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 interrupted.
Low-loss switches guarantee an input-to-output differ-
ential 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 disconnected
by strobing the RST input.
A battery-fail output signal indicates when the backup bat-
tery is below +2V, and a power-fail output signal indicates
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 pincompatible with the
DS1259, but consumes three times less supply current.
Commercial, extended, and military temperature range
devices are available.
●
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
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1259C/D
0°C to +70°C
Dice*
MAX1259CPE
0°C to +70°C
16 PDIP
MAX1259CWE
0°C to +70°C
16 Wide SO
MAX1259EPE
-40°C to +85°C
16 PDIP
MAX1259EWE
-40°C to +85°C
16 Wide SO
MAX1259MJE
-55°C to +125°C
16 CERDIP
*Contact factory for dice specifications.
Note:
Devices in PDIP and SO packages are available in both
leadedPb) and lead(Pb)-free packaging. Specify lead-free by
adding the “+” symbol at the end of the part number when
ordering. Lead-free not available for CERDIP package.
Applications
●
●
●
●
Battery Backup for CMOS RAM
Uninterruptible Power Supplies
Computers
Controllers
Functional Diagram
V
CCI
V
CCO
Pin Configuration
TOP VIEW
N.C.
1
16
V
CCI
V
CCI
N.C.
V
CCO
V
CCO
PF
V
BATT
V
BATT
2
15
RESET
LOGIC
MAX1259
RST
BF
3
14
N.C.
4
13
PF
BAT
5
12
RST
6
11
BF
GND
7
10
N.C.
REF
MAX1259
GND
8
9
N.C.
BAT
GND
DIP/SO
19-4638; Rev 3; 9/14
MAX1259
Battery Manager
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
V
IH
V
IL
V
BATT
BAT
(Note 1)
MAX1259C
Input High Voltage (Note 1)
MAX1259E/M
(Note 1)
Pin 2 (Note 2)
Pin 5 (Note 1)
2.0
2.4
-0.3
2.5
V
BATT
-
0.1
3.0
CONDITIONS
MIN
TYP
5.0
MAX
5.5
V
CCI
+
0.3
V
CCI
+
0.3
+0.8
3.7
UNITS
V
V
Input Low Voltage
Battery Voltage
Battery Output
V
V
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
Power-Fail Trip Point
SYMBOL
I
LO
I
OH
I
OL
I
CCI
I
CCO
V
TP
V
BATTF
V
OH
= 2.4V (Note 3)
V
OL
= 0.4V
(Note 4)
V
CCO
= V
CCI
- 0.2V, pins 12, 13
Pin 11 (Notes 2, 5)
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
V
Battery-Fail Trip Point
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
MAX1259C
MAX1259E
MAX1259M
Pin 5 (Note 9)
CONDITIONS
V
CCO
= V
BATT
- 0.2V, pins 12, 13 (Note 7)
MIN
TYP
MAX
15
100
150
10
100
UNITS
mA
nA
µA
µA
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Maxim Integrated
│
2
MAX1259
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
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
Note
Note
Note
Note
Note
Note
Note
Note
Note
Note
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
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
All voltages referenced to ground.
Trip-point voltage for power-fail detect: V
TP
= 1.26 x V
BATT
. For 5% operation: V
BATT
= 3.7V max.
50pF load capacity.
Measured with pins 3, 11, 12, 13, and open.
V
TP
is the point at which
PF
is driven low.
V
BATTF
is the point at which
BF
is driven low.
I
CCO2
may be limited by battery capacity.
Battery leakage is the internal energy consumed by the MAX1259.
See the
Typical Operating Characteristics
BAT Switch Drop vs. Battery Voltage graph.
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.
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Maxim Integrated
│
3
MAX1259
Battery Manager
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
V
BATT
- V
CCO
(mV)
150
V
BATT
= +2.5V
MAX1259toc03
200
V
CC
MODE
T
A
= +25°C
200
V
CC
MODE
T
A
= +75°C
V
CCI
= +4.5V
100
200
150
V
CCI
- V
CCO
(mV)
150
V
CCI
- V
CCO
(mV)
100
V
CCI
= +4.5V
100
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
250
0
0
5
I
CCO2
(mA)
10
15
0
0
50
100
150
200
I
CCO
(mA)
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
MAX1259toc04
POWER-FAIL TRIP POINT
vs. BATTERY VOLTAGE
MAX1259toc05
V
BATT
- V
CCO
(mV)
150
V
BATT
= +2.5V
100
POWER-FAIL TRIP POINT (V)
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
V
CCI
FALLING
V
CCI
RISING
BATTERY-FAIL TRIP POINT (V)
BATTERY-BACKUP MODE
T
A
= +75°C
4.8
T
A
= +25°C
V
CCI
= 5.0V
2.2
2.1
2.0
1.9
1.8
1.7
V
BATT
FALLING
V
BATT
RISING
50
V
BATT
= +3.0V
0
0
5
I
CCO2
(mA)
10
15
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
1.6
0
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
V
BATT
(V)
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
1.0
0.8
T
A
= +25°C
MAX1259toc08
3.0
2.5
I
CCI
(mA)
2.0
1.5
1.0
0.5
0
0
V
BATT
= 3.0V, I
CCO
= 0mA
T
A
= +25°C
80
V
BATT
- BAT (mV)
60
40
20
0
I
BAT
= 1mA
T
A
= +75°C
I
BAT
= 100µA
1
2
3
V
CCI
(V)
4
5
6
2.0
2.5
3.0
V
BATT
(V)
3.5
4.0
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
V
BATT
(V)
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Maxim Integrated
│
4
MAX1259toc09
3.5
2.0
100
BAT SWITCH DROP
vs. BATTERY VOLTAGE
MAX1259toc06
200
5.0
BATTERY-FAIL TRIP POINT
vs. TEMPERATURE
2.3
MAX1259
Battery Manager
V
CCI
+4.25V
+3V
PF
t
PF
t
F
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 switcho-
ver circuit compares V
CC
to the V
BATT
input, and con-
nects 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 guarantee 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 supply the
average current, which is much less.
The MAX1259 operates with battery voltages from 2.5V to
3.7V. High-value capacitors—either standard electrolytic
or farad-sized, double-layer capacitors—can also be used
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