PRODUCT BRIEF

The MT1550 is a low-cost programmable-gain power amplifier IC for use in CATV upstream applications. The Microtune® MT1550 is a 3.3 volt part optimized for the DOCSIS® 1.0, 1.1, 2.0 and Euro-DOCSIS™ upstream standard. An on-chip input anti-aliasing filter is included to reduce external system costs.

The device’s specified frequency range is from 5 MHz to 65 MHz, with an output P1dB > 67 dBmV through a 1:1 impedance-ratio transformer. A 3-wire digital serial bus controls the variable gain, with gain control available in 1 dB steps and a nominal 59 dB gain range.

The MT1550 may be disabled via an external control pin. The transmit disable mode not only minimizes output noise by shutting off the output stage, but also maintains its output impedance at nominal levels. Output transients are nominally less than 16 mVp-p at 61 dBmV output level during transmit enable/disable switching.

Operating from a single 3.3 V supply, the amplifier typically draws 247 mA at maximum gain or minimum attenuation. Additional internal circuitry reduces the amplifier’s power consumption depending on gain setting. Transmit-disable mode reduces the typical current draw to 60 mA, while shutdown mode further reduces it to 85 µA.

The MT1550 is available in a 20-pin Quad Flat No-Lead (QFN) package with an exposed pad for the extended industrial temperature range of -40°C to +85°C.

FEATURES

• Integrated on-chip anti aliasing filter

• P1dB of 67 dBmV

• Low power-up/down

transients of 16 mV p-p typical at 61 dBmV output

• Ultra low third harmonic distortion

• Single 3.3 V supply

• 59 dB gain range

• Gain programmable in 1 dB steps

• Low transmit output noise

floor: -50 dBmV in 160 kHz

• Low transmit-disable output noise: -68 dBmV

• Two power-down modes

• DOCSIS 1.0, 1.1, 2.0 and Euro-DOCSIS compatible

MT1550 APPLICATIONS

• Cable modems

• Telephony over cable

• Set-top box CATV