MAX2090 MAXIM [Maxim Integrated Products], MAX2090 Datasheet - Page 11

• Manufacturer Part Number: MAX2090
• Description: 50MHz to 1000MHz Analog VGA with Threshold Alarm Circuit and Error Amplifier for Level Control
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX2090 is a high-linearity analog VGA designed
to interface with 50I systems operating in the 50MHz
to 1000MHz frequency range. An external analog con-
trol voltage controls the analog attenuator. The device
features a gain range of -10.9dB to +26.1dB, a noise
figure of 4dB, OIP3 linearity of +38dBm, and a wide RF
bandwidth. Each of these features makes the device an
ideal VGA for numerous receiver and transmitter appli-
cations. In addition, the device operates from a single
+5.0V supply.
The device can operate in several different modes, as
summarized in
VGA-only mode operation consists of setting CTRL1 =
logic 1 and CTRL2 = logic 0, and applying a DC value to
PLVLSET between 0 and 2.5V DC to manually adjust the
attenuator and subsequently the RF_OUT power to any
desired value. The output power at RF_OUT increases at a
rate of 19.5dB/V as PLVLSET is increased. The error ampli-
fier and alarm are powered off in this mode, reducing the
supply current by 10mA typical. In VGA-only mode, com-
ponents R5, R7, C8, C9, and C16 can be left unpopulated.
Table 1. Mode Control Logic
Maxim Integrated
Alarm Circuit and Error Amplifier for Level Control
CTRL1
0
1
1
0
50MHz to 1000MHz Analog VGA with Threshold
CTRL2
Table
0
1
0
1
Applications Information
1.
VGA-Only Mode Operation
Detailed Description
Disabled
Enabled
Enabled
VGA
—
Modes of Operation
AMPLIFIER
Disabled
Disabled
Enabled
ERROR
—
ALC LOOP
Disabled
Disabled
Enabled
—
Closed-ALC mode operation consists of setting CTRL1 =
CTRL2 = logic 1. In this mode, the DET_IN input is driven
from an external detector through R7. Ideally, a power
detector with an output voltage range of 0.1V to 2.4V
DC is recommended, but the MAX2090 operates with
any detector whose output ranges from 0 to 2.5V DC.
PLVLSET is used to set the RF OUT power by comparing
it to the DET_VIN (pin 8) voltage in the error amplifier. As
PLVLSET increases, the power at RF_OUT also increas-
es. Components R5, C8, and C9 are installed to set the
response time of the loop. See the Typical Application
Circuit. This loops acts to maintain the input power to
the external detector by driving the attenuator in servo
fashion as the power level into RF_IN changes. PLVLSET
can be externally driven to a DC value between 0 and
2.5V, such that the desired power is present at RF_OUT.
The MAX2090 has four control inputs: CTRL1, CTRL2,
ALM_THRES, and PLVLSET.
voltages are applied to these pins. In cases where this
is not possible, a 200I 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
produce the 3V logic-high.
Disabled
Disabled
Enabled
ALARM
—
Power-down mode
Closed-ALC mode: ALC loop locks
DET_VIN to PLVLSET
VGA-only mode
Factory test mode (do not use)
Closed-ALC Mode Operation
FUNCTION DESCRIPTION
V
CC
must be present before
MAX2090
Control Inputs
V
CC
supply to
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