SGM2014

9

APPLICATION NOTES

When LDO is used in handheld products, attention must be paid to voltage spikes which could damage

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

be tested on the production line without 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 spikes will be generated at the battery connector. The voltage spikes will be very high, and 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 spikes in cell phone designs. The schematic is shown below.

SGM2014

4

4.7uF

2

1

Vcc

Input

EN

GND

BP

IN

Control

3

5

0.01uF

1uF

BZM55B5V6