Overview
The LMX2331LTMX, part of the LMX233xL family, is a monolithic, integrated dual frequency synthesizer designed for use in RF and first IF applications. Fabricated using National’s 0.5μm ABiC V silicon BiCMOS process, this device is optimized for low power consumption and high performance. It is particularly suited for portable wireless communications, cordless and cellular telephone systems, wireless local area networks (WLANs), and cable TV tuners (CATV). The LMX2331LTMX employs a digital phase locked loop technique combined with a high-quality reference oscillator to generate stable, low-noise signals for RF and IF local oscillators.
Key Specifications
| Parameter | Value | Units | Conditions |
|---|---|---|---|
| Supply Voltage (VCC) | 2.7 to 5.5 | V | |
| Power Supply Current (ICC) | 4.0 (RF & IF), 3.0 (RF only), 1.0 (IF only) | mA | VCC = 3.0V |
| Powerdown Current (ICC-PWDN) | 1 | mA | VCC = 3.0V |
| RF Operating Frequency | 0.2 to 2.0 GHz | GHz | |
| IF Operating Frequency | 45 to 510 MHz | MHz | |
| Oscillator Frequency | 5 to 40 MHz | MHz | |
| Maximum Phase Detector Frequency | 10 MHz | MHz | |
| RF Input Sensitivity | -15 to -4 dBm (VCC = 3.0V), -10 to -4 dBm (VCC = 5.0V) | dBm | |
| IF Input Sensitivity | -10 to -4 dBm | dBm | VCC = 2.7 to 5.5V |
| High-Level Input Voltage (VIH) | 0.8 VCC | V | |
| Low-Level Input Voltage (VIL) | 0.2 VCC | V | |
| High-Level Output Voltage (VOH) | VCC - 0.4 | V | IOH = -500 mA |
| Low-Level Output Voltage (VOL) | 0.4 | V | IOL = 500 mA |
Key Features
- Ultra-low current consumption
- Operates from 2.7V to 5.5V
- Selectable synchronous or asynchronous powerdown mode
- Dual modulus prescaler: RF (64-65 or 128-129), IF (8-9 or 16-17)
- Selectable charge pump TRI-STATE mode
- Selectable charge pump current levels
- Selectable Fastlock mode
- Upgrade and compatible to LMX233xA family
- Three-wire interface (Data, Enable, Clock) for serial data transfer
- High impedance CMOS inputs and outputs
- Available in a 20-pin TSSOP surface mount package
Applications
- Portable Wireless Communications (PCS, PCN, cordless)
- Cordless and cellular telephone systems
- Wireless Local Area Networks (WLANs)
- Cable TV tuners (CATV)
- Other wireless communication systems
Q & A
- What is the LMX2331LTMX used for?
The LMX2331LTMX is used as a local oscillator for RF and first IF in dual conversion transceivers, particularly in portable wireless communications, cordless and cellular telephone systems, WLANs, and cable TV tuners.
- What is the operating voltage range of the LMX2331LTMX?
The operating voltage range is from 2.7V to 5.5V.
- What are the typical current consumptions for the LMX2331LTMX?
The typical current consumptions are 4.0 mA for both RF and IF, 3.0 mA for RF only, and 1.0 mA for IF only at VCC = 3.0V.
- What are the RF and IF operating frequency ranges?
The RF operating frequency range is from 0.2 GHz to 2.0 GHz, and the IF operating frequency range is from 45 MHz to 510 MHz.
- What is the Fastlock mode and how is it activated?
The Fastlock mode is a feature that speeds up the locking process. It is activated when the RF loop’s lcpo magnitude bit is selected HIGH and the mode bits are set for Fastlock.
- What types of prescalers are available for the RF and IF synthesizers?
The RF synthesizer can use either a 64-65 or 128-129 prescaler, while the IF synthesizer can use either an 8-9 or 16-17 prescaler.
- How is data transferred into the LMX2331LTMX?
Data is transferred via a three-wire interface (Data, Enable, Clock) in a binary serial format, with data entered MSB first.
- What is the package type of the LMX2331LTMX?
The LMX2331LTMX is available in a 20-pin TSSOP surface mount package.
- What are the powerdown modes available for the LMX2331LTMX?
The device supports both synchronous and asynchronous powerdown modes.
- What is the significance of the FoLD pin in the LMX2331LTMX?
The FoLD pin provides multiplexed output of the RF and IF programmable or reference dividers, RF and IF lock detect signals, and Fastlock mode signals.
- Is the LMX2331LTMX ESD sensitive?
Yes, the LMX2331LTMX is ESD sensitive with an ESD rating of ±2 kV and should be handled at ESD protected workstations.
