APPLICATION NOTES
When LDO is used in handheld products, attention must be paid to voltage spikes which could damage
SGM2014. In such applications, voltage spikes will be generated at changer interface and V
BUS
pin of USB
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.
Vcc
Input
BZM55B5V6
1uF
C
1
1
IN
SGM2014
EN
3
GND
2
BP
4
V
OUT
5
C
2
4.7uF
V
OUT
0.01uF
Control
9
SGM2014
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
