MAX16033–MAX16040 Low-Power Battery

MAX16033–MAX16040 Low-Power Battery

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

General Description

The MAX16033–MAX16040 supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery-control functions in microprocessor (μP) systems. The devices significantly improve system reliability and accuracy compared to other

ICs or discrete components. The MAX16033–MAX16040 provide μP reset, backup-battery switchover, power-fail warning, watchdog, and chip-enable gating features.

The MAX16033–MAX16040 operate from supply voltages up to 5.5V. The factory-set reset threshold voltage ranges from 2.32V to 4.63V. The devices feature a manual-reset input (MAX16033/MAX16037), a watchdog timer input (MAX16034/MAX16038), a battery-on output

(MAX16035/MAX16039), an auxiliary adjustable-reset input (MAX16036/MAX16040), and chip-enable gating

(MAX16033–MAX16036). Each device includes a powerfail comparator and offers an active-low push-pull reset or an active-low open-drain reset.

The MAX16033–MAX16040 are available in 2mm x 2mm,

8-pin or 10-pin μDFN packages and are fully specified from -40°C to +85°C.

Features

● Low 1.2V Operating Supply Voltage

● Precision Monitoring of 5.0V, 3.3V, 3.0V, and 2.5V

Power-Supply Voltages

● Independent Power-Fail Comparator

● Debounced Manual-Reset Input

● Watchdog Timer, 1.6s Timeout

● Battery-On Output Indicator

● Auxiliary User-Adjustable RESETIN

● Low 13μA Quiescent Supply Current

● Two Available Output Structures:

Active-Low Push-Pull Reset

Active-Low Open-Drain Reset

● Active-Low Reset Valid Down to 1.2V

● Power-Supply Transient Immunity

● 140ms (min) Reset Timeout Period

● Small 2mm x 2mm, 8-Pin and 10-Pin μDFN Paclages

Ordering Information

PART*

MAX16033LLB_ _+T

MAX16033PLB_ _+T

TEMP RANGE PIN-PACKAGE

-40°C to +85°C 10 µDFN

-40°C to +85°C 10 µDFN

Applications

● Portable/Battery-

Powered Equipment

● POS Equipment

● Critical μP/μC Power

Monitoring

● Set-Top Boxes

● Controllers

● Computers

● Fax Machines

● Industrial Control

● Real-Time Clocks

● Intelligent Instrument

MAX16034LLB_ _+T

MAX16034PLB_ _+T

*These parts offer a choice of reset threshold voltages. From the Reset Threshold Ranges table, insert the desired threshold voltage code in the blank to complete the part number. See the

Selector Guide for a listing of device features.

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Ordering Information continued on last page.

Pin Configurations and Typical Operating Circuit appear at end of data sheet

Selector Guide

PART

MAX16033_

MR

ü

WATCHDOG BATTON RESETIN

CEIN/CEOUT

MAX16034_

MAX16035_

MAX16036_

MAX16037_

MAX16038_

ü

ü

ü

ü

ü

MAX16039_

MAX16040_

ü

ü

Note: Replace “_” with L for push-pull or P for open-drain RESET and PFO outputs.

ü

ü

ü

ü

-40°C to +85°C 10 µDFN

-40°C to +85°C 10 µDFN

PFI, PFO

ü

ü

ü

ü

ü

ü

ü

ü

PIN-PACKAGE

10 µDFN-10

10 µDFN-10

10 µDFN-10

10 µDFN-10

8 µDFN-8

8 µDFN-8

8 µDFN-8

8 µDFN-8

19-0882; Rev 1; 5/14

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Absolute Maximum Ratings

Terminal Voltages (with respect to GND)

V

CC

, BATT, OUT.......................................................-0.3V to +6V

RESET (open drain), PFO (open drain) ....................-0.3V to +6V

RESET (push-pull), PFO (push-pull), BATTON, RESETIN, WDI

+ 0.3V) MR, CEIN, CEOUT, PFI...........................-0.3V to (V

OUT

Input Current

V

CC

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

V

CC

Continuous............................................................250mA

BATT Peak....................................................................250mA

BATT Continuous............................................................40mA

GND................................................................................75mA

Output Current

OUT..................................Short-Circuit Protected for up to 5s

RESET, BATTON............................................................20mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin μDFN (derate 4.8mW/°C above +70°C)..........380.6mW

10-Pin μDFN (derate 5mW/°C above +70°C)...........402.8mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

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

= 2.25V to 5.5V, V

BATT

= 3V, RESET not asserted, T

A otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

= -40°C to +85°C, for MAX16039PLA31+T, T

A

= -55°C to +85°C, unless

PARAMETER

Operating Voltage Range

Supply Current

Supply Current in Battery

Backup Mode

BATT Standby Current (Note 3)

V

CC

to OUT On-Resistance

Output Voltage in Battery

Backup Mode

Battery-Switchover Threshold

SYMBOL

V

CC

, V

BATT

I

CC

I

BATT

R

ON

V

OUT

V

SW

No load (Note 2)

CONDITIONS

No load, V

V

V

BATT

CC

= 0V, excluding I

CC

> V

= 2.8V,

OUT

TH

V

CC

= 2.8V

V

CC

= 3.6V

V

CC

= 5.5V

T

A

= +25°C

T

A

= -40°C to +85°C

T

A

= -55°C

(MAX16039PLA31+T only)

