Features

• 17MHz I/Q Lowpass Output Noise Filters
• Wide Range 1.8V to 5.25V Supply Voltage
• Frequency Range: 40MHz to 500MHz
• THD < 0.14% (-57dBc) at 800mVP-P Differential Output Level
• IF Overload Detector
• Log Linear Gain Control Range: -7dB to 56dB
• Baseband I/Q Amplitude Imbalance: 0.2dB
• Baseband I/Q Phase Imbalance: 0.6°
• 7.8dB Noise Figure at Max Gain
• Input IP3 at Low Gain: -1dBm
• Low Supply Current: 24mA
• Low Delay Shift Over Gain Control Range: 2ps/dB
• Outputs Biased Up While in Standby
• 16-Lead QFN 4mm × 4mm Package with Exposed Pad

Typical Application

Description

The LT5546 is a 40MHz to 500MHz monolithic integrated quadrature demodulator with variable gain amplifier (VGA) and 17MHz I/Q baseband bandwidth designed for low voltage operation. It supports standards that use a linear modulation format. The chip consists of a VGA, quadrature downconverting mixers and 17MHz lowpass noise filters (LPF). The LO port consists of a divide-by-two stage and LO buffers. The IC provides all building blocks for IF down-conversion to I and Q baseband signals with a single supply voltage of 1.8V to 5.25V. The VGA gain has a linear-in-dB relationship to the control input voltage. Hard-clipping amplifiers at the mixer outputs reduce the recovery time from a signal overload condition. The lowpass filters reduce the out-of-band noise and spurious frequency components. The -3dB corner frequency of the noise filters is approximately 17MHz and has a first order rolloff.  The standby mode provides reduced supply current and fast transient response into the normal operating mode when the I/Q outputs are AC-coupled to a baseband chip.