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.
Applications
Battery Backup for CMOS RAM
Uninterruptible Power Supplies
Computers
Controllers
Automotive Systems
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
MAX1259
Battery Manager
________________________________________________________________ Maxim Integrated Products 1
19-4638; Rev 2; 11/05
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.
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
Pin Configuration
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
VCCI VCCO
VBATT
RESET
LOGIC
GND
BAT
RST
PF
BF
REF MAX1259
Functional Diagram
*
Contact factory for dice specifications.
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.
MAX1259
Battery Manager
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.
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
RECOMMENDED DC OPERATING CONDITIONS
(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
MAX1259C 2.0 VCCI +
0.3
Input High Voltage (Note 1) VIH
MAX1259E/M 2.4 VCCI +
0.3
V
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
DC ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, all grades, TA= TMIN to TMAX, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Leakage Current ILO -1.0 +1.0 µA
IOH VOH = 2.4V (Note 3) -1.0
Output Current PF, BF
IOL VOL = 0.4V 4.0 mA
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
DC ELECTRICAL CHARACTERISTICS
(VCCI < VBATT, all grades, TA= TMIN to TMAX, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCCO Output Current ICCO2 VCCO = VBATT - 0.2V, pins 12, 13 (Note 7) 15 mA
MAX1259C 100
MAX1259E 150 nA
Battery Leakage (Note 8) IBATT
MAX1259M 10 µA
BAT Output Current IBATOUT Pin 5 (Note 9) 100 µA
MAX1259
Battery Manager
_______________________________________________________________________________________ 3
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.
CAPACITANCE
(All grades, TA= +25°C, unless otherwise noted.) (Note 10)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Capacitance CIN 510pF
Output Capacitance COUT 510pF
AC ELECTRICAL CHARACTERISTICS
(VCC = 4.0V to 5.5V, all grades, TA= +25°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCCI Fall Time tF300 µs
VCCI Rise Time tR1µs
Power-Down to PF Low tPF 0µs
PF High After Power-Up tREC 100 µs
RST Pulse Width RSTPW 50 10 ns
Pin Description
PIN NAME FUNCTION
1, 4, 9, 10, 14 N.C. No Connection. Make no connection to these pins.
2V
BATT 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.
5 BAT 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
4 _______________________________________________________________________________________
Typical Operating 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 = +25°C
VCCI = +4.5V
VCCI = +5.0V
MAX1259toc01
0
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
0
3.0
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
04020 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
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
MAX1259
Battery Manager
_______________________________________________________________________________________ 5
VCCI
+4.25V
+3V
PF
BATTERY
CURRENT
tF
tPF
tRtREC
Figure 1. Power-Down/Power-Up Conditions
Detailed Description
Battery Switchover and VCCO
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).
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
Figure 2. Typical Application Circuit
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
Figure 3. Using a MAXCAP as a Backup Battery
MAX1259
Battery Manager
+5V
VCCI
VCCO
RST
0V
+5V
+3V
0V
+3V
0V
VIH
VIL
BAT
50ns MIN
HIGH IMPEDANCE
HIGH IMPEDANCE
Figure 4. Reset Timing
To achieve rated performance, the V
CC
input should be
connected to both V
CCI
pins (pins 15 and 16). As well,
the switched output should be connected to both V
CCO
pins (pins 12 and 13).
Power Fail
The power-fail (
PF
) output is high for V
CCI
greater than
1.26 x V
BATT
(V
TP
), indicating a valid V
CCI
voltage.
Battery Fail
If V
CCI
is at or above the voltage trip threshold (V
TP
)
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 V
CCI
falls below V
TP
,
BF
will be driven low.
BAT Output
During normal operation, the BAT output stays at the
battery voltage, regardless of the V
CCI
level. This pro-
vides 1mA battery current.
RESET (Digitally Controlled
Battery Disconnect)
To prevent battery discharge during shipping, the back-
up battery can be disconnected from V
CCO
to BAT.
This disconnect feature is activated by pulsing the
reset (RST) input high for a minimum of 50ns with V
CCI
greater than V
TP
(Figure 4). When primary power is
removed, the V
CCO
and BAT outputs will go high
impedance. The next time primary power is applied
with V
CCI
greater than 1.26 x V
BATT
(V
TP
), normal oper-
ation resumes. Note that when the MAX1259 is first
powered up, V
CCI
must be brought above 1.26 x
V
BATT
. This resets an internal flip-flop, ensuring that the
part is in normal V
CC
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.
6 _______________________________________________________________________________________
MAX1259
Battery Manager
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________
7
© 2005 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Chip Topography Package Information
For the latest package outline information, go to
www.maxim-ic.com/packages
.