Rainbow Electronics MAX16024 User Manual

General Description

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 V

CC

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

o System Monitoring for 5V, 3.3V, 3V, 2.5V, or 1.8V

Power-Supply Voltages

o 100mA Low-Dropout Regulator

o Factory-Trimmed and Adjustable Output Voltages

o 1.53V to 5.5V Operating Voltage Range

o Low-Power Consumption: 4µA (typ)

o Power-Fail Comparators for Monitoring Voltages

Down to 0.6V

o Battery-On Indicator

o Battery Freshness Seal

o On-Board Gating of CE Signals, 1.5ns

Propagation Delay (MAX16024)

o Debounced Manual-Reset Input

o 145ms (min) Reset Timeout Period

o Tiny 8-Pin and 10-Pin TDFN Packages

o UL

®

Certified to Conform to IEC60950-1

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

PIN-PACKAGE

MAX16023_TA_ _ _+T

8 TDFN-EP*

MAX16024_TB_ _ _+T

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.

Pin Configurations

UL is a registered trademark of Underwriters Laboratories, Inc.

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

OUT

8 7 6 5

MAX16023

+

1 2 3 4

CC

V

BATT

TDFN

*EP *EP

PFI

MR

*EP = EXPOSED PAD

OUT

MAX16024

CC

V

TDFN

RESET

BATT

CEOUT

10 9 8 7

+

1 2 3 4

CEIN

PFO

GND

RESET

GND

BATT ONSET

6

5

MR

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, TA= TJ= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical val-

ues are at T

A

= 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 (V

OUT

+ 0.3V)

PFI, CEIN, CEOUT to GND.......................-0.3V to (V

OUT

+ 0.3V)

MR to GND .................................................-0.3V to (V

CC

+ 0.3V)
Input Current
V

CC

Peak Current.....................................................................1A

V

CC

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 (T

A

= +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)

θ

JA

(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 four-

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial

.

Operating Voltage Range V

Supply Current I

Supply Current in Battery-Backup
Mode

BATT Standby Current VCC > V

SET Reference Voltage V

SET Input Leakage Current MAX16024_TB_, SET = 1.2V -20 +20 nA

Output Voltage Range V

Output Voltage Accuracy I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

CC

BATT

CC

I

BATT

SET

OUT

(Note 3) 1.53 5.5 V

VCC = LDO + 0.5V,
no load

VCC = LDO + 0.5V,
I

= 20mA

OUT

VCC = 0, V
no dropout, no load

BATT

MAX16024_TB_, VCC = 2.2V 1.144 1.2 1.272 V

MAX16024_TB_, VCC > V

= 1mA

OUT

LDO = 1.2V 4.3 6

LDO = 1.8V 4.7 7

LDO = 2.5V 5.2 7.5

LDO = 3V 5.5 8

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

= 3V,

BATT

+ 0.2V -0.01 +0.01 µA

OUT

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

3.5 5.26 µA

1.8 5.25 V

µA

V

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, TA= TJ= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical val-

ues are at T

A

= TJ= +25°C.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Line Regulation

Load Regulation VCC = V

Dropout Voltage

Output Current Limit

Battery Freshness Leakage
Current

RESET OUTPUT (RESET)

Reset Threshold V

VCC Falling to Reset Delay t

Reset Timeout Period t

RESET Output High Voltage
(Push-Pull Output)

RESET Output Leakage Current
(Open-Drain Output)

POWER-FAIL COMPARATOR (PFI, PFO)

PFI Input Threshold V

PFI Input Hysteresis V

PFI Input Current I

PFO Output Low Voltage

PFO Output High Voltage

(Push-Pull Output)
PFO Leakage Current

(Open-Drain Output)
PFO Delay Time (V

MANUAL RESET (MR)

Input Low Voltage V

Input High Voltage V

Pullup Resistance Pullup resistance to V

Glitch Immunity 100 ns
MR to Reset Delay 120 ns

V
I

OUT

I

OUT

CC

= (V

= 1mA

= 50mA

OUT

OUT

+ 1V, I

+ 1V) to (V

OUT

(Note 4)

