MLX90721

Auto Shut Off Timer

3901090721

Page 1 of 12

Data Sheet

Rev. 003

Oct/02

Features and Benefits

Low cost minimal external components

Small package (to92 for the 3 pins version,
pdip8, psop8 or cob for the 4pins version)

On chip calibrated timer

Drives different relay types, including low
cost 12V relays and most custom made
relays.

Low power consumption (low dissipation)

Applications

Household appliances

Heater

Hand-dryer

Ordering Information

Part No.

Temperature Suffix

Package Code

Option Code*

MLX90721

C (0°C to 70°C)

SA (TO-92)

CA / CB / CC / CD / CE / CF

MLX90721

C (0°C to 70°C)

AA (PDIP8)

MLX90721

C (0°C to 70°C)

DC (SOIC8)

*See Option Code Table for details

1. Functional Diagram

POR

Vreg

options

OSC

logic

VDDA

VSS

BUT

OUT

2. Description

The chip is intended to be used for switching on
and off a mains powered device, with the added
feature of automatic switch off after a well-defined
amount of time. Such device can replace
conventional switches in all appliances that might
be left on inadvertently. Besides saving energy, the
main goal is to prevent all hazards due to
appliances left on unattended.
The chip can be used in its 3-pin version, where
applying the supply to the chip does switching on.
In the 4-pin version switching on and off is done
with a single push-button.
As an alternative the fourth pin can also be used as
a reset pin, where the auto-shut-off time counter is
reset when pushing this button.
The auto-shut-off time is mask programmable and
can be almost anything between 2.5 minutes and
32 hours. The duty cycle of the relay driver can
also be adjusted by mask to adapt to almost any
kind of relay construction.

MLX90721

Auto Shut Off Timer

3901090721 Page

2 of 12 Data Sheet

Rev. 003

Oct/02

TABLE OF CONTENTS

FEATURES AND BENEFITS........................................................................................................................1

APPLICATIONS ............................................................................................................................................1

ORDERING INFORMATION .........................................................................................................................1

FUNCTIONAL DIAGRAM ...................................................................................................................

...1

DESCRIPTION ....................................................................................................................................

...1

ABSOLUTE MAXIMUM RATINGS........................................................................................................3

MLX90721 ELECTRICAL SPECIFICATIONS.......................................................................................3

MLX90721 SPECIFIC SPECIFICATIONS .............................................................................................3

GENERAL DESCRIPTION ....................................................................................................................5

PIN DESCRIPTION ................................................................................................................................6

APPLICATION INFORMATION.............................................................................................................6

8.1.

UTTON

NPUT

. .............................................................................................................................................. 6

8.2.

UTY

YCLE AND

UTO

HUT

-OFF O

PTIONS

............................................................................................... 7

8.3.

PTION

ODE

ABLE

..................................................................................................................................... 7

RELIABILITY INFORMATION...............................................................................................................8

10.

ESD PRECAUTIONS .............................................................................................................................8

11.

PACKAGE INFORMATION ...................................................................................................................9

12.

DISCLAIMER .......................................................................................................................................12

MLX90721

Auto Shut Off Timer

3901090721

Page 3 of 12

Data Sheet

Rev. 003

Oct/02

3. Absolute Maximum Ratings

Supply Voltage, V

DDA

(overvoltage)

70V

Supply Voltage, V

DDA

(operating)

68V

ESD Sensitivity (AEC Q100 002)

2kV

Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolute
maximum-rated conditions for extended periods may affect device reliability.

