SG2012

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Application Notes

When LDO is used in handheld products, Attention must be paid to voltage spike which would damage

interface when changer adapters and USB equipments are hot-inserted. Besides this, handheld products will

be tested on the production line on the condition of no battery. Test Engineer will apply power from the

connector pin which connects with positive pole of the battery. When external power supply is turned on

suddenly, the voltage spike will be generated at the battery connector. The voltage spike will be very high, it

always exceeds the absolute maximum input voltage (6.0V) of LDO. In order to get robust design. Design

Engineer needs to clear up this voltage spike. Zener diode is a cheap and effective solution to eliminate such

voltage spike. For example, BZM55B5V6 is a 5.6V small package Zener diode which can be used to remove

voltage spike in cell phone design. The schematic is shown in below:

SG2012

4.7uF

Vcc

Input

GND

IN

1uF

BZM55B5V6