LTC5505-1ES5#PBF Linear Technology, LTC5505-1ES5#PBF Datasheet - Page 6

• Manufacturer Part Number: LTC5505-1ES5#PBF
• Description: IC, RF POWER DETECTOR, 3GHZ, 5-SOT-23
• Manufacturer: Linear Technology

Specifications of LTC5505-1ES5#PBF

• Frequency Range: 300MHz To 3GHz
• Power Range: -28dBm To 18dBm
• Supply Current: 500µA
• Supply Voltage Range: 2.7V To 6V
• Rf Ic Case Style: SOT-23
• No. Of Pins: 5
• Rf Type: GSM
• Pin Count: 5
• Screening Level: Industrial
• Package Type: TSOT-23
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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
V
sion 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 60 A 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
LTC5505-1/LTC5505-2
6
OUT
t
t
t
1
2
3
: CIRCUITS POWER UP AND SETTLE.
: BASEBAND CONTROLLER STARTS RF POWER RAMP UP AT 22 s AFTER SHDN IS ASSERTED HIGH.
: PART COMES OUT OF SHUTDOWN 20 s MAXIMUM PRIOR TO BURST.
when coming out of shutdown and a gain compres-
U
RF INPUT
POWER
SHDN
V
OUT
U
t
1
Example of LTC5505-X GSM/DCS Power Control Timing Diagram
20 s
W
t
2
2 s
t
3
U
28 s
t
4
voltage gain is reduced to 0.7. The compression expands
the low power detector range due to higher gain.
Modes of Operation
MODE
Shutdown
Enable
Applications
The LTC5505-1 and LTC5505-2 can be used as self-
standing signal strength measuring receivers for a wide
range of input signals from –32dBm to 18dBm for fre-
quencies from 300MHz to 3.5GHz.
The LTC5505-1 and LTC5505-2 can be used as demodu-
lators 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 100 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.)
543 s
t
t
t
4
5
6
: BASEBAND CONTROLLER COMPLETES RAMP UP.
: BASEBAND CONTROLLER STARTS RF POWER RAMP DOWN AT END OF BURST.
: LTC5505-X RETURNS TO SHUTDOWN MODE BETWEEN BURSTS
t
5
28 s
SHDN
High
Low
t
6
5505 TD
OPERATION
Disabled
Power Detect
5505f