isl9212 Intersil Corporation, isl9212 Datasheet - Page 10

• Manufacturer Part Number: isl9212
• Description: Charging System Safety Circuit
• Manufacturer: Intersil Corporation

ISL9212
The over shoot caused by a hot insertion is not very
dependent on the decoupling capacitance value. Especially
when ceramic type capacitors are used for decoupling. In
theory, the over shoot can rise up to twice of the DC output
voltage of the AC adapter. The actual peak voltage is
dependent on the damping factor that is mainly determined
by the parasitic resistance (R in Figure 25).
In practice, the input decoupling capacitor is recommended
to use a 16V X5R dielectric ceramic capacitor with a value
between 0.1µF to 1µF.
The output of the ISL9212 and the input of the charging
circuit typically share one decoupling capacitor. The
selection of that capacitor is mainly determined by the
requirement of the charging circuit. When using the ISL6292
family chargers, a 1µF, 6.3V, X5R capacitor is
recommended.
Layout Recommendation
The ISL9212 uses a thermally enhanced DFN package. The
exposed pad under the package should be connected to the
ground plane electrically as well as thermally. A grid of
1.0mm to 1.2mm pitch thermal vias in two rows and 4 to 5
vias per row is recommended (refer to the ISL9212EVAL1
evaluation board layout). The vias should be about 0.3mm to
0.33mm in diameter. Use some copper on the component
layer if possible to further improve the thermal performance
but it is not mandatory.
Since the ISL9212 is a protection device, the layout should
also pay attention to the spacing between tracks. When the
distance between the edges of two tracks is less than
0.76mm, an FMEA (failure mechanism and effect analysis)
should be performed to ensure that a short between those
two tracks does not lead to the charger output exceeding the
“Lithium-Safe” region limits. Intersil will have the FMEA
document for the solution using the ISL9212 and the
ISL6292C chip set but the layout FMEA should be added as
part of the analysis.
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FN9280.1
May 8, 2006