ON Semiconductor NCV7694 User Manual

Safety Controller for Infra-Red LED Illumination to Complement the Image Sensor for Automotive Applications

NCV7694

The NCV7694 is a device which can drive a string of infra−red LEDs using an external mosfet. The IR LEDs are used to illuminate the surroundings of the image sensor. Since these LEDs can damage the end users’ eyes, the power feed to the LEDs needs to be turned off during a fault condition.

The NCV7694 driver features prevents the IR LEDs from being on too long due to an inappropriate exposure time or being turned on too frequently using external resistors. The value of the R defines the maximum T value of the R

resistor defines the maximum frequency of the

FRL

time of the emitted light intensity and the

FLASH signal from the image sensor.

A LED driver with hardware interlocks helps protect the users’ eyes in cases where the control signal has failed or a fault in the LED power path has occurred.

LED brightness level is easily programmed using an external resistor in series with the mosfet transistor.

The device can also detect Open Load, Short Circuit to GND and VS. Faults are reported to the DIAG pin, which can directly disable the DC/DC converter to prevent possible damage.

The device is available in 10 pin DFN package.

Features

• Constant Current Output for LED String Drive

• FLASH Input Pin

• Open LED Diagnostic Detection

• Short LED to GND and VS Detection

• Safety Feature Prevent Being ON too long

• Safety Feature Prevent Being ON too frequently

• External Resistor Defining max ON time

• External Resistor Defining min OFF time

• Protection against Short to Ground and Open of the External Resistors

• Detection and Protection Against Under−Voltage and over

Temperature

• AEC−Q100 Qualified and PPAP Capable

• ASIL−A safety design, ISO26262 compliant

• 10 Pin Packaging

• Wettable Flank Package for Enhanced Optical Inspection

• These are Pb−Free Devices

Applications

• In−Cabin Monitoring Sensor

• Infrared Illumination for Automotive Cameras

• Machine Vision Systems

• Surveillance Systems

ETL

resistor

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DFNW10, 3x3, 0.5P

CASE 507AG

MARKING DIAGRAM

NV76

94−0

ALYW

NV7694−0 = Specific Device Code A = Assembly Location L = Wafer Lot Y = Year W = Work Week S = Pb−Free Package

PIN CONNECTIONS

DIAG

FLASH

ETL

FRL

ORDERING INFORMATION

Device Package Shipping

NCV7694MW0R2G DFN10

†For information on tape and reel specifications,

including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specification Brochure, BRD8011/D.

NCV7694

Top View

(Pb−Free)

STRING

DET

GATE

GND

2500 / Tape &

Reel

†

February, 2021 − Rev. 2

1 Publication Order Number:

NCV7694/D

NCV7694

BAT

SUPPLY

VDD_MCU

controller /

Supply for MCU and Image Sensor

VDD_MCU

Micro−

Data

interface

VDD_AR

Image Sensor

AR 0135

DSP

Diag detection

GND

VDD_MCU

20k

FLASH

Define max

exposure time

FLASH

DIAG

ETL

FRL

Define max frequency

NCV7694

GND

EMC1

VSTR

1 kW

EMC2

DET

1 kW

EMC3

GATE

200 W

EMC4

750 W

Note1: 4x optional EMC shield resistors

Note2: Optional Zener diode

NVTFS5C478NL

Figure 1. Application Diagram − Powered Directly from Battery

BAT

SUPPLY

VDD_MCU

Micro−

controller /

DSP

GND

Supply for MCU and Image Sensor

Data

interface

VDD_AR

Image Sensor

VDD_MCU

AR 0135

Diag detection

GND

exposure time

VDD_MCU

20k

FLASH

Define max

FLASH

DIAG

ETL

FRL

Define max frequency

NCV7694

GND

DC /DC

NCV898031

VString

VSTR

DET

GATE

EMC1

1 kW

EMC2

1 kW

EMC3

200 W

EMC4

750 W

Note1: 4x optional EMC shield resistors

Note2: Optional Zener diode for Mosfet Gate protection

NVTFS5C478NL

Figure 2. Application Diagram − using DC/DC

RECOMMENDED EXTERNAL COMPONENTS FOR THE APPLICATION DIAGRAM

Component Function Min Typ Max Unit

C1 Decoupling capacitor 100 nF

R1 FB current sense resistor 100

R2 DIAG pull−up resistor 20

R3 Resistor for Exposure Time Limitation 0.8 15

R4 Resistor for Frame Rate Limitation 0.8 15

REMC1 Optional EMC shield resistor for VSTR pin 1000

REMC2 Optional EMC shield resistor for DET pin 1000

REMC3 Optional EMC shield resistor for GATE pin 200

REMC4 Optional EMC shield resistor for FB pin 750

(Note 1) Optional EMC serial resistor shall be used in case if the LEDs are detached far away from the NCV7694 device. The resistors improves the EMC susceptibility of the application.

