LTC5505-1ES5#TRPBF

LTC5505-1/LTC5505-2 RF Power Detector with Buffered Output and >40dB Dynamic Range U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ The LTC®5505-X is an RF power detector for RF applications operating in the 300MHz to 3.5GHz range. A temperature compensated Schottky diode peak detector and buffer amplifier are combined in a small 5-pin ThinSOT package. The supply voltage range is optimized for operation from a single lithium-ion cell or 3xNiMH. Internal Schottky Diode RF Detector with Two Input Power Ranges: LTC5505-1, –28dBm to 18dBm LTC5505-2, –32dBm to 12dBm Wide Input Frequency Range: 300MHz to 3GHz (LTC5505-1); 300MHz to 3.5GHz (LTC5505-2) Temperature Compensated Buffered Detector Output Wide VCC Range of 2.7V to 6V Low Operating Current: 0.5mA Low Shutdown Current: 16dBm, VCC minimum is 3V and an RF input series resistor of 20Ω is required to limit the input current. Note 7: Guaranteed by design. 5505f 3 LTC5505-1/LTC5505-2 U W TYPICAL PERFOR A CE CHARACTERISTICS 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C VOUT OUTPUT VOLTAGE (mV) VOUT OUTPUT VOLTAGE (mV) 10000 LTC5505-1 Typical Detector Characteristics, 2.45GHz LTC5505-1 Typical Detector Characteristics, 1.85GHz 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C VOUT OUTPUT VOLTAGE (mV) LTC5505-1 Typical Detector Characteristics, 0.85GHz 1000 1000 100 0 6 –30 –24 –18 –12 –6 RF INPUT POWER (dBm) 12 1000 100 –30 –24 –18 –12 –6 0 6 RF INPUT POWER (dBm) LTC5505-2 Typical Detector Characteristics, 0.85GHz 100 0 6 –30 –24 –18 –12 –6 RF INPUT POWER (dBm) 12 5505 G03 LTC5505-2 Typical Detector Characteristics, 1.85GHz 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C VOUT OUTPUT VOLTAGE (mV) VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C VOUT OUTPUT VOLTAGE (mV) 12 5505 G02 5505 G01 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C 1000 1000 100 –32 –26 –20 –14 –8 –2 4 RF INPUT POWER (dBm) 100 –32 10 –26 –20 –14 –8 –2 4 RF INPUT POWER (dBm) 5505 G04 5505 G05 LTC5505-2 Typical Detector Characteristics, 2.45GHz LTC5505-2 Typical Detector Characteristics, 3.5GHz 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C VOUT OUTPUT VOLTAGE (mV) VOUT OUTPUT VOLTAGE (mV) 10000 VCC = 2.7V TO 6V 0Ω SERIES TERMINATION –40°C 25°C 85°C 1000 1000 100 –32 10 –26 –20 –14 –8 –2 4 RF INPUT POWER (dBm) 10 5505 G06 100 –32 –26 –20 –14 –8 –2 4 RF INPUT POWER (dBm) 10 5505 G07 5505f 4 LTC5505-1/LTC5505-2 U U U PI FU CTIO S RFIN (Pin 1): RF Input Voltage. Referenced to VCC. An external coupling capacitor to the RF source is required. The frequency range is 300MHz to 3GHz. This pin has an internal 250Ω termination, an internal Schottky diode detector and peak detector capacitor. (See Note 6 in the Electrical Characteristics.) GND (Pin 2): System Ground. SHDN (Pin 3): Shutdown Input. A logic low on the SHDN pin places the part in shutdown mode. A logic high enables the part. SHDN has an internal 150k pull down resistor to ensure that the part is in shutdown when the drivers are in a tri-state condition. VOUT (Pin 4): Buffered and Level Shifted Detector Output Voltage. VCC (Pin 5): Power Supply Voltage, 2.7V to 6V. VCC should be bypassed appropriately with ceramic capacitors. W BLOCK DIAGRA VCC 5 GAIN COMPRESSION + BUFFER 4 VOUT – SHDN 30k 250Ω RFIN 1 30k 100Ω 100Ω + 28pF RF DET 130mV – 60µA 22k 60µA BIAS 150k GND 2 3 5505 BD SHDN 5505f 5 LTC5505-1/LTC5505-2 U U W U APPLICATIO S I FOR ATIO Operation The LTC5505-X RF detector integrates several functions to provide RF power detection over frequencies ranging from 300MHz to 3.5GHz. These functions include an internally compensated buffer amplifier, an