AN296238
MCO-0001095, Rev. 1
P0123

APPLICATION INFORMATIONCOMBINATION HALL SWITCH AND LED DRIVER ICSIMPLIFIES ENCLOSURE LIGHTING AND PROXIMITYSENSING
By Shashank Wekhande and Ranjit Farakate, AvantGarde Solutions Pvt Ltd.,
Consultants to Allegro Microsystems

ABSTRACT
Most of today’s white goods use LED lighting for internal illumination. For example, refrigerators, microwave ovens, andkitchen cabinets all use LEDs for interior illumination when thedoor opens. LEDs are also used for illumination in ice cream
freezers, vending machines, and other enclosures. Personal
mobility trunks and glove boxes such as on scooters and small
vehicles are other areas where LED actuation occurs. LEDs arecontrolled with a switch operated by the door opening/closing. When the door is opened, the switch closes and powers
on the LED.
Applications that combine proximity sensing with lighting
actuation can achieve reduced system footprints and design
simplification by the use of a single highly integrated circuit (IC).
Example use cases and technical considerations are presented
in this application note using the Allegro APS13568 combination switch and LED driver.

INTRODUCTION
Allegro MicroSystems has developed the APS13568, an
integrated LED driver with non-contact Hall-effect switch ina single-chip solution. This IC provides reliability and easeof design for contactless door opening illumination in white
goods, battery-operated cabinet lighting, two-wheeler bootlamp, and similar applications. The end results are a shorter
design phase and a faster time to market.

APS13568 INTEGRATED LED DRIVER
WITH HALL-EFFECT SWITCH
The APS13568 is an integrated circuit that combines an ultrasensitive, omnipolar, micropower Hall-effect switch with alinear programmable current regulator which can provide up
to 150 mA current to drive high brightness LEDs. This highly
integrated solution offers high reliability and ease of design
compared to a discrete solution.

FEATURES AND BENEFITS
•
•
•
•
•

Integrated LED driver and Hall-effect switch
Low quiescent current (25 μA, typical) when LED is off
Hall-effect switch output with selectable output polarity
Active-low LED drive enable pin
Linear, low-dropout LED drive up to 150 mA□ Set by external reference resistor□ Reverse battery and load dump protection□ Short-to-ground and thermal protection□ Programmable fade-in and fade-out duration withexternal capacitor

12 V BAT
C1
0.1 µFRP
4.7 kΩ

VIN

100 mA

SO
EN

RIREF
900 Ω

LA

HALL

POL

FADE

IREF

GND
APS13568

Figure 1: Typical Application Circuit of APS13568

CFADE
10 nF

AN296238
MCO-0001095, Rev. 1
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APPLICATION INFORMATIONCIRCUIT DESCRIPTION

FADE-IN AND FADE-OUT FEATURE

The APS13568 operates from 7 to 24 V—typically, a 12 V supply
is used for the input supply. Capacitor C1 is a bypass capacitor
placed close to the IC and is recommended for maximum EMI/
EMC compliance.

The FADE pin is connected to a ground through a CFADE capacitor to illuminate the LED slowly in order to avoid flash blindness
at night when the door opens. Fade timing is controlled by an
external capacitor CFADE on the FADE pin.

The current through the LEDs is set by a resistor connected to
the IREF pin. LED current is set using Equation 1 :Fade-in is trigged when the LED driver is enabled, and fade-out
triggered when the LED driver is disabled as shown in below
Figure 2. A 10 nF capacitor on the fade pin to ground pin will set
10 ms of the fade in; fade out time is achieved as shown in the
Figure 2. The fade time is approximated by using the Equation 2.

Equation 1:

ILA = 90 / RIREF

where ILA is in amps, RIREF is in ohms. A 900 Ω resistor connected between the IREF and GND pins sets the 100 mA current of the LED.

Equation 2:

tFADE = CFADE × 0.8 × 106

where tFADE is in seconds and CFADE is in farads.

Figure 2: Fade-in and fade-out (C4 = Output Current)

MAGNET AND APS13568 IC PLACEMENTThe IC is mounted on a stationary frame and the magnet is fitted on the door as shown in Figure 3. The magnet and IC arealigned such that the IC can detect magnetic field variation by
movement of the magnet.

MagnetAPS13568 IC
PCB

Figure 3: Magnet and APS13568 IC Placement

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AN296238
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APPLICATION INFORMATIONTHERMAL MONITOR FEATURE

HALL-EFFECT SWITCH OPERATIONThe APS13568 is a linear type of LED driver. These types of driver
use power based on input and output voltage differential andcurrent as shown in Equation 3.

