CMH82 Datasheet, PDF (9/10 Pages) TriQuint Semiconductor – CMH82

CMH82
CMH82 – Application Information
DC Biasing:
Supply Voltage.
One regulated voltage source is needed for CMH82. On the evaluation board, it is labeled
VDD.
Minimum LO Power for Proper Biasing
For proper biasing of the CMH82, a minimum LO input power is required. If the part is
turned ON without any LO drive applied, all currents will be extremely high. The minimum LO
required is approximately –12 dBm. Operation with LO input powers below the minimum
value causes the current to increase in all amplifier stages. For higher LO input power levels
the current stays relatively constant over a wide range of LO powers. Proper matching of the
LO amplifier is also important to achieve the lowest current consumption and to minimize the
required LO input power.
Adjustable Current Level
The CMH82 can operate in two different current/linearity modes: High Linearity (with
higher current) and Reduced Current (lower linearity). To operate with reduced current the
voltage on pin 19 (RCV) should be set LOW. Some additional current reduction can be
achieved by reducing the voltage at pin 14 by inserting a resistor between VDD and pin 14.
The current pulled by pin 14 is approximately 1 mA. Higher currents can be realized by using
a higher VDD voltage.
Tuning LO and IF Amplifiers:
The CMH82 can be tuned to utilize either high or low side LO frequencies and allows a
wide range of IF frequencies. Depending on the chosen frequency plan the off chip
components for the LO and IF amplifiers will need to be optimized. An application circuit with
all component values is provided for high side LO injection with IF frequency of 85 MHz (RF
freq 869 – 894 MHz).
Two external components (L9 and L8) are required for tuning the LO. L8 is critical for
setting the minimum current and to achieve the constant DC current over the operating band.
L9 sets the input match.
Components L7, C11 and C12 form the input match for the IF amplifiers and will vary
depending on the chosen IF frequency. The inductor on pin 8 allows adjustment to the gain
of the IF amplifiers. Output matching components shown in the application circuit provide a
transformation for a 50 Ohm load impedance. The output impedance for the CDMA IFA
(looking into pin 9) at 85 MHz is approximately (695 + j*135) Ohms. The AMPS output
impedance is approximately (172 + j*78) Ohms at 85 MHz.
CMH82 - Preliminary Datasheet (Rev 3nl, 1/02)
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