(V

BATT

< 5.5V

+ 0.2V) < V

CC

T

A

= +25°C

T

A

= -40°C to +85°C

V

CC

= 4.75V, V

CC

> V

TH

, I

OUT

= 150mA

V

CC

= 3.15V, V

CC

> V

TH

, I

OUT

= 65mA

V

CC

= 2.5V, V

CC

> V

TH

, I

OUT

= 25mA

V

BATT

= 4.50V, V

CC

= 0V, I

OUT

= 20mA

V

BATT

= 3.15V, V

CC

= 0V, I

OUT

= 10mA

V

BATT

= 2.5V, V

CC

= 0V, I

OUT

= 5mA

V

V

CC

CC

- V

< V

BATT

TH

,

V

CC

rising

V

CC

falling

MIN

0

-0.1

-0.3

TYP

V

BATT

- 0.2

V

BATT

- 0.15

V

BATT

- 0.15

0

-40

13

16

22

+0.02

+0.02

3.1

3.7

4.6

MAX UNITS

5.5

V

30

35

50

µA

1

2

µA

10

µA

V mV www.maximintegrated.com

Maxim Integrated │

2

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Electrical Characteristics (continued)

(V

CC

= 2.25V to 5.5V, V

BATT

= 3V, RESET not asserted, T

A otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

= -40°C to +85°C, for MAX16039PLA31+T, T

A

= -55°C to +85°C, unless

PARAMETER

RESET OUTPUT

SYMBOL CONDITIONS MIN TYP MAX UNITS

Reset Threshold

V

CC

Falling Reset Delay

Reset Active Timeout Period

RESET Output Low Voltage

RESET Output High Voltage

V

TH t

RP

V

OL

V

OH

MAX160_ _ _L_46

MAX160_ _ _L_44

MAX160_ _ _L_31

MAX160_ _ _L_29

MAX160_ _ _L_26

MAX160_ _ _L_23

V

CC

falling at 10V/ms

RESET asserted

I

SINK

= 1.6mA, V

CC

≥ 2.1V

I

SINK

= 100µA, V

CC

> 1.2V

MAX160_ _L only (push-pull), RESET not asserted, I

SOURCE

= 500µA, V

CC

> V

TH(MAX)

4.50

4.25

3.00

2.85

2.55

2.25

140

0.8 x

V

CC

4.63

4.38

3.08

2.93

2.63

2.32

25

4.75

4.50

3.15

3.00

2.70

2.38

280

0.3

0.4

V

µs ms

V

V

RESET Output Leakage

Current

POWER-FAIL COMPARATOR

PFI Input Threshold

PFI Hysteresis

PFI Input Current

PFO Output Low Voltage

PFO Output High Voltage

PFO Leakage Current

I

LKG

V

PFI

V

OL

V

OH

MAX160_ _P only (open drain), not asserted

V

PFI

falling

V

PFI

= 0V or V

CC

Output asserted

V

CC

> 2.1V, I

SINK

= 1.6mA

V

CC

> 1.2V, I

SINK

= 100µA

MAX160_ _L only (push-pull), V

V

TH(MAX), asserted

I

SOURCE

CC

>

= 500µA, output not

MAX160_ _P only (open drain), V

PFO not asserted

= 5.5V,

V

PFI

+ 100mV to V

PFI

- 100mV

1.185

1.235

1.285

1

-100 +100

0.3

0.4

0.8 x

V

CC

4

1

1

µA

V

% nA

V

V

µA

µs PFO Delay Time

MANUAL RESET (MAX16033/MAX16037)

MR Input Voltage

V

IL

V

IH

Pullup Resistance to V

CC

Minimum Pulse Width

Glitch Immunity

MR to Reset Delay

V

CC

= 3.3V

0.7 x V

CC

20

1

100

120

0.3 x V

CC

165

V kΩ

µs ns ns www.maximintegrated.com

Maxim Integrated │

3

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Electrical Characteristics (continued)

(V

CC

= 2.25V to 5.5V, V

BATT

= 3V, RESET not asserted, T

A otherwise noted. Typical values are at T

A

= +25°C.) (Note 1)

= -40°C to +85°C, for MAX16039PLA31+T, T

A

= -55°C to +85°C, unless

PARAMETER SYMBOL

WATCHDOG (MAX16034/MAX16038)

Watchdog Timeout Period

Minimum WDI Input Pulse Width

WDI Input Voltage t

WD t

WDI

V

IL

V

IH

WDI Input Current

BATTON (MAX16035/MAX16039)

Output Voltage V

OL

(Note 4)

CONDITIONS

Output Short-Circuit Current

I

SINK

= 3.2mA, V

BATT

= 2.1V

Sink current, V

CC

= 5V

Source current, V

BATT

> 2V

RESETIN (MAX16036/MAX16040)

RESETIN Threshold

RESETIN Input Current

V

RTH

RESETIN to Reset Delay (V

RTH

+ 100mV) to (V

RTH

- 100mV)

CHIP-ENABLE GATING (MAX16033–MAX16036)

CEIN Leakage Current RESET asserted

MIN

1.00

100

0.7 x V

-1.0

10

1.185

CC

TYP

1.65

60

30

1.235

0.01

1.5

MAX

2.25

0.3 x V

25

CC

+1.0

0.4

120

1.285

±1

CEIN to CEOUT Resistance

CEOUT Short-Circuit Current

CEIN to CEOUT Propagation

Delay (Note 4)

