B is 1156, set DB<24:12> as follows:

0010010000100 (4).

e. DB<28:25> sets the TEST_MUX. This allows the user to check via the microcontroller the state of the

TRF3762 by programming it to one of 6 states. The most common state to use is the Digital lock Detect

which places the pin in a logic high state with indicates the VCO is locked.

Table 4. MUX-Out Settings

STATE

DB<28:25>

STATE

DB<28:25>

3-state o/p ( High impedance state on Pin 39)

0000

RDiv o/p (Shows R-value on Pin 39)

0100

Digital lock Detect (High when locked on Pin 39)

0001

Analog lock detect (High when locked on Pin 39)

0101

N-Divider o/p (Shows N-value on Pin 39)

0010

Read back ( read back register settings)

0110

DVDD (internal TI use)

0011

DGND (internal TI use)

0111

f.

DB29 sets the START LOCK, which is set to 0, on the initial frequency setup and then set to 1 on

additional frequency changes.

Once all registers are written, the TRF3762 will lock to the desired frequency. In order to change the frequency

once the initial calibration is complete, only registers 2 and 3 need to be reprogrammed. No calibration is

required.

Assuming the TRF3762 is powered up and operational, a VCO calibration is also possible without powering

down the IC. To perform such calibration the following procedure is recommended:

• Set bit DB4 (RESET) of register 1 to 1. This performs a software reset and clears all registers of VCO

calibration data. Once the reset command is issued then DB4 of register 1 will need to be set to 0.

• Repeat the Initial Calibration and Frequency setup at Power up section, skipping the power up section and

performing the register programming sequence.

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