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SIM548C Hardware Design
DDLO charge and UVLO charge:
DDLO (deep discharge lock out) is the state of battery when its voltage under 2.4V. And UVLO
(under voltage lock out) means the battery voltage less than 3.2V and more than 2.4V. The battery
is not suitable for fast charge when its condition is DDLO or UVLO. The GSM part of the module
provides a small constant current to the battery when the battery is in DDLO or UVLO. In DDLO
charge, The GSM part of the module gives out 5mA current to the battery. And in UVLO charge,
The GSM part of the module provide about 30mA current to the battery.
DDLO charge terminated when the battery voltage reaches 2.4V. UVLO charge terminated when
the battery voltage is up to 3.2V. Both DDLO and UVLO charge are controlled by the GSM part
of the module hardware only.
Fast charge:
If there is a charger supply and battery present and the battery is not in DDLO and UVLO, the
GSM part of the module will enter fast charge state. Fast charge controlled by the software. Fast
charge delivers a strong and constant current (about 450mA) through VBAT pin to the battery
until battery voltage reach 4.2V.
Trickle charge:
After fast charging, the battery voltage is approach the whole battery capacity voltage, trick charge
begins .in this state, the GSM part of the module charge the battery under constant voltage.
3.5.4 Operating modes during charging
The battery can be charged during various operating mode. That means that when the GSM engine
is in Normal mode (SLEEP, IDLE, TALK, GPRS IDLE or GPRS DATA mode), charging can be
in progress while the GSM part of the module remains operational (In this case the voltage supply
should be sufficient). Here we name Charging in Normal mode as Charge mode.
If a charger is connected to the module’s VCHG pin and the battery is connected to the VBAT pin
while the GSM part of the module is in POWER DOWN mode, the GSM part of the module will
go into the GHOST mode (Off and charging). The following table gives the difference between
Charge mode and GHOST mode.
SIM548C_HD_V1.01
09.05.2008
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Содержание SIM548C HD V1.01
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