hf/rf ZONE Products for the week of January 21, 2002
Maxim Integrated Products Says . . .
MAX2361/3/5 Highly Integrated Transmit IC For Dual-Band
Cellular Phones
Maxim Integrated Products introduced the MAX2361/MAX2363/MAX2365 baseband-to-PA complete dual-band cellular phone transmit ICs. They are designed for dual-band, dual-mode, and single-mode N-CDMA, TDMA, GAIT, and W-CDMA cellular phones. A key feature of the MAX2361 series is high integration level, which dramatically reduces component count and size.
The MAX2361 includes I/Q-modulator, IF VGA, dual IF VCOs, dual synthesizers, upconverters, RF VGA, and 3 RF power amplifier drivers. The drivers' high +11dBm linear output power allows driving the power amplifiers directly. This typically eliminates two SAW filters and two external PA drivers. The wide frequency range and dual IF ports make the device ideal for a variety of different dual-band and dual-mode radio architectures.
The MAX2363 suits single-band PCS and W-CDMA applications, whereas the
MAX2365 suits single-band, dual-mode cellular-band applications.
analogZONE Says . . .
Strangely, it has turned out that one of the boons for the silicon manufacturer of cell phone ICs is the diversity of the systems in worldwide use; for most OEMs the different bands and different applications are a major complication in manufacturing -- and the same has turned out to be true for the vendors who are pushing their compound technologies like GaAs. For some reason GaAs suppliers have been unable to get control logic to operate, so for multiple bands or applications they are having to make modules with the RF in GaAs and the logic in silicon, driving their costs up even more beyond their more expensive process. I don't understand why there is a problem -- if you can make an amplifier surely you can make a switch?
Companies like Maxim don't have that problem, so when a particular RF architecture is "sold" to an OEM that part can be made at a lower price than the compound process vendor can make his. Here Maxim has taken integration of the handheld transmit channel to the extreme, taking the differential I/Q baseband right through to final RF, including drivers for the final power amplifiers. The most complex version of the three parts on offer is the MAX2361, giving AMPS, CDMA, TDMA and WCDMA in both band groups. +9 dBm of output power is provided and the quiescent reduces with reduced power levels. A 85-dB range of gain control is provided at the IF and a further 40 dB is provided at final frequency before the drivers; the gain of both is controlled by a single gain-control voltage to optimize linearity and to minimize current consumption, with quiescent for the 3.0-V nominal rail parts dependent on the modulation type and power level.
The MAX2361 accepts the dc-coupled differential I/Q inputs (with an external common-mode bias from the driver DACs) and modulates this to IF. Two IF ranges are provided, from 120 MHz to 235 MHz, and 180 MHz to 380 MHz. The signals are taken off-chip for filtering (usually 228 MHz and 263 MHz) and are then single-sideband upconverted with a 45 degree offsetting technique. (The single-sideband approach avoids the need for another off-chip SAW filter.) After gain control the signal feeds three PA driver stages for filtering off-chip and to be fed to external PA stages and suitable Tx/Rx duplexing and diplexing to the common antenna. The IF PLL and the RF PLL are fed from would normally be an external 19.68-MHz TCXO, although the usable range for other systems is from 5 to 30 MHz.
IF output noise level is down at -143 dBm/Hz measured at 20-MHz offset, and the worst alternate channel power ratio is -52 dBc with most of the numbers at about -70 dBc. The parts also have eight programmable registers with four for divide, one for current control, one for test, one for operational control, and one for configuration. Each register has 24 bits with the 4 LSBs used as address. Programming is from SPI/QSPI/MICROWIRE-compatible serial port.
Although designed principally for phone handset use these chips will also find their way into other communication systems because of the flexibility available. For the main market I have no doubt at all that they will be a singular commercial success, in sales volume and profit. I am impressed especially with the way the designer has been able to dual-use so many stages in the part -- this is somebody who really knows how to handle RF.
The MAX2361, MAX2363, and MAX2365 are in production in a 7 x 7 mm QFN-48
with pricing starting at $5.43 in 1000-piece lots. Maxim is holding the
full data sheet confidential.