Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 25 / 82
Figure 3: Voltage Ripple during Transmitting
3.3.2. Decrease Supply Voltage Drop
The power supply range of the module is 3.3V to 4.6V. Make sure that the input voltage will never drop
below 3.3V even in a burst transmission. 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 during burst
transmission. The width of trace should be no less than 2mm and the principle of the VBAT route is the
longer route, the wider trace.
Figure 4: Reference Circuit for the VBAT Input