UCC3957MTR-2 Datasheet, PDF (1/15 Pages) Texas Instruments – THREE - OR FOUR-CELL LITHIUM - ION PROTECTOR CIRCUIT

Not Recommended for New Designs
UCC3957Ć1, UCC3957Ć2, UCC3957Ć3, UCC3957Ć4
SLUS236B – JANUARY 1999 – REVISED SEPTEMBER 2002
THREEĆ OR FOURĆCELL LITHIUMĆION
PROTECTOR CIRCUIT
FEATURES
D Three- or Four-Cell Operation
D Two-Tier Overcurrent Limiting
D 30-µA Typical Supply-Current Consumption
D 3.5-µA Typical Supply Current in Sleep Mode
D Smart Discharge Minimizes Losses in
Overcharge Mode
D 6.5-V to 20-V VDD Supply Range
D Highly Accurate Internal Voltage Reference
D Externally Adjustable Delays in Overcurrent
Controller
D Detection of Loss-of-Cell Sense Connections
M PACKAGE
(TOP VIEW)
VDD 1
CLCNT 2
WU 3
AN1 4
AN2 5
AN3 6
AN4 7
BATLO 8
16 DVDD
15 AVDD
14 CDLY2
13 DCHG
12 CHG
11 AN4
10 CDLY1
9 CHGEN
DESCRIPTION
The UCC3957 is a BiCMOS three- or four-cell
lithium-ion battery pack protector designed to
operate with external P-channel MOSFETs.
Utilizing external P-channel MOSFETs provides
the benefits of no loss-of-system ground in an
overdischarge state, and protects the IC as well as
battery cells from damage during an overcharge
state. An internal state machine runs continuously
to protect each lithium-ion cell from overcharge
and overdischarge. A separate overcurrent-
protection block protects the battery pack from
excessive discharge currents.
If any cell voltage exceeds the overvoltage
threshold, the appropriate external P-channel
MOSFET is turned off, preventing further charge
current. An external N-channel MOSFET is
required to level shift to this high-side P-channel
MOSFET. Discharge current can still flow through
the second P-channel MOSFET. Likewise, if any
cell voltage falls below the undervoltage limit, the
second P-channel MOSFET is turned off and only
charge current is allowed. Such a cell-voltage
condition causes the chip to go into low-power
sleep mode. Attempting to charge the battery
pack wakes up the chip. A cell-count pin (CLCNT)
is provided to program the IC for three- or four-cell
operations.
A two-tiered overcurrent controller and external
current shunt protect the battery pack from
excessive discharge currents. If the first
overcurrent threshold level is exceeded, an
internal timing circuit charges an external
capacitor to provide a user programmable
blanking time. If at the end of the blanking time the
overcurrent condition still exists, the external
discharge FET is turned off for a period 17 times
longer than the first blanking period, and then the
discharge FET is turned back on. If at any time a
second higher overcurrent threshold is exceeded
for more than a user programmable time, the
discharge FET is turned off, and remains off for the
same period as the first tier off time. This two tiered
overcurrent-protection scheme allows for
charging capacitive loads while retaining effective
short-circuit protection.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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Copyright  2002, Texas Instruments Incorporated
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