19-4638; Rev 2; 11/05
Battery Manager
General Description
The MAX1259 battery manager provides backup-battery
switching for CMOS RAM, microprocessors, or other
low-power logic ICs. It automatically switches to the
backup battery when the primary power supply is inter-
rupted. Low-loss switches guarantee an input-to-output
differential of only 200mV while supplying 250mA from
the primary power supply or 15mA from the battery.
Battery discharge during shipping does not occur in the
MAX1259, since the backup battery can be disconnect-
ed by strobing the RST input.
A battery-fail output signal indicates when the backup
battery is below +2V, and a power-fail output signal indi-
cates when the primary power supply is low. The
MAX1259 monitors the backup battery, warns of
impending power failures, and switches the memory to
the battery when failures occur. The MAX1259 is pin-
compatible with the DS1259, but consumes three times
less supply current. Commercial, extended, and military
temperature range devices are available.
Features
♦
Switches to Backup Battery if Power Fails
♦
Consumes Less than 100nA of Battery Current
♦
Power-Fail Output Signals Primary
Power-Supply Loss
♦
Battery Monitor Indicates Low Battery
♦
Battery Can Be Disconnected to Prevent
Discharge During Shipping
♦
Battery Automatically Reconnected when
V
CC
is Applied
♦
Pin-Compatible with the DS1259
♦
Supply Current Three Times Lower than DS1259
♦
Available in Extended-Industrial and Military
Temperature Ranges
MAX1259
Ordering Information
PART
MAX1259C/D
MAX1259CPE
MAX1259CWE
MAX1259EPE
MAX1259EWE
MAX1259MJE
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
Dice*
16 PDIP
16 Wide SO
16 PDIP
16 Wide SO
16 CERDIP
Applications
Battery Backup for CMOS RAM
Uninterruptible Power Supplies
Computers
Controllers
Automotive Systems
*Contact
factory for dice specifications.
Functional Diagram
V
CCI
V
CCO
Devices in PDIP and SO packages are available in both leaded
and lead-free packaging. Specify lead free by adding the + sym-
bol at the end of the part number when ordering. Lead free not
available for CERDIP package.
Pin Configuration
TOP VIEW
1
16
V
CCI
N.C.
V
BATT
V
BATT
RESET
LOGIC
2
MAX1259
15
V
CCI
RST
BF
3
14
N.C.
N.C.
PF
4
13
V
CCO
BAT
5
12
V
CCO
BF
RST
6
11
PF
GND
REF
MAX1259
7
10
N.C.
GND
BAT
GND
8
9
N.C.
DIP/SO
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Battery Manager
MAX1259
ABSOLUTE MAXIMUM RATINGS
Voltage on Any Pin (with respect to GND) ............-0.3V to +7.0V
Operating Temperature Range
C Suffix................................................................0°C to +70°C
E Suffix .............................................................-40°C to +85°C
M Suffix ..........................................................-55°C to +125°C
Storage Temperature Range .............................-55°C to +125°C
Lead Temperature (soldering, 10s) .................................+300°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.
RECOMMENDED DC OPERATING CONDITIONS
(All grades, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Primary Power Supply
SYMBOL
V
CCI
(Note 1)
MAX1259C
Input High Voltage (Note 1)
V
IH
MAX1259E/M
Input Low Voltage
Battery Voltage
Battery Output
V
IL
V
BATT
BAT
(Note 1)