VCC = 1.6V 75

V

≥ 2V 150

CC

= 5.5V 10 nA

V

BATT

TH

VCC falling at 10V/ms 20 µs

RD

VCC rising 145 215 285 ms

RP

V

OL

V

OH

PFT

PFI-HYS

PFI

IL

IH

= 3.3V, I

OUT

V

= 1.8V, I

OUT

V

= 1.2V, I

OUT

VCC ≥ 1.1 x VTH, I
RESET deasserted

= 5.5V, reset deasserted 1 µA

V

RESET

V

falling, 1.6V ≤ VCC ≤ 5.5V 0.570 0.590 0.611 V

PFI

V

= 1.8V, I

OUT

=1.2V, I

V

OUT

I

V

= 100µA, PFO deasserted V

SOURCE

= 5.5V, PFO deasserted 1 µA

PFO

+ 100mV) to (V

PFI

= 3.2mA, RESET asserted 0.3

SINK

= 1mA, RESET asserted 0.3RESET Output Low Voltage V

SINK

= 100µA, RESET asserted 0.3

SINK

SOURCE

= 1mA, PFO asserted 0.3

SINK

= 100µA, PFO asserted 0.3

SINK

PFI

CC

+ 2V),

OUT

0.2 1.0 %/V

= 1mA to 2mA 0.15 1.0 %

LDO = 1.2V 500

LDO = 1.8V 200

LDO = 2.5V 180

LDO = 3V 150

LDO = 3.3V 150

(See Table 1) V

= 100µA,

V

- 0.3V V

OUT

30 mV

-1 +1 µA

- 0.3V V

OUT

- 100mV) 20 µs

0.3 x V

CC

0.7 x V

CC

20 30 kΩ

mV

mA

V

V

V

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, TA= TJ= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical val-

ues are at T

A

= TJ= +25°C.) (Note 2)

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: V

BATT

can be 0 anytime or VCCcan go down to 0 if V

BATT

is active (except at startup).

Note 4: Dropout voltage is defined as (V

IN

- V

OUT

) when V

OUT

is 2% below the value of V

OUT

when VIN= V

OUT

+ 1V.

Note 5: CEIN to CEOUT resistance is tested with VCC= 5V and V

CEIN

= 0 or 5V.

Note 6: Use external current-limiting resistor to limit current to 20mA (max).

BATTERY-ON INDICATOR (BATT ON)

Output Low Voltage V

Output High Voltage
(Push-Pull Output)

Output Leakage Current
(Open-Drain Output)

Output Short-Circuit Current

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

Output High Voltage V
Reset to CEOUT Delay 12 µs

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

= 1.2V, I

OUT

deasserted

V

= 1.8V, I

OL

V

OH

OH

OUT

deasserted

V

= 3.3V, I

OUT

deasserted

I

V

Sink current, V
(Note 6)

50Ω source, C

I

= 100µA, BATT ON asserted V

SOURCE

= 5.5V 1 µA

CC

= 100µA, reset asserted V

SOURCE

= 100µA, BATT ON

SINK

= 1mA, BATT ON

SINK

= 3.2mA, BATT ON

SINK

= 5V

CC

= 50pF, VCC = 4.75V 1.5 7 ns

LOAD

- 0.3V V

OUT

60 mA

- 0.3V V

OUT

0.3

0.3

0.3

V

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 0, TA= +25°C, unless otherwise noted.)

Table 1. Reset Threshold Ranges Table 2. Fixed Output Voltage

SUFFIX

RESET THRESHOLD RANGES (V)

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

33 3.3

30 3.0

25 2.5

18 1.8

12 1.2

NOMINAL OUTPUT

VOLTAGE (V)

25

20

15

10

SUPPLY CURRENT (μA)

CC

V

5

0

1.5 5.5

VCC SUPPLY CURRENT

SUPPLY VOLTAGE

vs. V

CC

MAX16024PTBS25+

3.02.5 4.52.0 3.5 5.04.0

VCC SUPPLY VOLTAGE (V)

VCC SUPPLY CURRENT

vs. TEMPERATURE

10

V
V

OUT

= 2.93V

TH

= 2.5V

MAX16023 toc01

9

8

7

6

5

4

SUPPLY CURRENT (μA)

3

CC

V

2

1

0

-40 85

TEMPERATURE (°C)

MAX16024PTBS25+

V
V

OUT

= 2.93V

TH

6010 35-15

= 2.5V

MAX16023 toc02

BATT SUPPLY CURRENT

SUPPLY VOLTAGE

vs. V

6

5

4

3

2

BATT SUPPLY CURRENT (μA)

1

0

0 3.5

CC

V

V

1.0 3.00.5 2.52.01.5

VCC SUPPLY VOLTAGE (V)

MAX16024PTBS25+

= 3.0V

BATT

= 2.8V

BATT

V
V

OUT

= 2.93V

TH

= 2.5V

MAX16023 toc03

BATTERY SUPPLY CURRENT

vs. TEMPERATURE

5

4

3

2

1

BATTERY SUPPLY CURRENT (μA)

0

-40 85

TEMPERATURE (°C)

MAX16024PTBS25+

V

BATT

= +3.0V

V

CC

6010 35-15

= 0

10

8

MAX16023 toc04

6

4

2

0

-2

-4

BATT STANDBY CURRENT (nA)