(Note 2) Optional Zener diode may be used if the VS supply is higher than V

voltage of the external transistor.

In case of Open Load on the LEDs, the GATE voltage will go high, the Zener diode will limit the maximum voltage

Figure 1 shows an example of the typical output drive configuration. The current through the external LEDs is equal to

= VFB / R

LEDs

Where:

• V

is internal feedback reference = 300 mV

• R

is feedback resistor which set the current

during eventual Open Load condition.

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Block Diagram

Exposure

Time Limit

FLASH

DIAG

ETL

Supply

monitoring

FLASH

ETL

NCV7694

Controlling,

Monitoring,

Filtering &

decoding

= V

str

Short Circuit

LED − Vstr

Short Circuit

LED − GND

SVth

1.22 V

− 1.22 V

SGth

350 mV

GATE

STRING

DETPull−up

DET

GATE

FRL

Frame Rate

Limit

RTL

FRL

= 1/ t

FRL

Open Load

GND

Figure 3. Simplified Block Diagram

reference

FBref

300mV

150 mV

OLth

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Timing Characteristics

e.g.: 45 Hz = 22 .2 ms period

NCV7694

FLASH

ET threhsold

Exposure Time

Counter

FR threshold

Frame Rate Counter

Typical pulse

ETL

Too long pulse

Short pulseTypical pulse

Double frequency pulse

FRL

LED output

Typical pulse Short pulse

Figure 4. Simplified Internal Timing Characteristic of the Internal ETL, FRL Counter

Safety Feature Behavior

External Resistor Approach

The resistor (RETL, RFRL) creates bias voltage on the pins. Internal oscillator speed is derived from value of the resistors. While FLASH signal is high, internal ETL counter is counting and when the threshold is exceeded, the output is disabled. When FLASH pin is low, the Frame Rate timer is starting to count. The next rising edge of the FLASH signal is propagated to the output only if FRL timer expires.

Rest of the pulse

is cut−OFF because “ET”

counter exceed the

threshold

The period of the internals counters can be adjusted by external resistors.

Total tolerance of the maximum T Rate limits will be affected by internal accuracy and accuracy of the external resistor by following equation: Using 1% external resistor approximately 13% tolerance can be achieved.

TOTAL

Driver is activated with

next rising edge of

FLASH pulse

+ a

device

) a

+ 13.02) 1

resistor

Second pulse is cut off

because “FR” counter is

not reach the threshold

or maximum Frame

+ 13.04 %

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NCV7694

PIN FUNCTION DESCRIPTION

10−pin DFN10

Package

Pin # Label Description

1 VS Supply voltage of the device

2 DIAG Diagnostic output

3 FLASH Logic input for flash exposure time

4 R

5 R

ETL

FRL

6 GND Ground

7 FB Feedback reference input 300 mV.

8 GATE Gate drive for external mosfet

9 DET LED short detection input

10 V

STRING

MAXIMUM RATINGS

Symbol Parameter Min. Max. Unit

Vmax_VS Continuous supply voltage

Vmax_FLASH Low Voltage Input pin −0.3 +3.6 V

Vmax_GATE Output voltage (during Open Load condition) −0.3 +VS V

Vmax_R

ETL

, R

FRL

Vmax_FB Low Voltage Input pin −0.3 +3.6 V

Vmax_DIAG Open Drain pin −0.3 +40 V

Vmax_DET,

STRING

Tjmax Junction Temperature, T

Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected.

1. Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied, damage may occur and reliability may be affected.