RF Schottky diode peak detector and level shift amplifier to convert the RF feedback signal to DC, a delay circuit to avoid voltage transients at VOUT when coming out of shutdown and a gain compression circuit to extend the detector dynamic range. Buffer Amplifier The buffer amplifier has a gain of two and is capable of driving a 2mA load. The buffer amplifier typically has an output voltage range of 0.25V to 1.75V. RF Detector The internal RF Schottky diode peak detector and level shift amplifier converts the RF input signal to a low frequency signal. The detector demonstrates excellent efficiency and linearity over a wide range of input power. The Schottky detector is biased at about 60µA and drives a peak detector capacitor of 28pF. Gain Compression The gain compression circuit changes the feedback ratio as the RF peak-detected input voltage increases above 100mV. Below 100mV, the voltage gain from the peak detector to the buffer output is 1.5. Above 200mV, the voltage gain is reduced to 0.7. The compression expands the low power detector range due to higher gain. Modes of Operation MODE SHDN OPERATION Shutdown Low Disabled Enable High Power Detect Applications The LTC5505-1 and LTC5505-2 can be used as selfstanding signal strength measuring receivers for a wide range of input signals from –32dBm to 18dBm for frequencies from 300MHz to 3.5GHz. The LTC5505-1 and LTC5505-2 can be used as demodulators for AM and ASK modulated signals with data rates up to 5MHz. Depending on specific application needs, the RSSI output can be split into two branches, providing AC-coupled data (or audio) output and DC-coupled, RSSI output for signal strength measurements and AGC. The LTC5505-1 and LTC5505-2 can be used for dual band mobile phone transmitter power control (refer to Typical Application schematic on first page). The circuit uses a capacitive tap at the Tx PA outputs. For example, a 0.3pF capacitor (C1) followed by a 100Ω resistor (R1) forms a coupling circuit with about a 20dB loss at the cellular band and 18dB loss at the PCS band, referenced to the LTC5505-2 IC RF input pin. For improved coupling accuracy, the C1 capacitor should be a high tolerance component (±0.05pF.) Example of LTC5505-X GSM/DCS Power Control Timing Diagram 20µs 2µs 28µs 543µs 28µs SHDN VOUT RF INPUT POWER 5505 TD t1 t2 t3 t4 t 1: PART COMES OUT OF SHUTDOWN 20µs MAXIMUM PRIOR TO BURST. t 2: CIRCUITS POWER UP AND SETTLE. t 3: BASEBAND CONTROLLER STARTS RF POWER RAMP UP AT 22µs AFTER SHDN IS ASSERTED HIGH. t5 t6 t 4: BASEBAND CONTROLLER COMPLETES RAMP UP. t 5: BASEBAND CONTROLLER STARTS RF POWER RAMP DOWN AT END OF BURST. t 6: LTC5505-X RETURNS TO SHUTDOWN MODE BETWEEN BURSTS 5505f 6 LTC5505-1/LTC5505-2 U TYPICAL APPLICATIO Dual Band Mobile Phone Tx Power Control with Directional Coupler 0Ω TO 20Ω 33pF 1 2 3 DISABLE ENABLE LTC5505-X VCC 5 RFIN 0.1µF GND SHDN VOUT 4 900MHz INPUT 1.8GHz INPUT MOBILE PHONE DSP Li-Ion BSEL Tx PA MODULE VPC DIRECTIONAL COUPLER DIPLEXER 900MHz OUTPUT 1.8GHz OUTPUT 50Ω 5505 TA02 U PACKAGE DESCRIPTIO S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 2.90 BSC (NOTE 4) 0.754 0.854 ± 0.127 3.254 2.80 BCS 1.50 – 1.75 (NOTE 4) 0.95 BSC 1.9 BSC PIN ONE RECOMMENDED SOLDER PAD LAYOUT 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.35 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 1.90 BSC S5 TSOT-23 0801 5505f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 7 LTC5505-1/LTC5505-2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1618 Constant Current/Constant Voltage, 1.4MHz, High Efficiency Boost Regulator Up to 16 White LEDs, VIN = 1.6V to 18V, VOUT Max = 34V, IQ = 1.8mA, ISD =