-6

-8

-10

-40 85

BATT STANDBY CURRENT

vs. TEMPERATURE

VCC = 3.3V

V

BATT

TEMPERATURE (°C)

= 3.0V

6010 35-15

1.0

MAX16023 toc05

0.8

0.6

0.4

OUTPUT VOLTAGE LOW (V)

0.2

0

02014610218

RESET OUTPUT VOLTAGE LOW

vs. SINK CURRENT

MAX16024PTBS25+

MAX16023 toc06

168124

SINK CURRENT (mA)

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 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+

V

OUT

= 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

01007030 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
01007030 5010 90

MAX16024PTBS25+

V

OUT

= 2.5V

TA = -40°C

TA = +25°C

TA = +85°C

OUTPUT VOLTAGE

vs. V

CC

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+

I

OUT

= 0

LOAD-TRANSIENT RESPONSE

MAX16023 toc14

1ms/div

OUT
AC-COUPLED
100mV/div

50mA
I

OUT

20mA/div

10mA

MAX16024PTBS25+

C

OUT

= 10μF

STARTUP RESPONSE

MAX16023 toc15

2ms/div

V

CC

2V/div

OUT
1V/div

MAX16024PTBS25+
I

OUT

= 0

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 0, TA= +25°C, unless otherwise noted.)

MR FALLING TO RESET DELAY

MAX16023 toc16

CHIP-ENABLE LOCKING OUT

SIGNAL DURING RESET

MAX16023 toc17

MR
5V/div

RESET
5V/div

200ns/div

40μs/div

RESET
5V/div

CEIN
2V/div

CEOUT
2V/div

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

8 _______________________________________________________________________________________

Pin Description

PIN

MAX16023 MAX16024

12VCCSupply Voltage Input. Bypass V

2 3 BATT

34MR

4 — PFI

5—PFO

6 7 GND Ground

78RESET

8 9 OUT

—1CEIN

— 5 SET

— 6 BATT ON

—10CEOUT

——EP

NAME FUNCTION

Backup Battery Input. If V
the regulator enters dropout, the regulator is powered from BATT. If V
the regulator is powered from V

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 V

Power-Fail Comparator Input. Connect PFI to a resistive divider to set the desired PFI
threshold. The PFI input is referenced to an internal V
internal hysteresis provides noise immunity. The power-fail comparator is powered
from OUT.

Active-Low, Power-Fail Comparator Output. PFO goes low when V
internal V
hysteresis.

Active-Low Reset Output. RESET asserts when V
MR is pulled low. RESET remains low for the duration of the reset timeout period after
V

CC

pull and open-drain options.

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.

Chip-Enable Input. The input to CE gating circuitry. Connect to GND or OUT if not
used.

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.

PFT

rises above the reset threshold and MR goes high. RESET is available in push-

through a 30kΩ pullup resistor.

CC

threshold and goes high when V

to GND with a 0.1µF capacitor.

CC

falls below its reset threshold (VTH), V

CC

. Bypass BATT to GND with a 0.1µF capacitor.

CC

threshold. A V

PFT

rises above V

PFI

falls below the reset threshold or

CC

BATT

BATT

falls below the

PFI

+ V

PFT

≥ VCC, and if

< VCC,

PFT-HYS

PFT-HYS

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

_______________________________________________________________________________________ 9

Functional Diagrams

BATT

V

CC

LOGIC

MR

DROPOUT

RESET DELAY

LDO

OUT

OUT

RESET

PFI

REF

OUT

PFO

MAX16023

GND

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

10 ______________________________________________________________________________________

Functional Diagrams (continued)

BATT

V

CC

OUT

LDO

SET

MR

CEIN

MAX16024

LOGIC

DROPOUT

RESET DELAY

CE OUTPUT

CONTROL

GND

V

REF

BATT ON

RESET

CC

CEOUT

Detailed Description

The

Typical Applications Circuit

shows a typical con­nection using the MAX16024. OUT powers the SRAM. If
VCCis higher than the reset threshold (VTH), or if V

CC

is

lower than V

TH

but higher than V

BATT

, the regulator is

powered from VCC. If V

CC

< VTH, VCC< V

BATT

, 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 V

CC

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) VCCis lower than the reset threshold.

2) VCCis lower than V

BATT

.

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 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.

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

______________________________________________________________________________________ 11

Figure 1. Reset and Chip-Enable Timing

V

RESET THRESHOLD V

CC

TH

CEIN

CEOUT

RESET-TO-CEOUT DELAY (12μs)

RESET

*

t

RD

t

RD

t

RP

*

IF CEIN GOES HIGH BEFORE RESET ASSERTS,
CEOUT GOES HIGH WITHOUT DELAY AS
CEIN GOES HIGH.

t

RP

MAX16023/MAX16024

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 VCCis 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 VCChas come up for the first time,
setting the latch. When VCCsubsequently turns off,
BATT begins to power OUT.