CEOUT Output-Voltage High

RESET not asserted, V

CC

V

CEIN

= V

CC

/2, I

SINK

= V

= 10mA

TH(MAX),

RESET asserted, V

CEOUT

= 0V

50Ω source impedance driver,

C

LOAD

= 50pF

V

CC

= 4.75V

V

CC

= 3.15V

V

CC

= 5V, V

CC

> V

BATT

, I

SOURCE

= 100µA

V

CC

= 0V, V

BATT

> 2.2V, I

SOURCE

= 1µA

0.7 x V

CC

V

BATT

- 0.1

1

1.5

2

RESET to CEOUT Delay 1

Note 1: All devices are 100% production tested at T

Note 2: V

BATT

can be 0V any time, or V

CC

= +25°C. All overtemperature limits are guaranteed by design.

can go down to 0V if V

BATT

is active (except at startup).

Note 3: Positive current flows into BATT.

Note 4: Guaranteed by design.

A

100

2.0

7

9

UNITS

s ns

V

µA

V mA

µA

V nA

µs

µA

Ω mA ns

V

µs www.maximintegrated.com

Maxim Integrated │

4

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Typical Operating Characteristics

(T

A

= +25°C, unless otherwise noted.)

1.4

1.2

20

19

18

17

16

15

14

13

12

11

10

-40

V

CC

= 5V

-15

V

CC

SUPPLY CURRENT vs. TEMPERATURE

10 35

TEMPERATURE (°C)

vs. TEMPERATURE

I

V

CC

OUT

= 2.5V

= 25mA

60

-TO-OUT ON-RESISTANCE

1.0

0.8

0.6

I

V

CC

OUT

= 3V

= 65mA

I

V

CC

OUT

0.4

0.2

0

-40 -25 -10 5 20 35 50

TEMPERATURE (°C)

= 4.5V

= 150mA

65 80

85

1.003

1.002

1.001

1.000

0.999

0.998

0.997

0.996

0.995

0.994

0.993

0.992

0.991

0.990

-40

NORMALIZED RESET THRESHOLD vs. TEMPERATURE

-20 0 20 40

TEMPERATURE (°C)

60 80

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

-40

BATTERY SUPPLY CURRENT

(BACKUP MODE) vs. TEMPERATURE

V

BATT

V

CC

= 3V

= 0V

-15 10 35

TEMPERATURE (°C)

60 85

RESET TIMEOUT PERIOD vs. TEMPERATURE

230

225

220

215

210

205

200

195

190

185

180

-40

V

CC

= 5V

-15 10 35

TEMPERATURE (°C)

60 85

300

250

BATT-TO-OUT ON-RESISTANCE

1.0

9

8

7

6

5

4

3

2

1

0

-40

V

CC

= 0V

-15

vs. TEMPERATURE

V

BATT

= 3V

V

BATT

= 2V

V

BATT

= 5V

10 35

TEMPERATURE (°C)

60 85

120

105

90

75

60

45

30

15

0

-40

V

CC

-TO-RESET PROPAGATION DELAY vs. TEMPERATURE

V

CC

FALLING

0.25V/ms

-20

1V/ms

10V/ms

0 20 40

TEMPERATURE (°C)

60 80

MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE

RESET OCCURS

ABOVE CURVE

200

150

100

50

MAX160_ _-46

(V

TH

= 4.63V)

MAX160_ _-29

(V

TH

= 2.93V)

0

1 10 100 1000 10,000

RESET THRESHOLD OVERDRIVE (V

TH

- V

CC

) (mV) www.maximintegrated.com

Maxim Integrated │

5

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Typical Operating Characteristics (continued)

(T

A

= +25°C, unless otherwise noted.)

BATTERY SUPPLY CURRENT vs. SUPPLY VOLTAGE

2.00

1.75

1.50

1.25

1.00

V

TH

= 2.93V

V

BATT

V

BATT

= 2.5V

= 2.8V

0.75

0.50

0.25

0

-0.25

0

V

BATT

= 2.3V

0.5

1.0 1.5 2.0 2.5

3.0 3.5

SUPPLY VOLTAGE (V)

4.0

4.5

5.0

3.0

2.5

2.0

1.5

1.0

0.5

0

0

CEIN PROPAGATION DELAY vs. CEOUT LOAD CAPACITANCE

V

CC

= 3V

V

CC

= 5V

25 50 75 100 125 150

CEOUT LOAD CAPACITANCE (pF)

175

0

-40

PFI-TO-PFO DELAY vs. TEMPERATURE

5.00

4.75

4.50

4.25

4.00

3.75

3.50

3.25

3.00

2.75

2.50

2.25

2.00

-40

FALLING EDGE

-15 10 35

TEMPERATURE (°C)

V

OD

= 30mV

60 85

20

15

10

5

30

25

1.250

1.245

1.240

1.235

1.230

1.225

1.220

1.215

1.210

-40

RESETIN THRESHOLD vs. TEMPERATURE

MAX16036/

MAX16040

-15 10 35

TEMPERATURE (°C)

60

CEIN TO CEOUT ON-RESISTANCE vs. TEMPERATURE

35

85

V

CC

= 3V

V

CC

= 5V

-15 10 35

TEMPERATURE (°C)

60 85

1.250

1.245

1.240

1.235

1.230

1.225

1.220

1.215

1.210

-40 -15 10 35

TEMPERATURE (°C)

