MAX4000

The MAX4000/MAX4001/MAX4002 low-cost, low-powerlogarithmic amplifiers are designed to control RF poweramplifiers (PA) operating in the 0.1GHz to 2.5GHz fre-quency range. A typical dynamic range of 45dB makesthis family of log amps useful in a variety of wireless appli-cations including cellular handset PA control, transmitterpower measurement, and RSSI for terminal devices.Logarithmic amplifiers provide much widermeasurementrange and superior accuracy to controllers based ondiode detectors. Excellent temperature stability isachieved over the fulloperating range of -40°C to +85°C.

The choice of three different input voltage ranges elimi-nates the need for external attenuators, thus simplifyingPA control-loop design. The logarithmic amplifier is a volt-age-measuring device with a typical signal range of -58dBV to -13dBV for the MAX4000, -48dBV to -3dBV forthe MAX4001, and -43dBV to +2dBV for the MAX4002.

The input signal for the MAX4000 is internally AC-coupledusing an on-chip 5pF capacitor in series with a 2kΩinputresistance. This highpass coupling, with a corner at16MHz, sets the lowest operating frequency and allowsthe input signal source to be DC grounded. TheMAX4001/MAX4002 require an external coupling capaci-tor in series with the RF input port. These PA controllersfeature a power-on delay when coming out of shutdown,holding OUT low for approximately 5µs to ensure glitch-free controller output.

The MAX4000/MAX4001/MAX4002 family is available inan 8-pin µMAX package and an 8-bump chip-scale pack-age (UCSP™). The device consumes 5.9mA with a 5.5Vsupply, and when powered down the typical shutdowncurrent is 13µA.