BD81A74MUV-M_技术文档

Datasheet

4ch White LED Driver Built-in Current Driver

Buck-Boost and Boost DC/DC Converter

for Automotive

BD81A74EFV-M BD81A74MUV-M

General Description

Key Specifications

BD81A74EFV-M / BD81A74MUV-M is a white LED

driver with the capability of withstanding high input

voltage (maximum 35 V). This driver has 4ch constant-

current drivers in 1-chip, where each channel can draw

up to 120 mA (Max), and it is suitable for high

illumination LED drive. Furthermore, a buck-boost

current mode DC/DC converter is also built to achieve

stable operation during power voltage fluctuation.

◼ Operating Input Voltage Range

4.5 V to 35 V

◼ Output LED Current Accuracy

±3.0 %@50 mA

◼ DC/DC Oscillation Frequency 200 kHz to 2200 kHz

◼ Operating Temperature

-40 °C to +125 °C

120 mA/ch

10,000:1@100 Hz

1.0 µs

◼ LED Maximum Output Current

◼ LED Maximum Dimming Ratio

◼ PWM Minimum Pulse Width

Light modulation (10,000:1@100 Hz dimming Packages

W (Typ) x D (Typ) x H (Max)

5.0 mm x 5.0 mm x 1.0 mm

9.7 mm x 6.4 mm x 1.0 mm

function) is possible by PWM input.

VQFN28SV5050

HTSSOP-B28

Features

◼ AEC-Q100 Qualified^*1

◼ 4ch Current Driver for LED Drive

◼ Buck-Boost Current Mode DC/DC Converter

◼ Control DC/DC Converter Oscillation Frequency by

External Synchronized Signal

◼ Spread Spectrum Function

◼ LSI Protection Function (UVLO, OVP, TSD, OCP, SCP)

◼ LED Abnormality Detection Function (Open/Short)

◼ VOUT Discharge Function (Buck-Boost Structure

Limitation)

VQFN28SV5050

BD81A74MUV-M

HTSSOP-B28

BD81A74EFV-M

*1 Grade 1

Applications

◼ Automotive CID (Center Information Display) Panel

◼ Car Navigation

◼ Cluster Panel

◼ HUD (Head Up Display)

◼ Small and Medium Type LCD Panels for Automotive

Use

Typical Application Circuit

〇Product structure : Silicon integrated circuit 〇This product has no designed protection against radioactive rays

〇This product is protected by U.S. Patent No.7,235,954, No.7,541,785, No.7,944,189.

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Pin Configuration

VQFN28SV5050 (TOP VIEW)

Pin Description

Pin No.

Pin Name

LEDEN1

LEDEN2

LED1

LED2

LED3

LED4

OVP

Function

Enable pin 1 for LED output

1

2

Enable pin 2 for LED output

LED output pin 1

3

4

LED output pin 2

5

LED output pin 3

6

LED output pin 4

7

Over voltage detection pin

LED output current setting pin

LED output GND pin

8

ISET

9

PGND

OUTL

DGND

VDISC

SW

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

-

Low side FET gate pin

DC/DC converter output GND pin

Output voltage discharge pin

High side FET source pin

High side FET gate pin

OUTH

BOOT

VREG

EN

High side FET driver power supply pin

Internal constant voltage

Enable pin

CS

DC/DC converter current sense pin

Input power supply pin

VCC

SS

“Soft Start” capacitor connection

Error Amp output

COMP

RT

Oscillation frequency setting resistor connect

External synchronization input pin

Spread spectrum setting capacitor pin

Small signal GND pin

SYNC

SSCG

GND

PWM

FAIL1

FAIL2

EXP-PAD

PWM light modulation signal input pin

“Failure” signal output pin 1

“Failure” signal output pin 2

Back side thermal PAD (Connect to GND)

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Pin Configuration

HTSSOP-B28 (TOP VIEW)

Pin Description

Pin No.

Pin Name

VCC

Function

Input power supply pin

1

2

SS

“Soft Start” capacitor connection

Error Amp output

3

COMP

RT

4

Oscillation frequency setting resistor connect

External synchronization input pin

Spread spectrum setting capacitor pin

Small signal GND pin

5

SYNC

SSCG

GND

6

7

8

PWM

FAIL1

FAIL2

LEDEN1

LEDEN2

LED1

LED2

LED3

LED4

OVP

PWM light modulation signal input pin

“Failure” signal output pin 1

“Failure” signal output pin 2

Enable pin 1 for LED output

Enable pin 2 for LED output

LED output pin 1

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

-

LED output pin 2

LED output pin 3

LED output pin 4

Over voltage detection pin

LED output current setting pin

LED output GND pin

ISET

PGND

OUTL

DGND

VDISC

SW

Low side FET gate pin

DC/DC converter output GND pin

Output voltage discharge pin

High side FET source pin

OUTH

BOOT

VREG

EN

High side FET gate pin

High side FET driver power supply pin

Internal constant voltage

Enable pin

CS

DC/DC converter current sense pin

Back side thermal PAD (Connect to GND)

EXP-PAD

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Block Diagram

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Description of Blocks

If there is no description, the mentioned values are typical value.