60

3.0

2.8

2.5

2.3

2.0

1.8

1.5

1.3

1.0

-40

RESETIN-TO-RESET PROPAGATION

DELAY vs. TEMPERATURE

MAX16036/

MAX16040

V

OD

= 50mV

-15 10 35

TEMPERATURE (°C)

60 85

WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

-40

V

CC

= 5V

-15 10 35

TEMPERATURE (°C)

60 85

PFI THRESHOLD vs. TEMPERATURE

85 www.maximintegrated.com

Maxim Integrated │

6

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Pin Description

PIN

MAX16033–

MAX16036

(10-pin µDFN)

MAX16037–

MAX16040

(8-pin µDFN)

NAME

1

5

6

7

8

2

3

4

9

10

1

5

6

7

2

3

4

8

FUNCTION

RESET

CEIN

PFI

GND

MR

WDI

BATTON

RESETIN

PFO

V

CC

OUT

BATT

CEOUT

Active-Low Reset Output. RESET remains low when V threshold (V

TH

CC

is below the reset

), the manual-reset input is low, or RESETIN is low. It asserts low in pulses when the internal watchdog times out. RESET remains low for the reset timeout period (t

RP

) after V

CC

rises above the reset threshold, after the manualreset input goes from low to high, after RESETIN goes high, or after the watchdog triggers a reset event. The MAX160_ _L is an active-low push-pull output, while the

MAX160_ _P is an active-low open-drain output.

Chip-Enable Input. The input to the chip-enable gating circuit. Connect to GND or

OUT if not used.

Power-Fail Input. PFO goes low when V

PFI

falls below 1.235V.

Ground

Manual-Reset Input (MAX16033/MAX16037). Driving MR low asserts RESET.

RESET remains asserted as long as MR is low and for the reset timeout period (t after MR transitions from low to high. Leave unconnected, or connect to V

CC used. MR has an internal 20kΩ pullup to V

CC

.

RP

if not

)

Watchdog Input (MAX16034/MAX16038). If WDI remains high or low for longer than the watchdog timeout period (t

WD

), the internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (t

RP

). The internal watchdog clears whenever RESET asserts or whenever WDI sees a rising or falling edge (Figure 2).

Battery-On Output (MAX16035/MAX16039). BATTON goes high during battery backup mode.

Reset Input (MAX16036/MAX16040). When RESETIN falls below 1.235V, RESET asserts. RESET remains asserted as long as RESETIN is low and for at least t after RESETIN goes high.

RP

Active-Low Power-Fail Output. PFO goes low when V stays low until V

PFI

falls below 1.235V. PFO

goes above 1.235V. PFO also goes low when V

CC

falls below the reset threshold voltage.

PFI

Supply Voltage, 1.2V to 5.5V

Output. OUT sources from V of V

CC

or BATT when V

CC

CC

when RESET is not asserted and from the greater

is below the reset threshold voltage.

Backup-Battery Input. When V

CC to BATT if V

BATT switches to V

CC slowly.

falls below the reset threshold, OUT switches

is 40mV greater than V

CC

. When V

CC

rises above V

BATT

. The 40mV hysteresis prevents repeated switching if V

CC

, OUT

falls

Chip-Enable Output. CEOUT goes low only when CEIN is low and reset is not asserted. When CEOUT is disconnected from CEIN, CEOUT is actively pulled up to OUT.

www.maximintegrated.com

Maxim Integrated │

7

MAX16033–MAX16040

Pin Description (continued)

Low-Power Battery-Backup

Circuits in Small μDFN Packages

1.235V

BATTON (MAX16035/MAX16039 ONLY)

MAX16033

MAX16040

V

CC

BATT

CEIN

(MAX16033–MAX16036 ONLY)

MR

(MAX16033/MAX16037 ONLY)

WDI

(MAX16034/MAX16038 ONLY)

RESETIN

(MAX16036/MAX16040 ONLY)

1.235V

GND

CHIP-ENABLE

OUTPUT

CONTROL

WATCHDOG

TRANSITION

DETECTOR

RESET

GENERATOR

WATCHDOG

TIMER

PFI

1.235V

OUT

CEOUT

RESET

PFO www.maximintegrated.com

Maxim Integrated │

8

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Detailed Description

The Typical Operating Circuit shows a typical connection for the MAX16033–MAX16040. OUT powers the static random-access memory (SRAM). If V

CC than the reset threshold (V

V

TH

If V

but higher than V

CC

is lower than V

BATT

TH

TH

, V

), or if V

CC

CC

and V

CC

is greater

is lower than

is connected to OUT.

is less than V

BATT

,

BATT is connected to OUT. OUT supplies up to 200mA from V

CC

. In battery-backup mode, an internal MOSFET connects the backup battery to OUT. The on-resistance of the MOSFET is a function of the backup-battery voltage and temperature and is shown in the BATT-to-OUT

On-Resistance vs. Temperature graph in the Typical

Operating Characteristics.

Chip-Enable Signal Gating

(MAX16033–MAX16036 Only)

The MAX16033–MAX16036 provide internal gating of chip-enable (CE) signals to prevent erroneous data from being written to CMOS RAM in the event of a power failure or brownout condition. During normal operation, the

CE gate is enabled and passes all CE transitions. When reset asserts, this path becomes disabled, preventing erroneous data from corrupting the CMOS RAM. The

MAX16033–MAX16036 provide a series transmission gate from CEIN to CEOUT. A 2ns (typ) propagation delay from CEIN to CEOUT allows these devices to be used with most μPs and high-speed DSPs.

