NE57607 Philipss, NE57607 Datasheet - Page 8

• Manufacturer Part Number: NE57607
• Description: Two-cell Lithium-ion battery protection with overcurrent / over- and under-voltage protection
• Manufacturer: Philipss

Philips Semiconductors
The R-C filters around the NE57607
One needs to place R-C filters on the positive input pins of the
NE57607. These are primarily to shield the IC from electrostatic
occurrences 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-Cs
then provide power during the first instance of the short circuit and
allow the IC to turn OFF the discharge MOSFET. The IC can then
enter an unpowered state. Lastly, the R-C filter on the node between
the two cells filters any noise voltage caused by noisy load current.
The values shown in Figure 6 are good for these purposes.
Selecting the Optimum MOSFETs:
For a 2-cell battery pack, a logic-level MOSFET should be used.
These MOSFETs have turn-on thresholds of 0.9 V and are
considered full-on at 4.5 V VGS. The total pack voltage will be a
maximum of 8.6 V which is within safe operating range of the gate
voltage which is typically more than two times the full-on voltage.
The MOSFETs should have a voltage rating greater than 20 V and
should have a high avalanche rating to survive any spikes
generated across the battery pack terminals.
The current rating of the MOSFETs should be greater than four
times the maximum “C-rating” of the cells. The current rating,
PACKING METHOD
2001 Oct 03
Two-cell Lithium-ion battery protection with
overcurrent, over- and under-voltage protection
GUARD
BARCODE
BAND
LABEL
BOX
TAPE
Figure 7. Tape and reel packing method.
REEL
ASSEMBLY
8
pack. The total resistance of the battery pack is given by Equation 1.
though, is more defined by the total series resistance of the battery
The total pack resistance is typically determined by the system
requirements. The total pack resistance directly determines how
much voltage droop will occur during pulses in load current.
Another consideration is the forward-biased safe operating area of
the MOSFET. During a short-circuit, the discharge current can easily
reach 10–15 times the “C-rating” of the cells. The MOSFET must
survive this current prior to the discharge MOSFET can be turned
OFF. So having an FBSOA envelope that exceeds 20 amperes for
5 ms would be safe.
The Charge MOSFET Circuit.
The NE57607 uses an isolated charge MOSFET drive arrangement.
This is to help keep ESD charges from entering the IC. The charge
MOSFET is normally ON until turned off by the IC. The CF pin uses
a current source to drive an external NPN transistor to turn OFF the
charge FET. If a charge has poor “compliance” or the no load voltage
of the charge can rise significantly above the rating of the battery
pack. This condition causes the source of the charge FET to go very
negative compared to the cell GND voltage after the charge FET
opens. This design allows the charge FET gate drive to “float” down
to this very negative voltage without upsetting the operation of the IC.
R bat(tot) = 2(R DS(ON) ) + 2R cell
TAPE DETAIL
(Equation 1)
COVER TAPE
NE57607
CARRIER TAPE
Product data
SL01305