PT8A2707 Datasheet, PDF(7/26 Page) Pericom Semiconductor Corporation – Charger Controller with Fuel-Guage & LCD/LED Display

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PT8A2707-12/17-19

Charger Controller

with Fuel-Guage & LCD/LED Display

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4) Fast-Charge Timer Cut-Off: The PT8A2707-12/2717-19 comes with 4 timer settings (30mins/60mins/90mins /150mins)

selectable externally through resistor divider. The fast-charge timer works as the last protection to prevent over-charging the

battery if none of the above 3 terminations takes effect. In general, the timer is chosen according to the required time to fully-

charge an empty battery with about 20-30% margins. The timer can be easily calculated at a given charging current and

battery capacity.

5) NTC Open or Short

During battery charging, the PT8A2707-12/2717-19 always detects NTC status by measure VT voltage value. If NTC

open/short is detected, all charging activities will be stopped and go to stop-charging mode.

After fast-charge, the battery is charged at a rate of 1/10C to compensate for the self-discharge rate so as to maintain the battery

capacity always at full as long as the cord is still connected. If the battery temperature continues to rise to 55ï°C during

maintenance, the PT8A2707-12/2717-19 will cut-off the charge current until the battery temperature reduces to below 55ï°C to

resume.

After full-charge is detected, the PT8A2707-12/2717-19 will restore the full-charge status until it measures its capacity drops 5%

of charge due to self-discharge (cord was removed) of battery or motor is turned on. During the time the PT8A2707-12/2717-19

keeps the full-charge status internally, if user detaches motor and plugs-in cord to charge the shaver again, the PT8A2707-

12/2717-19 will go to trickle-charge mode.

3. Discharging Mechanism (Motor is On while Cord is Not Connected)

SLIDE, TACT and DSTACT are motor running control switch inputs.

1) SLIDE Switch Mode: PT8A2707/17/10 uses a pull high slide switch to control motor running through SLIDE pin. When

slide switch is closed, the SLIDE pin is pulled high, and the motor is always turned on at 100% speed (full speed), else if

slide switch is open, the motor is always turned off to stop motor running.

2) TACT Switch Mode: PT8A2709/19/12 uses a pull high tact switch to control motor running through TACT pin. With 1st

pressing of TACT switch, the motor is always turned on at 100% speed (full speed), and with 2nd pressing of TACT switch,

the motor is always turned off to stop motor running. When using TACT switch mode, the key delay for tact switches to

reject multiple inputs are typically about 0.125s.

3) DSTACT Switch Mode: PT8A2708/18/11 uses a pull high tact switch to control motor running with Dual Speed through

DSTACT pin. With 1st pressing tact switch, the motor is turned on at 70% speed, with 2nd pressing of tact switch, the motor is

turned to 100% speed (full speed), and motor is turn off to stop running with 3rd pressing of tact switch. When using

DSTACT switch mode, the key delay for tact switches to reject multiple inputs are typically about 0.125s.

In above 3 models, battery over-discharge protection is available through auto-stop motor at once (<0.2s) when

ï Battery discharging current is higher than preset current limit for 3sec (there are three limit values selectable refer to âmotor-

over-current protection settingsâ)

ï Battery pack voltage is lower than the preset No-Power limit value (typically about 0.9-1.0V per cell).

ï NTC measures battery pack temperature higher than the preset limit (usually about 55-60ï°C)

The motor can be resumed when any of the above criteria is cleared. But for SLIDE switch model, user needs to turn off and turn

on SLIDE switch to start motor again; for TACT and DSTACT switch models, the user needs to press the tact switch once to start

motor.

4) Battery Low Alarm: The PT8A2707-12/2717-19 detects battery capacity through output voltage level by VBLOW pin.

When battery voltage is down to Battery-Low value (battery capacity is below 10%), Battery-Low alarm is alert, and controls

Battery-Low LCD screen or LED (which is connected to BLI pin10) to remind user that battery is under low capacity

condition. If battery voltage continues go down and decreases to No-Power value, the motor will self shut down to protect

battery be over discharged.

The Battery-Low LCD segment and LED indications as below table.

Table 6: Battery Alarm Conditions

Item

Condition

Battery-Low LED

Battery-Low LCD

No cord

Motor on

Motor off

blinking 5s

Cord is on

Motor on

Motor off

4. Cord is Connected While Motor is On

When cord is connected while motor is on, or vice versa, there are two scenarios:

1) The motor is turned on and draws more current than the AC/DC adapter can supply: In all cases, the PT8A2707-

12/2717-19 will enable the external PMOSFET to fully turn on to supply maximum current to the motor. There are three sub-

cases to observe:

12-07-0005

PT0268-1 07/05/12

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