ltm9005v Linear Technology Corporation, ltm9005v Datasheet - Page 20

• Manufacturer Part Number: ltm9005v
• Description: Ltm9005 - If Sampling Receiver Subsystem
• Manufacturer: Linear Technology Corporation

LTM9005
applicaTions inForMaTion
standard practice. It is recommended that all supply
inputs use the same low noise, 3.3V supply, but the ADC
and the amplifiers may be operated from a lower voltage
level if desired. All three rails can operate from the same
3.3V linear regulator but place a ferrite bead between
the supply pins. Separate linear regulators can be used
without additional supply sequencing circuitry if they have
common input supplies.
Grounding and Bypassing
The LTM9005 requires a printed circuit board with a clean
unbroken ground plane; a multilayer board with an internal
ground plane is recommended. The pinout of the LTM9005
has been optimized for a flow-through layout so that the
interaction between inputs and digital outputs is minimized.
The placement of critical pads allows for those signals to
be routed on the top layer.
The ground planes within the LTM9005 are broken in to
three areas: RF ground, IF ground and digital ground.
The mixer (V
ground. In Figure ?, this area is to the left of the line start-
ing between pads M6 and M7 and ending between pads
A10 and A11. The RF ground plane is bridged to the IF
20
CC1
) and first amplifier (V
A1
RF GND
CC2
) return to RF
Figure 13
ground plane by the SAW filter. All GND pins can connect
to the same ground plane. It is not necessary to break
these ground planes on the circuit board but the pads are
separated and available for use.
The second amplifier (V
ADC (V
of line described above are IF ground. The IF ground plane
is bridged to the digital ground plane by the ADC die. The
digital ground plane uses the OGND pads and extends
under all of the digital output pads.
The LTM9005 is internally bypassed with the mixer (V
first amplifier (V
(V
output supply (OV
bypass capacitance is optional and may be required if
power supply noise is significant.
Heat Transfer
Most of the heat generated by the LTM9005 is transferred
through the bottom-side ground pads. For good electrical
and thermal performance, it is critical that all ground pins
are connected to a ground plane of sufficient area with as
many vias as possible.
DD
) supplies returning to ground (GND). The digital
IF GND
DD
) return to IF ground. All GND pads to the right
DIGITAL GND
CC2
DD
), second amplifier (V
) is returned to OGND. Additional
CC3
) and the analog portion of the
9005 F13
CC3
) and ADC
CC1
9005p
),