SIM800C datasheet(18/52 Pages) SIMCOM

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SIM800C_Hardware_Design_V1.02

2015-4-27

following figure is the reference circuit.

Vin

V out

U101

LM 2596-A D J

100uH

MB R 360

L101

C 101

+ C 102

D 102

C 103

R 102

R 101

F B 101

330uF

VB AT

2.2K

100uF

1uF

C 104

100nF

270

DC input

P W R_CT RL

O n/O ff

Figure 7: Reference circuit of the DC-DC power supply

The single 3.7V Li-ion cell battery can be connected to SIM800C VBAT pins directly. But the Ni-Cd or Ni-MH

battery must be used carefully, since their maximum voltage can rise over the absolute maximum voltage of the

module and damage it.

When battery is used, the total impedance between battery and VBAT pins should be less than 150mΩ.

The following figure shows the VBAT voltage drop at the maximum power transmit phase, and the test condition

is as following:

VBAT=4.0V,

A VBAT bypass capacitor CA=100µF tantalum capacitor (ESR=0.7Ω),

Another VBAT bypass capacitor CB=1uF~10uF.

577us

4.615m s

B urst:2A

IVBAT

VB AT

M ax:350m V

Figure 8: VBAT voltage drop during transmit burst

4.1.1.

Power Supply Pin

Pin34 and Pin35 are VBAT input, Pin36 and Pin37 are GND of power supply, and VRTC pin is power supply of

the RTC circuit in the module. VDD_EXT output 2.8V when module is in normal operation mode.

When designing the power supply in customers’ application, pay special attention to power losses. Ensure that

the input voltage never drops below 3.0V even when current consumption rises to 2A in the transmit burst. If the

power voltage drops below 3.0V, the module may be shut down automatically. The PCB traces from the VBAT

pins to the power supply must be wide enough (at least 60mil) to decrease voltage drops in the transmit burst.

The power IC and the bypass capacitor should be placed to the module as close as possible.

VBAT

MIN :3.0V

Figure 9: The minimal VBAT voltage requirement at VBAT drop

Note: Hardware power off voltage is 3.0V.

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