1. Reference Voltage (VREG)

VREG Block generates 5 V at EN = High, and outputs to the VREG pin. This voltage (V_VREG) is used as power

supply for internal circuit. It is also used to fix each input pin to High voltage outside IC. It cannot supply power

to other parts than this IC. The VREG pin has UVLO function, and it starts operation at VCC ≥ 4.0 V and V_VREG

≥ 3.5 V and stops when at VCC ≤ 3.5 V or V_VREG≤ 2.0 V. About the condition to release/detect VREG voltage,

refer to Table 2 on section 4 4. Protection Feature. Connect a ceramic capacitor (C_VREG) to the VREG pin for

phase margin. C_VREGrange is 1.0 µF to 4.7 µF and recommended value is 2.2 µF. If the C_VREGis not connected,

it might occur unstable operation e.g. oscillation.

2. Current Driver

Table 1. LED Control Logic

If there is the constant-current driver output not to use, make the LED1 to LED4 pins ‘open’ and turn off the

channel, which is not used, with the LEDEN1 and LEDEN2 pins. The truth table for these pins is shown above.

If the unused constant-current driver output is set open without the process of the LEDEN1 and LEDEN2 pins,

the ‘open detection’ is activated. The LEDEN1 and LEDEN2 pins are pulled down internally in the IC and it is

low at ‘open’ condition. They can be connected to the VREG pin and fixed to logic High. Logic of the LEDEN1

and LEDEN2 pins are not switchable during these in operation.

(1) Output Current Setting (R_ISET

)

120

110

100

90

80

70

60

50

40

30

20

40 60 80 100 120 140 160 180 200 220 240

R_ISET[kΩ]

Figure 1. I_LEDvs R_ISET

The Output Current I_LEDcan be obtained by the following equation:

퐼_퐿퐸퐷= 5000/푅_ꢀ푆퐸푇[A]

The operating range of the R_ISETvalue is from 41 kΩ to 250 kΩ. Additionally, the R_ISETvalue could not be

changed during operation. In this IC, ISET-GND short protection is built-in to protect an LED element

from excess current when the ISET pin and GND are shorted. If the R_ISETvalue is 4.7 kΩ or less, the IC

detects ISET-GND short condition and LED current is turned off.

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2. Current Driver – continued

During PWM dimming, the LED pin voltage (V_LED) rises when PWM = Low because LED current doesn't flow,

and controls V_LEDto 1 V when PWM = High. When PWM rise up, V_LEDundershoot may occur depends on

LED current setting or external parts including the output capacitor. The undershoot is large especially at

high temperature and large LED current.

LED current may decrease instantly as Figure 2(a) shows by the undershoot. The undershoot and the

settable LED current are shown in Figure 2(b).

If the LED current is decreased with the undershoot, it may not see as the LED flicker. Evaluate with the

actual application certainly, and check at the visual perspective.

PWM

LED pin control voltage

V_LED

Undershoot

(ΔVdrop)

I_LED

(a) Timing Chart of V_LED, I_LEDat PWM Dimming

(b) Temperature(Ta) vs LED Current(I_LED)

Figure 2. Relation Between Undershoot of V_LEDand LED Current

(2) PWM Dimming Control

1 ms/Div

500 ns/Div

PWM

(2 V/Div)

PWM

(2 V/Div)

I_LED

(50 mA/Div)

I_LED

(50 mA/Div)

(a) PWM = 150 Hz, Duty = 0.02 %, I_LEDWaveform

(b) PWM = 150 Hz, Duty = 50.0 %, I_LEDWaveform

Figure 3. PWM Dimming Waveform

The current driver ON/OFF is controlled by the PWM pin. The duty ratio of the PWM pin becomes duty

ratio of I_LED. If PWM dimming is not totally used (i.e. 100 %), fix the PWM pin to High. Output light

intensity is the highest at 100 %.

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Description of Blocks – continued

3. Buck-Boost DC/DC Converter

(1) Number of LED in Series Connection

This IC controls output voltage to become 1.0 V by detecting LED cathode voltage (the LED1 to LED4 pins

voltage). When multiple LED outputs are operating, it controls LED pin voltage with the highest LED Vf to

become 1.0 V. Thus, the output voltage of other LED pins is higher by the variations of Vf. Set up Vf variation

to meet the formula below.

ꢁꢂꢃ ꢄ푒푟ꢅ푒푠 푁푢푚푏푒푟 × 푉푓 푉푎푟ꢅ푎푡ꢅ표푛

< ꢄℎ표푟푡 ꢃ푒푡푒푐푡ꢅ표푛 푉표푙푡푎푔푒 (푀ꢅ푛)－ ꢁꢂꢃ 퐶표푛푡푟표푙 푉표푙푡푎푔푒(푀푎푥)

(2) Over Voltage Protection (OVP)

The output voltage (VOUT) should be connected to the OVP pin via resistor voltage divider. If the OVP pin

voltage is 2.0 V or more, Over Voltage Protection (OVP) is active and stop the DC/DC converter switching.

Determine the setting value of OVP function by the total number of the LEDs in the series and the Vf

variation. When the OVP pin voltage drops less than 1.94 V after OVP operation, the OVP is released.

{

}

푉푂푈ꢆ ≥ (푅_ꢇꢈ푃1+ 푅_ꢇꢈ푃2) ∕ 푅_ꢇꢈ푃1× ꢉ.0

where:

푉푂푈ꢆ is the Output voltage.

푅_ꢇꢈ푃1is the GND side OVP resistance.

푅_ꢇꢈ푃2is the Output voltage side OVP resistance.

For example, OVP is active when VOUT ≥ 32 V if R_OVP1= 22 kΩ and R_OVP2= 330 kΩ.

