SC420AIMLTRT 查看數據表（PDF） - Semtech Corporation

零件编号

产品描述 (功能)

比赛名单

SC420AIMLTRT

High Speed, Combi-Sense™, Synchronous Power MOSFET Driver for Mobile Applications

Semtech Corporation 

POWER MANAGEMENT

Applications Information (Cont.)

SC420A

Fig 3: Typical Layout schematic for SC420A

Layout Guidelines

As shown in the above layout the traces used for

interconnections are not identical to each. The layout

using the above traces has significant advantages.

The traces used to interconnect C1, Dbst, Cbst, Rbst,

Vcc, GND, and Vbat are wider and heavy. This is done to

reduce the resistance and inductance of the current path.

As a result the voltage drop of the traces is significantly

reduced. This arrangement charges the Cbst capacitor

faster. Because of this, the FET gate capacitances are

also charged and discharged faster, improving the

efficiency of the system. Ceramic X7R capacitors are a

good choice for supply bypassing near the chip.

Wider traces are also used for TG and BG connects. This

is essential to decrease the delay of signal through the

trace and allow rapid charge and discharge of the FET

capacitance. Inductance is usually the dominant

impedance in the time range of interest (~10ns). As a

result, run the TG and BG connections with a

minimum aspect ratio (length to width) of 20:1. This

results in a 50 mil trace for a one inch connection.

In addition, minimize the loop area of the gate drive

loop. This is easy with BG, since the return path for

the current is GND. In the case of TG, the return

path for drivercurrent is DRN, so run these traces

together, as closely as possible.

Vias represent significant inductance and are to be

avoided wherever possible. BG is especially important

because when the HSFET switches off, the high dV/

dt of the DRN node will force current into the LSFET

gate via Cgd. A large inductance in the BG trace will

prevent the driver from holding BG down at this time.

The signal level traces are not critical because the

current levels are much smaller.

We can also see vias (circular dots) present in the

layout. The vias are important for interconnection

between different layers of the PCB. Also they are

important in heat transfer and aid in running the

system cooler.

© 2004 Semtech Corp.

13

United States Patent No. 6,441,597

www.semtech.com

Share Link: