MAX16023, MAX16024

MAX16023, MAX16024

19-4249; Rev 0; 8/08

Battery-Backup Circuits with

Regulated Output Voltage

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

UL is a registered trademark of Underwriters Laboratories, Inc.

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

Ordering Information

PART

MAX16023_TA_ _ _+T

MAX16024_TB_ _ _+T

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

PIN-PACKAGE

8 TDFN-EP*

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

8 7 6 5 10 9 8 7 6

+

1

MAX16023

2 3

*EP

4

+

1 2

MAX16024

3 4

*EP

5

TDFN

*EP = EXPOSED PAD

TDFN

________________________________________________________________ Maxim Integrated Products 1

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.

Battery-Backup Circuits with

Regulated Output Voltage

ABSOLUTE MAXIMUM RATINGS

V

CC

, 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

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

CC

+ 0.3V)

+ 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 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

(V

CC

= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, T

A

= T

J

= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical values are at T

A

= T

J

= +25°C.) (Note 2)

PARAMETER

Operating Voltage Range

Supply Current

Supply Current in Battery-Backup

Mode

BATT Standby Current

SET Reference Voltage

SET Input Leakage Current

Output Voltage Range

Output Voltage Accuracy

SYMBOL

V

CC,

V

BATT

(Note 3)

I

V

V

I

CC

BATT

SET

OUT

CONDITIONS

I

V no load

V

CC

CC

OUT

= LDO + 0.5V,

= LDO + 0.5V,

= 20mA

LDO = 1.2V

LDO = 1.8V

LDO = 2.5V

LDO = 3V

LDO = 3.3V

LDO = 1.2V

LDO = 1.8V

LDO = 2.5V

LDO = 3V

LDO = 3.3V

V

CC

= 0, V

BATT

= 3V, no dropout, no load

I

V

CC

> V

BATT

+ 0.2V

MAX16024_TB_, V

CC

= 2.2V

MAX16024_TB_, SET = 1.2V

MAX16024_TB_, V

CC

> V

OUT

LDO = 1.2V

OUT

= 1mA

LDO = 1.8V

LDO = 2.5V

LDO = 3V

LDO = 3.3V

MIN

1.53

-0.01

1.144

-20

1.8

1.145

1.704

2.368

2.837

3.114

TYP

3.5

1.2

1.2

1.8

2.5

3

3.3

4.3

4.7

5.2

5.5

5.7

16

16

16

17

17

+0.01

1.272

+20

5.25

1.270

1.900

2.634

3.165

3.482

MAX

5.5

6

7

7.5

8

8

20

21

18.1

18.6

19

5.26

UNITS

V

µA

µA

µA

V nA

V

V

2 _______________________________________________________________________________________

Battery-Backup Circuits with

Regulated Output Voltage

ELECTRICAL CHARACTERISTICS (continued)

(V

CC

= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, T

A

= T

J

= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical values are at T

A

= T

J

= +25°C.) (Note 2)

PARAMETER MIN TYP MAX UNITS

Line Regulation

Load Regulation

Dropout Voltage

Output Current Limit

SYMBOL CONDITIONS

I

V

CC

= (V

OUT

+ 1V) to (V

OUT

+ 2V),

I

OUT

= 1mA

V

CC

= V

OUT

+ 1V, I

OUT

= 1mA to 2mA

LDO = 1.2V

OUT

= 50mA

(Note 4)

LDO = 1.8V

LDO = 2.5V

LDO = 3V

LDO = 3.3V

V

CC

= 1.6V

V

CC

≥ 2V

0.2

0.15

500

200

180

150

150

75

150

1.0

1.0

%/V

% mV mA

Battery Freshness Leakage

Current

RESET OUTPUT (

RESET)

Reset Threshold

V

CC

Falling to Reset Delay

Reset Timeout Period

RESET Output Low Voltage

V

TH t

RD t

RP

V

OL

V

BATT

= 5.5V

V

CC

falling at 10V/ms

V

CC

rising

V

OUT

= 3.3V, I

SINK

= 3.2mA, RESET asserted

V

OUT

= 1.8V, I

SINK

= 1mA, RESET asserted

V

OUT

= 1.2V, I

SINK

= 100µA, RESET asserted

V

CC

≥ 1.1 x V

TH

, I

SOURCE

= 100µA,

RESET deasserted

145

(See Table 1)

20

215 285

0.3

0.3

0.3

V

OUT

- 0.3V

10 nA

V

µs ms

V

V

RESET Output High Voltage

(Push-Pull Output)

V

OH

RESET Output Leakage Current

(Open-Drain Output)

POWER-FAIL COMPARATOR (PFI,

PFO)

PFI Input Threshold

PFI Input Hysteresis

PFI Input Current

V

PFT

V

PFI-HYS

I

PFI

PFO Output Low Voltage

V

RESET

= 5.5V, reset deasserted

V

PFI

falling, 1.6V ≤ V

CC

≤ 5.5V

V

OUT

= 1.8V, I

SINK

= 1mA, PFO asserted

V

OUT

=1.2V, I

SINK

= 100µA, PFO asserted

1

0.570

0.590

0.611

30

-1 +1

0.3

0.3

µA

V mV

µA

V

PFO Output High Voltage

(Push-Pull Output)

PFO Leakage Current

(Open-Drain Output)

PFO Delay Time

MANUAL RESET (

MR)

Input Low Voltage

Input High Voltage

Pullup Resistance

Glitch Immunity

MR to Reset Delay

V

IL

V

IH

I

SOURCE

= 100µA, PFO deasserted

V

PFO

= 5.5V, PFO deasserted

(V

PFI

+ 100mV) to (V

PFI

- 100mV)

Pullup resistance to V

CC

V

OUT

- 0.3V

20

0.7 x V

CC

20 30

100

120

1

0.3 x V

CC

V

µA

µs

V k

Ω ns ns

_______________________________________________________________________________________ 3

Battery-Backup Circuits with

Regulated Output Voltage

ELECTRICAL CHARACTERISTICS (continued)

(V

CC

= 1.53V to 5.5V, V

BATT

= 3V, reset not asserted, T

A

= T

J

= -40°C to +85°C, C

OUT

= 10µF, unless otherwise noted. Typical values are at T

A

= T

J

= +25°C.) (Note 2)

PARAMETER SYMBOL

BATTERY-ON INDICATOR (BATT ON)

CONDITIONS MIN TYP MAX UNITS

V

OUT

= 1.2V, I

SINK

= 100µA, BATT ON deasserted

0.3

Output Low Voltage V

OL

V

OUT

= 1.8V, I

SINK

= 1mA, BATT ON deasserted

V

OUT

= 3.3V, I

SINK

= 3.2mA, BATT ON deasserted

0.3

0.3

V

Output High Voltage

(Push-Pull Output)

Output Leakage Current

(Open-Drain Output)

V

OH

I

SOURCE

V

CC

= 100µA, BATT ON asserted

= 5.5V

V

OUT

- 0.3V

1

V

µA

Output Short-Circuit Current

Sink current, V

CC

= 5V

(Note 6)

60 mA

CE GATING (

CEIN, CEOUT)

CEIN Leakage Current

CEIN to CEOUT Resistance

CEOUT Short-Circuit Current

CEIN to CEOUT Propagation

Delay

Output High Voltage

Reset to CEOUT Delay

Reset asserted, V

V

CC

CC

= 0.9 x V

= 5V, reset deasserted

Reset asserted, CEOUT = 0

50

Ω source, C

LOAD

= 50pF, V

TH

CC

or 0

= 4.75V

-1

8

0.75

1.5

+1

50

2

7

µA

Ω mA ns

V

OH

I

SOURCE

= 100µA, reset asserted V

OUT

- 0.3V

12

V

µs

Note 2: All devices are 100% production tested at T

A

= +25°C and T

A

= +85°C. Limits over temperature are guaranteed by design.

Note 3: V

BATT can be 0 anytime or V

CC can 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 V

IN

= V

OUT

+ 1V.

Note 5: CEIN to CEOUT resistance is tested with V

CC

= 5V and V

CEIN

= 0 or 5V.

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

4 _______________________________________________________________________________________

Battery-Backup Circuits with

Regulated Output Voltage

Y

W

V

T

S

L

M

R

Z

Table 1. Reset Threshold Ranges

SUFFIX

RESET THRESHOLD RANGES (V)

MIN TYP MAX

4.508

4.264

4.63

4.38

4.906

4.635

2.991

2.845

2.549

2.243

3.08

2.93

2.63

2.32

3.239

3.080

2.755

2.425

2.117

1.603

1.514

2.19

1.67

1.575

2.288

1.733

1.639

Table 2. Fixed Output Voltage

SUFFIX

33

30

25

18

12

NOMINAL OUTPUT

VOLTAGE (V)

3.3

3.0

2.5

1.8

1.2

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 0, T

A

= +25°C, unless otherwise noted.)

Typical Operating Characteristics

25

20

15

10

5

0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

V

CC

SUPPLY VOLTAGE (V)

5.0

5.5

BATTERY SUPPLY CURRENT vs. TEMPERATURE

5

4

MAX16024PTBS25+

V

BATT

= +3.0V

V

CC

= 0

3

2

1

0

-40

V

CC

SUPPLY CURRENT vs. V

CC

SUPPLY VOLTAGE

MAX16024PTBS25+

V

OUT

= 2.5V

V

TH

= 2.93V

-15 10 35

TEMPERATURE (

°C)

60 85

10

8

6

4

2

0

-2

-4

-6

-8

-10

-40

10

9

8

7

6

5

4

3

2

1

0

-40

V

CC

SUPPLY CURRENT vs. TEMPERATURE

MAX16024PTBS25+

V

OUT

= 2.5V

V

TH

= 2.93V

-15 10 35

TEMPERATURE (

°C)

60

BATT STANDBY CURRENT vs. TEMPERATURE

V

CC

= 3.3V

V

BATT

= 3.0V

85

-15 10 35

TEMPERATURE (

°C)

60 85

1.0

0

0 0.5

1.0

1.5

2.0

2.5

V

CC

SUPPLY VOLTAGE (V)

3.0

RESET OUTPUT VOLTAGE LOW vs. SINK CURRENT

3.5

MAX16024PTBS25+

0.8

0.6

0.4

0.2

6

5

4

3

2

1

BATT SUPPLY CURRENT vs. V

CC

SUPPLY VOLTAGE

MAX16024PTBS25+

V

OUT

V

TH

= 2.5V

= 2.93V

V

BATT

= 3.0V

V

BATT

= 2.8V

0

0 2 4 6 8 10 12 14

SINK CURRENT (mA)

16 18 20

_______________________________________________________________________________________ 5

Battery-Backup Circuits with

Regulated Output Voltage

Typical Operating Characteristics (continued)

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 0, T

A

= +25°C, unless otherwise noted.)

100

90

80

70

60

50

40

30

20

10

0

-40

V

CC

FALLING TO RESET DELAY vs. TEMPERATURE

V

CC

FALLING 10V/ms

-15 10 35

TEMPERATURE (

°C)

60 85

RESET TIMEOUT PERIOD vs. TEMPERATURE

220

215

210

205

200

195

190

185

180

-40 -15 10 35

TEMPERATURE (

°C)

60 85

1.020

1.015

1.010

1.005

1.000

0.995

0.990

0.985

0.980

-40

NORMALIZED RESET THRESHOLD vs. TEMPERATURE

MAX16024PTBS25+

V

OUT

= 2.5V

-15 10 35

TEMPERATURE (

°C)

60 85

200

175

150

125

100

75

50

25

0

0

MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE

RESET OCCURS ABOVE THE CURVE

200 400 600 800

RESET THRESHOLD OVERDRIVE (mV)

1000

DROPOUT VOLTAGE vs. LOAD CURRENT

500

450

400

350

300

250

200

150

100

50

0

0

MAX16024PTBS25+

10 20 30 40 50 60 70

LOAD CURRENT (mA)

80 90 100

OUTPUT VOLTAGE vs. LOAD CURRENT

2.70

2.66

2.62

2.58

2.54

2.50

2.46

2.42

2.38

2.34

2.30

0

T

A

= -40

T

A

°C

= +85

MAX16024PTBS25+

°C

T

A

V

OUT

= +25

= 2.5V

°C

10 20 30 40 50 60 70

LOAD CURRENT (mA)

80 90 100

6 _______________________________________________________________________________________

Battery-Backup Circuits with

Regulated Output Voltage

Typical Operating Characteristics (continued)

(V

CC

= 5V, V

BATT

= 0, I

OUT

= 0, T

A

= +25°C, unless otherwise noted.)

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

0 1

OUTPUT VOLTAGE vs. V

CC

VOLTAGE

MAX16024PTBS25+

I

OUT

= 0

2 3

V

CC

VOLTAGE (V)

4 5 6

LOAD-TRANSIENT RESPONSE

MAX16023 toc14

C

OUT

= 10

μF

OUT

AC-COUPLED

100mV/div

50mA

I

OUT

20mA/div

10mA

1ms/div

MAX16024PTBS25+

STARTUP RESPONSE

MAX16023 toc15

V

CC

2V/div

2ms/div

MAX16024PTBS25+

I

OUT

= 0

OUT

1V/div

MR FALLING TO RESET DELAY

MAX16023 toc16

200ns/div

MR

5V/div

RESET

5V/div

CHIP-ENABLE LOCKING OUT

SIGNAL DURING RESET

MAX16023 toc17

RESET

5V/div

CEIN

2V/div

CEOUT

2V/div

40

μs/div

_______________________________________________________________________________________ 7

Battery-Backup Circuits with

Regulated Output Voltage

Pin Description

MAX16023

1

PIN

MAX16024

2

2 3

3

4

5

6

7

8

4

7

8

9

1

5

6

10

NAME

V

CC

BATT

MR

PFI

PFO

GND

RESET

OUT

CEIN

SET

BATT ON

CEOUT

EP

FUNCTION

Supply Voltage Input. Bypass V

CC to GND with a 0.1µF capacitor.

Backup Battery Input. If V

CC

falls below its reset threshold (V

TH

), V

BATT

≥ V

CC

, and if the regulator enters dropout, the regulator is powered from BATT. If V

BATT

< V

CC

, the regulator is powered from V

CC

. Bypass BATT to GND with a 0.1µF capacitor.

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

CC through a 30k

Ω pullup resistor.

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

PFT

threshold. A V

PFT-HYS internal hysteresis provides noise immunity. The power-fail comparator is powered from OUT.

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

PFI

falls below the internal V

PFT

threshold and goes high when V

PFI

rises above V

PFT

+ V

PFT-HYS hysteresis.

Ground

Active-Low Reset Output. RESET asserts when V

CC falls below the reset threshold or

MR is pulled low. RESET remains low for the duration of the reset timeout period after

V

CC

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

8 _______________________________________________________________________________________

V

CC

MR

PFI

MAX16023

BATT

Battery-Backup Circuits with

Regulated Output Voltage

Functional Diagrams

OUT

LDO

LOGIC

DROPOUT

OUT

RESET DELAY

OUT

REF

RESET

PFO

GND

_______________________________________________________________________________________ 9

Battery-Backup Circuits with

Regulated Output Voltage

Functional Diagrams (continued)

BATT

V

CC

LDO

OUT

SET

MR

LOGIC

DROPOUT

RESET DELAY

V

CC

REF

CE OUTPUT

CONTROL

BATT ON

RESET

CEIN

MAX16024

CEOUT

GND

10 ______________________________________________________________________________________

Detailed Description

The Typical Applications Circuit shows a typical connection using the MAX16024. OUT powers the SRAM. If

V

CC is higher than the reset threshold (V

TH

), or if V

CC is lower than V

TH but higher than V

BATT

, the regulator is powered from V

CC

. If V

CC

< V

TH

, V

CC

< V

BATT

, and the regulator is in dropout, the regulator is powered from

BATT (see the Functional Diagrams). OUT supplies up to 100mA from V

CC

.

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) V

CC is lower than the reset threshold.

2) V

CC is lower than V

BATT

.

3) The regulator is in dropout (except for the 1.2V output version).

Battery-Backup Circuits with

Regulated Output Voltage

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.

V

CC

RESET THRESHOLD V

TH

CEIN

CEOUT

RESET-TO-CEOUT DELAY (12

μs) t

RD

RESET t

RP t

RD

* t

RP

*

IF CEIN GOES HIGH BEFORE RESET ASSERTS,

CEOUT GOES HIGH WITHOUT DELAY AS

CEIN GOES HIGH.

Figure 1. Reset and Chip-Enable Timing

______________________________________________________________________________________ 11

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 (t

RP has an internal 30k

Ω pullup resistor to V

CC

). MR

. 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 V

CC 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 V

CC has come up for the first time, setting the latch. When V

CC subsequently turns off,

BATT begins to power OUT.

To reenable the freshness seal (MAX16023/

MAX16024):

1) Connect a battery to BATT.

2) Bring V

CC to 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 V

CC is below the reset threshold and remains low for at least 145ms (t

RP

) after V

CC rises

1.53 TO 5.5V

0.1

μF

TO

μP 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 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.

V

CC

RESET

MAX16024

GND

OUT

SET

R1

R2

1.8V TO 5.25V

10

μF

V

OUT

= V

SET

(1 + R1/R2)

V

SET

= 1.2V

Figure 2. Setting the Adjustable Output Voltage (MAX16024

Only)

12 ______________________________________________________________________________________

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 V

CC 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 V

CC

. Connect the bottom of the resistive divider to the negative voltage to be monitored.

Battery-Backup Circuits with

Regulated Output Voltage

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 50k

Ω to prevent it from loading down PFO.

Capacitor C1 adds additional noise rejection.

R1

R2

V

2

V

1

0.1

μF

V

CC

RESET

PFI

MAX16023L

PFO

MR

GND

RESET

μP

ADDITIONAL SUPPLY RESET VOLTAGE

V

2(RESET)

= V

PFT

x

( )

R2

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

5V

0.1

μF

R1

V

CC

PFI PFO

R2

MAX16023

V-

GND

PFO

+5V

0

V

TRIP

Figure 4. Monitoring a Negative Supply

0

V

TRIP

= V

PFT

R2

R2

(

5 - V

PFT

)

V

TRIP

IS NEGATIVE

V-

______________________________________________________________________________________ 13

Battery-Backup Circuits with

Regulated Output Voltage

R1

R2

V

IN

C1*

R3

TO

μP

PFI

PFO

+5V

V

CC

MAX16023

GND

0.1

μF

V

TRIP

= V

PFT

x

( )

V

H

=

(

V

PFT

+ V

PFT - HYS

) x

(

+ + 1

)

R2

R1

R3

V

L

= R1 x

(

-

)

+ V

PFT

R2

V

CC

- V

PFT

R3

WHERE V

PFT

IS THE POWER-FAIL

THRESHOLD VOLTAGE.

Replacing the Backup Battery

When V

CC is above V

TH

, 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 V

CC

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 V

CC pin 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.

PFO

+5V

0

V

L

V

TRIP

V

H

V

IN

*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

OUTPUT

TYPE

MAX16023LTAL12+T Push-Pull

MAX16023LTAL18+T

MAX16023LTAL25+T

MAX16023LTAL33+T

MAX16023LTAM12+T

MAX16023LTAM18+T

MAX16023LTAM25+T

MAX16023LTAM33+T

MAX16023LTAT12+T

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

MAX16023LTAT18+T

MAX16023LTAT25+T

Push-Pull

Push-Pull

MAX16023LTAS12+T Push-Pull

MAX16023LTAS18+T Push-Pull

MAX16023LTAS25+T

MAX16023LTAR12+T

MAX16023LTAR18+T

MAX16023LTAR25+T

MAX16023LTAZ12+T

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Part Number Table

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)