The omnipolar Hall-effect switch provides contactless controlof the LED. The Hall-effect omnipolar switch operates witheither a north or a south magnetic pole. This offers ease of
production due to polarity-independent operation. The switch
output polarity can be set with an external pulldown on the POL
input pin. This allows the user to select whether the APS13568
output turns on and off when a magnet is present or when themagnetic field is removed. The magnetic characteristics of the
APS13568 is shown in Table 1.

Equation 3:

P = (VIN − VOUT) × ILED + (VIN × IIN)

For example, at 12 Vin, having a single LED with 3 V forward voltage driving at 100 mA can use about 0.9 W. This power loss will
increase driver IC temperature. A temperature monitor function
is available in the APS13568 which reduces the LED current as
the junction temperature increases above 130°C. This extends
the operation over a wide range of ambient temperature andoperating conditions.
As the junction temperature of the APS13568 increases beyond
130°C, the output current level is proportionally decreased,
reducing power dissipation in the APS13568 and in the LEDs.

In the closed-door condition, the magnet is on the surface of
the LED driver, such that the magnetic field is above BOP and
the internal Hall-effect switch turns off (POL = 1). In this case, theSO and EN pins are connected to the battery voltage throughthe pull-up resistor Rp.
When EN is HIGH (disabled), the LEDs turn off (POL = 1). Reverse
operation will happen in a POL = 0 (float) condition.
Table 1: Magnetic Characteristics of APS13568

Above 130°C temperature, the current will continue to decreaseat a lower rate until the temperature reaches the overtemperature shutdown threshold temperature (165°C). If the junction
temperature exceeds the overtemperature limit, the driver will
be disabled. The temperature will continue to be monitored
and the regulator will be reactivated when junction temperaturedrops below the threshold.

Characteristic

SymbolBOPS

Operate Point

BOPN
BRPS

Release Point

BRPN

Hysteresis

BHYS

Test Conditions|BFIELD|>|BOP||BFIELD|<|BRP||BOPX – BRPX|

Min. Typ. Max. Unit
–

40

70

G

–70

–40

–

G

5

25

–

G

–

–25

–5

G

5

15

25

G

APS13568 PROTOTYPE BOARD
The schematic of the APS13568 prototype board is as shown in
the Figure 4. The CoB (chip-on-board) LEDs (3 LEDs in series inside
the LED, chip-on-board), comes standard on this proto board.
12 V BAT

C1

VIN

LA

R1

100 mA

SO
EN

HALL

POL

FADE

IREF

GND

R3

C2

APS13568
Figure 4: Schematic of APS13568 Prototype Board

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AN296238
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APPLICATION INFORMATIONThe bill of materials of the APS13568 prototype board is shownin Table 2.
Table 2: Bill of Material of APS13568 Prototype Board
NumberPart Designator

Description

Package

Quantity

1

U1

APS13568 IC

SOIC-8

1

2

LED1

White CoB LEDs(CXA1304-0000-000C00B40E1)

CoB

1

3

C1

100 nF SMD capacitor, X7R

805

1

4

C2

10 nF SMD capacitor, X7R

805

1

5

R1

4.7 kΩ, SMD resistor

805

1

6

R2

0 Ω, SMD resistor

805

1

7

R3

900 Ω, SMD resistor

805

1

PRINTED CIRCUIT BOARD
A printed circuit board of the APS13568 IC is shown in Figure 5.
+V = Battery Voltage Input, LEDs connected between LA and
Ground pin.

Figure 6 shows the surface temperature of the APS13568 at
12 V supply voltage with white CoB LEDs (CXA1304-0000000C00B40E1) in series for 100 mA continuous current.

Figure 5: APS13568 PCB with CoB LEDs

Figure 6: Surface temperatures of APS13568 IC

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AN296238
MCO-0001095, Rev. 1
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APPLICATION INFORMATIONVARIOUS APPLICATIONS USING THE APS13568 IC
Door Opening Lights for Refrigerator or Microwave Oven
Typical white goods door opening illumination is shown in
Figure 7. LEDs are preferred for lighting as the offer longer
life and generate less heat than incandescent solutions. Also,mechanical switches tend to become stuck after some timeand do not continue to work properly.
The APS13568, which provides an LED driver and Hall-effectswitch in a single-chip solution, is an effective design for BOM
reduction as its features provide the contactless sensing and
LED lighting for applications like refrigerator or microwave
door opening. The application circuit for a refrigerator or
microwave is shown in Figure 1.