When RESET is deasserted, CEIN is connected to

CEOUT through a low on-resistance transmission gate. If

CEIN is high when RESET is asserted, CEOUT remains high regardless of any subsequent transitions on CEIN during the reset event.

If CEIN is low when RESET is asserted, CEOUT is held low for 1μs to allow completion of the read/write operation

(Figure 1). After the 1μs 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. The chipenable propagation delay is specified from the 50% point of CEIN to the 50% point of CEOUT, using a 50Ω driver and 50pF load capacitance. Minimize the capacitive load at CEOUT and use a low output-impedance driver to minimize propagation delay.

In high-impedance mode, the leakage current at CEIN is

±1μA (max) over temperature. In low-impedance mode, the impedance of CEIN appears as a 75Ω resistor in series with the load at CEOUT.

V

V

CC

TH

CEIN

CEOUT

*

RESET-TO-CEOUT DELAY t

RD t

RD t

RP t

RP

RESET

PFO

PFI > V

PFI

*

IF CEIN GOES HIGH BEFORE RESET ASSERTS,

CEOUT GOES HIGH WITHOUT DELAY AS CEIN GOES HIGH.

Figure 1. RESET and Chip-Enable Timing

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Maxim Integrated │

9

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Backup-Battery Switchover

To preserve the contents of the RAM in a brownout or power failure, the MAX16033–MAX16040 automatically switch to back up the battery installed at BATT when the following two conditions are met:

1) V

CC

falls below the reset threshold voltage.

2) V

CC

is below V

BATT

.

Table 1 lists the status of the inputs and outputs in batterybackup mode. The devices do not power up if the only voltage source is V

BATT at startup.

. OUT only powers up from V

CC

Table 1. Input and Output Status in

Battery-Backup Mode

PIN

V

CC

OUT

BATT

RESET

BATTON

MR, RESETIN,

CEIN, and WDI

CEOUT

PFO

STATUS

Disconnected from OUT

Connected to BATT

Connected to OUT. Current drawn from the battery is less than 1µA (at V excluding I

OUT

) when V

CC

BATT

= 0V.

= 2.8V,

Asserted

High state

Inputs ignored

Connected to OUT

Asserted

Manual-Reset Input

(MAX16033/MAX16037 Only)

Many μP-based products require manual-reset capability, allowing the user or external logic circuitry to initiate a reset. For the MAX16033/MAX16037, a logic-low on

MR asserts RESET. RESET remains asserted while MR is low and for a minimum of 140ms (t

RP

) after it returns high. MR has an internal 20kΩ (min) pullup resistor to

V

CC

. This input can be driven from TTL/CMOS logic outputs or with open-drain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manual-reset function; external debounce circuitry is not required. When driving MR from long cables, or when using the device in a noisy environment, connect a 0.1μF capacitor from MR to GND to provide additional noise immunity.

Watchdog Input

(MAX16034/MAX16038 Only)

The watchdog monitors μP activity through the watchdog input (WDI). RESET asserts when the μP fails to toggle

WDI. Connect WDI to a bus line or μP I/O line. A change of state (high to low, low to high, or a minimum 100ns pulse) resets the watchdog timer. If WDI remains high or low for longer than the watchdog timeout period (t

WD

), the internal watchdog timer runs out and triggers a reset pulse for the reset timeout period (t

RP

). The internal watchdog timer clears whenever RESET is asserted or whenever

WDI sees a rising or falling edge. If WDI remains in either a high or low state, a reset pulse periodically asserts after every watchdog timeout period (t

WD

); see Figure 2.

WDI t

WD

RESET t

WD t

RP

= WATCHDOG TIMEOUT PERIOD

= RESET TIMEOUT PERIOD t

RP t

WD t

RP

Figure 2. MAX16034/MAX16038 Watchdog Timeout Period and

Reset Active Time

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Maxim Integrated │

10

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

BATTON Indicator

(MAX16035/MAX16039 Only)

BATTON is a push-pull output that asserts high when in battery-backup mode. BATTON typically sinks 3.2mA at a 0.4V saturation voltage. In battery-backup mode, this terminal sources approximately 10μA from OUT. Use

BATTON to indicate battery-switchover status or to supply base drive to an external pass transistor for higher current applications (Figure 3).

RESETIN Comparator

(MAX16036/MAX16040 Only)

An internal 1.235V reference sets the RESETIN threshold voltage. RESET asserts when the voltage at RESETIN is below 1.235V. Use the RESETIN function to monitor a secondary power supply.

Use the following equations to set the reset threshold voltage (V

RTH

) of the secondary power supply (see Figure 4):

V

RTH

= V

REF

(R1/R2 + 1) where V

REF

= 1.235V. To simplify the resistor selection, choose a value for R2 and calculate R1:

R1 = R2 [(V

RTH

/V

REF

) - 1]

Since the input current at RESETIN is 25nA (max), large values (up to 1MΩ) can be used for R2 with no significant loss in accuracy.

Power-Fail Comparator

The MAX16033–MAX16040 issue an interrupt (nonmaskable or regular) to the μP when a power failure occurs.