4.63

3.08

3.08

2.93

2.93

2.93

2.63

2.63

2.63

2.32

4.63

4.63

4.63

4.38

4.38

4.38

4.38

3.08

1.2

2.5

1.2

1.8

2.5

1.2

1.8

2.5

1.2

1.8

1.8

2.5

3.3

1.2

1.8

2.5

3.3

1.2

PART

OUTPUT

TYPE

MAX16024LTBL12+T Push-Pull

MAX16024LTBL18+T

MAX16024LTBL25+T

Push-Pull

Push-Pull

MAX16024LTBL33+T Push-Pull

MAX16024LTBM12+T Push-Pull

MAX16024LTBM18+T Push-Pull

MAX16024LTBM25+T Push-Pull

MAX16024LTBM33+T Push-Pull

MAX16024LTBT12+T Push-Pull

MAX16024LTBT18+T

MAX16024LTBT25+T

MAX16024LTBS12+T

MAX16024LTBS18+T

MAX16024LTBS25+T

MAX16024LTBR12+T

MAX16024LTBR18+T

MAX16024LTBR25+T

MAX16024LTBZ12+T

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

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)

4.63

3.08

3.08

2.93

2.93

2.93

2.63

2.63

2.63

2.32

4.63

4.63

4.63

4.38

4.38

4.38

4.38

3.08

1.2

2.5

1.2

1.8

2.5

1.2

1.8

2.5

1.2

1.8

1.8

2.5

3.3

1.2

1.8

2.5

3.3

1.2

14 ______________________________________________________________________________________

Battery-Backup Circuits with

Regulated Output Voltage

Part Number Table (continued)

PART

OUTPUT

TYPE

MAX16023LTAZ18+T

MAX16023LTAY12+T

MAX16023LTAY18+T

MAX16023LTAW12+T

Push-Pull

Push-Pull

Push-Pull

Push-Pull

MAX16023LTAV12+T Push-Pull

MAX16023PTAL12+T Open-Drain

MAX16023PTAL18+T Open-Drain

MAX16023PTAL25+T Open-Drain

MAX16023PTAL33+T Open-Drain

MAX16023PTAM12+T Open-Drain

MAX16023PTAM18+T Open-Drain

MAX16023PTAM25+T Open-Drain

MAX16023PTAM33+T Open-Drain

MAX16023PTAT12+T Open-Drain

MAX16023PTAT18+T Open-Drain

MAX16023PTAT25+T Open-Drain

MAX16023PTAS12+T Open-Drain

MAX16023PTAS18+T Open-Drain

MAX16023PTAS25+T Open-Drain

MAX16023PTAR12+T Open-Drain

MAX16023PTAR18+T Open-Drain

MAX16023PTAR25+T Open-Drain

MAX16023PTAZ12+T Open-Drain

MAX16023PTAZ18+T Open-Drain

MAX16023PTAY12+T Open-Drain

MAX16023PTAY18+T Open-Drain

MAX16023PTAW12+T Open-Drain

MAX16023PTAV12+T Open-Drain

MAX16024PTBL+T Open-Drain

MAX16024PTBM+T

MAX16024PTBT+T

MAX16024PTBS+T

Open-Drain

Open-Drain

Open-Drain

MAX16024PTBR+T

MAX16024PTBZ+T

MAX16024PTBY+T

MAX16024PTBW+T

MAX16024PTBV+T

Open-Drain

Open-Drain

Open-Drain

Open-Drain

Open-Drain

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)