(3) Buck-Boost DC/DC Converter Oscillation Frequency (f_OSC

)

1000

100

1

10

100

R_RT[kΩ]

Figure 4. f_OSCvs R_RT

DC/DC oscillation frequency can be set via a resistor connected to the RT pin. This resistor determines the

charge/discharge current to the internal capacitor, thereby changing the oscillation frequency. Set the

resistance of R_RTusing the above data and the equation below.

= (8ꢋ × ꢋ0^ꢌ푅_ꢍ푇

)

[kHz]

⁄

푓

ꢇ푆ꢊ

81 x 10⁵is the constant value determined in the internal circuit.

Take note that operation could not be guaranteed in the case of settings other than the recommended range.

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3. Buck-Boost DC/DC Converter - continued

(4) Spread Spectrum Function

Operation in Spread Spectrum Clock Generation (SSCG) is possible by connecting capacitor to the SSCG pin.

The SSCG pin has a comparator and constant current circuit to assume 0.6 V/0.48 V reference voltage, and

changes into a triangular waveform. The average of noise can be reduced by changing the switching

frequency by a frequency (f_SSCG) decided in the SSCG pin capacity C_SSCG. The band of the switching frequency

becomes 100 % to 80 % of switching frequency when SSCG is not used.

Figure 5. SSCG Noise Reduction Image

Figure 6. SSCG System Diagram

f_SSCGcan be calculated by the following equation.

3

푓

푆푆ꢊ퐺

=

[Hz]

4×ꢊ

×ꢍ

ꢑꢒ

ꢎꢎꢏꢐ

Set it to satisfy the equation of 0.4 kHz ≤ f_SSCG≤ 30 kHz.

Furthermore, quantity of noise reduction S [dB] in SSCG can be roughly estimated by the equation below.

ꢔ

ꢎꢎꢏꢐ

ꢄ = −ꢋ0 × 푙표푔 ꢓ_{ꢔ ×ꢖ.2}ꢗ [dB]

ꢕꢎꢏ

Short the SSCG pin and the GND pin when SSCG function is not used.

(5) External Synchronization Oscillation Frequency

By clock signal input to the SYNC pin, the internal oscillation frequency can be synchronized externally. Do

not switch from external to internal oscillation if the DC/DC switching is active. The clock input to the SYNC

pin is valid only in rising edge. Input the external input frequency within ±20 % of internal oscillatory

frequency set by the RT pin resistance.

(6) Soft Start Function (SS)

The soft-start (SS) function can start the output voltage slowly while controlling the current during the start

by connecting the capacitance (C_SS) to the SS pin. In this way, output voltage overshoot and inrush current

can be prevented. When SS function is not used, set the SS pin open. Refer to Setting of the Soft Start Time

for the calculation of SS time.

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3. Buck-Boost DC/DC Converter - continued

(7) Maximum Duty

When DC/DC switching reaches Maximum Duty, expected VOUT voltage could be not output, and LED lights-

out might occur by the reduction of LED output current and detection of ground short protection. Set input

condition and load condition such that it does not reach Maximum Duty.

(8) DC/DC Switching Control at Over Voltage Output (LSDET)

When the lowest voltage in LED1 to LED4 pins (DC/DC feedback voltage) is more than 1.24 V, LSDET

function works and turns off the switching of the DC/DC converter and maintains the COMP voltage

(switching Duty). This function reduces the VOUT voltage quickly and intended to output stable switching

Duty when VOUT is higher than the aim voltage. For example, LSDET works at the time of the LED4 OPEN

detection. The timing chart example is described below.

(9) PWM Pulse and DC/DC Switching

After the fall of the PWM pulse, DC/DC switching is output 12 times and after that, turn off the DC/DC

switching during PWM = Low. When PWM becomes High again, the DC/DC switching is on. Because of this,

when PWM pulse width is short, it can maintain the output voltage and output the stable LED current.

PWM

+12 pulses

OUTL

VOUT

VOUT keep

Stable LED current output

I_LED

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Description of Blocks – continued

4. Protection Feature

Table 2. Detect Condition of Each Protection Feature and Operation during Detection

Detect Condition

[Release/Cancellation]

Function

Operation During Detection

[Detection]

VCC ≥ 4.0 V and

V_VREG≥ 3.5 V

UVLO

VCC ≤ 3.5 V or V_VREG≤ 2.0 V

All blocks shut down except VREG

TSD

OVP

OCP

Ta ≥ 175 °C

V_OVP≥ 2.0 V

Ta ≤ 150 °C

V_OVP≤ 1.94 V

V_CS> VCC-0.2 V

All blocks shut down except VREG

DC/DC switching OFF

V_CS≤ VCC-0.2 V

DC/DC switching OFF

V_OVP≤ 0.57 V

or

Any of V_LED1to V_LED4is

0.3 V or less

EN Reset

or

UVLO Reset

After SCP delay time,

all blocks latch OFF except VREG

SCP

(100 ms delay @300 kHz)

Any of V_LED1to V_LED4is

0.3 V or less

EN Reset

or

UVLO Reset

LED Open

Protection

Only detected channel

LED current latches OFF

and

V_OVP≥ 2.0 V

LED

Short

Any of V_LED1to V_LED4is

4.5 V and more

EN Reset

or

After LED Short delay time,

only detected channel

Protection

(100 ms delay @300 kHz)

UVLO Reset

LED current latches OFF

Protection Flag Output Block Diagram

FAIL1 becomes low when OVP or OCP protection is detected, whereas FAIL2 becomes low when SCP, LED

open or LED short is detected. If the FAIL1, FAIL2 pin is not used as a flag output, set the FAIL1, FAIL2 pin

open or connect it to GND. The output from the FAIL1 and FAIL2 pins are reset and return to High by

starting up of EN or release of UVLO. Also, those output is unstable when EN = Low and detecting UVLO.