4. MLX90721 Electrical Specifications

DC Operating Parameters T

= 0

C to 85

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Ambient temperature

Tamb

°C

Max. junction temperature

Tjm

125

°C

5. MLX90721 Specific Specifications

Supply Current

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Supply current at VDDA=48V

Idd1

VDDA=48V, OUT open BUT not

active

170 270 370 µA

Supply current at VDDA=55V

Idd2

VDDA=55V, OUT open BUT not
active

200 300 400 µA

Integrated Zener

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Zener voltage at VDDA

Vzen

Maximum sink current

Izm

Power On Reset

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

DPOR high level

Vdh

2.8

DPOR

hysteresis

Vdhys

0.9

APOR high level

VAPH

APOR hysteresis

VHYS

MLX90721

Auto Shut Off Timer

3901090721

Page 4 of 12

Data Sheet

Rev. 003

Oct/02

Relay Driver Output

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Maximum current in ON state

Ion

Output voltage in ON state

Von

Iout = 50mA

0.4

Leakage current in OFF state

Ioff

V(OUT)=Vzen

Over voltage protection

Vprot

Iout = 25mA Fast option

0.27

0.3

0.32

µs

Rise / fall times

Trf

Iout = 25mA Slow option

0.7

1.0

1.3

µs

Frequency of the relay driver

21.8

kHz

Duty cycle of the relay driver

DC1

See options

Var.

Internal Oscillator

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Nominal frequency

Fosc

VDDA = 60V, Tamb

437

kHz

Frequency tolerance

20V < VDDA < 68V

-6

Temp. coefficient of oscillator

frequency

TCf T=0°-100°C

1000

ppm

Button Input

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Threshold voltage

Vtr

Valid for APPL.1 and APL.2

2.5

Threshold current

Itr

Valid for APPL.3

+12

Max. source current

Im1

-350

Max. sink current

Im2

350

Clamp voltage 1

Vc1

APPL.3; Ibut = +4mA

Clamp voltage 2

Vc2

APPL.3; Ibut = -4mA

Timings

Parameter Symbol

Test

Conditions

Min

Typ

Max

Units

Switch ON delay time

Auto Shut-OFF time

See options

Increased Duty Cycle period

Tdub

In case this option is enabled

MLX90721

Auto Shut Off Timer

3901090721

Page 5 of 12

Data Sheet

Rev. 003

Oct/02

6. General Description

The chip is intended to be used for switching on
and off a mains powered device, with the added
feature of automatic switch off after a fixed
amount of time. Such device can replace
conventional switches in all appliances that might
be left on inadvertently.
Besides saving energy, the main goal is to
prevent all hazards due to appliances left on
unattended.
The chip is offered in a 3-pin version, where
applying the supply is switching the chip on. In its
4-pin version, switching on and off is done with a
single push-button.
As an alternative the fourth pin can also be used
as a reset pin, where the auto-shut-off time
counter is reset when pushing this button.
The chip application version (3 or 4 pins) and
auto-shut-off time are mask programmable. The
auto-shut-off time can be almost any value
between 2.5 minutes and 32 hours. The duty
cycle of the relay driver can also be adjusted by
the same mask to adapt to all types of relay
construction.

Power-On-Reset.

The Power-On-Reset of the ASIC is a
combination of a digital power-on-reset with
hysteresis DPOR, and an analog APOR.
DPOR is used to initialize the logic on the chip.
The APOR is characterized by a low level APL
signal and a high level APH signal, which are
debounced as follows:
low level debouncing approx. 25mS
high level debouncing approx. 3.5mS
The digital signal APOR is a logic combination of
the debounced signals APLd and APHd. APOR is
set to High when APHd = high and APOR is reset
to Low when APLd = low.
A transition to the active state is indicated by the
digital signal APOR=1 in case of application 1
and 2, or APOR=1 and START=1 in case of
application 3. The result is that the transistor at
the pin OUT is activated after a delay time Td,
and starts switching ON and OFF with the
specified frequency F1 and duty cycle DC1.
The digital signal APOR=0 immediately brings
the logic back to the INACTIVE state, i.e. the
output is disabled and the state of the digital
output signal from the start-stop/reset button (if
present in the particular application) is initialized
to non-pressed (released) state.

Auto Shut-OFF Function

When the ASIC is in the ACTIVE state and when
the delay period Td has elapsed, the output is
activated (with a well defined duty cycle) for a
predefined Auto Shut-OFF Time Ta. At the end of
that period Ta, the output is switched OFF, the
ASIC is brought to the INACTIVE state and the
state of the digital output signal from the start-
stop/reset button (if present) is initialized.