Transient Voltage (t < 500 ms, “load dump”)

DC voltage on Resistors −0.3 +3.6 V

High Voltage Input pin −0.3 +40 V

External resistor defines maximum Exposure Time Limit

External resistor defines maximum Frame Rate Limit

Short circuit reference voltage

−0.3

−

−40 +125

+40 +40

V V

°C

ATTRIBUTES

Parameer Value Unit

ESD Capability (Note 2)

HBM (Human Body Model) CDM (Charge Device Model) MM (Machine Model)

≥ ±4.0 ≥ ±1.0

≥ ±200

kV kV

Moisture Sensitivity (DFN10−EP) (Note 3) 1 MSL

Storage Temperature Range −40 to 150 °C

Package Thermal Resistance (DFN10−EP) (Note 4)

− Junction to Ambient, R

− Junction to Board, R

− Junction to Case (Top), R

62.5

5.5

2.7

°C/W °C/W °C/W

Ambient Temperature −40 to 105 °C

2. This device series incorporates ESD protection and is tested by the following methods:

ESD HBM tested per AEC−Q100−002 (EIA/JESD22−A114) ESD CDM tested per EIA/JES D22/C101, Field Induced Charge Model ESD MM according to AEC−Q100

3. For additional information, see or download ON Semiconductor’s Soldering and Mounting Techniques Reference Manual, SOLDERRM/D, and Application Note AND8003/D.

4. Values represent thermal resistances under natural convection are obtained in a simulation on a JEDEC−standard, 2S2P; High Effective Thermal Conductivity Test Board as specified in JESD51−7, in an environment described in JESD51−2a.

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NCV7694

ELECTRICAL CHARACTERISTICS

(

7 V < VS < 28 V, R

R1 = 100 mW, −40°C ≤ T

GENERAL

Supply Voltage

Supply Under−Voltage Lockout VSUV VS rising 4.0 4.5 5.0 V

Supply Under−Voltage hysteresis VSUVhys 150 300 550 mV

Supply Current in normal condition I_VS

Supply Current in Fault condition I_VSerr VS = 14 V,

Thermal Shutdown (TSD) 130 150 170

Thermal Hysteresis − 15 −

FB DRIVER

FB Regulation reference Gate ON voltage V

Propagation Delay FLASH rising – FB ON

Propagation Delay FLASH falling – FB OFF

FLASH propagation Delay Delta t

Output pull−down resistance R

FLASH INPUT PIN

Input High Threshold Input Low Threshold V Input pull−down resistance R

PROGRAMMING

Bias voltage V

ETL

ETL resistor operation range R

Maximum TON time (typ) T

ETL multiplication K

tolerance tol

ETL

Overcurrent protection R

Open Load protection R

= 4.99 kW, R

ETL

≤ 125°C, unless otherwise specified)

Characteristic

ETL

=1.96 kW, 4 V < V

FRL

< 28 V, Transistor = NVTFS5C478NL, LED = SFH 4725AS,

STRING

Symbol Conditions Min. Typ. Max. Unit

VS_OP Parametric operation 7 − 28 V

VS = 14 V,

− 4.0 6.0 mA FLASH = High, I

, I

FRL

VS = 14V,

subtracted

ETL

− 3.8 6.0 mA FLASH = Low, I

, I

FRL

subtracted

ETL

− 4.0 6.0 mA FLASH = High, Open Load condition, I

, I

subtracted

ETL

4.5 − − V

− 1.4 4

FBref

GATE

OFF

pd_delta

FRL

Under Voltage Lockout < VS 270 300 330 mV FB = 220 mV,

DET = 1.0 V 50% criterion − 8 15

50% criterion − 6.6 15

|(Falling time) – (Rising Time)|

50% criterion

GATE

inH

inL

FLASH

ETL

ONmax

ETL

ETL_lim

ETL_open

5 30 100

1.3 1.2 − V

− 1.15 1.1 V 30 120 190

ETL

1.0

4990

+ 200.4 mA

external resistor value operation

− 1.0 − V

0.8 − 15

range for R for R Derived from R

valid for

ETL

= 800 W => t

ETL

= 15 kW => t

ETL

and K

ETL

= 15 kW

4.99

2.5

= 320 ms;

ETL

= 6 ms

ETL

ETL(typ)

+ 1.996 ms

;

− − 6.0 ms

− 2.5 −

Tolerance of Exposure Time Limit ±13.0 % Short to ground

1.3 − − mA

Resistor detection for

< 750 W

ETL

Open Load detection

− − 57.5 Resistor detection for

> 17.5 kW

ETL

°C

μs

kW/s

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