If the FAIL pin is used as a flag output, it is recommended to pull-up the FAIL1, FAIL2 pins to the VREG pin.

The recommended value of pull-up resistance is 100 kΩ.

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4. Protection Feature - continued

(1) Under-Voltage Lock Out (UVLO)

The UVLO shuts down DC/DC converter and Current Driver when VCC ≤ 3.5 V or V_VREG≤ 2.0 V. And UVLO

is released by VCC ≥ 4.0 V and V_VREG≥ 3.5 V.

(2) Thermal Shutdown (TSD)

The TSD shuts down DC/DC converter and Current Driver when the Tj 175 °C or more, and releases when

the Tj becomes 150 °C or less.

(3) Over Voltage Protection (OVP)

The output voltage of DC/DC converter is detected from the OVP pin voltage, and the over voltage protection

is activate if the OVP pin voltage becomes ≥ 2.0 V. When OVP is activated, the switching operation of the

DC/DC converter turns off. And the OVP pin voltage becomes ≤ 1.94 V, OVP is released and the switching

operation of the DC/DC converter turns on.

(4) Over Current Protection (OCP)

The OCP detects the coil current by monitoring the voltage of the high side resistor, and activates when V_CS

≤ VCC-0.2 V. When the OCP is activated, the switching operation of the DC/DC converter turns off. And V_CS

> VCC-0.2 V, OCP is released and the switching operation of the DC/DC converter turns on.

(5) Short Circuit Protection (SCP)

The SCP can be operated when the SS pin voltage reaches 3.3 V while start-up. When any of the LED1 to

LED4 pins voltage becomes 0.3 V or less or V_OVP≤ 0.57 V, the built-in counter operation starts. The clock

frequency of counter is the oscillation frequency (f_OSC), which is determined by R_RT. After it counts 32770,

the DC/DC converter and the current driver are latched off. When fosc = 300 kHz, the count time is 100

ms and SCP operates after this count time. If all of the LED pin voltage becomes more than 0.3 V or V_OVP

≥ 1.0 V before 32770 count, the counter resets and SCP is not detected.

(6) LED Open Protection

When any of the LED pins voltage is 0.3 V or less and V_OVP2.0 V or more, LED open is detected and latches

off the open LED channel only.

(7) LED Short Protection

If any of V_LED1to V_LED4is 4.5 V or more, the built-in counter operation starts. The clock frequency of counter

is the oscillation frequency (f_OSC), which is determined by R_RT. After it counts 32770, latches off the short

LED channel only. When fosc = 300 kHz, the count time is 100 ms and SCP operates after this count time.

During PWM dimming, the LED Short Protection is carried out only when PWM = High. If the condition of

LED Short is reset while working the counter, the counter resets and LED Short is not detected.

(8) PWM Low Interval Detect

The low interval of PWM input is counted by built-in counter during EN = High. The clock frequency of

counter is the oscillation frequency (f_OSC), which is determined by R_RT. It stops the operation of circuits

except VREG at 32768 counts. When f_OSC= 300 kHz, the count time is 100 ms and the Low interval of PWM

is detected after this count time.

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4. Protection Feature - continued

(9) Output Voltage Discharge Circuit (VOUT Discharge Function)

If start-up with a charge remaining at VOUT, LED might occur flicker. To prevent this, it is necessary to

discharge of VOUT when starting-up. If use only resistance for setting OVP to discharge, it takes a lot time

for discharging VOUT. Therefore, this product has functionality of circuit for VOUT discharge. VOUT

discharge function is available at Buck-Boost application and Buck application. For this case, be sure to

connect VOUT and the VDISC pin. It discharges the residual electric charge of VOUT when DC/DC circuit is

OFF; changing EN High to Low or operating protect function. The discharge time (t_DISC) is expressed in the

following equations.

3×ꢈꢇꢘ푇×ꢊ

ꢕꢙꢒ

푡_퐷ꢀ푆ꢊ

=

[s]

4×ꢀ

ꢚꢛꢎꢏ

where:

푡_퐷ꢀ푆ꢊ

is the DC/DC converter output discharge time.

is the VOUT capacity.

퐶_ꢇꢘ푇

푉푂푈ꢆ

퐼_퐷ꢀ푆ꢊ

is the DC/DC converter output voltage.

is the discharge current.

From the graph below, find the I_DISCvalue in 25 % VOUT voltage, and substitute it in the above equation.

For example, substitute I_DISCvalue in VOUT = 5 V (approximately 76 mA) in the above equation when using

in VOUT = 20 V, and calculate the discharge time.

In order to suppress the flickering of the LED, the time of restarting EN = Low should be secured t_DISCor

more long.

Always check with actual machine because the t_DISCfound here is a reference level.