Doubled Duty cycle

Mechanical relays normally need a higher
magnetic field (and thus a higher coil current) to
move the contact away from his normal position,
then to keep the contact in that position.
Therefore it is possible to increase the current
supplied to the coil during the first 6 msec after
activation of the output driver. This is done by
doubling the duty cycle, which has been selected
by mask option.
With a proper dimensioning of the external
components the power consumption of the
module can be optimized in this way.

Test Mode

The test mode aims full verification of the above
specified logic functions and electrical
characteristics, both on wafer and packaged
device.
The test mode is defined under the following
conditions:

V(OUT) = 0V for approx. 5msec. The ASIC
enters test mode when on pin OUT is detected
short-circuit to GND. This detection is done after
a digital debouncing for a period of ~ 5mS and
the result is latched and saved in a test status
flip-flop.
When in test mode, pin OUT is used as input for
the test clock sequence, as well as an output for
the IC reaction. This is achieved by appropriate
definition of input/output signal levels.
V(OUT) < 9V. This restriction aims to make a
clear distinction between normal mode operation,
when V(OUT)=VDDA, and test mode. This
feature also ensures that if by mistake test mode
is activated during Normal Mode operation, and
at the same time on pin OUT is found a potential
higher than 9V, follows immediate reset of test
mode, and the IC is brought back to normal
mode.

MLX90721

Auto Shut Off Timer

3901090721

Page 6 of 12

Data Sheet

Rev. 003

Oct/02

7. Pin Description

Pin Name

Type

Description

1 VDDA

Supply

2 GND

Ground

OUT

Output

Relay driver output

4 (optional)

BUT

Input

Button input

8. Application Information

8.1. Button Input.

The Button input can have three different
functions, which determine the three different
applications: APPL.1, APPL.2 and APPL.3. The
function of the input is defined by the option
mask.

APPL.1-No Function. The BUT input is not used
and therefore not connected externally. BUT is an
internally pulled up digital input. In this case, the
transitions INACTIVE > ACTIVE state and vice
versa are defined only by the APOR signal.

MLX90721

LED (optional)

Load

VDD

GND

OUT

Appl.1 Auto Shut Off without button

BUT

APPL.2-Auto Shut-OFF Time Reset. The input
BUT can be connected to GND via an external
button. The input is an internally pulled up, active
Low, inverting digital input. In this case, the
transitions INACTIVE state > ACTIVE state and
vice versa are again defined only by the APOR
signal. Each time the button is pressed a Reset
signal is generated and the countdown for the
Auto Shut-Off Time starts from 0 again.
The state of this input (pressed or not) is checked
each 3.5mS. The high level (button pressed) at
the digital output is debounced for approx.
3.5mS.

MLX90721

LED (optional)

Load

VDD

GND

OUT

Appl.2 Auto Shut Off with time reset button

BUT

APPL.3-Start/Stop Toggle Function. The input
BUT is now an active High, zero cross input with
internal pull down. The input is connected via a
button and external resistor to the mains.

MLX90721

LED (optional)

Load

VDD

GND

OUT

Appl.3 Auto Shut Off with start/stop button

BUT

Each time when this button is pressed, the
internal START signal toggles and in combination
with the APOR signal it defines the logic
transitions in the following way:

APOR=1 and START=1 > transition to
ACTIVE state

APOR=1 and START=0 > transition to

MLX90721

Auto Shut Off Timer

3901090721

Page 7 of 12

Data Sheet

Rev. 003

Oct/02

INACTIVE state

APOR=0 defines the INACTIVE state and
initialization of a start signal START= 0

The digital output of the BUT input is debounced
as follows:

High level debouncing (button pressed)
approx. 3.5mS

Low level debouncing (button released)
approx. 100mS

The first time the button is pressed after

initialization sets START=1. Once the logic has
found that the button is pressed, it has to detect a
released button in order to interpret correctly
consecutive activation of the button. Each next
pressing toggles the START signal.