APS13568 features suitable for door opening light applications:• Low quiescent current (25 μA, typical) when LED is off• Hall-effect switch output with selectable output polarity• Linear low-dropout LED driver, up to 150 mA□ Set by external reference resistor□ Programmable fade-in and fade-out duration withexternal capacitor□ External input pin for LED control and dimming (PWM)

A magnet is attached to the door, and the IC is placed perpendicular to the magnet inside the refrigerator. When thedoor opens, the magnet moves away from the sensor, applying lower magnetic field, which pulls the SO pin (active-low
open-drain output) low. This pulls the EN pin to low throughresistor RPU and enables the driver. Resistor RIREF sets thecurrent. When the door closes, the magnet moves close to
the driver and the SO pin goes high. This pulls the EN pinhigh to disable the driver.

Figure 7: Refrigerator and microwave door opening lighting applications

Ice Cream Freezer and Beverage Dispenser Applications
Traditional incandescent bulbs generate significant heat which isan additional burden on a cooling compressor. This is especially
important for devices with a glass opening such as a beverage
dispenser or ice cream freezer as shown in Figure 8.
Working Principle

APS13568 features suitable for ice cream freezer or beverage dispenser application:• Hall-effect switch output with selectable output polarity• Linear low-dropout LED driver with programmable output
current up to 150 mA, set by external reference resistor

A magnet is attached to the side of the door and the IC is placed
perpendicular to the magnet inside the ice cream freezer. Whendoor is in a closed condition, the magnet is close to the driver,and the magnetic field is higher than the BOP level such that theSO̅pin goes high. The driver is always enabled with the EN pin
connected to ground and LEDs illuminated by the current set
with the R1 resistor.
When the door opens, the magnet moves away from the driverand the magnetic field is lower than the BRP level such that theSO̅pin goes low. When the SO̅pin goes low, it draws R1 andR2 in parallel and illuminates the light with double intensity with
the̅EN pin connected to ground.

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Figure 8: Ice cream freezer

5AN296238
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APPLICATION INFORMATION

12 V BAT
VIN
C1
0.1 µFLA

SO

R2
1.8 kΩ

HALL

IREF

R1
1.8 kΩ

POL

FADE

EN

GND

R3
APS13568
Figure 9: Application circuit of APS13568 for door opening lights for ice cream freezer or beverage dispenser

Battery-Operated Inner Cabinet Lighting
For existing inner cabinet lighting, customers are using an IR
sensor switch to turn on and off the LED when the door opens
and closes. The inner cabinet lighting picture is as shown in the
Figure 10 and 11 when the LED lights turns on in the door open
condition and turns off in the door close condition.
The APS13568 operates on a 12 V battery, and it is possible touse three white LEDs for higher brightness. When the LEDs isin the off condition, the APS13568 has lower leakage current,
less than 25 µA, which increases battery life.
APS13568 features suitable for battery-operated innercabinet lighting application• Low quiescent current (25 μA, typical) when LED is off

Figure 10: Inner cabinet lighting (LED turns on when door opens)• Hall-effect switch output with selectable output polarity• Linear low-dropout LED driver, up to 150 mA□ Set by external reference resistor□ Programmable fade-in and fade-out duration withexternal capacitor.
□ External input pin for LED control and dimming (PWM)

Figure 11: Inner cabinet lighting (LED turns off when door closes)

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APPLICATION INFORMATION

Boot Lamp Application
In two-wheeler scooters, boot space is provided to store accessories. This boot is normally illuminated by an incandescentlamp through a mechanical switch. This boot lamp is operated
directly from the battery before the ignition switches on, so it
is very important that the LED driver has a very low quiescentcurrent when the LED is off to avoid battery drain.
The APS13568 has 25 μA of quiescent current along with theHall-effect switch—suitable for this application.

APS13568 features suitable for boot lamp application• Low quiescent current (25 μA, typical) when LED is off• Hall-effect switch output with selectable output polarity• Linear low-dropout LED driver, up to 150 mA□ Set by external reference resistor□ Reverse battery and load dump protection□ Short-to-ground and thermal protection□ Programmable fade-in and fade-out duration withexternal capacitor

The APS13568, which provides an LED driver and Hall-effectswitch in a single-chip solution, provides contactless LED lighting for the boot lamp application. The application circuit of
the APS13568 for a boot lamp application for a two-wheeler
scooter is as shown in Figure 1.