0.12

0.10

0.08

0.06

0.04

0.02

0.00

0

5

10

15

20

25

30

35

40

VOUT [V]

Figure 7. I_DISCvs VOUT

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Absolute Maximum Ratings (Ta = 25 °C)

Parameter

Symbol

Rating

Unit

Power Supply Voltage

VCC

V_BOOT, V_OUTH

V_SW, V_CS

40

V

BOOT, OUTH Pin Voltage

SW, CS Pin Voltage

45

40

BOOT-SW Pin Voltage

V_BOOT-SW

7

40

LED1 to LED4, VDISC Pin Voltage

PWM, SYNC, EN Pin Voltage

VREG, OVP, FAIL1, FAIL2,

SS, RT, SSCG Pin Voltage

LEDEN1, LEDEN2, ISET,

COMP, OUTL Pin Voltage

Maximum Junction Temperature

Storage Temperature Range

LED Maximum Output Current

V_{LEDn (n = 1 to 4)}, V_VDISC

V_PWM, V_SYNC, V_EN

V_VREG, V_OVP, V_FAIL1, V_FAIL2

V_SS, V_RT, V_SSCG

V_LEDEN1, V_LEDEN2, V_ISET

V_COMP, V_OUTL

Tjmax

-0.3 to +7

,

-0.3 to +7 < VCC

-0.3 to +7 < V_VREG

V

150

-55 to +150

120^*1

°C

Tstg

I_LED

mA

Caution 1: Operating the IC over the absolute maximum ratings may damage the IC. The damage can either be a short circuit between pins or

an open circuit between pins and the internal circuitry. Therefore, it is important to consider circuit protection measures, such as adding

a fuse, in case the IC is operated over the absolute maximum ratings.

Caution 2: Should by any chance the maximum junction temperature rating be exceeded the rise in temperature of the chip may result in

deterioration of the properties of the chip. In case of exceeding this absolute maximum rating, design a PCB board with thermal

resistance taken into consideration by increasing board size and copper area so as not to exceed the maximum junction temperature

rating.

*1 Current level per channel. Set the LED current that does not over Junction Temperature Range (Tj) maximum.

Thermal Resistance^*1

Thermal Resistance (Typ)

Parameter

Symbol

Unit

1s^*3

2s2p^*4

VQFN28SV5050

Junction to Ambient

Junction to Top Characterization Parameter^*2

θ_JA

128.50

12

31.50

9

°C/W

Ψ_JT

HTSSOP-B28

Junction to Ambient

Junction to Top Characterization Parameter^*2

θ_JA

107.00

6

25.10

3

°C/W

Ψ_JT

Layer Number of

Material

Board Size

Measurement Board

Single

FR-4

114.3 mm x 76.2 mm x 1.57 mmt

Top

Copper Pattern

Thickness

70 μm

Footprints and Traces

Layer Number of

Measurement Board

Thermal Via^*5

Material

FR-4

Board Size

114.3 mm x 76.2 mm x 1.6 mmt

2 Internal Layers

Pitch

1.20 mm

Diameter

Φ0.30 mm

4 Layers

Top

Bottom

Copper Pattern

74.2 mm x 74.2 mm

Copper Pattern

Thickness

70 μm

Copper Pattern

Thickness

35 μm

Thickness

70 μm

Footprints and Traces

74.2 mm x 74.2 mm

*1 Based on JESD51-2A(Still-Air)

*2 The thermal characterization parameter to report the difference between junction temperature and the temperature at the top center of the outside

surface of the component package.

*3 Using a PCB board based on JESD51-3.

*4 Using a PCB board based on JESD51-5, 7.

*5 This thermal via connects with the copper pattern of all layers.

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Recommended Operating Conditions

Parameter

Symbol

Min

Typ

Max

Unit

Power Supply Voltage^*1

Operating Temperature

DC/DC Oscillation Frequency

VCC

Topr

f_OSC

4.5

-40

200

35

V

12

+25

300

+125

2200

°C

kHz

*2

External Synchronized Frequency

Higher of 200

or f_OSCx 0.8

Lower of 2200

or f_OSCx 1.2

f_SYNC

300

50

kHz

%

*3

External Synchronized Pulse Duty

D_SYNC

40

60

*1 This indicates the voltage near the VCC pin. Be careful of voltage drop by the impedance of power line.

*2 When external synchronization frequency is not used, connect the SYNC pin to open or GND.

*3 When external synchronization frequency is used, do not change to internal oscillation frequency along the way.

Operating Conditions (External Constant Range)

Parameter

VREG Capacity

Symbol

Min

Typ

Max

Unit

C_VREG

R_ISET

1.0

41

2.2

4.7

μF

LED Current Setting Resistance

Oscillation Frequency Setting

Resistance

100

250

kΩ

R_RT

3.6

27

41

kΩ

Soft Start Capacity Setting

C_SS

0.047

4.7

0.1

10

0.47

47

μF

nF

Spread Spectrum Setting Capacity

C_SSCG

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Electrical Characteristics(Unless otherwise specified, VCC = 12 V, Ta = -40 °C to +125 °C)

Parameter

Symbol

Min

Typ

Max

Unit

mA

μA

Conditions

EN = High, SYNC = High,

RT = OPEN, PWM = Low,

ISET = OPEN, CIN = 10 μF

EN = Low, VDISC = OPEN

Circuit Current

I_CC

-

10

Standby Current

[VREG]

I_ST

10

Reference Voltage

[OUTH]

V_VREG

4.5

5.0

5.5

V

I_VREG= -5 mA, C_VREG= 2.2 μF

OUTH High Side ON-Resistor

OUTH Low Side ON-Resistor

OCP Detection Voltage

この行は削除してください

[OUTL]

R_ONHH

R_ONHL

1.5

0.8

3.5

2.5

7.0

5.5

Ω

I_OUTH= -10 mA

I_OUTH= 10 mA

V_OLIMIT

t_OLIMIT

VCC-0.22 VCC-0.20 VCC-0.18

V

-

30

-

ns

V_CS= VCC-0.5V

OUTL High Side ON-Resistor

OUTL Low Side ON-Resistor

[SW]