The power line is monitored by two external resistors connected to the power-fail input (PFI). When the voltage at PFI falls below 1.235V, the power-fail output (PFO) drives the processor’s NMI input low. An earlier power-fail warning can be generated if the unregulated DC input of the regulator is available for monitoring. The MAX16033–

MAX16040 turn off the power-fail comparator and force

PFO low when V

CC

falls below the reset threshold voltage

(Figure 1). The MAX160_ _L devices provide push-pull

PFO outputs. The MAX160_ _P devices provide opendrain PFO outputs.

V

CC

R1

V

IN

R2

MAX16036

MAX16040

RESETIN

Figure 4. Setting RESETIN Voltage for the MAX16036/

MAX16040

2.4V TO 5.5V

0.1µF

V

CC

BATT

BATTON

OUT

(CEOUT)

MAX16035

MAX16039

(CEIN)

CE

GND RESET

( ) FOR MAX16035 ONLY

Figure 3. MAX16035/MAX16039 BATTON Driving an External Pass Transistor

ADDRESS

DECODE

CMOS RAM

A0–A15

µP

RESET www.maximintegrated.com

Maxim Integrated │

11

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

RESET

A μP’s reset input puts the μP in a known state.

The MAX16033–MAX16040 μP supervisory circuits assert a reset to prevent code-execution errors during power-up, power-down, and brownout conditions. RESET asserts when V

CC

is below the reset threshold voltage and for at least 140ms (t

RP

) after V

CC

rises above the reset threshold. RESET also asserts when MR is low (MAX16033/MAX16037) or when RESETIN is below 1.235V (MAX16036/MAX16040). The MAX16034/

MAX16038 watchdog function causes RESET to assert in pulses following a watchdog timeout (Figure 2). The

MAX160_ _L devices provide push-pull RESET outputs.

The MAX160_ _P devices provide open-drain RESET outputs.

Applications Information

Operation Without a Backup Power Source

The MAX16033–MAX16040 provide a battery-backup function. If a backup power source is not used, connect

BATT to GND and OUT to V

CC

.

Using a Super Cap as a

Backup Power Source

Super caps are capacitors with extremely high capacitance, such as 0.47F. Figure 5 shows two methods to use a super cap as a backup power source. Connect the super cap through a diode to the 3V input (Figure 5a) or connect the super cap through a diode to 5V (Figure

5b), if a 5V supply is available. The 5V supply charges the super cap to a voltage close to 5V, allowing a longer backup period. Since V

BATT

can be higher than V

CC while V

CC is above the reset threshold voltage, there are no special precautions required when using these μP supervisors with a super cap.

3V OR 3.3V

1N4148

V

CC

MAX16033

MAX16040

BATT

0.47F

(a)

Figure 5. Using a Super Cap as a Backup Source

3V OR 3.3V

1N4148

5V

V

CC

MAX16033

MAX16040

BATT

0.47F

(b) www.maximintegrated.com

Maxim Integrated │

12

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

START

SET

WDI

LOW

SUBROUTINE

OR PROGRAM LOOP

SET

WDI HIGH

RETURN

V

CC

V

CC

RESET

MAX16033

MAX16040

V+

R1

MR

R2

PFI

GND

PFO

TO µP

END

Figure 6. Watchdog Flow Diagram

Watchdog Software Considerations

One way to help the watchdog timer to monitor software execution more closely is to set and reset the watchdog at different points in the program, rather than pulsing the watchdog input periodically. Figure 6 shows a flow diagram where the I/O driving the watchdog is set low in the beginning of the program, set high at the beginning of every subroutine or loop, and set low again when the program returns to the beginning. If the program should hang in any subroutine, the watchdog would timeout and reset the μP.

Replacing the Backup Battery

Decouple BATT to GND with a 0.1μF capacitor. The backup power source can be removed while V

CC

remains valid without the danger of triggering a reset pulse. The device does not enter battery-backup mode when V

CC stays above the reset threshold voltage.

Power-Fail Comparator

Monitoring an Additional Power Supply

Monitor another voltage by connecting a resistive divider to PFI, as shown in Figure 7. The threshold voltage is:

V

TH(PFI)

= 1.235 (R1/R2 + 1) where V

TH(PFI)

is the threshold at which the monitored voltage will trip PFO.

To simplify the resistor selection, choose a value for R2 and calculate R1:

R1 = R2 [(V

TH(PFI)

/1.235) - 1]

Figure 7. Monitoring an Additional Power Supply

Connect PFO to MR in applications that require RESET to assert when the second voltage falls below its threshold.

RESET remains asserted as long as PFO holds MR low, and for 140ms (min) after PFO goes high.

Adding Hysteresis to the Power-Fail Comparator

The power-fail comparator provides a typical hysteresis of 12mV, which is sufficient for most applications where a power-supply line is being monitored through an external voltage-divider. Connect a voltage-divider between PFI and PFO, as shown in Figure 8a, to provide additional noise immunity. Select the ratio of R1 and R2 such that

V

(V

PFI

falls to 1.235V when V

TRIP

IN

drops to its trip point

). R3 adds hysteresis and is typically more than

10 times the value of R1 or R2. The hysteresis window extends above (V

H

) and below (V

L

) the original trip point,

. Connecting an ordinary signal diode in series with V

TRIP

R3, as shown in Figure 8b, causes the lower trip point (V to coincide with the trip point without hysteresis (V

TRIP

L

)

).

This method provides additional noise margin without compromising the accuracy of the power-fail threshold when the monitored voltage is falling. Set the current through R1 and R2 to be at least 10μA to ensure that the

100nA (max) PFI input current does not shift the trip point.

