LG -P500 Service Manual page 42

3.10.3. Charging control
A programmable charging block in PM7540 is used for battery charging. It is possible to set limits for the
charging current. The external supply typically connects directly to pin (VCHG). The voltage on this pin
(VCHG) is monitored by detection circuitry to ascertain whether a valid external supply is applied or not. For
additional accuracy or to capture variations over time, this voltage is routed internally to the housekeeping
ADC via the analog multiplexer. PM7540 circuits monitor voltages at VCHARGER and ICHARGE pins to
determine which supply should be used and when to switch between the two supplies. These pins are
connected to the Source (or emitter) and Drain (or collector) contacts of the pass transistor respectively.
3.10.3.1. Trickle Charging
Trickle Charging of the main battery, enabled through SBI control and powered from VDD, is provided by the
PM7540 IC, The trickle charger is on-chip programmable current source that supplies current from VDD to
pin (VBAT). Trickle charging can be used for lithium-ion and nickel-based batteries, with its performance
specified below (3.2V). The charging current is set to 80mA.
Parameter
Trickle Current
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Only for training and service purposes
Min Typ
60 80
Figure. PM7540 Charging Flow (TC Charging)
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3. TECHNICAL BRIEF
Max Unit
100 mA
LGE Internal Use Only