General Description
The MAX16023/MAX16024 low-power battery-backup cir-
cuits with a regulated output are capable of delivering up
to 100mA output current. The MAX16023/MAX16024
include a low-dropout regulator, a microprocessor (µP)
reset circuit, and a battery switchover circuit. Additional
available features include a manual reset, a power-fail
comparator, and a battery-on indicator. These devices
reduce the number of external components to minimize
board space and improve reliability.
The MAX16023/MAX16024 are ideally suited for provid-
ing power for backing up critical memory such as static
random-access memory (SRAM) or real-time clocks
(RTCs). The regulated output is powered by VCC when it
is present and switches over to the backup power dur-
ing brownout. The MAX16023/MAX16024 accept an
input voltage from 1.53V to 5.5V and provide fixed stan-
dard output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V.
The MAX16024 offers the ability to externally set the out-
put voltage using a resistive divider. All outputs are
available with push-pull or open-drain configurations.
The MAX16023 offers a power-fail comparator for monitor-
ing an additional voltage or for providing an early power-
fail warning. Another feature includes a manual-reset input
(MAX16023/MAX16024). The MAX16024 also features
a battery-on indicator and chip-enable gating function.
The MAX16023/MAX16024 are offered in 8- and 10-pin
TDFN packages and are fully specified from -40°C to
+85°C temperature range.
Applications
Main/Backup Power for RTCs/SRAM
Industrial Controls
GPS Systems
Set-Top Boxes
Point-of-Sale Equipment
Portable/Battery Equipment
Features
♦System Monitoring for 5V, 3.3V, 3V, 2.5V, or 1.8V
Power-Supply Voltages
♦100mA Low-Dropout Regulator
♦Factory-Trimmed and Adjustable Output Voltages
♦1.53V to 5.5V Operating Voltage Range
♦Low-Power Consumption: 4µA (typ)
♦Power-Fail Comparators for Monitoring Voltages
Down to 0.6V
♦Battery-On Indicator
♦Battery Freshness Seal
♦On-Board Gating of CE Signals, 1.5ns
Propagation Delay (MAX16024)
♦Debounced Manual-Reset Input
♦145ms (min) Reset Timeout Period
♦Tiny 8-Pin and 10-Pin TDFN Packages
♦UL®Certified to Conform to IEC 60950-1
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
________________________________________________________________
Maxim Integrated Products
1
19-4249; Rev 0; 8/08
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.
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX16023_TA_ _ _+T
-40°C to +85°C
8 TDFN-EP*
MAX16024_TB_ _ _+T
-40°C to +85°C
10 TDFN-EP*
The first placeholder “_” designates reset output options. A letter
“L” in this placeholder indicates a push-pull output and letter “P”
indicates an open-drain output. The next placeholder “_” desig-
nates the reset threshold (Table 1). The last two placeholders
“_ _” designate output voltage (Table 2). For the MAX16024 with
adjustable output voltage version, there are no last two place-
holders.
+
Denotes a lead-free/RoHS-compliant package.
T = Tape and reel.
*
EP = Exposed pad.
Pin Configurations
8 7 6 5
1 2 3 4
PFO
GND
*EP *EP
*EP = EXPOSED PAD
RESET
OUT
PFI
MR
BATT
VCC
MAX16023
TDFN
10 9 8 7
1 2 3 4
GND
OUT
RESET
CEOUT
BATT
CEIN
VCC
MR
6
5
BATT ONSET
MAX16024
TDFN
++
UL is a registered trademark of Underwriters Laboratories, Inc.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA= TJ= -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical val-
ues are at TA= TJ= +25°C.) (Note 2)
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.
