19-4249; Rev 0; 8/08
Battery-Backup Circuits with
Regulated Output Voltage
The MAX16023/MAX16024 low-power battery-backup circuits 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 providing 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 during brownout. The MAX16023/MAX16024 accept an
input voltage from 1.53V to 5.5V and provide fixed standard output voltages of 1.2V, 1.8V, 2.5V, 3.0V, and 3.3V.
The MAX16024 offers the ability to externally set the output voltage using a resistive divider. All outputs are
available with push-pull or open-drain configurations.
The MAX16023 offers a power-fail comparator for monitoring an additional voltage or for providing an early powerfail 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
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 “_” designates 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 placeholders.
+Denotes a lead-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
UL is a registered trademark of Underwriters Laboratories, Inc.
OUT
RESET
GND
PFO
CEOUT
OUT
RESET
GND
BATT ON
Pin Configurations
8
7
6
5
10
9
8
7
6
MAX16023
MAX16024
*EP
*EP = EXPOSED PAD
MR
PFI
2
3
4
5
SET
BATT
TDFN
1
MR
4
BATT
3
VCC
2
*EP
+
CEIN
1
VCC
+
TDFN
________________________________________________________________ Maxim Integrated Products
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.
1
MAX16023/MAX16024
General Description
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
ABSOLUTE MAXIMUM RATINGS
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
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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.
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 values are at TA = TJ = +25°C.) (Note 2)
PARAMETER
Operating Voltage Range
SYMBOL
VCC, VBATT
CONDITIONS
(Note 3)
VCC = LDO + 0.5V,
no load
Supply Current
ICC
VCC = LDO + 0.5V,
IOUT = 20mA
Supply Current in Battery-Backup
Mode
IBATT
BATT Standby Current
SET Reference Voltage
VSET
SET Input Leakage Current
Output Voltage Range
Output Voltage Accuracy
2
VOUT
MIN
MAX
UNITS
5.5
V
LDO = 1.2V
4.3
LDO = 1.8V
4.7
7
LDO = 2.5V
5.2
7.5
LDO = 3V
5.5
8
6
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
LDO = 3.3V
17
19
3.5
5.26
µA
+0.01
µA
VCC = 0, VBATT = 3V,
no dropout, no load
VCC > VBATT + 0.2V
-0.01
MAX16024_TB_, VCC = 2.2V
1.144
MAX16024_TB_, SET = 1.2V
-20
MAX16024_TB_, VCC > VOUT
IOUT = 1mA
TYP
1.53
1.2
1.8
1.272
V
+20
nA
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
LDO = 3.3V
3.114
3.3
3.482
_______________________________________________________________________________________
µA
V
Battery-Backup Circuits with
Regulated Output Voltage
(VCC = 1.53V to 5.5V, VBATT = 3V, reset not asserted, TA = TJ = -40°C to +85°C, COUT = 10µF, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 2)
PARAMETER
SYMBOL
TYP
MAX
UNITS
Line Regulation
VCC = (VOUT + 1V) to (VOUT + 2V),
IOUT = 1mA
CONDITIONS
0.2
1.0
%/V
Load Regulation
VCC = VOUT + 1V, IOUT = 1mA to 2mA
0.15
1.0
%
IOUT = 50mA
(Note 4)
Dropout Voltage
Output Current Limit
Battery Freshness Leakage
Current
MIN
LDO = 1.2V
500
LDO = 1.8V
200
LDO = 2.5V
180
LDO = 3V
150
LDO = 3.3V
150
VCC = 1.6V
75
VCC ≥ 2V
150
mV
