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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 Min Typ Max Unit
Trickle Current 60 80 100 mA
Figure. PM7540 Charging Flow (TC Charging)
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