R_ONLH

R_ONLL

1.5

0.8

3.5

2.5

10.0

5.5

Ω

I_OUTL= -10 mA

I_OUTL= 10 mA

SW ON-Resistor

R_{ON_SW}

4.0

10.0

25.0

Ω

I_SW= 10 mA

[ERRAMP]

LED Control Voltage

V_LED

0.9

35

1.0

80

1.1

V

V_LEDn= 2 V (n = 1 to 4),

V_COMP= 1 V

COMP Sink Current

I_COMPSINK

145

μA

V_LEDn= 0.5 V (n = 1 to 4),

V_COMP= 1 V

COMP Source Current

I_COMPSOUCE

-145

-80

-35

μA

[Oscillator]

Oscillation Frequency 1

Oscillation Frequency 2

[OVP]

f_OSC1

f_OSC2

285

300

315

kHz R_RT= 27 kΩ

kHz R_RT= 3.9 kΩ

1800

2000

2200

OVP Detection Voltage

OVP Hysteresis Width

V_OVP1

1.9

2.0

2.1

V

V_OVP: Sweep up

V_OVPHYS1

0.02

0.06

0.10

V_OVP: Sweep down

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Electrical Characteristics - continued(Unless otherwise specified, VCC = 12 V, Ta = -40 °C to +125 °C)

Parameter

Symbol

Min

Typ

Max

Unit

Conditions

[UVLO]

UVLO Detection Voltage

UVLO Hysteresis Width

[LED Output]

V_UVLO

V_UHYS

3.2

3.5

3.8

V

VCC: Sweep down

VCC: Sweep up,

V_VREG> 3.5 V

0.25

0.50

0.75

I_LED= 50 mA, Ta = 25 °C

ΔI_LED1= (I_LEDn/I_{LEDn_AVG}-1)x 100

(n = 1 to 4)

-3

-5

-3

-5

-

+3

+5

+3

+5

%

LED Current Relative

Dispersion

I_LED1

I_LED= 50 mA,

Ta = -40 °C to +125 °C

ΔI_LED1= (I_LEDn/I_{LEDn_AVG}-1)x 100

(n = 1 to 4)

I_LED= 50 mA, Ta = 25 °C

ΔI_LED2= (I_LEDn/50mA-1) x 100

(n = 1 to 4)

LED Current Absolute

Dispersion

I_LED2

I_LED= 50 mA,

Ta = -40 °C to +125 °C

ΔI_LED2= (I_LEDn/50mA-1) x 100

(n = 1 to 4)

ISET Voltage

V_ISET

t_MIN

0.9

1

1.0

1.1

-

V

R_ISET= 100 kΩ

f_PWM= 100 Hz to 20 kHz,

I_LED= 20 mA to 100 mA

PWM Minimum Pulse Width

-

μs

PWM Frequency

f_PWM

0.1

20

kHz

[Protection Circuit]

V_LEDn:(n = 1 to 4)

Sweep down

LED Open Detection Voltage

LED Short Detection Voltage

V_OPEN

V_SHORT

t_SHORT

0.2

4.2

70

0.3

4.5

100

0.4

4.8

130

V

V_LEDn:(n = 1 to 4)

Sweep up

LED Short Detection Latch OFF

Delay Time

ms R_RT= 27 kΩ

SCP Latch OFF Delay Time

PWM Latch OFF Delay Time

t_SCP

70

100

130

ms R_RT= 27 kΩ

t_PWM

ISET-GND Short Protection

Impedance

I_SETPROT

V_LSDET

-

4.7

-

kΩ

V

LSDET Detection Voltage

1.24

[Logic Input Voltage]

EN, SYNC, PWM,

LEDEN1, LEDEN2

EN, SYNC, PWM,

LEDEN1, LEDEN2

Input High Voltage

Input Low Voltage

Input Current

V_INH

V_INL

I_IN

2.1

GND

15

-

V_VREG

0.8

V

V_IN= 5 V (EN, SYNC,

PWM, LEDEN1, LEDEN2)

50

100

μA

[FAIL Output (Open Drain)]

FAIL Low Voltage

V_OL

-

0.1

0.2

V

I_FAIL= 0.1 mA

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Typical Performance Curves

(Reference Data. Unless otherwise specified, Ta = -40 °C to +125 °C)

Figure 8. Circuit Current vs Power Supply Voltage

(VCC = 4.5 V to 35 V, V_EN= 3.3 V, V_PWM= 0 V)

Figure 9. Reference Voltage vs Temperature

(VCC = 12 V, V_EN= 3.3 V, V_PWM= 0 V)

Figure 10. Oscillation Frequency 1 vs Temperature

(@300 kHz, VCC = 12 V, V_EN= 3.3 V, R_RT= 27 kΩ)

Figure 11. Oscillation Frequency 2 vs Temperature

(@2000 kHz, VCC = 12 V, V_EN= 3.3 V, R_RT= 3.6

kΩ)

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Typical Performance Curves - continued

(Reference Data. Unless otherwise specified, Ta = -40 °C to +125 °C)

Figure 12. LED Current vs LED Voltage

(Ta = 25°C, VCC = 12 V, V_EN= 3.3 V,

V_LEDn= sweep (n = 1 to 4))

Figure 13. LED Current vs Temperature

(VCC = 12 V, V_EN= 3.3 V,

V_LEDn= 2 V (n = 1 to 4), V_PWM= V_VREG

)

Figure 14. Efficiency vs LED Current(n = 1 to 4)

(Buck-Boost Application)

Figure 15. Efficiency vs LED Current(n = 1 to 4)

(Boost Application)

(Ta = 25 °C, VCC = 12 V,V_EN= 3.3 V, V_PWM= V_VREG

,

(Ta = 25 °C, VCC = 12 V,V_EN= 3.3 V, V_PWM= V_VREG

,

4 LED loads per channel, all channels have loads)

8 LED loads per channel, all channels have loads)

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Timing Chart (Start-up and Protection)

*1 EN is input after input VCC in the timing chart above, but there is no problem to input EN, PWM, and SYNC before input VCC. EN is judged as

Low at V_ENis 0.8 V or less and as High at V_ENis 2.1 V or more. Do not use this IC in the condition of V_ENis between 0.8 V and 2.1 V.

