Power Supply Pins On The Board-To-Board Connector; Minimizing Power Losses - SimCom SIM5218E Hardware Design

SIM5218E Hardware Design
Figure 3：VBAT 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 = 100 µF tantalum
A
capacitor (ESR=0.7Ω) and C =1µF.
B
Figure 4 ：VBAT voltage drop at the maximum power transmit phase (GSM)
And make sure that the capacitor is close to Vbat pins of 70 pins connector. If a DC/DC or LDO is
used for power supply of module, you should make sure that the peak current of power supply can
rise up to 2A. The reference design is putting one big capacity at the output of the DC/DC or LDO,
and another big capacity beside the 70 pins connector.

3.3.1 Power supply pins on the board-to-board connector

Six VBAT pins of the board-to-board connector are dedicated to connect the supply voltage; six
GND pins are recommended for grounding. VRTC pin can be used to back up the RTC.

3.3.2 Minimizing power losses

Please pay special attention to the supply power when you are designing your applications.
Please make sure that the input voltage will never drop below 3.4V even in a transmit burst
during which the current consumption may rise up to 2A. If the power voltage drops below
3.4V, the module may be switched off. Using the board-to-board connector will be the best
way to reduce the voltage drops. You should also remove the resistance from the power
supply lines on the host board or from battery pack into account.
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SIM5218E_HD_V1.03 11.06.2009