WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 289

• Manufacturer Part Number: WM8311GEB/V
• Description: POWER MANAGEMENT SUBSYSTEM, 121BGA
• Manufacturer: Wolfson Microelectronics

Specifications of WM8311GEB/V

• Supply Voltage: 5.5V
• No. Of Step-down Dc - Dc Converters: 4
• No. Of Ldo Regulators: 7
• Digital Ic Case Style: BGA
• No. Of Pins: 121
• No. Of Regulated Outputs: 9
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Pre-Production
30.7 PCB LAYOUT
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Poor PCB layout will degrade the performance and be a contributory factor in EMI, ground bounce
and resistive voltage losses. Poor regulation and instability can result.
Simple design rules can be implemented to negate these effects:
External input and output capacitors should be placed as close to the device as possible using short
wide traces between the external power components.
Route output voltage feedback as an independent connection to the top of the output capacitor to
create a true sense of the output voltage, routing away from noisy signals such as the LX connection.
Use a local ground island for each individual converter connected at a single point onto a fully
flooded ground plane.
Current loop areas should be kept as small as possible with loop areas changing little during
alternating switching cycles.
Studying the layout below shows, for example, DC-DC1 layout with external components C3, L3 and
C6. The input capacitor, C6, is close into the IC and shares a small ground island with the output
capacitor C3. The inductor, L3, is situated in close proximity to C3 in order to keep loop area small
and current flowing in the same direction during alternating switching cycles. Note also the use of
short wide traces with all power tracking on a single (top) layer. Note that the illustration below shows
the WM8310 device, not the WM8311.
PP, December 2009, Rev 3.0
WM8311
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