skusim tu postnut vytah z toho listu suciastky, snad to niekoho presvedci, ze iPhone ma superinteligentny obvod nabijania baterie a power managementu:
Battery Charger
The LTC4088-1/LTC4088-2 includes a constant-current/
constant-voltage battery charger with automatic recharge,
automatic termination by safety timer, low voltage trickle
charging, bad cell detection and thermistor sensor input
for out of temperature charge pausing
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
battery voltage is below VTRKL, typically 2.85V, an automatic
trickle charge feature sets the battery charge current to
10% of the programmed value. If the low voltage persists
for more than 1/2 hour, the battery charger automatically
terminates and indicates, via the CHRG pin, that the battery
was unresponsive.
Once the battery voltage is above VTRKL, the charger begins
charging in full power constant-current mode. The current
delivered to the battery will try to reach 1031V/RPROG.
Depending on available input power and external load
conditions, the battery charger may or may not be able to
charge at the full programmed rate. The external load will
always be prioritized over the battery charge current. The
USB current limit programming will always be observed
and only additional power will be available to charge the
battery. When system loads are light, battery charge current
will be maximized.
Charge Termination
The battery charger has a built-in safety timer. Once the
voltage on the battery reaches the pre-programmed float
voltage of 4.200V, the charger will regulate the battery voltage
there and the charge current will decrease naturally.
Once the charger detects that the battery has reached
4.200V, the 4-hour safety timer is started. After the safety
timer expires, charging of the battery will discontinue and
no more current will be delivered.
Automatic Recharge
Once the battery charger terminates, it will remain off
drawing only microamperes of current from the battery.
If the portable product remains in this state long enough,
the battery will eventually self discharge. To ensure that
the battery is always topped off, a charge cycle will automatically
begin when the battery voltage falls below
VRECHRG (typically 4.1V). In the event that the safety timer
is running when the battery voltage falls below VRECHRG, it
will reset back to zero. To prevent brief excursions below
VRECHRG from resetting the safety timer, the battery voltage
must be below VRECHRG for more than 1.5ms. The charge
cycle and safety timer will also restart if the VBUS UVLO
cycles low and then high (e.g., VBUS is removed and then
replaced) or if the charger is momentarily disabled using
the D2 pin.
Charge Current
The charge current is programmed using a single resistor
from PROG to ground. 1/1031th of the battery charge current
is delivered to PROG, which will attempt to servo to
1.000V. Thus, the battery charge current will try to reach
1031 times the current in the PROG pin. The program
resistor and the charge current are calculated using the
following equations:
In either the constant-current or constant-voltage charging
modes, the voltage at the PROG pin will be proportional
to the actual charge current delivered to the battery. The
charge current can be determined at any time by monitoring
the PROG pin voltage and using the following equation:
In many cases, the actual battery charge current, IBAT, will
be lower than the programmed current, ICHG, due to limited
input power available and prioritization to the system load
drawn from VOUT.
Charge Status Indication
The CHRG pin indicates the status of the battery charger.
Four possible states are represented by CHRG which include
charging, not charging (or fl oat charge current less than
programmed end of charge indication current), unresponsive
battery and battery temperature out of range.
The signal at the CHRG pin can be easily recognized as
one of the above four states by either a human or a microprocessor.
An open-drain output, the CHRG pin can
drive an indicator LED through a current limiting resistor
for human interfacing or simply a pull-up resistor for
microprocessor interfacing.
NTC (Pin 1): Input to the NTC Thermistor Monitoring
Circuits. The NTC pin connects to a negative temperature
coeffi cient thermistor which is typically co-packaged with
the battery pack to determine if the battery is too hot or
too cold to charge. If the battery?s temperature is out of
range, charging is paused until the battery temperature reenters
the valid range. A low drift bias resistor is required
from VBUS to NTC and a thermistor is required from NTC
to ground. If the NTC function is not desired, the NTC pin
Battery Charger
VFLOAT BAT Regulated Output Voltage
Normalny maximalny prud tymto obvodom je 1,25A
hranicny prud je 2A, za touto hranicou dojde k zniceniu obvodu.
ten obvod odpoji iPhone od napajania v pripade prekrocenia akehokolvek parametru, teplota, napatie, prud a takisto prekrocenia casu 4 hod.
v data sheete je dalsich 10 stran textu a tabuliek a grafov a schem, ktore objasnuju cinnost tohto inteligentneho obvodu napajania usb a nabijaca baterky iPhonu.
http://pdf1.alldatasheet.com/datasheet- ... 088-2.htmlDesigned specifically for USB applications, the
LTC4088-1/LTC4088-2?s switching regulator automatically
limits its input current to either 100mA, 500mA
or 1A via logic control,
cize po laicky povedane iPhone rozozna pomocou logickeho ovladania /kombinacia odporov medzi vodicmi USB/ na co je pripojeny a ci moze TAHAT zo zdroja 100, 500 mA, alebo 1A.
Cize nie nabijacka tlaci prud do iPhone. Ale iPhone si kontroluje, co don tecie.