8.2. Duty Cycle and Auto Shut-OFF Options

The function of input BUT as well as the doubled duty cycle function can be defined by mask option.
The following options can be defined by mask option:

Parameter Symbol

Conditions

Min

Typ

Max

Units

Relay Frequency Duty Cycle

In steps of 2.5%

37.5

Interval

AUTO SHUT-OFF TIMES

0 1 H

2.5

7.5

12.5

17.5

22.5

25 30 35 37.5

40 45 50

52.5

min

1 2 H

1h10m

1h15m

1h20m

1h30m

1h40m

1h45m

2 3 H

2h20m

2h30m

2h40m

3 4 H

3h20m

3h30m

4 5 H

4h40m

5 6 H

5h20m

6 7 H

6h40m

7 9 H

9 10 H

9h20m

10 11 H

10h

10h40

12h 14h 16h 20h 24h 28h 32h

8.3. Option Code Table

The table below lists all option values for the available option codes.

OPTION

CA CB CC CD CE CF

BUT

input

APPL.1 APPL.1 APPL.1 APPL.1 APPL.1 APPL.1

Auto Shut Off time

2 h

1 h

30 min

10 h

15 min

1 h

Duty

Cycle

10% 10

% 10% 20% 10% 10%

Double Duty

No No No No No No

Output

Rise/Fall

times

Fast Slow Fast Fast Fast Fast

MLX90721

Auto Shut Off Timer

3901090721

Page 8 of 12

Data Sheet

Rev. 003

Oct/02

9. Reliability Information

Melexis devices are classified and qualified regarding suitability for infrared, vapor phase and wave
soldering with usual (63/37 SnPb-) solder (melting point at 183degC).
The following test methods are applied:

IPC/JEDEC J-STD-020A (issue April 1999)
Moisture/Reflow Sensitivity Classification For Nonhermetic Solid State Surface Mount Devices
CECC00802 (issue 1994)
Standard Method For The Specification of Surface Mounting Components (SMDs) of Assessed Quality
MIL 883 Method 2003 / JEDEC-STD-22 Test Method B102
Solderability

For all soldering technologies deviating from above mentioned standard conditions (regarding peak
temperature, temperature gradient, temperature profile etc) additional classification and qualification tests
have to be agreed upon with Melexis.

The application of Wave Soldering for SMD's is allowed only after consulting Melexis regarding assurance
of adhesive strength between device and board

For more information on manufacturability/solderability see quality page at our website:

http://www.melexis.com/

10. ESD Precautions

Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).
Always observe Electro Static Discharge control procedures whenever handling semiconductor products.

MLX90721

Auto Shut Off Timer

3901090721

Page 12 of 12

Data Sheet

Rev. 003

Oct/02

12. Disclaimer

Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in
its Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the
information set forth herein or regarding the freedom of the described devices from patent infringement.
Melexis reserves the right to change specifications and prices at any time and without notice. Therefore,
prior to designing this product into a system, it is necessary to check with Melexis for current information.
This product is intended for use in normal commercial applications. Applications requiring extended
temperature range, unusual environmental requirements, or high reliability applications, such as military,
medical life-support or life-sustaining equipment are specifically not recommended without additional
processing by Melexis for each application.
The information furnished by Melexis is believed to be correct and accurate. However, Melexis shall not
be liable to recipient or any third party for any damages, including but not limited to personal injury,
property damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or
consequential damages, of any kind, in connection with or arising out of the furnishing, performance or
use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow
out of Melexis' rendering of technical or other services.
© 2002 Melexis NV. All rights reserved.

For the latest version of this document,

go to our website at:

www.melexis.com

Or for additional information contact Melexis Direct:

Europe and Japan:

All other locations:

Phone: +32 13 67 04 95

Phone: +1 603 223 2362

E-mail: sales_europe@melexis.com

E-mail: sales_usa@melexis.com

QS9000, VDA6.1 and ISO14001 Certified

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