UCC3911-1, UCC3911-2
UCC3911-3, UCC3911-4
SLUS429B鈥?FEBRUARY 2000 鈥?REVISED NOVEMBER 2002
LITHIUM ION AND LITHIUM POLYMER
BATTERY PROTECTOR
FEATURES
D
Protects Sensitive Lithium-Ion and
D
D
D
D
D
D
D
Lithium-Polymer Cells from Overcharging
and Overdischarging
Used for Two-Cell Battery Packs
No External FETs Required
Provides Protection Against Battery Pack
Output Short Circuit
Extremely Low Power Drain on Batteries of
About 20
碌A
Low Internal FET Switch Voltage Drop
User Controllable Delay for Tripping Short
Circuit Current Protector
3-A Current Capacity
DESCRIPTION
The UCC3911 is a two-cell lithium-ion (Li-Ion) and
lithium-polymer (Li-Pol) battery pack protector
device that incorporates an on-chip series FET
switch thus reducing manufacturing costs and
increasing reliability. The device鈥檚 primary
function is to protect both Li-Ion and Li-Pol cells in
a two-cell battery pack from being either
overcharged (overvoltage) or overdischarged
(undervoltage). It employs a precision bandgap
voltage reference that is used to detect when
either cell is approaching an overvoltage or
undervoltage state. When on-board logic detects
either condition, the series FET switch opens to
protect the cells.
A negative feedback loop controls the FET switch
when the battery pack is in either the overvoltage
or undervoltage state. In the overvoltage state the
action of the feedback loop is to allow only
discharge current to pass through the FET switch.
In the undervoltage state, only charging current is
allowed to flow. The operational amplifier that
drives the loop is powered only when in one of
these two states. In the undervoltage state the
chip enters sleep mode until it senses that the
pack is being charged.
The FET switch is driven by a charge pump when
the battery pack is in a normally charged state to
achieve the lowest possible R
DS(on)
. In this state
the negative feedback loop鈥檚 operational amplifier
is powered down to conserve battery power. Short
circuit protection for the battery pack is provided
and has a nominal delay of 100
碌s
before tripping.
An external capacitor may be connected between
CDLY and B0 to increase this delay time to allow
longer overcurrent transients.
A chip enable (CE) pin is provided that when held
low, inhibits normal operation of the device to
facilitate assembly of the battery pack.
APPLICATIONS
D
PDA, Camcorder, Digital Camera, Private
Mobile Radio
SIMPLIFIED APPLICATION DIAGRAM
UCC3911
B2
1
2
3
ISOLATED
COPPER
PAD
4
5
6
7
8
NC
OV
UV
CDLY
B1
15
14
13
12
11
10
9
UDG鈥?1075
16
+
SUBS SUBS
SUBS SUBS
GND
GND
B0
B0
ISOLATED
COPPER
PAD
+
LPWARN CE
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.
Copyright
铮?/div>
2000鈥?003, Texas Instruments Incorporated
www.ti.com
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