Data Sheet

Smart Machine Smart Decision

SIM800F_Hardware Design_V1.00 21 2015-07-31

Figure 7: Reference circuit of the VBAT input

Where C

is a 100uF tantalum capacitor with low ESR; C

could be a 1~10uF ceramic capacitor; 33PF and 10PF

capacitors are used for eliminating the high frequency interference; 5.1V/500mW zener diode can protect the

module against voltage surge.

All of these components should be placed as close to VBAT pins as possible.

Table 5: Recommended zener diode

Vendor Part number Power(watts) Packages

1 On semi MMSZ5231BT1G 500mW SOD123

2 Prisemi PZ3D4V2H 500mW SOD323

3 Vishay MMSZ4689-V 500mW SOD123

4 Crownpo CDZ55C5V1SM 500mW 0805

In addition, VBAT voltage will drop during the transmitting. The following figure shows the VBAT voltage drop

during maximum power transmitting under the condition:

VBAT=4.0V

=100µF tantalum capacitor (ESR=0.7)

=1µF ceramic capacitor

Figure 8: VBAT voltage drop during max power transmitting

However, hardware may shutdown once the voltage drops below 3.0V, which must be avoid.