Datasheet

MAX2065
50MHz to 1000MHz High-Linearity, Serial/
Parallel-Controlled Analog/Digital VGA
22 ______________________________________________________________________________________
The user can employ the STATE_A and STATE_B logic-
input pins to apply each step as required (Table 4).
Toggling just the STATE_A pin (one control bit) yields
two preprogrammed attenuation states; toggling both
the STATE_A and STATE_B pins together (two control
bits) yield four preprogrammed attenuation states.
As an example, assume that the AGC application
requires a static attenuation adjustment to trim out gain
inconsistencies within a receiver lineup. The same AGC
circuit can also be called upon to dynamically attenuate
an unwanted blocker signal that could de-sense the
receiver and lead to an ADC overdrive condition. In this
example, the MAX2065 would be preprogrammed
(through the SPI bus) with two customized attenuation
states—one to address the static gain trim adjustment,
the second to counter the unwanted blocker condition.
Toggling just the STATE_A control bit enables the user
to switch quickly between the static and dynamic atten-
uation settings with only one I/O pin.
If desired, the user can also program two additional
attenuation states by using the STATE_B control bit as
a second I/O pin. These two additional attenuation set-
tings are useful for software-defined radio applications
where multiple static gain settings may be needed to
account for different frequencies of operation, or where
multiple dynamic attenuation settings are needed to
account for different blocker levels (as defined by multi-
ple wireless standards).
Cascaded OIP3 Considerations
Due to both attenuator’s finite IP3 performance, the
cascaded OIP3 degrades when both attenuators are
set at higher attenuation states.
External Bias
Bias currents for the driver amplifier are set and opti-
mized through external resistors. Resistors R1 and R1A
connected to RSET (pin 18) set the bias current for the
amplifier. The external biasing resistor values can be
increased for reduced current operation at the expense
of performance.
Table 4. Preprogrammed Attenuation
State Settings
STATE_A STATE_B DIGITAL ATTENUATOR
0 0 Preprogrammed attenuation state 1
1 0 Preprogrammed attenuation state 2
0 1 Preprogrammed attenuation state 3
1 1 Preprogrammed attenuation state 4
Table 5. Typical Application Circuit Component Values (HC Mode)
DESIGNATION VALUE SIZE VENDOR DESCRIPTION
C1, C2, C7, C11 10nF 0402 Murata Mfg. Co., Ltd. X7R
C3, C4, C6, C8, C9, C10 1000pF 0402 Murata Mfg. Co., Ltd. C0G ceramic capacitor
C12, C13 150pF 0402 Murata Mfg. Co., Ltd. C0G ceramic capacitor
L1 470nH 1008 Coilcraft, Inc. 1008CS-471XJLC
R1, R1A 10Ω 0402 Panasonic Corp. 1%
R2 (+3.3V applications only) 1kΩ 0402 Panasonic Corp. 1%
R3 (+3.3V applications only) 2kΩ 0402 Panasonic Corp. 1%
R4 (+5V applications and
using internal DAC only)
47kΩ 0402 Panasonic Corp. 1%
U1 —
40-pin thin QFN-EP
(6mm x 6mm)
Maxim Integrated
Products, Inc.
MAX2065ETL+