The MAX4000/MAX4001/MAX4002 low-cost, low-power logarithmic amplifiers are designed to control RF power amplifiers (PA) operating in the 0.1GHz to 2.5GHz frequency range. A typical dynamic range of 45dB makes this family of log amps useful in a variety of wireless applications including cellular handset PA control, transmitter power measurement, and RSSI for terminal devices. Logarithmic amplifiers provide much wider measurement range and superior accuracy to controllers based on diode detectors. Excellent temperature stability is achieved over the full operating range of -40°C to +85°C.
The choice of three different input voltage ranges eliminates the need for external attenuators, thus simplifying PA control-loop design. The logarithmic amplifier is a voltage-measuring device with a typical signal range of
-58dBV to -13dBV for the MAX4000, -48dBV to -3dBV for the MAX4001, and -43dBV to +2dBV for the MAX4002.
The input signal for the MAX4000 is internally AC-coupled using an on-chip 5pF capacitor in series with a 2kΩ input resistance. This highpass coupling, with a corner at 16MHz, sets the lowest operating frequency and allows the input signal source to be DC grounded. The MAX4001/MAX4002 require an external coupling capacitor in series with the RF input port. These PA controllers feature 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 in an 8-pin µMAX® package and an 8-bump chip-scale package (UCSP™). The device consumes 5.9mA with a 5.5V supply, and when powered down the typical shutdown current is 13µA.
Applications
- Cellular Handsets (TDMA, CDMA, GPRS, GSM)
- RSSI for Fiber Modules
- Transmitter Power Measurement and Control
- TSSI for Wireless Terminal Devices