Pin 2 (Note 2)
Pin 5 (Note 1)
2.4
-0.3
2.5
V
BATT
-
0.1
3.0
2.0
CONDITIONS
MIN
TYP
5.0
MAX
5.5
V
CCI
+
0.3
V
V
CCI
+
0.3
+0.8
3.7
V
V
V
UNITS
V
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +4.5V to +5.5V, all grades, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Leakage Current
Output Current
PF, BF
Input Supply Current
V
CCO
Output Current
SYMBOL
I
LO
I
OH
I
OL
I
CCI
I
CCO
V
OH
= 2.4V (Note 3)
V
OL
= 0.4V
(Note 4)
V
CCO
= V
CCI
- 0.2V, pins 12, 13
1.26 x
V
BATT
-
250mV
1.26 x
V
BATT
2.0
2.00
CONDITIONS
MIN
-1.0
-1.0
4.0
3.33
250
1.26 x
V
BATT
+
250mV
TYP
MAX
+1.0
UNITS
µA
mA
mA
mA
Power-Fail Trip Point
V
TP
Pin 11 (Notes 2, 5)
V
Battery-Fail Trip Point
V
BATTF
Pin 3 (BF detect) (Note 6)
V
DC ELECTRICAL CHARACTERISTICS
(V
CCI
< V
BATT
, all grades, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
V
CCO
Output Current
Battery Leakage (Note 8)
BAT Output Current
SYMBOL
I
CCO2
I
BATT
I
BATOUT
CONDITIONS
V
CCO
= V
BATT
- 0.2V, pins 12, 13 (Note 7)
MAX1259C
MAX1259E
MAX1259M
Pin 5 (Note 9)
MIN
TYP
MAX
15
100
150
10
100
UNITS
mA
nA
µA
µA
2
_______________________________________________________________________________________
Battery Manager
CAPACITANCE
(All grades, T
A
= +25°C, unless otherwise noted.) (Note 10)
PARAMETER
Input Capacitance
Output Capacitance
SYMBOL
C
IN
C
OUT
CONDITIONS
MIN
TYP
5
5
MAX
10
10
UNITS
pF
pF
MAX1259
AC ELECTRICAL CHARACTERISTICS
(V
CC
= 4.0V to 5.5V, all grades, T
A
= +25°C, unless otherwise noted.)
PARAMETER
V
CCI
Fall Time
V
CCI
Rise Time
Power-Down to
PF
Low
PF
High After Power-Up
RST Pulse Width
SYMBOL
t
F
t
R
t
PF
t
REC
RST
PW
50
10
CONDITIONS
MIN
300
1
0
100
TYP
MAX
UNITS
µs
µs
µs
µs
ns
Note 1:
All voltages referenced to ground.
Note 2:
Trip-point voltage for power-fail detect: V
TP
= 1.26 x V
BATT
. For 5% operation: V
BATT
= 3.7V max.
Note 3:
50pF load capacity.
Note 4:
Measured with pins 3, 11, 12, 13, and open.
Note 5:
V
TP
is the point at which
PF
is driven low.
Note 6:
V
BATTF
is the point at which
BF
is driven low.
Note 7:
I
CCO2
may be limited by battery capacity.
Note 8:
Battery leakage is the internal energy consumed by the MAX1259.
Note 9:
See the
Typical Operating Characteristics
BAT Switch Drop vs. Battery Voltage graph.
Note 10:
Guaranteed by design. Not tested.
Pin Description
PIN
1, 4, 9, 10, 14
2
3
5
6
7, 8
11
12, 13
15, 16
NAME
N.C.
V
BATT
BF
BAT
RST
GND
PF
V
CCO
V
CCI
Backup Battery Input
Battery-Fail Output.
BF
is high for V
CCI
at or above V
TP
and the backup battery greater than 2V. If the
backup battery is below 2V or V
CCI
falls below V
TP
,
BF
will be driven low.
Battery Output. During normal operation, the BAT output supplies up to 1mA of continuous battery
current. In shipping mode, the BAT output is high impedance.
Battery-Disconnect Input. The RST input is used to prevent battery discharge during shipping.
Pulsing the RST input disconnects the backup battery from the V
CCO
and BAT outputs.
Ground
Power-Fail Output.
PF
is high for V
CCI
greater than 1.26 x V
BATT
(V
TP
), indicating a valid V
CCI
voltage.
CMOS RAM is Powered from V
CCO
. The battery switchover circuit compares V
CCI
to the V
BATT
input,
and connects V
CCO
to whichever is higher.
+5V V
CC
Input
FUNCTION
No Connection. Make no connection to these pins.
