50 MHz to 3.5 GHz 40 dB Logarithmic Power Detector for
CDMA and WCDMA
The LMV221 is a 40 dB RF power detector intended for use
in CDMA and WCDMA applications. The device has an RF
frequency range from 50 MHz to 3.5 GHz. It provides an ac-
curate temperature and supply compensated output voltage
that relates linearly to the RF input power in dBm. The circuit
operates with a single supply from 2.7V to 3.3V.
The LMV221 has an RF power detection range from −45 dBm
to −5 dBm and is ideally suited for direct use in combination
with a 30 dB directional coupler. Additional low-pass filtering
of the output signal can be realized by means of an external
resistor and capacitor. Figure (a) shows a detector with an
additional output low pass filter. The filter frequency is set with
RS and CS.
Figure (b) shows a detector with an additional feedback low
pass filter. Resistor RP is optional and will lower the Trans
impedance gain (RTRANS). The filter frequency is set with
CP//CTRANS and RP//RTRANS.
The device is active for Enable = High, otherwise it is in a low
power consumption shutdown mode. To save power and pre-
vent discharge of an external filter capacitance, the output
(OUT) is high-impedance during shutdown.
The LMV221 power detector is offered in the small 2.2 mm x
2.5 mm x 0.8 mm LLP package.
■ 40 dB linear in dB power detection range
■ Output voltage range 0.3 to 2V
■ Multi-band operation from 50 MHz to 3.5 GHz
■ 0.5 dB accurate temperature compensation
■ External configurable output filter bandwidth
■ 2.2 mm x 2.5 mm x 0.8 mm LLP 6 package
■ UMTS/CDMA/WCDMA RF power control
■ GSM/GPRS RF power control
■ PA modules
■ IEEE 802.11b, g (WLAN)
(a) LMV221 with output RC Low Pass Filter
(b) LMV221 with feedback (R)C Low Pass Filter
© 2006 National Semiconductor Corporation 201737