VCC, BATT, OUT to GND..........................................-0.3V to +6V
RESET, PFO, BATT ON (all open drain)
to GND..................................................................-0.3V to +6V
RESET, PFO, BATT ON (all push-pull)
to GND .................................................-0.3V to (VOUT + 0.3V)
PFI, CEIN, CEOUT to GND.......................-0.3V to (VOUT + 0.3V)
MR to GND .................................................-0.3V to (VCC + 0.3V)
Input Current
VCC Peak Current.....................................................................1A
VCC Continuous Current ...............................................250mA
BATT Peak Current .......................................................500mA
BATT Continuous Current ...............................................70mA
Output Current
OUT Short Circuit to GND Duration ....................................10s
RESET, BATT ON, CEOUT..............................................20mA
Continuous Power Dissipation (TA= +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW
10-Pin TDFN (derate 24.4mW/°C above +70°C) .......1951mW
Thermal Resistance (Note 1)
θJA (8-Pin and 10-Pin TDFN)........................................41°C/W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Voltage Range VCC
,
VBATT (Note 3) 1.53 5.5 V
LDO = 1.2V 4.3 6
LDO = 1.8V 4.7 7
LDO = 2.5V 5.2 7.5
LDO = 3V 5.5 8
VCC = LDO + 0.5V,
no load
LDO = 3.3V 5.7 8
LDO = 1.2V 16 20
LDO = 1.8V 16 21
LDO = 2.5V 16 18.1
LDO = 3V 17 18.6
Supply Current ICC
VCC = LDO + 0.5V,
IOUT = 20mA
LDO = 3.3V 17 19
µA
Supply Current in Battery-Backup
Mode IBATT VCC = 0, VBATT = 3V,
no dropout, no load 3.5 5.26 µA
BATT Standby Current VCC > VBATT + 0.2V -0.01 +0.01 µA
SET Reference Voltage VSET MAX16024_TB_, VCC = 2.2V 1.144 1.2 1.272 V
SET Input Leakage Current MAX16024_TB_, SET = 1.2V -20 +20 nA
Output Voltage Range VOUT MAX16024_TB_, VCC > VOUT 1.8 5.25 V
LDO = 1.2V 1.145 1.2 1.270
LDO = 1.8V 1.704 1.8 1.900
LDO = 2.5V 2.368 2.5 2.634
LDO = 3V 2.837 3 3.165
Output Voltage Accuracy IOUT = 1mA
LDO = 3.3V 3.114 3.3 3.482
V
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________ 3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Line Regulation VCC = (VOUT + 1V) to (VOUT + 2V),
IOUT = 1mA 0.2 1.0 %/V
Load Regulation VCC = VOUT + 1V, IOUT = 1mA to 2mA 0.15 1.0 %
LDO = 1.2V 500
LDO = 1.8V 200
LDO = 2.5V 180
LDO = 3V 150
Dropout Voltage IOUT = 50mA
(Note 4)
LDO = 3.3V 150
mV
VCC = 1.6V 75
Output Current Limit VCC ≥ 2V 150 mA
Battery Freshness Leakage
Current VBATT = 5.5V 10 nA
RESET OUTPUT (RESET)
Reset Threshold VTH (See Table 1) V
VCC Falling to Reset Delay tRD VCC falling at 10V/ms 20 µs
Reset Timeout Period tRP VCC rising 145 215 285 ms
VOUT = 3.3V, ISINK = 3.2mA, RESET asserted 0.3
VOUT = 1.8V, ISINK = 1mA, RESET asserted 0.3RESET Output Low Voltage VOL
VOUT = 1.2V, ISINK = 100µA, RESET asserted 0.3
V
RESET Output High Voltage
(Push-Pull Output) VOH VCC ≥ 1.1 x VTH, ISOURCE = 100µA,
RESET deasserted VOUT - 0.3V V
RESET Output Leakage Current
(Open-Drain Output) V
RESET = 5.5V, reset deasserted 1 µA
POWER-FAIL COMPARATOR (PFI, PFO)
PFI Input Threshold VPFT VPFI falling, 1.6V ≤ VCC ≤ 5.5V 0.570 0.590 0.611 V
PFI Input Hysteresis VPFI-HYS 30 mV
PFI Input Current IPFI -1 +1 µA
VOUT = 1.8V, ISINK = 1mA, PFO asserted 0.3
PFO Output Low Voltage VOUT =1.2V, ISINK = 100µA, PFO asserted 0.3 V
PFO Output High Voltage
(Push-Pull Output) ISOURCE = 100µA, PFO deasserted VOUT - 0.3V V
PFO Leakage Current
(Open-Drain Output) V
PFO = 5.5V, PFO deasserted 1 µA
PFO Delay Time (VPFI + 100mV) to (VPFI - 100mV) 20 µs
MANUAL RESET (MR)
Input Low Voltage VIL 0.3 x VCC
Input High Voltage VIH 0.7 x VCC
V
Pullup Resistance Pullup resistance to VCC 20 30 kΩ
Glitch Immunity 100 ns
MR to Reset Delay 120 ns
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA= TJ= -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical val-
ues are at TA= TJ= +25°C.) (Note 2)
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA= TJ= -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical val-
ues are at TA= TJ= +25°C.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
BATTERY-ON INDICATOR (BATT ON)
VOUT = 1.2V, ISINK = 100µA, BATT ON
deasserted 0.3
VOUT = 1.8V, ISINK = 1mA, BATT ON
deasserted 0.3
Output Low Voltage VOL
VOUT = 3.3V, ISINK = 3.2mA, BATT ON
deasserted 0.3
V
Output High Voltage
(Push-Pull Output) VOH ISOURCE = 100µA, BATT ON asserted VOUT - 0.3V V
Output Leakage Current
(Open-Drain Output) VCC = 5.5V 1 µA
Output Short-Circuit Current Sink current, VCC = 5V
(Note 6) 60 mA
CE GATING (CEIN, CEOUT)
CEIN Leakage Current Reset asserted, VCC = 0.9 x VTH or 0 -1 +1 µA
CEIN to CEOUT Resistance VCC = 5V, reset deasserted 8 50 Ω
CEOUT Short-Circuit Current Reset asserted, CEOUT = 0 0.75 2 mA
CEIN to CEOUT Propagation
Delay 50Ω source, CLOAD = 50pF, VCC = 4.75V 1.5 7 ns
Output High Voltage VOH ISOURCE = 100µA, reset asserted VOUT - 0.3V V
Reset to CEOUT Delay 12 µs
Note 2: All devices are 100% production tested at TA= +25°C and TA= +85°C. Limits over temperature are guaranteed by design.
