LTM9003 datasheet(21/24 Pages) LINER

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LTM9003

9003p

Grounding and Bypassing

The LTM9003 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

LTM9003 has been optimized for a ﬂow-through layout

so that the interaction between inputs and digital outputs

is minimized. Ample ground pads facilitate a layout that

ensures that digital and analog signal lines are separated

as much as possible.

The LTM9003 is internally bypassed with the ADC (VDD),

ampliﬁer (VCC2) and mixer (VCC1) supplies returning to a

common ground (GND). The digital output supply (OVDD)

is returned to OGND. Additional bypass capacitance is

optional and may be required if power supply noise is

signiﬁcant.

Heat Transfer

Most of the heat generated by the LTM9003 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.

Recommended Layout

The high integration of the LTM9003 makes the PCB board

layout very simple and easy. However, to optimize its electri-

cal and thermal performance, some layout considerations

are still necessary.

• Use large PCB copper areas for ground. This helps to

dissipate heat in the package through the board and also

helps to shield sensitive on-board analog signals. Common

ground (GND) and output ground (OGND) are electrically

isolated on the LTM9003, but can be connected on the PCB

underneath the part to provide a common return path.

• Use multiple ground vias. Using as many vias as pos-

sible helps to improve the thermal performance of the

board and creates necessary barriers separating analog

and digital traces on the board at high frequencies.

• Separate analog and digital traces as much as possible,

using vias to create high-frequency barriers. This will re-

duce digital feedback that can reduce the signal-to-noise

ratio (SNR) and dynamic range of the LTM9003.

Figures 12 through 15 give a good example of the recom-

mended layout.

The quality of the paste print is an important factor in

producing high yield assemblies. It is recommended to

use a type 3 or 4 printing no-clean solder paste. The solder

stencil design should follow the guidelines outlined in

Application Note 100.

The LTM9003 employs gold-ﬁnished pads for use with

Pb-based or tin-based solder paste. It is inherently Pb-free

and complies with the JEDEC (e4) standard. The materi-

als declaration is available online at http://www.linear.

com/leadfree/mat_dec.jsp.

APPLICATIONS INFORMATION

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