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112602
FEATURES
Rechargeable Lithium-Ion (Li+) Safety
Circuit
- Overvoltage Protection
- Overcurrent/Short-Circuit Protection
- Undervoltage Protection
- Overtemperature Protection
Controls High-Side N-Channel Power
MOSFETs Driven from 9V Charge Pump
System Power Management and Control
Feature Support
Eight Bytes of Lockable EEPROM
Dallas 1-Wire
Interface with Unique 64-Bit
Device Address
8-Pin mSOP Package
Low Power Consumption:
- Active Current: 12.5
mA typ
- Sleep Current:
1.5
mA typ
PIN CONFIGURATION
PIN DESCRIPTION
PLS - Battery-Pack Positive Terminal Input
PS
- Power-Switch Sense Input
DQ - Data Input/Output
V
SS
- Device Ground
V
DD
- Power-Supply Input
CP - Reservoir Capacitor
CC - Charge Control Output
DC - Discharge Control Output
DESCRIPTION
The DS2720 single-cell rechargeable Li+ protection IC provides electronic safety functions required for
rechargeable Li+ applications including protecting the battery during charge, protection of the circuit
from damage during periods of excess current flow and maximization of battery life by limiting the level
of cell depletion. Protection is facilitated by electronically disconnecting the charge and discharge
conduction path with switching devices such as low-cost N-channel power MOSFETs.
Since the DS2720 provides high-side drive to external N-channel protection MOSFETs from a 9V charge
pump, superior on-resistance performance results compared to common low-side protector circuits using
the same FETs. The FET on-resistance actually decreases as the battery discharges.
Adding to the uniqueness of the DS2720 is the ability of the system to control the FETs from either the
data interface or a dedicated input thereby eliminating the power-switch control redundancy of
rechargeable Li+ battery systems.
Through its 1-Wire interface, the DS2720 gives the host system read/write access to status and control
registers, instrumentation registers, and general-purpose data storage. Each device has a factory-
programmed 64-bit net address that allows it to be individually addressed by the host system.
DS2720U
mSOP
PS
3
2
1
4
5
6
7
8
PLS
DQ
V
SS
V
DD
CC
DC
CP
DS2720
Efficient, Addressable Single-Cell
Rechargeable Lithium Protection IC
www.maxim-ic.com
1-Wire is a registered trademark of Dallas Semiconductor.
DS2720
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Two types of user-memory are provided on the DS2720 for battery information storage: EEPROM and
lockable EEPROM. EEPROM memory saves important battery data in true nonvolatile (NV) memory
that is unaffected by severe battery depletion, accidental shorts, or ESD events. Lockable EEPROM
becomes ROM when locked to provide additional security for unchanging battery data.
ORDERING INFORMATION
PART
DESCRIPTION
DS2720AU
DS2720 in 8-Lead
m
SOP in Bulk with V
OVA
= 4.275V
DS2720AU/T&R
DS2720 in 8-Lead
m
SOP in Tape-and-Reel with V
OVA
= 4.275V
DS2720BU
DS2720 in 8-Lead
m
SOP in Bulk with V
OVB
= 4.35V
DS2720BU/T&R
DS2720 in 8-Lead
m
SOP in Tape-and-Reel with V
OVB
= 4.35V
DS2720CU
DS2720 in 8-Lead
m
SOP in Bulk with V
OVC
= 4.30V
DS2720CU/T&R
DS2720 in 8-Lead
m
SOP in Tape-and-Reel with V
OVC
= 4.30V
DS2720
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+
+
+
+
Figure 1. BLOCK DIAGRAM
1) Normally open, closed to enable test current, I
TST
2) Normally open, closed to enable test current, I
TST
, and recovery charge
(See Rechargeable Li+ Protection Circuitry section for more information.)
64-BIT ROM
1-WIRE INTERFACE
AND CONTROL
DQ
V
DD
V
OV
+
+
DELAY
t
OVD
V
SS
V
OC
+
+
DELAY
t
UVD
DELAY
t
SCD
DELAY
t
OCD
LOCKABLE EEPROM
STATUS/CONTROL
TEMP
SENSOR
(Tdevice)
S
R
Q
V
SC
V
CH
+
+
PLS
OUTPUT BUFFER
CC
DC
CP
V
CE
+
+
V
UV
S
R
Q
R
TST
L
O
G
I
C
T
MAX
+
+
PS
(1)
(2)
DS2720
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Table 1. DETAILED PIN DESCRIPTION
SYMBOL
DESCRIPTION
PLS
Battery-Pack Positive Terminal Input. The device monitors the state of the battery
pack's positive terminal through this pin in order to detect events such as the attachment
of a charger or the removal of a short circuit. Connect PLS to the pack positive terminal
through a 100
W resistor.
