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Superheterodyne receiver with AGC

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MAXIM Integrated Products, represented by Arrow Electronics , has introduced the MAX1473, the world's first 300MHz to 450MHz superheterodyne ASK receiver, featuring -114dBm sensitivity, >50dB user-selectable centre frequency image rejection, and the option of running from either a 3V or 5V supply.

The MAX1473 includes a one-step AGC circuit that drops the LNA gain by 35dB when the RF input signal is greater than -57dBm.

The receiver uses a 10.7MHz IF filter with received signal strength indicator (RSSI) and has an on-chip PLL with VCO and analogue baseband data recovery circuitry.

The MAX1473 operates in a wide variety of power-sensitive applications such as remote-keyless entry (RKE) systems, car alarms, home security systems, remote controls, and garage-door openers.

The device draws less than 1.5μA in shutdown mode and only 5.2mA in receive mode.

The centre frequency of the fully differential image-rejection mixer can be selected by the user at 315MHz, 375MHz, or 433MHz.

Depending on the components selected, the MAX1473 can receive data rates up to 100kbps and transitions from shutdown to valid data out in less than 250 microseconds.

In power-cycled applications, this quick transition minimises the time the system is in receive mode.

The MAX1473's integrated PLL is fully self-contained, requiring no external components.

The PLL block contains a phase detector, charge pump/integrated loop filter, VCO, asynchronous 32x or 64x clock divider, and crystal oscillator.

For an input RF frequency of 315MHz, the quadrature VCO is centred at the nominal LO frequency of 304.3MHz.

A reference frequency of 9.5194MHz or 4.7547MHz is needed for a 10.7MHz IF frequency (low-side injection is required). The MAX1473 is packaged in a 28-pin SSOP.

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