The LMX2487E device is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. It is fabricated using TI’s advanced process.
With delta-sigma architecture, fractional spurs at lower offset frequencies are pushed to higher frequencies outside the loop bandwidth. The ability to push close in spur and phase noise energy to higher frequencies is a direct function of the modulator order. Unlike analog compensation, the digital feedback technique used in the LMX2487E is highly resistant to changes in temperature and variations in wafer processing. The LMX2487E delta-sigma modulator is programmable up to fourth order, which allows the designer to select the optimum modulator order to fit the phase noise, spur, and lock time requirements of the system.
Serial data for programming the LMX2487E is transferred through a three-line, high-speed (20-MHz) MICROWIRE interface. The LMX2487E offers fine frequency resolution, low spurs, fast programming speed, and a single-word write to change the frequency. This makes it ideal for direct digital modulation applications, where the N-counter is directly modulated with information. The LMX2487E is available in a 24-lead 4.0 × 4.0 × 0.8 mm WQFN package.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LMX2487E | WQFN (24) | 4.00 mm × 4.00 mm |
Changes from A Revision (March 2013) to B Revision
Changes from * Revision (March 2013) to A Revision
PIN | I/O | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
0 | GND | — | Ground Substrate. This is on the bottom of the package and must be grounded. |
1 | CPoutRF | O | RF PLL charge pump output. |
2 | GND | — | RF PLL analog ground. |
3 | VddRF1 | — | RF PLL analog power supply. |
4 | FinRF | I | RF PLL high-frequency input pin. |
5 | FinRF* | I | RF PLL complementary high-frequency input pin. Shunt to ground with a 100-pF capacitor. |
6 | LE | I | MICROWIRE Load Enable. High-impedance CMOS input. Data stored in the shift registers is loaded into the internal latches when LE goes HIGH |
7 | DATA | I | MICROWIRE Data. High-impedance binary serial data input. |
8 | CLK | I | MICROWIRE Clock. High-impedance CMOS Clock input. Data for the various counters is clocked into the 24-bit shift register on the rising edge |
9 | VddRF2 | — | Power supply for RF PLL digital circuitry. |
10 | CE | I | Chip Enable control pin. Must be pulled high for normal operation. |
11 | VddRF5 | I | Power supply for RF PLL digital circuitry. |
12 | Ftest/LD | O | Test frequency output / Lock Detect. |
13 | FinIF | I | IF PLL high-frequency input pin. |
14 | VddIF1 | — | IF PLL analog power supply. |
15 | GND | — | IF PLL digital ground. |
16 | CPoutIF | O | IF PLL charge pump output |
17 | VddIF2 | — | IF PLL power supply. |
18 | OSCout | O | Buffered output of the OSCin signal. |
19 | ENOSC | I | Oscillator enable. When this is set to high, the OSCout pin is enabled regardless of the state of other pins or register bits. |
20 | OSCin | I | Reference Input. |
21 | NC | I | This pin must be left open. |
22 | VddRF3 | — | Power supply for RF PLL digital circuitry. |
23 | FLoutRF | O | RF PLL Fastlock Output. Also functions as Programmable TRI-STATE CMOS output. |
24 | VddRF4 | — | RF PLL analog power supply. |