M50 Hardware Design
M50_HD_V2.0
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1) Use the EMERG_OFF pin only while failing to turn off the module by the command
“AT+QPOWD=1” and the PWRKEY pin. Please refer to the Section 3.4.2.4.
3.3. Power supply
3.3.1. Power features of module
The power supply is one of the key issues in the designing GSM terminals. Due to the 577us radio
burst emission in GSM every 4.615ms, power supply must be able to deliver high current peaks in
a burst period. During these peaks, drops on the supply voltage must not exceed minimum
working voltage of module.
For the M50 module, the max current consumption could reach to 1.6A during a transmit burst. It
will cause a large voltage drops on the VBAT. In order to ensure stable operation of the module, it
is recommended that the max voltage drop during the transmit burst does not exceed 400mV.
Vdrop
4.615ms
577us
I
VBAT
VBAT
Burst:1.6A
Figure 3: Voltage ripple during transmitting
3.3.2. Decrease supply voltage drop
The power supply rang of the module is 3.3V to 4.6V. Make sure that the input voltage will never
drop below 3.3V even in a transmitting burst. If the power voltage drops below 3.3V, the module
could turn off automatically. For better power performance, it is recommended to place a 100uF
tantalum capacitor with low ESR (ESR=0.7Ω) and ceramic capacitor
100nF, 33pF and 10pF near
the VBAT pin. The reference circuit is illustrated in Figure 4.
The VBAT route should be wide enough to ensure that there is not too much voltage drop
occurring during transmit burst. The width of trace should be no less than 2mm and the principle
of the VBAT route is the longer route, the wider trace.
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