AD8348 Analog Devices, AD8348 Datasheet - Page 12

• Manufacturer Part Number: AD8348
• Description: 50-1000 MHz Quadrature Demodulator
• Manufacturer: Analog Devices

AD8348
Component
+Vs, GND
SW11, ENBL
SW13, R15,
VGIN
SW12
IFIP, R31, R32
MXIP, MXIN
T41, R42
C42, C43
LK11, VCMO
C8, C9, R4, R5
(I and Q)
C10 (I and Q)
C1 – C7
R1, R2
L1 – L3
(I and Q)
LK5 (I and Q)
Function
Power Supply and Ground Vector Pins
Device Enable: Place SW11 in the ENBL position to connect the ENBL
pin to +Vs. Place in the DENBL position to disable the device by
grounding the pin ENBL through a 50 Ohm pull down resistor. The
device may also be enabled via an external voltage applied to ENBL or
VENB.
Gain Control Selection: With SW13 in the POT position the gain of the
VGA can be set using the potentiometer R15. With SW13 in the EXT
position the VGA gain can be set by an external voltage to SMA connector
VGIN. For VGA operation the VGA must first be enabled by setting
SW12 to the IF position.
VGA Enable Selection: With SW12 in the IF position, the ENVG pin is
connected to +Vs and the VGA is enabled. The IF input should be used
when SW12 is in the IF position. With SW12 in the MX position the
ENVG pin is grounded and the VGA is disabled. The MX inputs should
be used when SW12 is in the MX position.
IF Input: The single-ended IF signal should be connected to this SMA
connector. R31 and R32 form a L-pad that presents a 50 Ohm termination
to the input.
Mixer Inputs: These inputs can be configured for either differential or
single-ended operation. The default is single-ended operation with T41
and R42 installed. In single-ended mode the input is applied to the 50
Ohm SMA connector MXIP. For differential drive, T41 should be
removed along with resistor R42. DC blocking capacitors (C42, C43)
should be installed in place of T41. This will present a nominal
differential impedance of 200 Ohms (100 Ohms each side). The
differential inputs should then be fed into SMA connectors MXIP and
MXIN.
Baseband Amplifier Output Bias: Installing LK11 connects VREF to
VCMO. This sets the bias level on the baseband amplifiers to V
is equal to approximately 1V. Alternatively, with LK11 removed, the bias
level of the baseband amplifiers can be set by applying an external voltage
to the VCMO testpoint.
Baseband Amplifier Outputs and Output Filter: Additional low-pass
filtering can be provided at the baseband output with these filters.
Mixer Output DC Blocking Capacitors: The mixer outputs are biased to
VCMO. To prevent damage to test equipment that cannot tolerate DC
biases, C10 is provided to block the DC component, thus protecting the
test equipment.
Baseband Filter: These components are provided for baseband filtering
between the mixer outputs and the baseband amplifier inputs. The
baseband amplifier input impedance is high and the filter termination
impedance is set by R2. See Table II below for jumper settings.
Offset Compensation Loop Disable: Installing these jumpers will
disable the offset compensation loop for the corresponding channel.
Table I Evaluation Board Configuration Options
- 12 -
REF
which
Default Condition
Not Applicable
SW11 = ENBL
SW2 = POT
SW12 = IF
R31 = 57.6 Ohms
R32 = 174 Ohms
T41 = ETC4-1-2
R42 = 0 Ohms
LK11 Installed
R4, R5 = 0 Ohms
C10 = 0 Ohms
All = OPEN
LK5x = OPEN
Rev. PrF
2/11/03