To reenable the freshness seal (MAX16023/
MAX16024):

1) Connect a battery to BATT.

2) Bring VCCto 0.

3) Drive MR higher than V

BATT

+ 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 power­up, power-down, and brownout conditions. RESET
asserts when VCCis below the reset threshold and
remains low for at least 145ms (tRP) after VCCrises

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 V

PFT

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
V

PFT-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 ______________________________________________________________________________________

Figure 2. Setting the Adjustable Output Voltage (MAX16024
Only)

1.53 TO 5.5V

0.1μF

V

CC

MAX16024

RESETTO μP

GND

OUT

SET

1.8V TO 5.25V

10μF

R1

R2

= V

OUT
SET

= 1.2V

(1 + R1/R2)

SET

V
V

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 VCCand 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.

Adding Hysteresis to PFI

The power-fail comparators have a typical input hys­teresis of V

PFT-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 V

PFT

when V

IN

falls to the desired trip point (V

TRIP

). 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.

MAX16023/MAX16024

Battery-Backup Circuits with

Regulated Output Voltage

______________________________________________________________________________________ 13

Figure 3. Monitoring an Additional Supply by Connecting PFO
to MR

Figure 4. Monitoring a Negative Supply

V

1

0.1μF

V

2

V

CC

R1

PFI

MAX16023L

R2

RESET

PFO

MR

RESET

μP

5V

R1

R2

V-

0.1μF

V

CC

PFI

MAX16023

PFO

GND

ADDITIONAL SUPPLY RESET VOLTAGE

= V

PFT

R1 + R2

x

( )

R2

V

2(RESET)

GND

+5V

PFO

0

V

TRIP

V

V

0

= V

TRIP

IS NEGATIVE

TRIP

R2

- (5 - V

PFT

R2

V-

PFT

)

MAX16023/MAX16024

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.

Replacing the Backup Battery

When VCCis 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
V

CC

stays above the reset threshold voltage.

Negative-Going VCCTransients

The MAX16023/MAX16024 are relatively immune to
short duration, negative-going VCCtransients.
Resetting the µP when VCCexperiences only small
glitches is usually not desirable. A 0.1µF bypass
capacitor mounted close to the VCCpin provides addi­tional transient immunity.

Capacitor Selection and

Regulator Stability

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.

Battery-Backup Circuits with
Regulated Output Voltage

14 ______________________________________________________________________________________

Figure 5. Adding Hysteresis to the Power-Fail Comparator

Part Number Table

+5V

V

IN

V

GND

V

0.1μF

CC

V

L

TRIP

V

V

TRIP

VH = (V

VL = R1 x

WHERE V
THRESHOLD VOLTAGE.

H

R1 + R2

= V

x

PFT

( )

+ V

PFT

PFT - HYS

V

PFT

( - )

R2

IS THE POWER-FAIL

PFT

V

IN

R2

)

VCC - V

R3

*OPTIONAL

R1R2R1

x ( +

PFT

+ V

R1

PFI

C1*

R2

PFO

R3

TO μP

+5V

0

MAX16023

PFO

PART

OUTPUT

TYPE

R ESET

T H R ESH O L D

VO L T A G E

( V)

REGUL ATED

VO LTA GE

+ 1

R3

PFT

OU TPU T

( V)

)

R ESET

PART

OUTPUT

TYPE

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)

Bold parts denote standard versions. Samples are generally available on standard versions.
Contact factory for availability of nonstandard versions.

R ESET

PART

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

OUTPUT

TYPE

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)

MAX16023/MAX16024

Battery-Backup Circuits with
Regulated Output Voltage

16 ______________________________________________________________________________________

Typical Applications Circuit

Selector Guide

OUTPUTS

PART

MAX16023L Push-Pull √√ √ — — Fixed
MAX16023P Open Drain √√ √ — — Fixed
MAX16024L Push-Pull √√ — √√Fixed/adjustable
MAX16024P Open Drain √√ — √√Fixed/adjustable

(RESET, PFO,

BATT ON )

RESET MR

POWER-FAIL

COMPARATOR

CE

GATE

BATT ON

3.3V

REGULATOR

OUTPUT VOLTAGE

0.1μF

BATT

0.1μF

3V

MAX16024L

MR

PUSHBUTTON

SET

V

GND

0.1μF

V

CC

RESET

BATT ON

OUT

CEOUT

CEIN

10μF

ADDRESS

DECODE

RST

CC

μP

A0–A15

RAM

CE

RTC

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