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 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.
Applications
●Battery Backup for CMOS RAM
●Uninterruptible Power Supplies
●Computers
●Controllers
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 VCC is
Applied
●Pin-Compatible with the DS1259
●Supply Current Three Times Lower than DS1259
●Available in Extended-Industrial and Military
Temperature Ranges
19-4638; Rev 3; 9/14
*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.
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
VCCI VCCO
VBATT
RESET
LOGIC
GND
BAT
RST
PF
BF
REF MAX1259
DIP/SO
VCCI
VCCO
VCCO
VCCI
V
N.C.
BF
N.C.
N.C.
MAX1259
1
2
3
4
16
15
14
13
BAT
RST
GND
GND N.C.
N.C.
PF
5
6
7
8
12
11
10
9
BATT
TOP VIEW
MAX1259 Battery Manager
Functional Diagram
Pin Conguration
Ordering Information
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
(All grades, TA = TMIN to TMAX, unless otherwise noted.)
(VCC = +4.5V to +5.5V, all grades, TA = TMIN to TMAX, unless otherwise noted.)
(VCCI < VBATT, all grades, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Primary Power Supply VCCI (Note 1) 5.0 5.5 V
Input High Voltage (Note 1) VIH
MAX1259C 2.0 VCCI +
0.3
V
MAX1259E/M 2.4 VCCI +
0.3
Input Low Voltage VIL (Note 1) -0.3 +0.8 V
Battery Voltage VBATT Pin 2 (Note 2) 2.5 3.0 3.7 V
Battery Output BAT Pin 5 (Note 1) VBATT -
0.1 V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Leakage Current ILO -1.0 +1.0 µA
Output Current PF, BF IOH VOH = 2.4V (Note 3) -1.0 mA
IOL VOL = 0.4V 4.0
Input Supply Current ICCI (Note 4) 2.00 3.33 mA
VCCO Output Current ICCO VCCO = VCCI - 0.2V, pins 12, 13 250 mA
Power-Fail Trip Point VTP Pin 11 (Notes 2, 5)
1.26 x
VBATT -
250mV
1.26 x
VBATT
1.26 x
VBATT
+
250mV
V
Battery-Fail Trip Point VBATTF Pin 3 (BF detect) (Note 6) 2.0 V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCCO Output Current ICCO2 VCCO = VBATT - 0.2V, pins 12, 13 (Note 7) 15 mA
Battery Leakage (Note 8) IBATT
MAX1259C 100 nA
MAX1259E 150
MAX1259M 10 µA
BAT Output Current IBATOUT Pin 5 (Note 9) 100 µA
MAX1259 Battery Manager
www.maximintegrated.com Maxim Integrated
│
2
Absolute Maximum Ratings
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
DC Electrical Characteristics
DC Electrical Characteristics
(All grades, TA = +25°C, unless otherwise noted.) (Note 10)
(VCC = 4.0V to 5.5V, all grades, TA = +25°C, unless otherwise noted.)
Note 1: All voltages referenced to ground.
Note 2: Trip-point voltage for power-fail detect: VTP = 1.26 x VBATT. For 5% operation: VBATT = 3.7V max.
Note 3: 50pF load capacity.
Note 4: Measured with pins 3, 11, 12, 13, and open.
Note 5: VTP is the point at which PF is driven low.
Note 6: VBATTF is the point at which BF is driven low.
Note 7: ICCO2 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.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Capacitance CIN 5 10 pF
Output Capacitance COUT 5 10 pF
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCCI Fall Time tF300 µs
VCCI Rise Time tR1 µs
Power-Down to PF Low tPF 0 µs
PF High After Power-Up tREC 100 µs
RST Pulse Width RSTPW 50 10 ns
PIN NAME FUNCTION
1, 4, 9, 10, 14 N.C. No Connection. Make no connection to these pins.
2 VBATT Backup Battery Input
3BF Battery-Fail Output. BF is high for VCCI at or above VTP and the backup battery greater than 2V. If the
backup battery is below 2V or VCCI falls below VTP, BF will be driven low.
5BAT 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.
6 RST Battery-Disconnect Input. The RST input is used to prevent battery discharge during shipping. Pulsing
the RST input disconnects the backup battery from the VCCO and BAT outputs.
7, 8 GND Ground
11 PF Power-Fail Output. PF is high for VCCI greater than 1.26 x VBATT (VTP), indicating a valid VCCI voltage.
12, 13 VCCO CMOS RAM is Powered from VCCO. The battery switchover circuit compares VCCI to the VBATT input,
and connects VCCO to whichever is higher.
15, 16 VCCI +5V VCC Input
MAX1259 Battery Manager
www.maximintegrated.com Maxim Integrated
│
3
Capacitance
Pin Description
AC Electrical Characteristics
(TA = +25°C, unless otherwise noted.)
