ltc2978 Linear Technology Corporation, ltc2978 Datasheet - Page 61

• Manufacturer Part Number: ltc2978
• Description: Octal Pmbus Power Supply Monitor And Controller With Eeprom
• Manufacturer: Linear Technology Corporation

applicaTions inForMaTion
PCB ASSEMBLY AND LAYOUT SUGGESTIONS
Bypass Capacitor Placement
The LTC2978 requires 0.1µF bypass capacitors between
the V
REFP pin and REFM pin. If the chip is being powered from
the V
to GND by a 0.1µF capacitor. In order to be effective,
these capacitors should be made of high quality ceramic
dielectric such as X5R or X7R and be placed as close to
the chip as possible.
Exposed Pad Stencil Design
The LTC2978’s package is thermally and electrically
efficient. This is enabled by the exposed die attach pad
on the under side of the package which must be soldered
down to the PCB or mother board substrate. It is a good
DD33
PWR
pins and GND, the V
input, then that pin should also be bypassed
DD25
Figure 21. Suggested Screen Pattern for Die Attach Pad
pin and GND, and the
practice to minimize the presence of voids within the
exposed pad inter-connection. Total elimination of voids
is difficult, but the design of the exposed pad stencil is
key. Figure 21 shows a suggested screen print pattern.
The proposed stencil design enables out-gassing of the
solder paste during reflow as well as regulating the finished
solder thickness.
PC Board Layout
Mechanical stress on a PC board and soldering-induced
stress can cause the LTC2978’s reference voltage and
voltage drift to shift. A simple way to reduce these stress-
related shifts is to mount the IC near the short edge of the
PC board, or in a corner. The board edge acts as a stress
boundary, or a region where the flexure of the board is
minimal.
2978 F11
LTC2978

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