Set R3 to be higher than 10kΩ to reduce the load at PFO.

Capacitor C1 adds additional noise rejection.

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Maxim Integrated │

13

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

(a)

V

CC

PFO

0V

V

IN

R1

R2

MAX16033

MAX16040

C1

R3

PFI

TO µP

PFO (PUSH-PULL)

GND

V

L

V

TRIP

V

H

V

IN

(b)

V

CC

PFO

0V

V

IN

R1

R2

C1

R3

PFI

MAX16033

MAX16040

TO µP

PFO (PUSH-PULL)

GND

V

TRIP

V

H

V

IN

V

TRIP

=

PFT 

+

R1

R2

=

PFT

+

PFH

+

R1 R1

R2 R3

=

V

PFT

=

V

PFH

=

PFT

+

R1 R1

R1

R2 R3 R3

CC

V

TRIP

=

PFT 

+

R1

R2

=

PFT

+

PFH

+

R1 R1

R2 R3

R1

R3

D

L

=

PFT

=

TRIP

V 1.235V

V

PFH

=

=

Figure 8. (a) Adding Additional Hysteresis to the Power-Fail Comparator. (b) Shifting the Additional Hysteresis above VTRIP

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Maxim Integrated │

14

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Monitoring a Negative Voltage

Connect the circuit, as shown in Figure 9, to use the power-fail comparator to monitor a negative supply rail.

PFO stays low when V- is good. When V- rises to cause

PFI to be above +1.235V, PFO goes high. Ensure V

CC comes up before the negative supply.

Negative-Going V

CC

Transients

The MAX16033–MAX16040 are relatively immune to short-duration, negative-going V the μP when V

CC usually desired.

CC

transients. Resetting

experiences only small glitches is not

The Typical Operating Characteristics section contains a Maximum Transient Duration vs. Reset Threshold

Overdrive graph. The graph shows the maximum pulse width of a negative-going V

CC

transient that would not trigger a reset pulse. As the amplitude of the transient increases (i.e., goes further below the reset threshold voltage), the maximum allowable pulse width decreases.

Typically, a V

CC

transient that goes 100mV below the reset threshold and lasts for 25μs does not trigger a reset pulse.

A 0.1μF bypass capacitor mounted close to V

CC additional transient immunity.

provides

PFO

R1

R2

V-

3.0V OR 3.3V

V

CC

PFI

MAX16033

MAX16040

PFO

GND

V

L

V

TRIP

0V

V-

V

TRIP

=

(

PFT

+

PFH

)

1

+

1

R1 R2

=

(

PFT

)