Note 3: VBATT can be 0 anytime or VCC can go down to 0 if VBATT is active (except at startup).
Note 4: Dropout voltage is defined as (VIN - VOUT) when VOUT is 2% below the value of VOUT when VIN = VOUT + 1V.
Note 5: CEIN to CEOUT resistance is tested with VCC = 5V and VCEIN = 0 or 5V.
Note 6: Use external current-limiting resistor to limit current to 20mA (max).
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________ 5
VCC SUPPLY CURRENT
vs. VCC SUPPLY VOLTAGE
MAX16023 toc01
VCC SUPPLY VOLTAGE (V)
VCC SUPPLY CURRENT (μA)
3.02.5 4.52.0 3.5 5.04.0
5
10
15
20
25
0
1.5 5.5
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
VCC SUPPLY CURRENT
vs. TEMPERATURE
MAX16023 toc02
TEMPERATURE (°C)
VCC SUPPLY CURRENT (μA)
6010 35-15
2
4
6
8
10
1
3
5
7
9
0
-40 85
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
BATT SUPPLY CURRENT
vs. VCC SUPPLY VOLTAGE
MAX16023 toc03
VCC SUPPLY VOLTAGE (V)
BATT SUPPLY CURRENT (μA)
1.0 3.00.5 2.52.01.5
2
4
6
1
3
5
0
0 3.5
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
VBATT = 3.0V
VBATT = 2.8V
BATTERY SUPPLY CURRENT
vs. TEMPERATURE
MAX16023 toc04
TEMPERATURE (°C)
BATTERY SUPPLY CURRENT (μA)
6010 35-15
1
2
3
4
5
0
-40 85
MAX16024PTBS25+
VBATT = +3.0V
VCC = 0
BATT STANDBY CURRENT
vs. TEMPERATURE
MAX16023 toc05
TEMPERATURE (°C)
BATT STANDBY CURRENT (nA)
6010 35-15
-6
-2
2
6
10
-8
-4
0
4
8
-10
-40 85
VCC = 3.3V
VBATT = 3.0V
RESET OUTPUT VOLTAGE LOW
vs. SINK CURRENT
MAX16023 toc06
SINK CURRENT (mA)
OUTPUT VOLTAGE LOW (V)
168124
0.2
0.4
0.6
0.8
1.0
0
02014610218
MAX16024PTBS25+
Typical Operating Characteristics
(VCC = 5V, VBATT = 0, IOUT = 0, TA= +25°C, unless otherwise noted.)
Table 1. Reset Threshold Ranges Table 2. Fixed Output Voltage
RESET THRESHOLD RANGES (V)
SUFFIX MIN TYP MAX
L 4.508 4.63 4.906
M 4.264 4.38 4.635
T 2.991 3.08 3.239
S 2.845 2.93 3.080
R 2.549 2.63 2.755
Z 2.243 2.32 2.425
Y 2.117 2.19 2.288
W 1.603 1.67 1.733
V 1.514 1.575 1.639
SUFFIX NOMINAL OUTPUT
VOLTAGE (V)
33 3.3
30 3.0
25 2.5
18 1.8
12 1.2
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = 5V, VBATT = 0, IOUT = 0, TA= +25°C, unless otherwise noted.)
