900MHz Image-Reject Receivers with Transmit Mixer

The MAX2424/MAX2426 highly integrated front-end ICs provide the lowest cost solution for cordless and ISM-band radios operating in the 900MHz band. Both devices incorporate a receive image-reject mixer (to reduce filter cost) as well as a versatile transmit mixer. The devices operate from a +2.7V to +4.8V single power supply, allowing direct connection to a 3-cell battery stack.

The receive path incorporates an adjustable-gain LNA and an image-reject downconverter with 35dB image suppression. These features yield excellent combined downconverter noise figure (4dB) and high linearity with an input third-order intercept point (IIP3) of up to +2dBm.

The transmitter consists of a double-balanced mixer and a power amplifier (PA) predriver that produces up to 0dBm (in some applications serving as the final power stage). It can be used in a variety of configurations, including BPSK modulation, direct VCO modulation, and transmitter upconversion. For devices featuring transmit as well as receive image rejection, refer to the MAX2420/MAX2421/MAX2422/MAX2460/MAX2463 data sheet.

The MAX2424/MAX2426 have an on-chip local oscillator (LO), requiring only an external varactor-tuned LC tank for operation. The integrated divide-by-64/65 dual-modulus prescaler can also be set to a direct mode, in which it acts as an LO buffer amplifier. Four separate power-down inputs can be used for system power management, including a 0.5µA shutdown mode.

The MAX2424/MAX2426 come in a 28-pin SSOP package.

Applications

* Cordless Phones * Spread-Spectrum Communications * Two-Way Paging * Wireless Networks * Wireless Telemetry

* Receive Mixer with 35dB Image Rejection

* Adjustable-Gain LNA

* Up to +2dBm Combined Receiver Input IP3

* 4dB Combined Receiver Noise Figure

* Optimized for Common Receiver IF Frequencies:

* 10.7MHz (MAX2424)

* 70MHz (MAX2426)

* PA Predriver Provides up to 0dBm

* Low Current Consumption:

* 23mA Receive

* 20mA Transmit

* 9.5mA Oscillator

* 0.5µA Shutdown Mode

* Operates from Single +2.7V to +4.8V Supply