SIM802 Hardware Design
is drained. The following figure is the reference design of +5V input source power supply. The
designed output for the power supply is 4V, thus a linear regulator can be used. If there’s a big
difference between the input source and the desired output (VBAT), a switching converter power
supply will be preferable because of its better efficiency especially with the 2A peak current in
burst mode of the module.
The single 3.6V Li-Ion cell battery type can be connected to the power supply of the SIM802
VBAT directly. But the Ni_Cd or Ni_MH battery types must be used carefully, since their
maximum voltage can rise over the absolute maximum voltage for the module and damage it.
Figure
4: Reference circuit of the source power supply input
The following figure is the VBAT voltage ripple wave at the maximum power transmit phase, the
test condition is VBAT=4.0V, VBAT maximum output current =2A, C
A
=100µF tantalum
capacitor (ESR=0.7
Ω
) and C
B
=1µF.
Max:400mV
VBAT
Burst:2A
I
VBAT
4.615ms
577us
Figure
5: VBAT voltage drop during transmit burst
3.3.1 Power supply pins
Two VBAT pins of SIM802 are dedicated to connect the supply voltage. Twelve GND pins and
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