200
150
100
50
0 10050 150 200 250
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
ICCO (mA)
VCCI - VCCO (mV)
VCC MODE
TA = +75°C
VCCI = +4.5V
VCCI = +5.0V
MAX1259toc02
0
200
150
100
50
0 5 10 15
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
ICCO2 (mA)
VBATT - VCCO (mV)
BATTERY-BACKUP MODE
TA = +25°C
VBATT = +2.5V
VBATT = +3.0V
MAX1259toc03
0
200
150
100
50
0 5 10 15
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
ICCO2 (mA)
VBATT - VCCO (mV)
BATTERY-BACKUP MODE
TA = +75°C
VBATT = +2.5V
VBATT = +3.0V
MAX1259toc04
03.0
3.6
3.4
3.2
4.0
3.8
4.8
4.6
4.4
4.2
5.0
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8
POWER-FAIL TRIP POINT
vs. BATTERY VOLTAGE
VBATT (V)
POWER-FAIL TRIP POINT (V)
TA = +25°C
VCCI RISING
VCCI FALLING
MAX1259toc05
1.6
1.8
1.7
2.0
1.9
2.2
2.1
2.3
0 4020 60 8010 5030 70 90 100
BATTERY-FAIL TRIP POINT
vs. TEMPERATURE
TEMPERATURE (°C)
BATTERY-FAIL TRIP POINT (V)
VCCI = 5.0V
VBATT RISING
VBATT FALLING
MAX1259toc06
1.0
0.5
2.0
1.5
3.0
2.5
3.5
0 2 31 4 5 6
QUIESCENT SUPPLY CURRENT
vs. POWER SUPPLY
VCCI (V)
ICCI (mA)
VBATT = 3.0V, ICCO = 0mA
TA = +25°C
MAX1259toc07
0
200
150
100
50
0 10050 150 200 250
SWITCH VOLTAGE DROP
vs. LOAD CURRENT
ICCO (mA)
VCCI - VCCO (mV)
VCC MODE
TA = +25°C
VCCI = +4.5V
VCCI = +5.0V
MAX1259toc01
0
0.8
1.2
1.0
1.6
1.4
1.8
2.0
2.0 3.02.5 3.5 4.0
BAT CURRENT
vs. BATTERY VOLTAGE
VBATT (V)
IBAT (mA)
VBATT - BAT = 100mV
TA = +75°C
TA = +25°C
MAX1259toc08
0
20
40
60
80
100
2.2 2.8 3.02.4 2.6 3.2 3.4 3.6 3.8 4.0
BAT SWITCH DROP
vs. BATTERY VOLTAGE
VBATT (V)
VBATT - BAT (mV)
IBAT = 100µA
IBAT = 1mA
MAX1259toc09
Maxim Integrated
│
4
www.maximintegrated.com
MAX1259 Battery Manager
Typical Operating Characteristics
Detailed Description
Battery Switchover and VCCO
Figure 2 shows a typical application for the MAX1259.
CMOS RAM is powered from VCCO. The battery switcho-
ver circuit compares VCC to the VBATT input, and con-
nects VCCO to whichever is higher.
Switchover occurs when VCC equals VBATT as VCC falls,
and when VCC is 60mV greater than VBATT as VCC rises.
This hysteresis prevents repeated, rapid switching if VCC
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 VCCO output can supply the high
instantaneous current, while VCCO 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
for short-term memory backup (Figure 3).
Figure 1. Power-Down/Power-Up Conditions
Figure 2. Typical Application Circuit Figure 3. Using a MAXCAP as a Backup Battery
VCCI
+4.25V
+3V
PF
BATTERY
CURRENT
tF
tPF
tRtREC
MAX1259
VCCI
VCC
VBATT
VCCO
GND
PF
15, 16
7, 8
12, 13
11
2
µP
NMI ADDRESS
DECODE
RAM1
RAM2
RAM16
CE15
CE1
CE0
TO RAM
12, 13
15, 16
3kΩ
6.2kΩ
2N3904 2
VCC
VBATT
VCCI VCC0
0.22F
MAXCAP
GND
7, 8
NOTE: LARGE VALUE CAPACITORS, SUCH AS A 0.22F MAXCAP,
MAY BE USED FOR SHORT-TERM MEMORY BACKUP.
MAX1259
MAX1259 Battery Manager
www.maximintegrated.com Maxim Integrated
│
5
To achieve rated performance, the VCC input should be
connected to both VCCI pins (pins 15 and 16). As well, the
switched output should be connected to both VCCO pins
(pins 12 and 13).
Power Fail
The power-fail (PF) output is high for VCCI greater than
1.26 x VBATT (VTP), indicating a valid VCCI voltage.
Battery Fail
If VCCI is at or above the voltage trip threshold (VTP) and
the backup battery is greater than 2V, the battery-fail (BF)
output will be held high, indicating a charged battery. If the
backup battery drops below 2V or VCCI falls below VTP,
BF will be driven low.
BAT Output
During normal operation, the BAT output stays at the bat-
tery voltage, regardless of the VCCI level. This provides
1mA battery current.
RESET (Digitally Controlled
Battery Disconnect)
To prevent battery discharge during shipping, the backup
battery can be disconnected from VCCO to BAT.
This disconnect feature is activated by pulsing the reset
(RST) input high for a minimum of 50ns with VCCI greater
than VTP (Figure 4). When primary power is removed,
the VCCO and BAT outputs will go high impedance. The
next time primary power is applied with VCCI greater than
1.26 x VBATT (VTP), normal operation resumes. Note that
when the MAX1259 is first powered up, VCCI must be
brought above 1.26 x VBATT. This resets an internal flip-
flop, ensuring that the part is in normal VCC mode and not
in shipping mode.
Applications Information
If a protection diode is placed in series with the backup
battery, pin 2 must be bypassed with at least a 0.01μF
capacitor to ground.
Figure 4. Reset Timing
+5V
VCCI
VCCO
RST
0V
+5V
+3V
0V
+3V
0V
VIH
VIL
BAT
50ns MIN
HIGH IMPEDANCE
HIGH IMPEDANCE
MAX1259 Battery Manager
www.maximintegrated.com Maxim Integrated
│
6
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
16 PDIP P16+2 21-0043 —
16 Wide SO W16+2 21-0042 90-0107
16 CERDIP J16-3 21-0045 —
MAX1259 Battery Manager
www.maximintegrated.com Maxim Integrated
│
7
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Chip Topography
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 9/14 Removed automotive reference from Applications 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2014 Maxim Integrated Products, Inc.
│
8
MAX1259 Battery Manager
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
