PT8A2707 Datasheet, PDF (9/26 Pages) Pericom Semiconductor Corporation – Charger Controller with Fuel-Guage & LCD/LED Display

PT8A2707-12/17-19
Charger Controller
with Fuel-Guage & LCD/LED Display
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7. First-Time Power-Up
Initial Fuel Count & First-Time Charging: Upon power-up, the PT8A2707-12/2717-19 resets for all internal memory and
resumes all default settings, the fuel-gauge counter will be initialized as zero count. The initialization may take a few seconds
before PT8A2707-12/2717-19 boots up to operate normally.
For the first-time charging, the fuel-gauge counter counts up to a default internal maximum fuel value (which is determined by the
fast-charge timer selected externally. E.g. a 90mins timer means roughly it is a 1-hour charger, the initial maximum fuel value is
assumed for 1hr for 1C charging current. Similarly, a 150min timer is assumed for a 120mins for 0.5C charging current, etc.)
measured by the external current sense resistor. Fuel-gauge LCD segments or LEDs are light up according to the initial maximum
fuel value. The 100% fuel LCD segment (or LED) keeps on flashing even though the fuel-gauge count reaches the default
maximum value. In this moment, the fuel-gauge counter learns the battery capacity by continuing to roll up its counter until fast-
charging is completed. This new battery capacity is therefore memorized and used as the maximum value for next charging cycles.
Similarly, if full-charge is detected earlier than the counter reaches its initial maximum fuel value, the maximum fuel value is
updated but progressively.
8. Fuel-Gauge Display
The PT8A2707/08/09/17/18/19 use LCD screen for the fuel gauge display and PT8A2710/11/ 12 use LEDs for fuel gauge display.
For both LCD screen and LED models, there are 3 different display modes: Charging Mode, Discharging Mode and Idle Mode,
as described in LED/LCD pattern section in pages 12-13.
1) Charging Mode:
a) Cord Mode with Motor off: When cord is connected, the fuel gauge display is turned on to “Charging Mode”. As soon as
cord is removed, the fuel-gauge LED display continues to display the fuel gauge level according to the “Discharging Mode”
for 5s.
b) Motor-On Mode with Cord: When motor is turned on while cord is plugged in, or vice versa, the PT8A2707-12/2717-19
displays fuel-gauge with accordance to the actual charge or discharge amount. The fuel-gauge always displays in the
“Charging Mode” no matter whether there is net current charging into the battery or not. If the motor is drawing less current
than the adapter can supply, the DC/DC converter will regulate the battery charging current at a slow-rate (1/10 of the fast
charge current). The high-precision ADC in PT8A2707-12/2717-19 is still to calculate this small charging current to add into
the fuel-gauge counter.
2) Discharging Mode:
a) Motor-On Mode without Cord: When motor is turned on while no cord is connected, the fuel gauge is displayed continuously
in the “Discharging Mode”. After motor is turned off, the fuel-gauge display will still continue to display for 5 seconds.
b) Motor-On Mode with Cord: The fuel-gauge always displays in the "Charging Mode" no matter whether there is net current
charging into the battery or not. If the motor is drawing more current than the adapter can supply, there will be some amount
of current being drawn from the battery pack. The high-precision ADC in PT8A2707-12/2717-19 is still capable to calculate
this small discharging current to subtract from the fuel-gauge counter.
3) Idle Mode:
LED display will be OFF in idle state. For LCD mode, the display of PT8A2707/08/ 09 will be continued on until battery has no
power; but the display of PT8A2717/18/19 will be off.
12-07-0005
PT0268-1 07/05/12
9