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DS2731E+

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
General Description
The DS2731 is a complete power-management solution
for modular backup applications. It is well-suited for 2.5V
and below memory bus voltages, with an input voltage of
12V. The DS2731 includes an internal MOSFET switching
power stage for charging a one-cell lithium chemistry bat-
tery. It has a fully integrated synchronous buck regulator
capable of supplying up to 450mA of cache backup sup-
ply current, and the necessary logic and power devices
for handling the switchover from system power to battery
power. The battery charging method of the DS2731 is
constant current/constant voltage (CCCV). Output voltage
can be margined from 3.8V to 4.6V using a resistor-
divider. Charge is terminated when the charging current
falls below 5% of full charge current. Switchover to battery
backup is initiated by an internal comparator and occurs
automatically when a sensed-input voltage drops below
2.93V. At light loads, the 2MHz internal synchronous buck
regulator operates in burst mode for maximum efficiency.
All nonessential functions of the DS2731 are disabled
while supplying holdup current to the cache memory, and
the IC goes into very low-current dormant mode when the
battery voltage drops below a user-settable threshold.
The DS2731 keeps track of charge status and signals the
user through open-drain I/O pins that can be used to
drive LEDs.
Applications
RAID Controller Card
Features
o Lithium Chemistry CCCV Charger
o Adjustable Regulated Charging Up to 1.5A DC
o Adjustable Charge Voltage from 3.8V to 4.6V
o External and Internal Thermal Protection
o Safety Timer Secondary Termination
o LED Indicator Outputs
o Detects Power Outage and Switches Between
Normal Power and Backup Battery
o Adjustable High-Efficiency Synchronous Buck
Regulator with Skip Mode at Light Loads
o Low-Power Consumption in Discharge Mode
DS2731
Cache-Memory Battery-Backup Management IC
________________________________________________________________
Maxim Integrated Products
1
+
TOP VIEW
DS2731
TSSOP
254 SNSAUX
263 BATT+CTG
272 RSETSTMR
28
1 THMMARGIN
227
CHG1CIN
236 VINVREG
218 CHG2LX
209 CGND1SGND
1910 CGND2AGND
1811 CHARGEREF
1712 FAULTLO_BATT
1613 DONEDIV
245 CGATECBIAS
1514 ENCENS
*EP
*EXPOSED PAD
Pin Configuration
Ordering Information
SWITCH MODE
CHARGER
(CCCV)
LITHIUM
BACKUP
CELL
CACHE
MEMORY
POWER
MANAGEMENT
AUXILIARY
POWER
SWITCHING
REGULATOR
DS2731
MAIN
POWER
Typical Operating Circuit
Rev 1; 1/09
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
*
EP = Exposed pad.
PART TEMP RANGE
PIN-
PACKAGE
TOP
MARK
DS2731E+ -20°C to +70°C
28 TSSOP-EP*
(173 mils)
DS2731
DS2731E+T&R -20°C to +70°C
28 TSSOP-EP*
(173 mils)
DS2731
DS2731
Cache-Memory Battery-Backup Management IC
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS
(V
IN
= +10.8V to +13.2V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage Range on CGND1, CGND2, and
SGND Pins Relative to AGND ...........................-0.3V to +0.3V
Voltage Range on VIN, CHG1, CHG2, and
CGATE Pins Relative to AGND........................-0.3V to +16.0V
Voltage Range on CHARGE, FAULT, and
DONE Pins Relative to AGND .........................-0.3V to +16.0V
Voltage Range on Any Other Pin Relative
to AGND ............................................................-0.3V to +6.0V
Continuous Sink Current on VIN, CGND1,
CGND2, SGND, AUX, BATT+ Pins ......................750mA each
Continuous Source Current on CHG1,
CHG2, and LX Pins ..............................................750mA each