VCC FALLING TO RESET DELAY
vs. TEMPERATURE
MAX16023 toc07
TEMPERATURE (°C)
DELAY (µs)
6010 35-15
20
40
60
80
100
10
30
50
70
90
0
-40 85
VCC FALLING 10V/ms
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX16023 toc08
TEMPERATURE (°C)
RESET TIMEOUT PERIOD (ms)
6035-15 10
185
190
195
200
210
205
215
220
180
-40 85
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX16023 toc09
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
6010 35-15
0.990
1.005
1.015
1.020
0.985
0.995
1.000
1.010
0.980
-40 85
MAX16024PTBS25+
VOUT = 2.5V
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
RESET THRESHOLD OVERDRIVE (mV)
TRANSIENT DURATION (ms)
MAX16023 toc10
0 200 400 600 800 1000
0
25
50
75
100
125
150
175
200
RESET OCCURS ABOVE THE CURVE
DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX16023 toc11
LOAD CURRENT (mA)
DROPOUT VOLTAGE (mV)
8040 6020
150
350
450
500
100
300
50
200
250
400
0
0 1007030 5010 90
MAX16024PTBS25+
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX16023 toc12
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
8040 6020
2.42
2.58
2.66
2.70
2.38
2.54
2.34
2.46
2.50
2.62
2.30
0 1007030 5010 90
MAX16024PTBS25+
VOUT = 2.5V
TA = -40°C
TA = +25°C
TA = +85°C
OUTPUT VOLTAGE
vs. VCC VOLTAGE
MAX16023 toc13
VCC VOLTAGE (V)
OUTPUT VOLTAGE (V)
14
2.1
2.5
2.7
2.8
2.0
2.4
1.9
1.8
1.7
1.6
2.2
2.3
2.6
1.5
0623 5
MAX16024PTBS25+
IOUT = 0
LOAD-TRANSIENT RESPONSE
MAX16023 toc14
1ms/div
OUT
AC-COUPLED
100mV/div
50mA
IOUT
20mA/div
10mA
MAX16024PTBS25+
COUT = 10µF
STARTUP RESPONSE
MAX16023 toc15
2ms/div
VCC
2V/div
OUT
1V/div
MAX16024PTBS25+
IOUT = 0
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________ 7
MR FALLING TO RESET DELAY
MAX16023 toc16
200ns/div
MR
5V/div
RESET
5V/div
CHIP-ENABLE LOCKING OUT
SIGNAL DURING RESET
MAX16023 toc17
40
µ
s/div
CEIN
2V/div
CEOUT
2V/div
RESET
5V/div
Typical Operating Characteristics (continued)
(VCC = 5V, VBATT = 0, IOUT = 0, TA= +25°C, unless otherwise noted.)
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
8 _______________________________________________________________________________________
Pin Description
PIN
MAX16023 MAX16024 NAME FUNCTION
12V
CC Supply Voltage Input. Bypass VCC to GND with a 0.1µF capacitor.
2 3 BATT
Backup Battery Input. If VCC falls below its reset threshold (VTH), VBATT ≥ VCC, and if
the regulator enters dropout, the regulator is powered from BATT. If VBATT < VCC,
the regulator is powered from VCC. Bypass BATT to GND with a 0.1µF capacitor.
34MR
Active-Low, Manual-Reset Input. RESET asserts when MR is pulled low. RESET
remains low for the duration of reset timeout period after MR transitions from low to
high. Connect MR to OUT or leave unconnected if not used. MR is internally
connected to VCC through a 30kΩ pullup resistor.
4 — PFI
Power-Fail Comparator Input. Connect PFI to a resistive divider to set the desired PFI
threshold. The PFI input is referenced to an internal VPFT threshold. A VPFI-HYS
internal hysteresis provides noise immunity. The power-fail comparator is powered
from OUT.
5—PFO
Active-Low, Power-Fail Comparator Output. PFO goes low when VPFI falls below the
internal VPFT threshold and goes high when VPFI rises above VPFT + VPFI-HYS
hysteresis.
6 7 GND Ground
78RESET
Active-Low Reset Output. RESET asserts when VCC falls below the reset threshold or
MR is pulled low. RESET remains low for the duration of the reset timeout period after
VCC rises above the reset threshold and MR goes high. RESET is available in push-
pull and open-drain options.
8 9 OUT
Linear Regulator Output Voltage. Available in the following factory-fixed voltages of
1.2V, 1.8V, 2.5V, 3.0V, or 3.3V for all devices. The MAX16024 is also available with
an adjustable output voltage (1.8V to 5.25V). Bypass OUT to GND with a 10µF
capacitor.
—1CEIN Chip-Enable Input. The input to CE gating circuitry. Connect to GND or OUT if not
used.
— 5 SET
Set Output Voltage Input. For the fixed output voltage versions (MAX16024_TB_ _ _),
SET is not used. Connect SET to GND. For MAX16024_TB_, connect SET to an
external resistive divider to set the desired output voltage between 1.8V and 5.25V.
— 6 BATT ON Active-High, Battery-On Output. BATT ON goes high when in the battery backup
mode.
—10CEOUT
Active-Low, Chip-Enable Output. CEOUT goes low only when CEIN is low and reset
is not asserted. If CEIN is low when reset is asserted, CEOUT stays low for 12µs (typ)
or until CEIN goes high, whichever occurs first.
——EP
Exposed Pad. Internally connected to GND. Connect EP to a large ground plane to
aid heat dissipation. Do not use EP as the only ground connection for the device.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
_______________________________________________________________________________________ 9
Functional Diagrams
MAX16023
PFI
PFO
OUT
GND
VCC
MR
RESET DELAY
LOGIC
LDO
REF
OUT
RESET
BATT
DROPOUT
OUT
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
10 ______________________________________________________________________________________
Functional Diagrams (continued)
MAX16024
CEIN CEOUT
GND
VCC
MR
RESET DELAY
LOGIC
LDO
REF
VCC
CE OUTPUT
CONTROL
BATT
DROPOUT
OUT
SET
RESET
BATT ON
Detailed Description
The
Typical Applications Circuit
shows a typical con-
nection using the MAX16024. OUT powers the SRAM. If
VCC is higher than the reset threshold (VTH), or if VCC is
lower than VTH but higher than VBATT, the regulator is
powered from VCC. If VCC < VTH, VCC < VBATT, and the
regulator is in dropout, the regulator is powered from
BATT (see the
Functional Diagrams
). OUT supplies up
to 100mA from VCC.
