The MAX3503 programmable power amplifier is designed for use in CATV upstream applications. The MAX3503 drives 61dBmV (QPSK) into a 75Ω load when driven with a 34dBmV nominal input signal. Both input and output ports are differential, requiring that an external balun be used at the output port. The variable gain feature provides greater than 56dB of dynamic range, which is controlled by an SPI™ 3-wire interface. Gain control is available in 0.5dB steps. The device operates over a 5MHz to 65MHz frequency range. The MAX3503 is internally matched for use with a 1:1 balun.
This device operates from a single 3.3V DC supply and draws 235mA during transmit (100% duty cycle, 61dBmV out). The bias current is automatically
adjusted, based on the output level to increase efficiency. Additionally, the device can be disabled between bursts to minimize noise and save power while maintaining a match at the output port. A shutdown mode is available to disable all circuitry and reduce current consumption to 5µA (typ).
The MAX3503 is available in a 20-pin QFN package. The device operates in the extended industrial temperature range (-40°C to +85°C).
Key Features
Applications/Uses
Single 3.3V Supply Operation
Accurate Gain Control, ±1dB over 53dB Range
Gain Programmable in 0.5dB Steps
-55dBc Harmonic Distortion at 65MHz
Low Burst On/Off Transient
High Efficiency: 182mW at 34dBmV Out;
16mW in Transmit-Disable Mode
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