_______________________________________________________________________________________
3
Battery Manager
MAX1259
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
MAX1259toc01
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
MAX1259toc02
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
BATTERY-BACKUP MODE
T
A
= +25°C
150
V
BATT
- V
CCO
(mV)
MAX1259toc03
200
V
CC
MODE
T
A
= +25°C
150
V
CCI
- V
CCO
(mV)
200
V
CC
MODE
T
A
= +75°C
150
V
CCI
- V
CCO
(mV)
V
CCI
= +4.5V
100
200
V
BATT
= +2.5V
100
100
V
CCI
= +4.5V
50
V
CCI
= +5.0V
0
0
50
100
150
200
250
I
CCO
(mA)
50
V
CCI
= +5.0V
50
V
BATT
= +3.0V
0
0
50
100
150
200
250
I
CCO
(mA)
0
0
5
I
CCO2
(mA)
10
15
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
MAX1259toc04
POWER-FAIL TRIP POINT
vs. BATTERY VOLTAGE
MAX1259toc05
BATTERY-FAIL TRIP POINT
vs. TEMPERATURE
V
CCI
= 5.0V
2.2
BATTERY-FAIL TRIP POINT (V)
2.1
2.0
1.9
1.8
1.7
1.6
V
BATT
FALLING
V
BATT
RISING
MAX1259toc06
MAX1259toc09
200
BATTERY-BACKUP MODE
T
A
= +75°C
150
V
BATT
- V
CCO
(mV)
V
BATT
= +2.5V
100
5.0
4.8
POWER-FAIL TRIP POINT (V)
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
V
CCI
FALLING
V
CCI
RISING
T
A
= +25°C
2.3
50
V
BATT
= +3.0V
0
0
5
I
CCO2
(mA)
10
15
3.0
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
V
BATT
(V)
0
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
QUIESCENT SUPPLY CURRENT
vs. POWER SUPPLY
MAX1259toc07
BAT CURRENT
vs. BATTERY VOLTAGE
V
BATT
- BAT = 100mV
1.8
1.6
I
BAT
(mA)
1.4
1.2
T
A
= +25°C
MAX1259toc08
BAT SWITCH DROP
vs. BATTERY VOLTAGE
100
I
BAT
= 1mA
3.5
3.0
2.5
I
CCI
(mA)
2.0
1.5
1.0
0.5
0
0
1
2
3
V
CCI
(V)
4
5
6
V
BATT
= 3.0V, I
CCO
= 0mA
T
A
= +25°C
2.0
80
V
BATT
- BAT (mV)
60
40
I
BAT
= 100μA
20
T
A
= +75°C
1.0
0.8
2.0
2.5
3.0
V
BATT
(V)
3.5
4.0
0
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
V
BATT
(V)
4
_______________________________________________________________________________________
Battery Manager
MAX1259
V
CCI
+4.25V
+3V
t
F
t
PF
PF
t
R
t
REC
BATTERY
CURRENT
Figure 1. Power-Down/Power-Up Conditions
Detailed Description
Battery Switchover and V
CCO
Figure 2 shows a typical application for the MAX1259.
CMOS RAM is powered from V
CCO
. The battery
switchover circuit compares V
CC
to the V
BATT
input,
and connects V
CCO
to whichever is higher.
Switchover occurs when V
CC
equals V
BATT
as V
CC
falls, and when V
CC
is 60mV greater than V
BATT
as
V
CC
rises. This hysteresis prevents repeated, rapid
switching if V
CC
falls very slowly or remains nearly
equal to the battery voltage. Low-loss switches guaran-
tee an input-to-output differential of only 200mV, while
supplying 250mA from the primary power supply or
15mA from the battery.
Note:
With adequate filtering, the MAX1259 need only
supply the average current drawn by the CMOS RAM.
Many RAM data sheets specify a 75mA maximum sup-
ply current, but this peak current spike lasts only 100ns.
If the sum of the peak currents is greater than 250mA, a
capacitor placed on the V
CCO
output can supply the
high instantaneous current, while V
CCO
need only sup-
ply the average current, which is much less.
The MAX1259 operates with battery voltages from 2.5V
to 3.7V. High-value capacitors—either standard elec-
trolytic or farad-sized, double-layer capacitors—can
also be used for short-term memory backup (Figure 3).
V
CC
RAM16
RAM2
RAM1
12, 13
CE0
6.2kΩ
11
V
BATT
GND
7, 8
PF
NMI
μP
ADDRESS
DECODE
0.22F
MAXCAP
CE1
CE15
3kΩ
15, 16
V
CCI
V
CC0
12, 13
TO RAM
MAX1259
2N3904
V
CC
15, 16
V
CCI
V
CCO
2
V
BATT
GND
7, 8
MAX1259
2
NOTE:
LARGE VALUE CAPACITORS, SUCH AS A 0.22F MAXCAP,
MAY BE USED FOR SHORT-TERM MEMORY BACKUP.
Figure 2. Typical Application Circuit
Figure 3. Using a MAXCAP as a Backup Battery
5
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