*2 The count time of 32770 clk x 1/f_OSC. In case of fosc=300 kHz, the count time is 100 ms(typ).

*3 The above timing chart is when the FAIL1 and FAIL2 pins are pulled up to the VREG pin.

① When V_OVPis less than 1.0 V, regardless of PWM input, the DC/DC switching operation is active (Pre-Boost

function). And if V_OVPreaches 1.0 V, the Pre-Boost is finished. Only when PWM is activated, switches to the

Normal mode which operates the DC/DC switching.

② When V_LED2is 0.3 V or less and V_OVPis 2.0 V or more, LED Open Protect is active and LED2 is turned OFF.

Then FAIL2 becomes Low.

③ If the condition of V_LED3is 4.5 V or more and passes 100 ms (@f_OSC= 300 kHz), LED3 is turned OFF. Then

FAIL2 becomes Low.

④ When V_LED4is shorted to GND, increase the VOUT voltage. Then V_OVPrises 2.0 V or more and detect OVP.

FAIL1 becomes Low. If OVP occurs, DC/DC switching is OFF and decrease the VOUT voltage, then OVP

repeats ON/OFF. And DC/DC switching and LED current of each channel is turned OFF after 100 ms by

detecting ground short protection. (In case of f_OSC= 300 kHz).

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Timing Chart (Start-up and EN Restart)

*1 The Low section during EN restart requires 2.0 ms or more.

Restart after VOUT voltage is discharged. VOUT discharge function or external discharge switch is recommended.

If EN is restarted with remaining VOUT voltage, LED flickering might occur.

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Application Examples

When using as Boost DC/DC converter

Figure 16. Boost application Circuit

If the VOUT pin or the LED pin is shorted in this case, the overcurrent from V_INcannot be prevented. To

prevent overcurrent, carry out measure such as inserting fuse of which value is OCP setting value or more

and is part’s rating current or less in between VCC and R_CS.

When using as Buck DC/DC Converter

Figure 17. Buck Application Circuit

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PCB Application Circuit Diagram

Figure 18. PCB Application Circuit

・ Arrange R_RTresistor near the RT pin and do not attach capacitor.

・ Arrange R_ISETresistor near the ISET pin and do not attach capacitor.

・ Attach the decoupling capacitor of C_INand C_VREGto IC pin as close as possible.

・ Keep the impedance low because large current might flow into DGND and PGND.

・ Be careful not to occur noise in the ISET, RT, and COMP pins.

・ Since PWM, OUTH, OUTL, SW, SYNC and LED1 to LED4 have switching, avoid affecting the surrounding patterns.

・ The SW, OUTH, BOOT pin to each components, keep shortest wiring and minimum impedance.

・ There is thermal PAD at the back of package. Solder the board GND for thermal PAD.

・ Set the gate resistor of FET (M1) to 0 Ω. If resistor is connected, M1 OFF timing is delayed in M1 parasitic

capacity and gate resistor, and the penetrating current flows to the internal transistor of M1 and SW. The

penetrating current might worsen the efficiency or detect OCP.

・ To reduce noise, consider the board layout in the shortest wiring and minimum impedance for Boost loop (D2

→CVOUT→DGND→M2→D2) and Buck loop (VCC→RCS→M1→D1→DGND→GND→CIN→VCC).

・ The ringing of Low-side FET can be suppressed by RG, but there is a concern that efficiency might worsen

when RG increases. When using RG, decide the resistance value after full evaluation.

・ When PWM min pulse width satisfies the following formula, please do not connect a capacitor to LED1 to

LED4 pins. It might misdetect LED short protection. When the connection of the capacitor is necessary for

noise measures, please refer to us.

ꢋ0

푡_ꢜꢀꢝ

≤

푓

ꢇ푆ꢊ

푡_ꢜꢀꢝ：PWM min pulse width

푓_ꢇ푆ꢊ：DCDC frequency target

・ Wire both ends of R_CS1and R_CS2(Red line of below figure) most shortly. If a wiring is long, it may lead to false

detection of OCP by an inductance.

VCC

R_CS3

CS

R_CS3

CS

Figure 19. The Case of R_CSParallel

Figure 20. The case of R_CSSeries

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PCB Board External Components List (Buck-Boost Application)

* The above components are modified according to operating conditions and load to be used.

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Selection of Components Externally Connected

Select the external components following the steps below.

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Selection of Components Externally Connected - continued

1. Derivation of Maximum Input Leak Current I_{L_MAX}

V_IN

Internal IC

I_L

R_CS

CS

M1

OUTH

L

D2

VOUT

SW

D1

C_OUT

M2

OUTL

Output Application Circuit Diagram (Buck-Boost Application)

(1) Maximum Output Voltage (VOUT_{_MAX}) Computation

Consider the Vf variation and number of LED connection in series for VOUT_{_MAX}derivation

푉푂푈ꢆ

= (푉푓 + ∆푉푓) × 푁 + ꢋ.ꢋ

_ꢜ퐴푋

where:

푉푂푈ꢆ

is the maximum output voltage.

is the LED Vf voltage.