Backup-Battery Switchover
In a brownout or power failure, it may be necessary to
preserve the contents of the RAM. With a backup-bat-
tery installed at BATT, the MAX16023/MAX16024 auto-
matically switch the RAM to backup power when VCC
falls. The MAX16024 has a BATT ON output that goes
high when in battery-backup mode. Three conditions
must be met for these devices to switch to battery
backup mode:
1) VCC is lower than the reset threshold.
2) VCC is lower than VBATT.
3) The regulator is in dropout (except for the 1.2V out-
put version).
Chip-Enable Signal Gating (MAX16024)
The MAX16024 provides internal gating of CE signals to
prevent erroneous data from being written to CMOS
RAM in the event of a power failure or brownout. During
normal operation, the CE gate enables and passes all
CE transitions. When the reset output asserts, this path
becomes disabled, preventing erroneous data from cor-
rupting the CMOS RAM and CEOUT is pulled up to OUT
through an internal current source. The 1.5ns propaga-
tion delay from CEIN to CEOUT allows the devices to
be used with most µPs and high-speed DSPs.
During normal operation (reset not asserted), CEIN is
connected to CEOUT through a low on-resistance
transmission gate. If CEIN is high when a reset asserts,
CEOUT remains high regardless of any subsequent
transition on CEIN during the reset event.
If CEIN is low when reset asserts, CEOUT is held low for
12µs to allow completion of the read/write operation.
After the 12µs delay expires, CEOUT goes high and
stays high regardless of any subsequent transitions on
CEIN during the reset event. When CEOUT is discon-
nected from CEIN, CEOUT is actively pulled up to OUT.
The propagation delay through the chip-enable circuitry
depends on both the source impedance of the drive to
CEIN and the capacitive loading at CEOUT. Minimize
the capacitive load at CEOUT to minimize propagation
delay, and use a low-output-impedance driver.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________ 11
VCC
RESET THRESHOLD VTH
CEIN
CEOUT
RESET
*
tRD tRD
tRP tRP
IF CEIN GOES HIGH BEFORE RESET ASSERTS,
CEOUT GOES HIGH WITHOUT DELAY AS
CEIN GOES HIGH.
RESET-TO-CEOUT DELAY (12µs)
*
Figure 1. Reset and Chip-Enable Timing
MAX16023/MAX16024
Manual-Reset Input
(MAX16023/MAX16024)
Many µP-based products require manual-reset capabili-
ty, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. For the MAX16023/
MAX16024, a logic-low on MR asserts RESET. RESET
remains asserted while MR is low. When MR goes high,
RESET deasserts after a minimum of 145ms (tRP). MR
has an internal 30kΩpullup resistor to VCC. MR can be
driven with TTL/CMOS logic levels or with open-
drain/collector outputs. Connect a normally open
momentary switch from MR to GND to create a manual-
reset function; external debounce circuitry is not
required. If MR is driven from a long cable or the device
is used in a noisy environment, connect a 0.1µF capaci-
tor from MR to GND to provide additional noise immunity.
Battery-On Indicator (MAX16024)
The MAX16024’s BATT ON output goes high when in
battery-backup mode. Use BATT ON to indicate bat-
tery-switchover status.
Battery Freshness Seal
The MAX16023/MAX16024 battery freshness seal dis-
connects the backup battery from internal circuitry and
OUT until VCC is applied. This ensures the backup bat-
tery connected to BATT is fresh when the final product
is used for the first time.
The internal freshness seal latch prevents BATT from
powering OUT until VCC has come up for the first time,
setting the latch. When VCC subsequently turns off,
BATT begins to power OUT.
To reenable the freshness seal (MAX16023/
MAX16024):
1) Connect a battery to BATT.
2) Bring VCC to 0.
3) Drive MR higher than VBATT + 1.2V for at least 3µs.
4) Pull OUT to 0.
Reset Output (MAX16023/MAX16024)
A µP’s reset input starts the µP in a known state. The
MAX16023/MAX16024 µP supervisory circuits assert a
reset to prevent code-execution errors during power-
up, power-down, and brownout conditions. RESET
asserts when VCC is below the reset threshold and
remains low for at least 145ms (tRP) after VCC rises
above the reset threshold. RESET also asserts when
MR is low. RESET is available in both push-pull and
open-drain configurations.
