MAX2092 Datasheet, PDF (10/15 Pages) Maxim Integrated Products – 700MHz to 2700MHz Analog VGA with Threshold Alarm Circuit and Error Amplifier for Level Control

MAX2092
700MHz to 2700MHz Analog VGA with Threshold
Alarm Circuit and Error Amplifier for Level Control
Detailed Description
The MAX2092 is a high-linearity analog VGA designed
to interface with 50Ω systems operating in the 700MHz
to 2700MHz frequency range. The analog attenuator is
controlled by an external analog control voltage. The
device features a gain range of 18.1dB to -22.3dB, a
noise figure of 5.2dB, OIP3 linearity of +32.5dBm, and
a wide RF bandwidth. Each of these features makes the
device an ideal VGA for numerous receiver and transmit-
ter applications. In addition, the device operates from a
single +5V supply.
Applications Information
Modes of Operation
The device can operate in several different modes, as
summarized in Table 1.
VGA-Only Mode Operation
VGA-only mode operation consists of setting CTRL1 =
logic 1 and CTRL2 = logic 0, and applying a DC value to
PLVLSET between 0V and 2.5V DC to manually adjust the
attenuation, and subsequently the RF_OUT power to any
desired value. The output power at RF_OUT increases at
a rate of 19.4dB/V as PLVLSET is increased. In VGA-only
mode, operation components R5, R6, R7, and C8–C11 can
be left unpopulated, and CTRL2 needs to be tied directly
to ground.
Closed-ALC Mode Operation
Closed-ALC mode operation consists of setting CTRL1
= CTRL2 = logic 1. The voltage on PLVLSET is set exter-
nally to adjust output power from -20dBm to +5dBm
when input power is in the recommended power range,
typically -6dBm. See the Typical Application Circuit. As
PLVLSET increases, the output power also increases at a
rate set by the external detector chosen. Ideally, a detec-
tor with an output voltage range of 0.1V DC to 2.4V DC is
recommended, but the device operates with any detec-
tor whose output ranges from 0V DC to 2.5V DC (output
coupler at RF_OUT already taken into account). An error
amplifier compares the DET_VIN voltage to PLVLSET,
and drives the attenuator in servo fashion until the error-
amplifier’s differential input error voltage is near zero. The
servo loop acts to maintain a regulated output power level
over an input power range depending on the setting of
PLVLSET.
When used in conjunction with the MAX2091 IF VGA, it
is recommended that an external voltage of 1.65V be
applied to the IF PLVLSET. This ensures that a nominal
RF signal level of approximately -3dBm is output from the
MAX2091. With this specific level setting, the complete
MAX2091 + MAX2092 cascade yields a constant RF
output power of -20.5dBm to +5dBm (depending on the
setting of RF PLVLSET) over an IF input power range of
–24dBm to +1dBm. See Figure 1 for details. Contact
the factory for additional details surrounding Maxim’s
MAX2091 + MAX2092 reference design.
Control Inputs
The device has three control inputs: CTRL1, CTRL2,
and PLVLSET. V_CC must be present before voltages are
applied to these pins. In cases where this is not pos-
sible, a 200Ω resistor must be included in series with
the control inputs to limit on-chip ESD diode conduction.
CTRL1 and CTRL2 are 3V logic controls, and cannot be
driven from 5V logic. In the case where no logic control
is available and a logic high is required, a voltage divider
can be used from the 5V VCC supply to produce the 3V
logic-high.
Alarm Operation
The alarm remains in logic-high state when the voltage
on DET_VIN (pin 8) is within the 0.175V to 2.25V range.
The alarm threshold amount is an internal fixed value to
the device with a nominal hysteresis of approximately
29mV.
Table 1. Control Mode Logic
CTRL1
0
1
CTRL2
0
0
VGA
Disabled
Enabled
ALC LOOP
Disabled
Disabled
1
1
Enabled
Enabled
0
1
—
—
ALARM
Disabled
Disabled
Enabled
—
FUNCTIONAL DESCRIPTION
Power-Down Mode
VGA-Only Mode
Closed ALC Mode. ALC loop locks DET_VIN to
PLVLSET.
Factory Test Mode (Do Not Use)
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