Application Notes
When LDO is used in handheld products, Attention must be paid to voltage spike which would damage
SGM2008. In such applications, voltage spike will be generated at changer interface and VBUS pin of USB
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:
Vcc
1
5
IN
VOUT
VOUT
Input
SGM2008
1uF
C1
C2
4.7uF
BZM55B5V6
EN
3
GND
2
BP/FP
4
0.01uF
Control
９
SGM2008
SGMICRO [ Shengbang Microelectronics Co, Ltd ]