V

PFT

1.235V

V

PFH

12mV

1

+

1

R1 R2

V

CC

R1

V

CC

R1

Figure 9. Monitoring a Negative Voltage

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Maxim Integrated │

15

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Device Marking Codes

PART

TOP

MARK

PART

TOP

MARK

PART

TOP

MARK

PART

TOP

MARK

MAX16033LLB23+T +ABE MAX16035LLB23+T +ACC MAX16037LLA23+T +ABX MAX16039LLA23+T +ACV

MAX16033LLB26+T +ABF MAX16035LLB26+T +ACD MAX16037LLA26+T +ABY MAX16039LLA26+T +ACW

MAX16033LLB29+T +ABG MAX16035LLB29+T +ACE MAX16037LLA29+T +ABZ MAX16039LLA29+T +ACX

MAX16033LLB31+T +ABH MAX16035LLB31+T +ACF MAX16037LLA31+T +ACA MAX16039LLA31+T +ACY

MAX16033LLB44+T +ABI MAX16035LLB44+T +ACG MAX16037LLA44+T +ACB MAX16039LLA44+T +ACZ

MAX16033LLB46+T +ABJ MAX16035LLB46+T +ACH MAX16037LLA46+T +ACC MAX16039LLA46+T +ADA

MAX16033PLB23+T +ABK MAX16035PLB23+T +ACI MAX16037PLA23+T +ACD MAX16039PLA23+T +ADB

MAX16033PLB26+T +ABL MAX16035PLB26+T +ACJ MAX16037PLA26+T +ACE MAX16039PLA26+T +ADC

MAX16033PLB29+T +ABM MAX16035PLB29+T +ACK MAX16037PLA29+T +ACF MAX16039PLA29+T +ADD

MAX16033PLB31+T +ABN MAX16035PLB31+T +ACL MAX16037PLA31+T +ACG MAX16039PLA31+T +ADE

MAX16033PLB44+T +ABO MAX16035PLB44+T +ACM MAX16037PLA44+T +ACH MAX16039PLA44+T +ADF

MAX16033PLB46+T +ABP MAX16035PLB46+T +ACN MAX16037PLA46+T +ACI MAX16039PLA46+T +ADG

MAX16034LLB23+T +ABQ MAX16036LLB23+T +ACO MAX16038LLA23+T +ACJ MAX16040LLA23+T +ADH

MAX16034LLB26+T +ABR MAX16036LLB26+T +ACP MAX16038LLA26+T +ACK MAX16040LLA26+T +ADI

MAX16034LLB29+T +ABS MAX16036LLB29+T +ACQ MAX16038LLA29+T +ACL MAX16040LLA29+T +ADJ

MAX16034LLB31+T +ABT MAX16036LLB31+T +ACR MAX16038LLA31+T +ACM MAX16040LLA31+T +ADK

MAX16034LLB44+T +ABU MAX16036LLB44+T +ACS MAX16038LLA44+T +ACN MAX16040LLA44+T +ADL

MAX16034LLB46+T +ABV MAX16036LLB46+T +ACT MAX16038LLA46+T +ACO MAX16040LLA46+T +ADM

MAX16034PLB23+T +ABW MAX16036PLB23+T +ACU MAX16038PLA23+T +ACP MAX16040PLA23+T +ADN

MAX16034PLB26+T +ABX MAX16036PLB26+T +ACV MAX16038PLA26+T +ACQ MAX16040PLA26+T +ADO

MAX16034PLB29+T +ABY MAX16036PLB29+T +ACW MAX16038PLA29+T +ACR MAX16040PLA29+T +ADP

MAX16034PLB31+T ABZ MAX16036PLB31+T +ACX MAX16038PLA31+T +ACS MAX16040PAL31+T +ADQ

MAX16034PLB44+T +ACA MAX16036PLB44+T +ACY MAX16038PLA44+T +ACT MAX16040PLA44+T +ADR

MAX16034PLB46+T +ACB MAX16036PLB46+T +ACZ MAX16038PLA46+T +ACU MAX16040PLA46+T +ADS

Note: 48 standard versions shown in bold are available. Sample stock is generally held on standard versions only. Contact factory for nonstandard versions availability.

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Maxim Integrated │

16

MAX16033–MAX16040

Pin Configurations

TOP VIEW

10 9 8 7 6

MAX16033

MAX16034

+

1 2 3 4 5

10-µDFN

( ) FOR MAX16034 ONLY

8 7 6 5

+

1

MAX16037

MAX16038

2 3 4

8-µDFN

( ) FOR MAX16038 ONLY

+ DENOTES A LEAD(Pb)-FREE PACKAGE.

Low-Power Battery-Backup

Circuits in Small μDFN Packages

10 9 8 7 6

MAX16035

MAX16036

+

1 2 3 4 5

10-µDFN

( ) FOR MAX16036 ONLY

8 7 6 5

+

1

MAX16039

MAX16040

2 3 4

8-µDFN

( ) FOR MAX16040 ONLY www.maximintegrated.com

Maxim Integrated │

17

MAX16033–MAX16040

Typical Operating Circuit

Low-Power Battery-Backup

Circuits in Small μDFN Packages

ADDITIONAL

DC VOLTAGE

R3

2.4V TO 5.5V

0.1µF

V

CC

BATT

MAX16033

MAX16040

RESETIN*

OUT

R4

ADDITIONAL

DC VOLTAGE

R1

R2

PFI

CEIN**

GND

RESET

PFO

WDI***

CEOUT**

0.1µF

CMOS

RAM

CE

ADDRESS

DECODE

* RESETIN APPLIES TO MAX16035/MAX16039 ONLY.

**CEIN AND CEOUT APPLY TO MAX16033–MAX16036 ONLY.

***WDI APPLIES TO MAX16034/MAX16038 ONLY.

REAL-

TIME

CLOCK

A0–A15

RESET

I/O

µP

I/O www.maximintegrated.com

Maxim Integrated │

18

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Ordering Information (continued)

PART*

MAX16035LLB_ _+T

MAX16035PLB_ _+T

TEMP RANGE PIN-PACKAGE

-40°C to +85°C 10 µDFN

-40°C to +85°C 10 µDFN

MAX16036LLB_ _+T

MAX16036PLB_ _+T

MAX16037LLA_ _+T

MAX16037PLA_ _+T

MAX16038LLA_ _+T

MAX16038PLA_ _+T

MAX16039LLA_ _+T

MAX16039PLA_ _+T

MAX16039PLA31+T

-40°C to +85°C

-40°C to +85°C 10 µDFN

-40°C to +85°C 8 µDFN

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

10 µDFN

8 µDFN

8 µDFN

8 µDFN

8 µDFN

-40°C to +85°C 8 µDFN

-55°C to +85°C 8 µDFN

MAX16040LLA_ _+T

MAX16040PLA_ _+T

-40°C to +85°C 8 µDFN

-40°C to +85°C 8 µDFN

*These parts offer a choice of reset threshold voltages. From the Reset Threshold Ranges table, insert the desired threshold voltage code in the blank to complete the part number. See the

Selector Guide for a listing of device features.

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Reset Threshold Ranges

SUFFIX

29

26

23

46

44

31

RESET-THRESHOLD VOLTAGE (V)

MIN TYP MAX

4.50

4.63

4.75

4.25

3.00

2.85

2.55

2.25

4.38

3.08

2.93

2.63

2.32

4.50

3.15

3.00

2.70

2.38

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns

(footprints), go to

www.maximintegrated.com/packages

. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

PACKAGE

TYPE

8 μDFN

10 μDFN

PACKAGE

CODE

L822+1

L1022+1

OUTLINE

NO.

21-0164

21-0164

LAND

PATTERN NO.

90-0005

90-0006

www.maximintegrated.com

Maxim Integrated │

19

MAX16033–MAX16040 Low-Power Battery-Backup

Circuits in Small μDFN Packages

Revision History

REVISION

NUMBER

REVISION

DATE

1 5/14

DESCRIPTION

Data sheet rebranded; updated Electrical Characteristics and Ordering Information tables to support MAX16039PLA31+T option at -55°C

PAGES

CHANGED

2, 19

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.

© 2014 Maxim Integrated Products, Inc. │ 20

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