2.32

2.19

2.19

1.67

1.575

4.63

4.63

4.63

4.63

4.38

4.38

4.38

4.38

3.08

3.08

3.08

2.93

2.93

2.93

2.63

2.63

2.63

2.32

2.32

2.19

2.19

1.67

1.575

4.63

4.38

3.08

2.93

2.63

2.32

2.19

1.67

1.575

PART

OUTPUT

TYPE

1.2

1.2

1.8

2.5

1.8

1.2

1.8

1.2

MAX16024LTBZ18+T Push-Pull

MAX16024LTBY12+T Push-Pull

MAX16024LTBY18+T Push-Pull

MAX16024LTBW12+T Push-Pull

MAX16024LTBV12+T Push-Pull

MAX16024PTBL12+T Open-Drain

MAX16024PTBL18+T Open-Drain

MAX16024PTBL25+T Open-Drain

3.3

1.2

1.8

2.5

3.3

1.2

1.8

2.5

MAX16024PTBL33+T Open-Drain

MAX16024PTBM12+T Open-Drain

MAX16024PTBM18+T Open-Drain

MAX16024PTBM25+T Open-Drain

4.63

4.38

4.38

4.38

MAX16024PTBM33+T Open-Drain

MAX16024PTBS12+T Open-Drain

4.38

3.08

MAX16024PTBS18+T Open-Drain 3.08

MAX16024PTBS25+T O p e n - D r a i n 3.08

2.93

2.93

2.93

1.2

1.8

MAX16024PTBT12+T Open-Drain

MAX16024PTBT18+T Open-Drain

MAX16024PTBT25+T Open-Drain

2.5

1.2

1.8

2.5

1.2

1.8

1.2

1.8

1.2

MAX16024PTBR12+T Open-Drain

MAX16024PTBR18+T Open-Drain

MAX16024PTBR25+T

MAX16024PTBZ12+T

Open-Drain

Open-Drain

MAX16024PTBZ18+T Open-Drain

MAX16024PTBY12+T Open-Drain

MAX16024PTBY18+T

MAX16024PTBW12+T

Open-Drain

Open-Drain

1.2

MAX16024PTBV12+T Open-Drain

Adjustable MAX16024LTBL+T Push-Pull

Adjustable

Adjustable

Adjustable

MAX16024LTBM+T

MAX16024LTBT+T

MAX16024LTBS+T

Push-Pull

Push-Pull

Push-Pull

2.63

2.63

2.63

2.32

2.32

2.19

2.19

1.67

1.575

4.63

4.38

3.08

2.93

Adjustable MAX16024LTBR+T

Adjustable MAX16024LTBZ+T

Adjustable MAX16024LTBY+T

Adjustable MAX16024LTBW+T

Adjustable MAX16024LTBV+T

Push-Pull

Push-Pull

Push-Pull

Push-Pull

Push-Pull

2.32

2.19

2.19

1.67

1.575

4.63

4.63

4.63

2.63

2.32

2.19

1.67

1.575

Bold parts denote standard versions. Samples are generally available on standard versions.

Contact factory for availability of nonstandard versions.

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)

1.2

Adjustable

Adjustable

Adjustable

Adjustable

Adjustable

Adjustable

Adjustable

Adjustable

Adjustable

1.8

1.2

1.8

1.2

1.2

1.8

2.5

1.2

3.3

1.2

1.8

2.5

3.3

1.2

1.8

2.5

1.2

1.8

2.5

1.2

1.2

1.8

2.5

1.8

1.2

1.8

1.2

______________________________________________________________________________________ 15

Battery-Backup Circuits with

Regulated Output Voltage

PART

MAX16023L

MAX16023P

MAX16024L

MAX16024P

OUTPUTS

(

RESET, PFO,

BATT ON )

Push-Pull

Open Drain

Push-Pull

Open Drain

RESET

MR

POWER-FAIL

COMPARATOR

CE

GATE

Selector Guide

BATT ON

REGULATOR

OUTPUT VOLTAGE

Fixed

Fixed

Fixed/adjustable

Fixed/adjustable

Typical Applications Circuit

3.3V

3V

0.1

μF

PUSHBUTTON

0.1

μF

V

CC

RESET

BATT

MR

BATT ON

MAX16024L

OUT

10

μF

CEOUT

SET

GND

CEIN

ADDRESS

DECODE

RAM

CE

V

CC

RST

μP

A0–A15

0.1

μF

RTC

16 ______________________________________________________________________________________

PROCESS: BiCMOS

Battery-Backup Circuits with

Regulated Output Voltage

Chip Information

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

10 TDFN

T833-2

T1033-1

21-0137

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.

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