The MAX9989/MAX9990 are MAXIM’s high output LO buffers that provide +14dBm to +20dBm of output power to drive the LO inputs of high-linearity passive mixers while offering 40dB reverse isolation to prevent LO pulling. The MAX9989 is internally matched for the cellular/GSM bands, and the MAX9990 is matched for the DCS/PCS/UMTS bands. The typical application circuit provides a nominal +17dBm output power with ±1dB variation over supply, temperature, and input power. With two optional resistors, the output power can be precision set from +14dBm to +20dBm. The devices offer more than 35dB main driver output to PLL amp output isolation. Each device is offered in a 5mm x 5mm 20-pin thin QFN package with exposed paddle. Applications include cellular/GSM/DCS/PCS/UMTS base station Tx/Rx LO drives, coherent receivers, ISM wireless LAN, wireless local loop, local multipoint distribution service, and point-to-point systems.
The MAX9989 and MAX9990 are LO buffer ICs designed for cellular/GSM (MAX9989) and DCS/PCS/UMTS (MAX9990) bands. They provide high output power (‑14 dBm to +20 dBm) with tight ±1 dB variation across supply, temperature, and input power, and feature more than 35 dB driver‑to‑PLL isolation.
Both devices are offered in a 5 mm × 5 mm 20‑pin thin QFN package with an exposed paddle. Typical applications include base‑station transmit/receive LO drives, coherent receivers, and wireless LAN systems. The datasheet includes absolute maximum ratings, DC electrical characteristics, and detailed pin descriptions.
| Output Power Range | +14 dBm to +20 dBm |
|---|---|
| Reverse Isolation | 40 dB |
| Supply Voltage | 4.75 V to 5.25 V |
| Supply Current (high power) | ≈110 mA at +17 dBm |
| Operating Frequency (MAX9989) | 700 MHz – 1100 MHz |
| Operating Frequency (MAX9990) | 1500 MHz – 2200 MHz |
| Output Noise Power Density | -170 dBc/Hz at +17 dBm |
The devices deliver output power from +14 dBm up to +20 dBm, with a typical value of +17 dBm and ±1 dB variation.
Both buffers provide 40 dB of reverse isolation to prevent LO pulling.
The ICs operate with a supply voltage between 4.75 V and 5.25 V.
MAX9989 covers 700 MHz to 1100 MHz, while MAX9990 covers 1500 MHz to 2200 MHz.