Power-Fail Comparator (MAX16023)
The MAX16023 offers an additional undervoltage com-
parator. The output PFO goes low when the voltage at
PFI falls below its VPFT threshold. Common uses for the
power-fail comparator include monitoring the input of the
power supply (such as a battery) before any voltage reg-
ulation to provide an early power-fail warning, so soft-
ware can conduct an orderly system shutdown. The
power-fail comparator has a typical input hysteresis of
VPFI-HYS and is powered from OUT, making it indepen-
dent of the reset circuit. Connect PFI to GND, if not used.
Regulator Output
Fixed output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and
3.3V are available for all devices. The regulator output
delivers up to 100mA of load current.
The MAX16024 is available with both fixed and
adjustable output-voltage options. Use an external
resistive divider network connected between OUT, SET,
and GND (Figure 2) to set the adjustable output voltage
from 1.8V to 5.25V. Connect SET to GND for parts with
fixed output voltage option.
Battery-Backup Circuits with
Regulated Output Voltage
12 ______________________________________________________________________________________
MAX16024
0.1µF
1.53 TO 5.5V
GND
VCC
RESETTO µP
R1
R2
SET
10µF
1.8V TO 5.25V
VOUT = VSET (1 + R1/R2)
VSET = 1.2V
OUT
Figure 2. Setting the Adjustable Output Voltage (MAX16024
Only)
Applications Information
The MAX16023/MAX16024 are protected for typical
short-circuit conditions of 10s or less. Shorting OUT to
ground for longer than 10s might damage the device.
Bypass VCC and BATT to GND with a 0.1µF capacitor
each. Connect a 10µF low-ESR capacitor from OUT to
GND. All capacitors should be mounted as close as
possible to the device.
Monitoring an Additional Supply
The MAX16023 power-fail comparator can monitor
either positive or negative supplies using a resistive
divider to PFI (Figures 3 and 4). PFO can be used to
generate an interrupt to the µP or to trigger a reset. To
monitor a negative supply, connect the top of the resis-
tive divider to VCC. Connect the bottom of the resistive
divider to the negative voltage to be monitored.
Adding Hysteresis to PFI
The power-fail comparators have a typical input hys-
teresis of VPFI-HYS. This is sufficient for most applica-
tions where a power-supply line is being monitored
through an external voltage-divider (see the
Monitoring
an Additional Supply
section). Figure 5 shows how to
add hysteresis to the power-fail comparator. Select the
ratio of R1 and R2 such that PFI sees VPFT when VIN
falls to the desired trip point (VTRIP). Resistor R3 adds
hysteresis. R3 is typically an order of magnitude greater
than R1 or R2. The current through R1 and R2 should
be at least 100µA to ensure that the 1µA (max) PFI
input current does not shift the trip point. R3 should be
larger than 50kΩto prevent it from loading down PFO.
Capacitor C1 adds additional noise rejection.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________ 13
MAX16023L
0.1µF
GND
PFI
R2
R1
MR
PFO
ADDITIONAL SUPPLY RESET VOLTAGE
RESET
V2
VCC
V1
RESET
µP
V2(RESET) = VPFT x ( )
R1 + R2
R2
Figure 3. Monitoring an Additional Supply by Connecting PFO
to MR
MAX16023
0.1μF
GND
PFI
R2
R1
PFO
VCC
VTRIP = VPFT - (5 - VPFT)
R2
R1
VTRIP IS NEGATIVE
V-
5V
PFO 0
+5V
VTRIP V-
0
Figure 4. Monitoring a Negative Supply
MAX16023/MAX16024
Operation Without a Backup
Power Source
The MAX16023/MAX16024 provide battery-backup
functions. If a backup power source is not used, con-
nect BATT to GND.
Replacing the Backup Battery
When VCC is above VTH, the backup power source can
be removed without danger of triggering a reset pulse.
The device does not enter battery-backup mode when
VCC stays above the reset threshold voltage.
Negative-Going VCC Transients
The MAX16023/MAX16024 are relatively immune to
short duration, negative-going VCC transients.
Resetting the µP when VCC experiences only small
glitches is usually not desirable. A 0.1µF bypass
capacitor mounted close to the VCC pin provides addi-
tional transient immunity.
Capacitor Selection and
Regulator Stability
For stable operation, connect a low-ESR 10µF (min) out-
put capacitor from OUT to GND. To reduce noise and
improve load-transient response and power-supply rejec-
tion, use larger output capacitor values.
Battery-Backup Circuits with
Regulated Output Voltage
14 ______________________________________________________________________________________
MAX16023
0.1µF
GND
PFI
PFO
R2
R1
R3
VCC
VH = (VPFT + VPFI - HYS)
x ( + + 1)
R1
R2
R1
R3
VL = R1 x ( - ) + VPFT
VPFT
R2
VCC - VPFT
R3
WHERE VPFT IS THE POWER-FAIL
THRESHOLD VOLTAGE.
