AD8339ACPZ-RL

The AD8339ACPZ-RL is a quad I/Q demodulator configured to be driven by a low noise preamplifier with differential outputs. It is optimized for the LNA in the AD8332/AD8334/AD8335 family of VGAs. The part consists of four identical I/Q demodulators with a 4× local oscillator (LO) input that divides this signal and generates the necessary 0° and 90° phases of the internal LO that drive the mixers. The four I/Q demodulators can be used independently of each other (assuming that a common LO is acceptable) because each has a separate RF input.

Continuous wave (CW) analog beamforming (ABF) and I/Q demodulation are combined in a single 40-lead ultracompact chip scale device, making the AD8339ACPZ-RL particularly applicable in high density ultrasound scanners. In an ABF system, time domain coherency is achieved following the appropriate phase alignment and summation of multiple receiver channels. A reset pin synchronizes multiple ICs to start each LO divider in the same quadrant. Sixteen programmable 22.5° phase increments are available for each channel. For example, if Channel 1 is used as a reference and Channel 2 has an I/Q phase lead of 45°, then the user can phase align Channel 2 with Channel 1 by choosing the correct code.

The mixer outputs are in current form for convenient summation. The independent I and Q mixer output currents are summed and converted to a voltage by a low noise, high dynamic range, current-to-voltage (I-V) transimpedance amplifier, such as the AD8021 or the AD829. Following the current summation, the combined signal is applied to a high resolution analog-to-digital converter (ADC), such as the AD7665 (16-bit, 570 kSPS).

An SPI-compatible serial interface port is provided to easily program the phase of each channel; the interface allows daisy chaining by shifting the data through each chip from SDI to SDO. The SPI also allows for power-down of each individual channel and the complete chip. During power-down, the serial interface remains active so that the device can be programmed again.

The dynamic range is typically 160 dB/Hz at the I and Q outputs. The AD8339ACPZ-RL is available in a 6 mm × 6 mm, 40-lead LFCSP and is specified over the industrial temperature range of −40°C to +85°C.

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