Diodes APM8601 - Manual (Page 9)

APM8601
DUAL CHANNEL SINGLE CELL LINEAR LITHIUM BATTERY
CHARGER WITH 28V OVP and PROGRAMMABLE CHARGE
TIMER
APM8601
Document number: DS35138 Rev. 1 - 2
9 of 14
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December 2010
© Diodes Incorporated
NEW PROD
UC
T
Functional Description (continued)
USEL Pin 6 allows the selection of the USB charging current. When low, I
BAT
is limited to 95mA (one USB power allocation
unit) and when High I
BAT
is limited to 475mA (5 USB power allocation units, High Power), when drawing power from the USB
input. This pin does not affect the device operation when power is being drawn from DC.
CT The Charge Timer input on pin 5 allows selection of how long the system timers for Prequal, Charge and Top-off
states last. They are set by selecting the value of capacitor, C
CT
:
⎟
⎠
⎞
⎜
⎝
⎛
× =
nF 68
CCT
min 334 TCHARGE
⎟
⎠
⎞
⎜
⎝
⎛
× = =
nF 68
CCT
min 34.8 TTOPOFF TPREQUAL
The charge timer will hold its current value if the charging was stopped via the thermistor and continue when the battery is in
a valid temperature range for charging.
OUTPUTS
BAT Pins 1 and 7 are the current-controlled charging outputs for the battery cell. They should be connected together and
to the positive terminal of the battery. The chip monitors the voltage on these pins. There should be a 2.2µF capacitor
connected from BAT to GND.
POK The POK flag on pin 10 is pulled low when a valid power input is available on either DC or USB inputs. It will go high
when no valid power is available and the device will enter the Disable state.
CHG The CHG flag at pin 11 is pulled low when the device is in the Charge state. It will be high in Prequal and Top-off
states. If the thermistor trips the circuit into the THM state (from Prequal or Charge states), CHG will hold its previous value.
FLT The FLT flag on pin 14 indicates a battery fault, as determined by a time-out in either the Prequal or Charge states.
If the battery voltage does not reach 3V after the prequal timer (default 34.8mins), or does not reduce charging current to
7.5% after the charge timer (default 334mins), this indicates that the battery has failed or is failing and this will trigger the FLT
flag. This flag will not automatically reset, and can only be cleared by cycling the power input or the EN pin.