SLWS230E September   2011  – December 2015 TRF3765


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 4WI Timing: Write Operation
    7. 6.7 Readback 4WI Timing
    8. 6.8 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Lock Detect
      2. 7.3.2 LO Divider
      3. 7.3.3 Selecting the VCO and VCO Frequency Control
      4. 7.3.4 External VCO
    4. 7.4 Device Functional Modes
      1. 7.4.1 VCO_TEST_MODE
      2. 7.4.2 Readback Mode
      3. 7.4.3 Integer and Fractional Mode Selection
      4. 7.4.4 PLL Architecture
        1. Selecting PLL Divider Values
        2. Setup Example for Integer Mode
        3. Setup Example for Fractional Mode
      5. 7.4.5 Fractional Mode Setup
    5. 7.5 Register Maps
      1. 7.5.1 PLL 4WI Registers
        1. Register 1
          1. CAL_CLK_SEL[3..0]
          2. ICP[4..0]
        2. Register 2
          1. PLL_DIV <1.0>
          2. VCOSEL_MODE
        3. Register 3
        4. Register 4
        5. Register 5
        6. Register 6
      2. 7.5.2 Readback from the Internal Register Banks
        1. Register 0 Write
          1. Register 0 Read
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedures
        1. Power Supply
        2. Loop Filter
        3. Reference Clock
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Trademarks
    2. 11.2 Electrostatic Discharge Caution
    3. 11.3 Glossary
  12. 12Mechanical, Packaging, and Orderable Information



8 Application and Implementation


Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The TRF3765 is a wideband integer-N/Fractional-N frequency synthesizer with an integrated, wideband voltage-controlled oscillator (VCO). Programmable output dividers enable continuous frequency coverage from 300 MHz to 4.8GHz. Four separate differential, open-collector RF outputs allow multiple devices to be driven in parallel without the need of external splitters. TRF3765 is applicable to the wireless infrastructure standards such as CDMA, TDMA, WCDMA, LTE and Advanced-LTE. It can also be used in wireless point-to-point access and wireless local loop communication links.

8.2 Typical Application

Figure 77 shows an example block diagram for multi-band and multi-mode for 2G, 3G, and 4G cellular transmitters. By adopting DAC38J84 and TRF3720, number of transmitter can be increased up to 8 antenna system as each of DAC38J84 can supports 2 transmitters of I/Q pair and each of TRF3765 can provide 4 high sampling clocks with 4 DAC38J84 devices. TRF3720 is an IQ modulator with fully integrated PLL/VCO and LO frequency ranges from 300 MHz to 4.8 GHz.

This is a good example of improved transmitter diversity to service multiple users simultaneously. The internal PLL of TRF3765 can be used to generate four high sampling clocks up to 4.8 GHz.

TRF3765 TRF3765_Appss_Block_v3.gif Figure 77. TRF3765 Application Block Diagram

8.2.1 Design Requirements

For this design example, use the input parameters in Table 18.

Table 18. Design Parameters

Input voltage 3.3 V
Current 121 mA
Input reference frequency 122.88 MHz
Output frequency 900 MHz

Table 19. Termination Requirements and Interfacing

3 DATA 4WI data input: digital input, high impedance
4 CLOCK 4WI clock input: digital input, high impedance
5 STROBE 4WI latch enable: digital input, high impedance
6 READBACK Readback output; digital output pins can source or sink up to 8 mA of current
9 through 16 LO_OUT Local oscillator output: open-collector output. A pullup resistor is required, normally ac-coupled. Any unused output differential pairs may be left open.
18 EXTVCO_IN External local oscillator input: high impedance, normally ac-coupled
19 EXTVCO_CTRL Power-down control pin for optional external VCO; digital output pins can source or sink up to 8 mA of current
30 REF_IN Reference clock input: high impedance, normally ac-coupled
32 LD Lock detector digital output, as configured by MUX_CTRL; digital output pins can source or sink up to 8 mA of current

8.2.2 Detailed Design Procedures Power Supply

A clean power supply is critical to optimal phase noise performance of synthesizer. Linear power supplies are the best sources available. Switching power supplies degrade in-band phase noise by 10 dB compared to linear laboratory supplies. VCC3 can be used to drive VCC_TK, a 3.3-V or 5-V tolerant supply on the TRF3765. VCC_TK is normally driven by the 3.3 V VCC2 supply, but some applications perform better with 5 V supply on VCC_TK. A power supply filter can be used for TRF3765 and this filter reduces in-band frequency noise from a switching power supply so that external supply can drive 5 V on VCC_TK. Loop Filter

Loop-filter components are also critical to optimal phase noise performance. The loop filter must be matched to the selected phase noise frequency detector (PFD) frequency. To use different PFD frequency, the loop-filter components must be updated. Below is an example of loop filter design. Reference Clock

External oscillator or the output of PLL device can be installed for the reference clock input to TRF3765 device. The external reference clock is AC-coupled to the TRF3765 input pin. The range is reference frequency is from 0.5 MHz to 350 MHz. The minimum of reference input sensitivity is 0.2 Vpp and 3.3 Vpp for the maximum value.

8.2.3 Application Curves

The phase noise performance of 900-MHz output is shown in Figure 78. Figure 79 shows phase noise performances from different power supplies such as 3.3 V, 2.7 V, 2.5 V, 2.2 V, 2.1 V and 2 V at room temperature.

TRF3765 app_curve_slws230.gif
Figure 78. Phase Noise Curve for 900MHz
TRF3765 output_power_vs_vcc.png
Figure 79. Different Supply vs Output Power at Different Temperatures