TS2207 datasheet(4/6 Pages) TSC

4 / 6 page

TS2207A/B series

4-6

2003/12 rev. B

Operation Description

COM1 (Over-Charge Detector)

COM1 is the monitor of the voltage at the VDD pin. COM1 senses an over charging condition and if this condition

continues longer than the delay time (tC1), When the voltage at VDD exceeds the over charge detector threshold VC1.

the COUT pin goes to a “L” level thus turns off the external charge control N-ch MOSFET. An internal level shifter is

incorporated in the buffer driver at the COUT pin to drive the “L” level of COUT equal to the V- pin voltage. By the way,

the “H” level of COUT is set equal to VDD.

The delay time (tC1) of over-charging is decided by the external capacitor C3 connected between the Vss and Cext pin,

it can be estimated as tC1 = [C3 x (VDD-0.7)] / (0.48 x 10

-6). However, if the over-charge condition is not long enough

to cover the time delay window, COUT will not go “L” and the charging process continues.

Required Conditions to Reset COM1 from Over Charging

After the MOSFET, the charge control is turns off, COM1 can be reset under two conditions. As resetting COM1

means COUT returns to “H” again and the charging path is reconnected to restart of charging process. One of the

condition to reset COM1 is when VDD falls to lower than “VC1 - VHYS” as a result of battery cell internal discharge.

Disconnecting the battery pack from the charger can also reset COM1 even when VDD is still within the hysteresis

window (VC1 - VHYS ≤VDD < VC1).

After the battery pack is disconnected from the charger, connecting a system load to the battery pack allows current to

flow through the parasitic diode of external charge control MOSFET. This discharging current will bring VDD down a

little over some time and once VDD drops below VC1, COUT will become “H”.

COM2 (Over-Discharge Detector)

COM2 monitors the cell voltage at the VDD pin. When VDD drops below the over-discharge threshold VD2 during the

discharging process, COM1 senses an over-charging condition and after delay time (tD1), the DOUT pin goes to a “L”

level and thus turning off the external discharge control N-ch MOSFET. As soon as this happens, the V- pin will be

pulled “H” by an internal PMOS and TS2207A/B series will be enter a standby mode.

Connecting the battery pack to a charger is a necessary condition for TS2207A/B series to recover from standby

mode. With the charger connected, the charge current can flow through the parasitic diode of the external discharge

control N-ch MOSFET while VDD is still lower than the over-discharge threshold. Once VDD is charged up to a value

higher than VD1, the DOUT pin goes “H”. This leads to the “ON” state of both the charge and discharge control

MOSFETs, and the charge process proceeds on as long as the charger is connected. Connecting a charger to the

battery pack when VDD voltage is already higher then VD1 will make DOUT instantaneously “H”.

COM3 (Over Current Detector, Short Circuit Protector)

The over current detector and short circuit protector can work when both the charge and discharge control N-ch

MOSFETs are “ON”.

Under normal operation, the V- pin voltage will be either slightly higher or lower than Vss (dependent on the

impedance of the two MOSFETs). However, when the V- pin voltage rises to a value between the short protection

voltage Vshort and over current threshold VOC, the TS2207A/B series detect an excess current condition. As a result,

the external discharge control N-ch MOSFET goes “OFF” with the DOUT pin being at “L”. An output delay time for the

over current detection is internally fixed. A quick recovery of V- from a value between Vshort and VOC to the normal

value within the delay time keeps the discharge control FET staying at the “ON” state.

Short circuit may as well be explained as a “serious” over current condition. When the V- pin voltage rises to a value

not only higher than VOC but also higher than Vshort, the short circuit protector will shut the discharge MOSFET down

immediately to protect battery pack from being damaged or exploding.

The V- pin has a built-in pull down resistor. Thus once the cause of over current or short circuit is removed, the V- pin

will be pulled down to the ground level through the internal resistor. Therefore, with V- lower than the over current and

short circuit protection threshold, DOUT will be turned back on and the TS2207A/B series can continue normal charge

or discharge operation.

When over current or short circuit occurs, the TS2207A/B series will not enter a standby mode.

TS2207 Datasheet(PDF) 4 Page - Taiwan Semiconductor Company, Ltd

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