*OPTIONAL
+5V
VIN
C1*
TO µP
PFO 0
+5V
VTRIP
VLVHVIN
VTRIP = VPFT x ( )
R1 + R2
R2
Figure 5. Adding Hysteresis to the Power-Fail Comparator
Part Number Table
PART OUTPUT
TYPE
R ESET
T H R ESH O L D
VO L T A G E
( V)
REGUL ATED
OU TPU T
VO LTA GE
( V)
PART OUTPUT
TYPE
R ESET
T H R ESH O L D
VO L T A G E
( V)
R EG U L A T ED
O U T PU T
VO L T A G E
( V)
MAX16023LTAL12+T Push-Pull 4.63 1.2 MAX16024LTBL12+T Push-Pull 4.63 1.2
MAX16023LTAL18+T Push-Pull 4.63 1.8 MAX16024LTBL18+T Push-Pull 4.63 1.8
MAX16023LTAL25+T Push-Pull 4.63 2.5 MAX16024LTBL25+T Push-Pull 4.63 2.5
MAX16023LTAL33+T Push-Pull 4.63 3.3 MAX16024LTBL33+T Push-Pull 4.63 3.3
MAX16023LTAM12+T Push-Pull 4.38 1.2 MAX16024LTBM12+T Push-Pull 4.38 1.2
MAX16023LTAM18+T Push-Pull 4.38 1.8 MAX16024LTBM18+T Push-Pull 4.38 1.8
MAX16023LTAM25+T Push-Pull 4.38 2.5 MAX16024LTBM25+T Push-Pull 4.38 2.5
MAX16023LTAM33+T Push-Pull 4.38 3.3 MAX16024LTBM33+T Push-Pull 4.38 3.3
MAX16023LTAT12+T Push-Pull 3.08 1.2 MAX16024LTBT12+T Push-Pull 3.08 1.2
MAX16023LTAT18+T Push-Pull 3.08 1.8 MAX16024LTBT18+T Push-Pull 3.08 1.8
MAX16023LTAT25+T Push-Pull 3.08 2.5 MAX16024LTBT25+T Push-Pull 3.08 2.5
MAX16023LTAS12+T Push-Pull 2.93 1.2 MAX16024LTBS12+T Push-Pull 2.93 1.2
MAX16023LTAS18+T Push-Pull 2.93 1.8 MAX16024LTBS18+T Push-Pull 2.93 1.8
MAX16023LTAS25+T Push-Pull 2.93 2.5 MAX16024LTBS25+T Push-Pull 2.93 2.5
MAX16023LTAR12+T Push-Pull 2.63 1.2 MAX16024LTBR12+T Push-Pull 2.63 1.2
MAX16023LTAR18+T Push-Pull 2.63 1.8 MAX16024LTBR18+T Push-Pull 2.63 1.8
MAX16023LTAR25+T Push-Pull 2.63 2.5 MAX16024LTBR25+T Push-Pull 2.63 2.5
MAX16023LTAZ12+T Push-Pull 2.32 1.2 MAX16024LTBZ12+T Push-Pull 2.32 1.2
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
______________________________________________________________________________________ 15
Part Number Table (continued)
PART OUTPUT
TYPE
R ESET
T H R ESH O L D
VO L T A G E
( V)
REGUL ATED
OU TPU T
VO LTA GE
( V)
PART OUTPUT
TYPE
R ESET
T H R ESH O L D
VO L T A G E
( V)
R EG U L A T ED
O U T PU T
VO L T A G E
( V)
MAX16023LTAZ18+T Push-Pull 2.32 1.8 MAX16024LTBZ18+T Push-Pull 2.32 1.8
MAX16023LTAY12+T Push-Pull 2.19 1.2 MAX16024LTBY12+T Push-Pull 2.19 1.2
MAX16023LTAY18+T Push-Pull 2.19 1.8 MAX16024LTBY18+T Push-Pull 2.19 1.8
MAX16023LTAW12+T Push-Pull 1.67 1.2 MAX16024LTBW12+T Push-Pull 1.67 1.2
MAX16023LTAV12+T Push-Pull 1.575 1.2 MAX16024LTBV12+T Push-Pull 1.575 1.2
MAX16023PTAL12+T Open-Drain 4.63 1.2 MAX16024PTBL12+T Open-Drain 4.63 1.2
MAX16023PTAL18+T Open-Drain 4.63 1.8 MAX16024PTBL18+T Open-Drain 4.63 1.8
MAX16023PTAL25+T Open-Drain 4.63 2.5 MAX16024PTBL25+T Open-Drain 4.63 2.5
MAX16023PTAL33+T Open-Drain 4.63 3.3 MAX16024PTBL33+T Open-Drain 4.63 3.3
MAX16023PTAM12+T Open-Drain 4.38 1.2 MAX16024PTBM12+T Open-Drain 4.38 1.2
MAX16023PTAM18+T Open-Drain 4.38 1.8 MAX16024PTBM18+T Open-Drain 4.38 1.8
MAX16023PTAM25+T Open-Drain 4.38 2.5 MAX16024PTBM25+T Open-Drain 4.38 2.5