mA
VBATT = 5.5V
10
nA
RESET OUTPUT (RESET)
Reset Threshold
VTH
VCC Falling to Reset Delay
tRD
VCC falling at 10V/ms
Reset Timeout Period
tRP
VCC rising
RESET Output Low Voltage
VOL
RESET Output High Voltage
(Push-Pull Output)
VOH
RESET Output Leakage Current
(Open-Drain Output)
(See Table 1)
V
20
µs
145
215
285
VOUT = 3.3V, ISINK = 3.2mA, RESET asserted
0.3
VOUT = 1.8V, ISINK = 1mA, RESET asserted
0.3
VOUT = 1.2V, ISINK = 100µA, RESET asserted
0.3
VCC ≥ 1.1 x VTH, ISOURCE = 100µA,
RESET deasserted
VOUT - 0.3V
ms
V
V
V RESET = 5.5V, reset deasserted
1
µA
POWER-FAIL COMPARATOR (PFI, PFO)
PFI Input Threshold
VPFT
PFI Input Hysteresis
VPFI-HYS
PFI Input Current
VPFI falling, 1.6V ≤ VCC ≤ 5.5V
0.590
0.611
30
IPFI
PFO Output Low Voltage
0.570
-1
+1
VOUT = 1.8V, ISINK = 1mA, PFO asserted
0.3
VOUT =1.2V, ISINK = 100µA, PFO asserted
0.3
PFO Output High Voltage
(Push-Pull Output)
ISOURCE = 100µA, PFO deasserted
PFO Leakage Current
(Open-Drain Output)
V PFO = 5.5V, PFO deasserted
PFO Delay Time
(VPFI + 100mV) to (VPFI - 100mV)
V
mV
VOUT - 0.3V
µA
V
V
1
20
µA
µs
MANUAL RESET (MR)
Input Low Voltage
VIL
Input High Voltage
VIH
Pullup Resistance
0.3 x VCC
0.7 x VCC
Pullup resistance to VCC
20
V
30
kΩ
Glitch Immunity
100
ns
MR to Reset Delay
120
ns
_______________________________________________________________________________________
3
MAX16023/MAX16024
ELECTRICAL CHARACTERISTICS (continued)
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
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 values are at TA = TJ = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
BATTERY-ON INDICATOR (BATT ON)
Output Low Voltage
Output High Voltage
(Push-Pull Output)
VOL
VOH
VOUT = 1.2V, ISINK = 100µA, BATT ON
deasserted
0.3
VOUT = 1.8V, ISINK = 1mA, BATT ON
deasserted
0.3
VOUT = 3.3V, ISINK = 3.2mA, BATT ON
deasserted
0.3
ISOURCE = 100µA, BATT ON asserted
Output Leakage Current
(Open-Drain Output)
VCC = 5.5V
Output Short-Circuit Current
Sink current, VCC = 5V
(Note 6)
VOUT - 0.3V
V
V
1
60
µA
mA
CE GATING (CEIN, CEOUT)
CEIN Leakage Current
Reset asserted, VCC = 0.9 x VTH or 0
+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
Reset to CEOUT Delay
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
4
VOH
ISOURCE = 100µA, reset asserted
-1
VOUT - 0.3V
V
12
µs
All devices are 100% production tested at TA = +25°C and TA = +85°C. Limits over temperature are guaranteed by design.
VBATT can be 0 anytime or VCC can go down to 0 if VBATT is active (except at startup).
Dropout voltage is defined as (VIN - VOUT) when VOUT is 2% below the value of VOUT when VIN = VOUT + 1V.
CEIN to CEOUT resistance is tested with VCC = 5V and V CEIN = 0 or 5V.
Use external current-limiting resistor to limit current to 20mA (max).
_______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
Table 2. Fixed Output Voltage
RESET THRESHOLD RANGES (V)
SUFFIX
MIN
TYP
MAX
SUFFIX
NOMINAL OUTPUT
VOLTAGE (V)
L
4.508
4.63
4.906
33
3.3
M
4.264
4.38
4.635
30
3.0
T
2.991
3.08
3.239
25
2.5
S
2.845
2.93
3.080
18
1.8
R
2.549
2.63
2.755
12
1.2
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
Typical Operating Characteristics
(VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.)
