Philips Semiconductors

Product data

NE57600

One-cell Lithium-ion battery protection with

over/undercharge and overcurrent protection

2001 Oct 03

9

APPLICATION INFORMATION

The NE57600 drives the series N-Channel MOSFETs to states

determined by the cell’s voltage and the battery pack load current.

During normal operation, both the discharge and charge MOSFETs

are ON, allowing bidirectional current flow.

If the battery pack is being charged, and the cell’s voltage exceeds

the overvoltage threshold, then the charge MOSFET is turned OFF.

The cell’s voltage must fall lower than the overvoltage hysteresis

If the battery pack is being discharged and the undervoltage

turned OFF. It will not turn back ON until a charger is applied to the

pack’s external terminals AND the cell’s voltage rises above the

When the battery pack is being discharged, if the load current

causes the voltage across the discharge MOSFET to exceed the

MOSFET is turned OFF after a fixed 7–18 ms delay. If short-circuit

is placed across the pack’s terminals, then the discharge MOSFET

is turned OFF after a 100–300 ms delay to avoid damaging the

MOSFETs.

from electrostatic energy and spikes on the terminals of the battery

pack. A secondary need is during the occurrence of a short-circuit

across the battery pack terminals. Here, the Li-ion cell voltage could

collapse and cause the IC to enter an unpowered state. The R-C

filter provides power during the first instant of the short circuit,

allowing the IC to turn OFF the discharge MOSFET before the IC

loses power. The R-C filter also filters any voltage noise caused by

noisy load current. The values shown in Figure 9 are adequate for

these purposes.

SL01556

NE57600

6

5

4

3

2

1

VM

CF

GND

DF

CHARGER

DETECTOR

OC REF

OV DEADTIME

CONTROL

UV DEADTIME

CONTROL

OV REF

UV REF

Figure 9.

Functional diagram.

SL01557

6

54

3

2

1

VM

CF

GND

DF

V+

V–

NE57600

DISCHARGE

FET

CHARGE

FET

Li-ION CELL

CHARGER

OR

LOADER

–

+

4.7 k

Ω

910 k

Ω

1.0

µF

1.0

µF

330

Ω

Figure 10.

Typical application circuit.