MAX16023PTAM33+T Open-Drain 4.38 3.3 MAX16024PTBM33+T Open-Drain 4.38 3.3
MAX16023PTAT12+T Open-Drain 3.08 1.2 MAX16024PTBS12+T Open-Drain 3.08 1.2
MAX16023PTAT18+T Open-Drain 3.08 1.8 MAX16024PTBS18+T Open-Drain 3.08 1.8
MAX16023PTAT25+T Open-Drain 3.08 2.5 MAX16024PTBS25+T O p e n - D r a i n 3.08 2.5
MAX16023PTAS12+T Open-Drain 2.93 1.2 MAX16024PTBT12+T Open-Drain 2.93 1.2
MAX16023PTAS18+T Open-Drain 2.93 1.8 MAX16024PTBT18+T Open-Drain 2.93 1.8
MAX16023PTAS25+T Open-Drain 2.93 2.5 MAX16024PTBT25+T Open-Drain 2.93 2.5
MAX16023PTAR12+T Open-Drain 2.63 1.2 MAX16024PTBR12+T Open-Drain 2.63 1.2
MAX16023PTAR18+T Open-Drain 2.63 1.8 MAX16024PTBR18+T Open-Drain 2.63 1.8
MAX16023PTAR25+T Open-Drain 2.63 2.5 MAX16024PTBR25+T Open-Drain 2.63 2.5
MAX16023PTAZ12+T Open-Drain 2.32 1.2 MAX16024PTBZ12+T Open-Drain 2.32 1.2
MAX16023PTAZ18+T Open-Drain 2.32 1.8 MAX16024PTBZ18+T Open-Drain 2.32 1.8
MAX16023PTAY12+T Open-Drain 2.19 1.2 MAX16024PTBY12+T Open-Drain 2.19 1.2
MAX16023PTAY18+T Open-Drain 2.19 1.8 MAX16024PTBY18+T Open-Drain 2.19 1.8
MAX16023PTAW12+T Open-Drain 1.67 1.2 MAX16024PTBW12+T Open-Drain 1.67 1.2
MAX16023PTAV12+T Open-Drain 1.575 1.2 MAX16024PTBV12+T Open-Drain 1.575 1.2
MAX16024PTBL+T Open-Drain 4.63 Adjustable MAX16024LTBL+T Push-Pull 4.63 Adjustable
MAX16024PTBM+T Open-Drain 4.38 Adjustable MAX16024LTBM+T Push-Pull 4.38 Adjustable
MAX16024PTBT+T Open-Drain 3.08 Adjustable MAX16024LTBT+T Push-Pull 3.08 Adjustable
MAX16024PTBS+T Open-Drain 2.93 Adjustable MAX16024LTBS+T Push-Pull 2.93 Adjustable
MAX16024PTBR+T Open-Drain 2.63 Adjustable MAX16024LTBR+T Push-Pull 2.63 Adjustable
MAX16024PTBZ+T Open-Drain 2.32 Adjustable MAX16024LTBZ+T Push-Pull 2.32 Adjustable
MAX16024PTBY+T Open-Drain 2.19 Adjustable MAX16024LTBY+T Push-Pull 2.19 Adjustable
MAX16024PTBW+T Open-Drain 1.67 Adjustable MAX16024LTBW+T Push-Pull 1.67 Adjustable
MAX16024PTBV+T Open-Drain 1.575 Adjustable MAX16024LTBV+T Push-Pull 1.575 Adjustable
Bold parts denote standard versions. Samples are generally available on standard versions.
Contact factory for availability of nonstandard versions.
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
16 ______________________________________________________________________________________
Typical Applications Circuit
MAX16024L
0.1µF
3V
0.1µF0.1µF
10µF
BATT
GND
SET
PUSHBUTTON
CEIN
CEOUT
BATT ON
OUT
RESET
ADDRESS
DECODE
RTC
RAM
VCC
CE
MR
µP
RST
A0–A15
3.3V
VCC
PART
OUTPUTS
(RESET, PFO,
BATT ON )
RESET MR POWER-FAIL
COMPARATOR
CE
GATE BATT ON REGULATOR
OUTPUT VOLTAGE
MAX16023L Push-Pull √√ √ — — Fixed
MAX16023P Open Drain √√ √ — — Fixed
MAX16024L Push-Pull √√ —√√Fixed/adjustable
MAX16024P Open Drain √√ —√√Fixed/adjustable
Selector Guide
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
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 ____________________
17
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TDFN T833-2 21-0137
10 TDFN T1033-1 21-0137
Chip Information
PROCESS: BiCMOS