Figure 12: Boot lamp of scooter

Glove Box Lamp Application
In four-wheeler vehicles, glove box space is provided tostore accessories. This glove box is normally illuminated byan incandescent lamp through a mechanical switch. This
glove box lamp is operated directly from the battery before
the ignition switches on, so it is very important that the LED
driver has a very low quiescent current when the LED is off toavoid battery drain.
The APS13568 has 25 μA of quiescent current along with theHall-effect switch—suitable for this application.

APS13568 features suitable for glove box application• Low quiescent current (25 μA, typical) when LED is off.
• Hall-effect switch output with selectable output polarity• Linear low-dropout LED driver, up to 150 mA□ Set by external reference resistor□ Reverse battery and load dump protection□ Short-to-ground and thermal protection□ Programmable fade-in and fade-out duration withexternal capacitor

The APS13568, which provides an LED driver and Hall-effectswitch in a single-chip solution, is an effective design for BOM
reduction, as its features provide both contactless sensing and
LED lighting for the boot lamp application. The application
circuit of the APS13568 for the glove box lamp application fora four-wheeler car is shown in Figure 1.

Figure 13: Glove box lamp application

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AN296238
MCO-0001095, Rev. 1
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APPLICATION INFORMATIONCHOOSING LEDS FOR APS13568 IC
Choosing LEDs for the APS13568 LED driver with Hall-effectswitch depends on current and supply voltage. The APS13568
IC’s maximum current is 150 mA, so select LEDs up to 200 to
300 mA current range. The number of series LEDs is dependent
on the supply voltage. If the battery supply is 12 V, then use threewhite LEDs in series, and if the battery voltage is 9 V, then use
two white LEDs in series.

Power Dissipation Example for the Single and
CoB LEDs for 12 V Supply Voltage
Power dissipation for single white LED:
Forward Voltage of White LED = 3 V
Output LED Current = 100 mA
Supply Voltage (VIN) = 12 V
Supply Current (IIN) = 4 mA
Printed Circuit Board Size: 44.8 mm length, 39 mm widthPower Dissipation (W)= (VIN − VLED) × ILED + (VIN × IIN)			= (12 – 3) × 100 + 12 × 0.004

			= 0.948 W

Figure 14: APS13568 with Single White LED (top)and Surface Temperature of IC (bottom)

The printed circuit board of the APS13568 IC with a single
white LED and surface temperature for 12 V supply voltage
at 100 mA continuous current is shown in Figure 14.
Power dissipation for single white LED with sense resistor:
Forward Voltage of White LED = 3 V
Output LED Current = 100 mA
Supply Voltage (VIN) = 12 V
Supply Current (IIN) = 4 mA
Rsense Resistor = 75 Ω
Printed Circuit Board Size: 44.8 mm length, 39 mm widthPower Dissipation (W)			= (VIN − (VLED + (Rsense × ILED))× ILED) + (VIN × IIN)

			
			

= (12 – (3 + (75 × 0.100))
× 0.100) + (12 × 0.004)

			= 0.198W
The printed circuit board of the APS13568 IC with a single
white LED with sense resistor and surface temperature for
12 V supply voltage at 100 mA continuous current is shownin Figure 15.

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Figure 15: APS13568 with Single White LED and Sense Resistor (top)and Surface Temperature of IC (bottom)

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AN296238
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APPLICATION INFORMATIONPower dissipation in linear type LED driver limits output current.
For higher brightness, use CoB LEDs.
Power dissipation for CoB LED:
Forward Voltage of White LED = 9 V
Output LED Current = 100 mA
Supply Voltage (VIN) = 12 V
Supply Current (IIN) = 4 mA
Printed Circuit Board Size: 44.8 mm length, 39 mm widthPower Dissipation (W) = (VIN − VLED) × ILED + (VIN × IIN)
Power Dissipation (W) = (12 – 9) × 100 + (12 × 0.004)
Power Dissipation (W) = 0.348 W
The printed circuit board of the APS13568 IC with white
CoB LEDs is shown in Figure 5, and the surface temperaturefor 12 V supply voltage at 100 mA continuous current is asshown in Figure 6.

