TIP

CAUTION

The wireless modem has insufficient internal capacitance to supply the large current peaks during GSM burst transmission - use the following general guidelines in designing the application power supply.

•Fit a low ESR electrolytic capacitor close to the wireless modem (>1,000 ∝F, with an ESR < 100 mΩ)

•Ensure power supply to wireless modem line resistance is < 200 mΩ

The module has approximately 40∝F of internal capacitance across the VCC pins. During initial power-up the host power supply will have to charge this capacitance to the operating voltage. This initial in-rush current may exceed the module’s normal peak current, sometimes greater than an order of magnitude higher (depending upon the power supply design) for a short duration (generally a few microseconds).

LZT 123 1836

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