PS
Power-Switch Sense Input. The device wakes up from sleep mode when it senses the
closure of a switch to V
SS
on this pin.
PS
has a high-impedance internal pullup.
DQ
Data Input/Out. 1-Wire data line. Open-drain output driver. Connect this pin to the
DATA terminal of the battery pack. DQ has an internal 0.5
mA pull-down.
V
SS
Device Ground. Connect directly to the negative terminal of the battery cell.
V
DD
Power Supply Input. Connect V
DD
to the positive terminal of the battery cell through a
decoupling network.
CP
Charge Pump Output. The internal charge pump regulates CP to 9V which supplies
the ON state drive to the protection FETs. Connect a 0.1
mF reservoir capacitor from CP
to V
SS
.
CC
Charge Protection Control Output. Controls an external N-channel high-side charge
protection FET.
DC
Discharge Protection Control Output. Controls an external N-channel high-side
discharge protection FET.
Figure 2. APPLICATION EXAMPLE
CP
CC
DC
PS
PLS
VDD
VSS
DQ
DS2720
1-CELL Li+
1k
102
102
104
PACK+
PS
DATA
PACK-
100
330
330
10
104
102
1k
DS2720
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POWER MODES
The DS2720 has two power modes: active and sleep. While in active mode, the DS2720 continuously
performs safety monitoring. In sleep mode, the DS2720 ceases monitoring activities and drives both the
charge and discharge protection FETs to an "off state". Upon returning to the active mode from the sleep
mode, DS2720 resumes safety monitoring and conditionally turns on the protection FETs.
Table 2. POWER MODE TRANSITION CONDITIONS
Active
Sleep
Sleep
Active
(1)
V
DD
< V
UV
PS
pulled to V
SS
or
V
PLS
> V
DD
+ V
CH
(1) DS2720 does not transition to Active Mode if V
DD
< V
SC
.
RECHARGEABLE Li+ PROTECTION CIRCUITRY
During active mode, the DS2720 constantly monitors cell voltage and voltage drop across the FETs to
protect the battery from overcharge (overvoltage), overdischarge (undervoltage), and excessive discharge
currents (overcurrent, short circuit). Conditions and DS2720 responses are described in the sections
below and summarized in Table 3 and Figure 3.
Table 3. PROTECTION CONDITIONS AND DS2720 RESPONSES
ACTIVATION
CONDITION
NAME
THRESHOLD
DELAY
RESPONSE
RELEASE
THRESHOLD
Overvoltage
V
DD
> V
OV
t
OVD
(1)
CC = V
OLCC
V
DD
< V
CE
or
V
DD
- V
PLS
> V
OC
Undervoltage
V
SC
< V
DD
< V
UV
t
UVD
CC = V
OLCC
DC = V
OLDC
V
PLS
> V
DD
+ V
CH
and
V
DD
> V
UV
(charger connected)
Recovery Charge
V
DD
< V
SC
or
(while in active
mode) V
DD
< V
CE
R
TST
enabled
(2)
V
DD
V
CE
Overcurrent
V
DD
- V
PLS
> V
OC
t
OCD
CC = V
OLCC
DC = V
OLCC
V
PLS
> V
DD
- V
OC
(3)
Short Circuit
V
DD
< V
SC
t
SCD
CC = V
OLCC
DC = V
OLDC
V
PLS
> V
DD
- V
OC
(3)
Overtemperature
T
device
> T
MAX
CC = V
OLCC
DC = V
OLDC
T
device
< T
MAX
All voltages are with respect to V
SS
.
(1) During transition from sleep to active, t
OVD
= 0.
(2) Recovery charge current is limited by R
TST
and forward voltage of blocking diode, which prevents discharging through
R
TST
when recovery charge enabled.
(3) With test current I
TST
flowing from V
DD
to PLS (pullup on PLS).
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