Continuous Sink Current on CHARGE,
FAULT, and DONE Pins .........................................20mA each
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature...........................Refer to the IPC/JEDEC
J-STD-020 Specification.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Charger Supply Voltage V
IN
(Note 1) 10.8 12.0 13.2 V
Auxiliary Supply Voltage V
AUX
(Note 1) 3.0 3.6 V
Battery Voltage V
BATT+
Operating as input (Note 1) 2.7 5.0 V
LED Voltage
(CHARGE, FAULT, DONE Pins)
(Note 1) 0
V
IN
+ 0.3
V
Charger Enable (ENC) (Notes 1, 2) 0
V
CBIAS
+ 0.3
V
Switcher Enable (ENS) (Notes 1, 2) 0
V
CIN
+ 0.3
V
CHARGER CIRCUIT ELECTRICAL CHARACTERISTICS
(V
IN
= +10.8V to +13.2V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Charger Idle Supply Current I
IN
V
IN
> V
UVLO-CHG
(Note 3),
V
AUX
= 3.3V
1 mA
I
AUX
V
AUX
> V
TRIP
100 µA
I
BATT+
V
AUX
< V
TRIP
,
V
BATT+
> V
SLEEP
, ENS disabled
100 150 µA
Regulator Supply Current
(Note 3)
I
SLEEP
V
IN
= V
AUX
= 0.0V,
V
BATT+
< V
SLEEP
10 µA
C
BIAS
Regulator Voltage V
CBIAS
3.3 V
C
GATE
Regulator Voltage V
CGATE
V
IN
- 4.0 V
C
GATE
Capacitance C
CGATE
2.2 µF
C
BIAS
Capacitance C
CBIAS
0.22 µF
Enable Logic-Low (ENS, ENC) V
IL
(Notes 4, 5) 0.4 V
Enable Logic-High (ENS, ENC) V
IH
(Notes 5, 6) 1.6 V
DS2731
Cache-Memory Battery-Backup Management IC
_______________________________________________________________________________________ 3
CHARGER CIRCUIT ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +10.8V to +13.2V, T
A
= -20°C to +70°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Enable Hysteresis (ENS, ENC) V
HYS-EN
35 70 140 mV
Pulldown Resistance (ENS, ENC) R
PD
100 200 300 k
LED Outputs Low
(CHARGE, DONE, FAULT)
V
OL
I
OL
= 10mA 1.0 V
Fault LED Flash Rate f
FAULT
4 Hz
Preconditioning Charge
Threshold
V
MIN
(Note 1) 2.55 2.60 2.70 V
Preconditioning Hysteresis V
HYS
50 100 mV
Preconditioning Charge Current I
PRE
V
BATT+
< V
MIN
5.0 10.0 15.0
% of
I
CHG
Precondition Timeout t
PRE
27 30 33 min
0.5 1.5 A
Charge-Current Range
(RSET Resistance)
I
CHG
Charge current determined by RSET
(Note 7)
5.0 1.6 k
Charge-Current Accuracy I
ERR-CHG
RSET resistor tolerance 0.1%,
R
SNS
= 0.050
-5 +5 %
Overcurrent Clamp I
OVERCURRENT
RSET = 0 or R
SNS
= 0 1.7 2.5 A
Constant-Voltage Threshold
Range
V
CV
Charge voltage determined by MARGIN
pin voltage
3.6 4.2 4.6 V
MARGIN Pin Leakage I
LEAKAGE
-2 +2 µA
Constant-Voltage Charge
Accuracy
V
ERR-CV
-25.0 +25.0 mV
Charge Termination (CV) Current I
TERMINATE
In constant-voltage mode 4.0 5.0 6.0
% of
I
CHG
Charge-Restart Threshold V
DELTA
(Note 8) 94 95 96
% of
V
CV
1 10 hr
Safety Timeout Range
(STMR Resistance)
t
SAFETY
22 220 k
Safety Timeout Error t
ERR-SAFETY
R
STMR
= 22,000 -5 +5 %
Battery Charger Switching Period t
SW-CHG
Full load (1.5A) (Note 9) 0.83 1.00 µs
Charger Undervoltage Lockout V
UVLO-CHG
8 10 V
High-Side MOSFET
On
-Resistance
R
DSON-CP
I
CHG
= 1A, V
IN
= 10.8V
(Note 10)
0.4
Low-Side MOSFET On-Resistance R
DSON-CN
I
CHG
= 1A, V
IN
= 10.8V (Note 10) 0.15
Reverse Leakage of Charge FET
(CHG1, CHG2)
I
REVERSE
V
IN
= 0V, V
CV
= 4.2V, ENC = 0V 10 µA
Forward Leakage of Charge FET
(CHG1, CHG2)
I
FORWARD
V
IN
= 12V, V
CV
= 4.2V, ENC = 0V 10 µA
SNS Leakage Current I
LKG-CHG
No charge current, V
IN
= 12V -2 +2 µA
Startup Time t
START
Using typical application components 1 ms
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

DS2731E+

Mfr. #:
Buy DS2731E+
Manufacturer:
Maxim Integrated
Description:
Battery Management Cache-Memory Battery-Backup
Lifecycle:
New from this manufacturer.
Delivery:
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