Maxim Introduces Fully Programmable, Multi-State, Dual Analog and Digital IF/RF Variable Gain Amplifiers

Photocoupler

Maxim introduces the industry's only fully programmable, multi-state, dual-channel analog and digital IF/RF variable gain amplifier ( VGA ) MAX2062 . The device is easy to control, with unparalleled VGA performance, programming features and component integration. Similar to the previously introduced single-channel MAX2065, the MAX2062 also offers a unique "fast-fire" gain selection feature that allows four custom attenuation states to be selected for each channel. In addition, the device features fast digital switching of 25ns and extremely low digital VGA overshoot/undershoot. The MAX2062 also allows adjustment of two analog attenuators via an SPITM interface to control an on-chip 8-bit DAC. The device is ideal for "fast-response" automatic gain control (AGC) circuits in all 2.5G/3G/4G wireless infrastructure transceivers such as GSM/EDGE, CDMA, WCDMA, LTE and WiMAX.

The MAX2062 can be used as an IF or RF general-purpose VGA that can be directly connected to a 50Ω system operating in the 50MHz to 1000MHz frequency range. Since each stage of the circuit has its own RF input and RF output, the MAX2062 can be configured to optimize the noise figure (configuring the amplifier as a first stage in a cascade configuration) or linearity specification (the amplifier is configured as the last one) Level), it is also possible to make a compromise between the two parameters (the amplifier is configured as the second stage). In a typical configuration (digital attenuator analog attenuator driver amplifier), the cascaded structure has a total gain range of 64dB, a maximum gain of 19.4dB, and a noise figure of 7.3dB. The linearity of the cascade structure is also excellent, with OIP3 of +41dBm, OIP2 of +56dBm and OP1dB of +19dBm. In receiver applications, excellent linearity directly increases the receiver's ability to reject strong blocking signals. The second and third harmonic distortions (HD2 and HD3) are limited to -55dBc and -72.7dBc, respectively. This feature simplifies harmonic filtering design requirements near the center frequency, allowing for a simpler, more cost-effective filter design.

The device's unique "fast-fire" gain selection feature allows the user to quickly select any of the four custom digital attenuation states without the delay required to reprogram the device over the SPI bus. In addition, the digital attenuator I/O can be further reduced by a factor of 5 or 2.5 depending on the number of states required (5 control bits are compared to 1 or 2 control bits, respectively). The proprietary 8-bit control DAC allows the user to easily adjust the amount of analog attenuation (0.12dB steps) with simple SPI commands. By integrating this feature, the device not only eliminates the need for external control of the DAC and voltage reference, but also greatly simplifies the overall design. There is no need to program additional SPI peripherals or to route additional analog control lines on the PCB.

The MAX2062 integrates nine different circuit functions in a compact single chip. Compared to the equivalent circuit with two MAX2065 VGAs, this latest dual-channel VGA can reduce the overall size of the circuit by 31%. This cost- and space-saving feature makes it possible to implement next-generation wireless infrastructure designs that are critical to transceiver price and density. The MAX2062 is available in a 48-pin TQFN lead-free package. Pin-compatible digital (MAX2063) and analog (MAX2064) versions are also available. For more information, see