Below are two LEDs part numbers suitable for the APS13568
IC with 12 V and 9 V battery supply voltage.
High Power LEDs – White (for 12 V battery supply)
Manufacture Part Number: CXA1304-0000-000C00B40E1

High Power LEDs – White 3030 Mid Power LED White (for
9 V battery supply)

Product: White CoB LEDs
Forward Current: 400 mA
Forward Voltage: 9 V

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Manufacture Part Number: MP-3030-2100-50-80
Product: White CoB LEDs
Forward Current: 150 mA
Forward Voltage: 6.1 V

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APPLICATION INFORMATIONCHOOSING A MAGNET FOR APS13568 IC
Magnets are available in different materials, shapes, and sizes;
customers can select the magnet as per the application requirements. The magnet must have sufficient flux density to generate
the desired switching output at the working air gap requiredby the application.
Magnetic material properties are shown in Table 3. The flux density of the magnet is required to be greater than 70 gauss (southpole) or –70 gauss (north pole) on the surface of the sensor forswitching the output at the desired air gap. Select the magnet
size such that magnet should cover the sensor face properly.

market. Where size constraint is a problem, a NdFeB magnet issuitable. The NdFeB magnet provides a stronger magnetic field
than the ferrite magnet for a smaller size of magnet.
By using simple formulas, it is also possible to calculate the flux
density of the magnet. Calculations of the flux density of cylindrical and rectangular magnets is shown in the formulas below.
Table 3: Properties of Magnetic Material
Material

For the door/boot opening application, a ferrite magnet issuitable. Ferrite magnets are cheap and readily available on the

Br (gauss) Hc (oersted)

BHmax(MGOe)

Tcoef of Br(%/°C)

Cost

NdFeB

12,80012,300

40

–0.12

High

Alnico

12500

640

5.5

–0.02

MediumFerrite

3,900

3,200

3.5

–0.2

Low

Cylindrical Magnet

Rectangular Magnet

Equation 4 gives an approximate formula for selecting theappropriate magnet based on required magnetic flux density [2],which is useful for calculating the magnetic flux density at d mmfrom the cylindrical magnet surface as shown in Figure 16.

Equation 5 gives an approximate formula for selecting theappropriate magnet dimensions based on required magnetic
flux density [2], which is useful for calculation the magnetic
flux density at d mm from the rectangular magnet surface asshown in Figure 17.

Equation 4:

Equation 5:

Bd = Magnetic flux density

Bd = Magnetic flux density

Br = Residual flux density

Br = Residual flux density

L = Length

R = Radius of the magnet

d = Air gap (magnet surface to the sensor Hall element)

2R

L = Length
B = Width

A = Heightd = Air gap (magnet surface to the sensor Hall element)

B

L

d

Figure 16: Cylindrical Magnet

A

L

d

Figure 17: Rectangular Magnet

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APPLICATION INFORMATIONSUMMARYREFERENCES

Different applications are presented in this article along with areduced size actuated lighting solution suitable for door opening lights of white goods, inner cabinet/drawers, two- wheelerboot lamps, study/desk light applications, etc.

[1] https://www.allegromicro.com/en/products/regulate/
led-drivers/led-drivers-for-lighting

The APS13568 LED driver combines an ultrasensitive, omnipolar micropower Hall-effect switch with a linear programmable
LED driver and offers high reliability and ease of design withminimal external components. This IC has an integrated 150 mA
LED driver and proximity switch for contactless operation of
the door opening.

[2] https://www.intemag.com/magnet-design-guide[3] https://www.allegromicro.com/en/search?q=AN296207[4] https://marketbusinessnews.com/financial-glossary/
white-goods-definition-meaning[5] https://en.wikipedia.org/wiki/Scooter_(motorcycle)[6] https://en.wikipedia.org/wiki/Building_automation#:~:text=Building%20automation%20is%20the%20automatic,Building%20Automation%20System%20(BAS).

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APPLICATION INFORMATION

Revision History
NumberDate

Description

Responsibility–

May 27, 2021

Initial release

S. Wekhande,
R. Farakate

1

May 16, 2022

Changes to title and abstract only.

S. Wekhande,
R. Farakate

Copyright 2022, Allegro MicroSystems.

The information contained in this document does not constitute any representation, warranty, assurance, guaranty, or inducement by Allegro to the customer with respect to the subject matter of this document. The information being provided does notguarantee that a process based on this information will be reliable, or that Allegro has explored all of the possible failure modes.
It is the customer’s responsibility to do sufficient qualification testing of the final product to ensure that it is reliable and meetsall design requirements.
Copies of this document are considered uncontrolled documents.

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