VCC SUPPLY CURRENT
vs. TEMPERATURE
15
10
8
7
6
5
4
3
2
5
6
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
5
MAX16023 toc03
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
9
BATT SUPPLY CURRENT (μA)
20
10
BATT SUPPLY CURRENT
vs. VCC SUPPLY VOLTAGE
MAX16023 toc02
MAX16024PTBS25+
VOUT = 2.5V
VTH = 2.93V
VCC SUPPLY CURRENT (μA)
VCC SUPPLY CURRENT (μA)
25
MAX16023 toc01
VCC SUPPLY CURRENT
vs. VCC SUPPLY VOLTAGE
4
3
VBATT = 3.0V
2
VBATT = 2.8V
1
1
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
-15
10
35
60
85
0
0.5
1.0
1.5
2.0
2.5
3.0
TEMPERATURE (°C)
VCC SUPPLY VOLTAGE (V)
BATTERY SUPPLY CURRENT
vs. TEMPERATURE
BATT STANDBY CURRENT
vs. TEMPERATURE
RESET OUTPUT VOLTAGE LOW
vs. SINK CURRENT
3
2
1
VCC = 3.3V
VBATT = 3.0V
8
6
4
2
0
-2
-4
-6
1.0
MAX16024PTBS25+
OUTPUT VOLTAGE LOW (V)
4
10
BATT STANDBY CURRENT (nA)
MAX16024PTBS25+
VBATT = +3.0V
VCC = 0
MAX16023 toc05
VCC SUPPLY VOLTAGE (V)
5
BATTERY SUPPLY CURRENT (μA)
0
-40
5.5
MAX16023 toc04
1.5
0.8
3.5
MAX16023 toc06
0
0.6
0.4
0.2
-8
-10
0
-40
-15
10
35
TEMPERATURE (°C)
60
85
0
-40
-15
10
35
TEMPERATURE (°C)
60
85
0
2
4
6
8
10 12
14 16
18 20
SINK CURRENT (mA)
_______________________________________________________________________________________
5
MAX16023/MAX16024
Table 1. Reset Threshold Ranges
Typical Operating Characteristics (continued)
(VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.)
RESET TIMEOUT PERIOD
vs. TEMPERATURE
60
50
40
30
210
205
200
195
190
20
185
10
-15
10
35
60
0.990
-15
10
35
60
85
-40
10
35
60
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
DROPOUT VOLTAGE
vs. LOAD CURRENT
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX16023 toc10
500
RESET OCCURS ABOVE THE CURVE
50
400
2.70
350
300
250
200
150
2.62
2.50
2.42
2.38
2.34
0
0
2.30
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
TA = +25°C
2.46
50
0
TA = -40°C
2.54
25
1000
85
2.58
100
200
400
600
800
RESET THRESHOLD OVERDRIVE (mV)
MAX16024PTBS25+
VOUT = 2.5V
2.66
OUTPUT VOLTAGE (V)
100
MAX16024PTBS25+
450
DROPOUT VOLTAGE (mV)
125
0
-15
TEMPERATURE (°C)
150
MAX16023 toc09
0.995
TEMPERATURE (°C)
175
6
1.000
TEMPERATURE (°C)
200
75
1.005
0.980
-40
85
MAX16023 toc11
-40
1.010
0.985
180
0
MAX16024PTBS25+
VOUT = 2.5V
1.015
MAX16023 toc12
DELAY (µs)
70
215
1.020
NORMALIZED RESET THRESHOLD
80
220
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX16023 toc08
VCC FALLING 10V/ms
90
RESET TIMEOUT PERIOD (ms)
100
MAX16023 toc07
VCC FALLING TO RESET DELAY
vs. TEMPERATURE
TRANSIENT DURATION (ms)
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
TA = +85°C
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
_______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE
vs. VCC VOLTAGE
STARTUP RESPONSE
LOAD-TRANSIENT RESPONSE
MAX16023 toc15
MAX16023 toc14
MAX16023 toc13
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
MAX16024PTBS25+
IOUT = 0
COUT = 10µF
OUT
AC-COUPLED
100mV/div
VCC
2V/div
50mA
IOUT
20mA/div
10mA
OUT
1V/div
MAX16024PTBS25+
IOUT = 0
MAX16024PTBS25+
0
1
2
3
4
5
6
2ms/div
1ms/div
VCC VOLTAGE (V)
CHIP-ENABLE LOCKING OUT
SIGNAL DURING RESET
MR FALLING TO RESET DELAY
MAX16023 toc16
MAX16023 toc17
RESET
5V/div
MR
5V/div
CEIN
2V/div
RESET
5V/div
200ns/div
CEOUT
2V/div
40µs/div
_______________________________________________________________________________________
7
MAX16023/MAX16024
Typical Operating Characteristics (continued)
(VCC = 5V, VBATT = 0, IOUT = 0, TA = +25°C, unless otherwise noted.)
