UCC3911-3
PARAMETER NAME:
UCC3911-3
Cells Protected (max)
2
Overvoltage Threshold (V)
4.3
Protection FETs
Internal
Overcurrent Protection
Yes
Overcurrent Delay
Yes
Serial Bus
No
Shutdown Current (uA)
3.5
Target
Wireless phone, pager, PDA, consumer electronics
UCC3911-3, 2-Cell Lithium-Ion Battery
Protection IC W/Internal FET And Vov = 4.30V
DEVICE STATUS: ACTIVE
FEATURES:
Protects Sensitive Lithium-Ion and 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 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's
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 con-
dition, 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's 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 us 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.
The UCC3911 is specified for operation over the temperature range of 20C to 70C, the typical operating and
storage temperature range of Li-Ion and Li-Pol batteries.
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