Battery-Backup Circuits with
Regulated Output Voltage
MAX16023/MAX16024
Pin Description
PIN
FUNCTION
MAX16024
1
2
VCC
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.
3
4
MR
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
7
8
NAME
MAX16023
8
RESET
Ground
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 pushpull 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.
—
1
CEIN
Chip-Enable Input. The input to CE gating circuitry. Connect to GND or OUT if not
used.
—
5
SET
—
6
BATT ON
—
10
CEOUT
—
—
EP
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.
Active-High, Battery-On Output. BATT ON goes high when in the battery backup
mode.
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.
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.
_______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
BATT
LDO
OUT
VCC
LOGIC
DROPOUT
MR
RESET
DELAY
RESET
OUT
REF
OUT
PFO
PFI
MAX16023
GND
_______________________________________________________________________________________
9
MAX16023/MAX16024
Functional Diagrams
Battery-Backup Circuits with
Regulated Output Voltage
MAX16023/MAX16024
Functional Diagrams (continued)
BATT
OUT
LDO
VCC
SET
LOGIC
BATT ON
DROPOUT
MR
RESET
DELAY
RESET
VCC
REF
CE OUTPUT
CONTROL
CEIN
CEOUT
MAX16024
GND
10
______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
The Typical Applications Circuit shows a typical connection 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-battery installed at BATT, the MAX16023/MAX16024 automatically 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 output 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 corrupting the CMOS RAM and CEOUT is pulled up to OUT
through an internal current source. The 1.5ns propagation 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 disconnected 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.
VCC
RESET THRESHOLD VTH
CEIN
CEOUT
*
RESET-TO-CEOUT DELAY (12µs)
tRD
RESET
tRD
tRP
tRP
* IF CEIN GOES HIGH BEFORE RESET ASSERTS,
CEOUT GOES HIGH WITHOUT DELAY AS
CEIN GOES HIGH.
Figure 1. Reset and Chip-Enable Timing
______________________________________________________________________________________
11
MAX16023/MAX16024
Detailed Description
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
Manual-Reset Input
(MAX16023/MAX16024)
Many µP-based products require manual-reset capability, 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 30kΩ pullup resistor to VCC. MR can be
driven with TTL/CMOS logic levels or with opendrain/collector outputs. Connect a normally open
momentary switch from MR to GND to create a manualreset 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 capacitor 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 battery-switchover status.
Battery Freshness Seal
The MAX16023/MAX16024 battery freshness seal disconnects the backup battery from internal circuitry and
OUT until VCC is applied. This ensures the backup battery 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.
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 comparator. 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 regulation to provide an early power-fail warning, so software 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 independent 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.
1.53 TO 5.5V
VCC
1.8V TO 5.25V
OUT
0.1µF
10µF
MAX16024
R1
TO µP
RESET
SET
R2
GND
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 powerup, power-down, and brownout conditions. RESET
asserts when V CC is below the reset threshold and
remains low for at least 145ms (tRP) after VCC rises
12
VOUT = VSET (1 + R1/R2)
VSET = 1.2V
Figure 2. Setting the Adjustable Output Voltage (MAX16024
Only)
______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
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 resistive divider to VCC. Connect the bottom of the resistive
divider to the negative voltage to be monitored.
V1
Adding Hysteresis to PFI
The power-fail comparators have a typical input hysteresis of VPFI-HYS. This is sufficient for most applications 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 50kΩ to prevent it from loading down PFO.
Capacitor C1 adds additional noise rejection.
5V
0.1μF
0.1µF
R1
V2
VCC
VCC
RESET
R1
RESET
PFI
PFO
µP
PFI
R2
MAX16023
MAX16023L
PFO
R2
MR
V-
(
VTRIP = VPFT - R2 5 - VPFT
R1
GND
GND
)
VTRIP IS NEGATIVE
ADDITIONAL SUPPLY RESET VOLTAGE
(
V2(RESET) = VPFT x R1 + R2
R2
)
Figure 3. Monitoring an Additional Supply by Connecting PFO
to MR
PFO
+5V
0
VTRIP
0
V-
Figure 4. Monitoring a Negative Supply
______________________________________________________________________________________
13
MAX16023/MAX16024
Applications Information
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
+5V
Replacing the Backup Battery
VCC
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.
VIN
0.1µF
R1
PFI
R2
(
)
) x ( R1R2 +
-V
)+V
R3
VTRIP = VPFT x R1 + R2
R2
C1*
(
VH = VPFT + VPFI - HYS
R3
MAX16023
(
VL = R1 x VPFT - VCC
R2
PFT
)
R1 + 1
R3
PFT
WHERE VPFT IS THE POWER-FAIL
THRESHOLD VOLTAGE.
PFO
GND
TO µP
Negative-Going VCC Transients
The MAX16023/MAX16024 are relatively immune to
short duration, negative-going V CC transients.
Resetting the µP when V CC experiences only small
glitches is usually not desirable. A 0.1µF bypass
capacitor mounted close to the VCC pin provides additional transient immunity.
Capacitor Selection and
Regulator Stability
+5V
PFO
For stable operation, connect a low-ESR 10µF (min) output capacitor from OUT to GND. To reduce noise and
improve load-transient response and power-supply rejection, use larger output capacitor values.
0
VL
VTRIP VH
VIN
*OPTIONAL
Figure 5. Adding Hysteresis to the Power-Fail Comparator
Operation Without a Backup
Power Source
The MAX16023/MAX16024 provide battery-backup
functions. If a backup power source is not used, connect BATT to GND.
Part Number Table
PART
OUTPUT
TYPE
RESET
REGULATED
THRESHOLD
OUTPUT
VOLTAGE
VOLTAGE
(V)
(V)
PART
OUTPUT
TYPE
RESET
REGULATED
THRESHOLD
OUTPUT
VOLTAGE
VOLTAGE
(V)
(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
14
______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
RESET
REGULATED
THRESHOLD
OUTPUT
VOLTAGE
VOLTAGE
(V)
(V)
RESET
REGULATED
THRESHOLD
OUTPUT
VOLTAGE
VOLTAGE
(V)
(V)
PART
OUTPUT
TYPE
1.8
MAX16024LTBZ18+T
Push-Pull
2.32
1.8
1.2
MAX16024LTBY12+T
Push-Pull
2.19
1.2
2.19
1.8
MAX16024LTBY18+T
Push-Pull
2.19
1.8
1.67
1.2
MAX16024LTBW12+T
Push-Pull
1.67
1.2
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
Open-Drain
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
PART
OUTPUT
TYPE
MAX16023LTAZ18+T
Push-Pull
2.32
MAX16023LTAY12+T
Push-Pull
2.19
MAX16023LTAY18+T
Push-Pull
MAX16023LTAW12+T
Push-Pull
MAX16023LTAV12+T
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.
______________________________________________________________________________________
15
MAX16023/MAX16024
Part Number Table (continued)
MAX16023/MAX16024
Battery-Backup Circuits with
Regulated Output Voltage
Selector Guide
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
PART
Typical Applications Circuit
3.3V
0.1µF
0.1µF
VCC
VCC
RST
RESET
µP
BATT
3V
0.1µF
BATT ON
A0–A15
MAX16024L
OUT
10µF
MR
RAM
PUSHBUTTON
RTC
CEOUT
CE
SET
CEIN
GND
16
ADDRESS
DECODE
______________________________________________________________________________________
Battery-Backup Circuits with
Regulated Output Voltage
PROCESS: BiCMOS
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
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.
MAX16023/MAX16024
Package Information
Chip Information
工商网监
湘ICP备2023018690号