_ꢜ퐴푋

푉

ꢔ

∆푉

is the LED Vf voltage variation.

is the LED series number.

ꢔ

푁

(2) Maximum Output Current I_{OUT_MAX}Computation

퐼_{ꢇꢘ푇_ꢜ퐴푋}= 퐼_퐿퐸퐷× ꢋ.05 × 푀

where:

퐼_{ꢇꢘ푇_ꢜ퐴푋}

퐼_퐿퐸퐷

is the maximum output current.

is the output current per channel.

is the LED parallel number.

푀

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1. Derivation of Maximum Input Leak Current I_{L_MAX}- continued

(3) Maximum Input Peak Current I_{L_MAX}Computation

ꢋ

퐼_{퐿_ꢜ퐴푋}= 퐼_{퐿_퐴ꢈ퐺}

+

∆퐼_퐿

ꢉ

where:

퐼_{퐿_ꢜ퐴푋}

퐼_{퐿_퐴ꢈ퐺}

∆퐼_퐿

is the maximum input current.

is the maximum input average current.

is the coil current amplification.

(In case of Boost Application)

퐼_{ꢇꢘ푇_ꢜ퐴푋}

휂 × 푉퐶퐶

퐼_{퐿_퐴ꢈ퐺}= 푉푂푈ꢆ

×

_ꢜ퐴푋

푉퐶퐶

ꢁ

ꢋ

푉푂푈ꢆ

− 푉퐶퐶

_ꢜ퐴푋

∆퐼_퐿=

×

푓

푉푂푈ꢆ

ꢇ푆ꢊ

_ꢜ퐴푋

(In case of Buck-Boost application)

퐼_{ꢇꢘ푇_ꢜ퐴푋}

휂 × 푉퐶퐶

퐼_{퐿_퐴ꢈ퐺}= (푉퐶퐶 + 푉푂푈ꢆ_{_ꢜ퐴푋}) ×

푉퐶퐶

ꢁ

ꢋ

푉푂푈ꢆ

_ꢜ퐴푋

∆퐼_퐿=

×

푓

푉퐶퐶 + 푉_{ꢇꢘ푇_ꢜ퐴푋}

ꢇ푆ꢊ

(In case of Buck application)

퐼_{퐿_퐴ꢈ퐺}= 퐼_{ꢇꢘ푇_ꢜ퐴푋}∕ 휂

푉푂푈ꢆ

ꢁ

ꢋ

푉퐶퐶 − 푉푂푈ꢆ

_ꢜ퐴푋

∆퐼_퐿=

×

푓

푉퐶퐶

ꢇ푆ꢊ

where:

푉퐶퐶

휂

is the supply voltage.

is the efficiency.

푓

is the DC/DC oscillation frequency.

is the coil value.

ꢇ푆ꢊ

ꢁ

•

The worst case for VCC is minimum, so the minimum value should be applied in the equation.

BD81A74EFV-M / BD81A74MUV-M adopts the current mode DC/DC converter control and is

appropriately designed for coil value. The abovementioned value is recommended according to

efficiency and stability. If choose the L values outside this recommended range, it not to be

guaranteed the stable continuous operation. For example, it may cause irregular switching waveform.

η (efficiency) is around 80 %.

•

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Selection of Components Externally Connected - continued

2. Setting of Over Current Protection Value (I_OCP

)

ꢈ

ꢕꢏꢞ_ꢟꢛꢠ

퐼_ꢇꢊ푃

=

> 퐼_{퐿_ꢜ퐴푋}[A]

ꢍ

ꢏꢎ

where:

퐼_{ꢇꢊ푃_ꢜꢀꢝ}is the overcurrent protection detect voltage.

푉_{ꢇꢊ푃_ꢜꢀꢝ}is the overcurrent protection detect voltage (0.18 V).

푅_ꢊ푆

is the current detect resistance.

퐼_{퐿_ꢜ퐴푋}

is the maximum input peak current.

R_CSshould be selected by the above equation.

3. Selection of Inductor

In order to achieve stable operation of the current mode DC/DC converter, it is recommended adjusting the L

value within the range indicated below.

ꢈꢇꢘ푇×ꢍ

ꢖ.ꢡ3×ꢔ

ꢏꢎ

ꢕꢎꢏ

0.05 <

<

[V/μs]

6

퐿×1ꢖ

1ꢖ

where:

푉푂푈ꢆ is the DC/DC converter output voltage.

푅_ꢊ푆

ꢁ

is the current detect resistance.

is the coil value.

푓

ꢇ푆ꢊ

is the DC/DC oscillation frequency.

Consider the deviation of L value and set with enough margins.

ꢈꢇꢘ푇×ꢍ

It is more stable by reducing the value of

^ꢏꢎ, however it slows down the response time.

6

퐿×1ꢖ

Also, the following equation should be satisfied during coil selection in case it is used in VCC = 5 V or less.

ꢋꢉ × 푉퐶퐶 × 푉퐶퐶 × 휂

ꢁ <

푉푂푈ꢆ × 퐼_퐿퐸퐷× 푀 × 푓

ꢇ푆ꢊ

where:

ꢁ

is the coil value.

푉퐶퐶 is the supply voltage.

is the efficiency.

휂

푉푂푈ꢆ is the DC/DC converter output voltage.

퐼_퐿퐸퐷is the LED current per channel.

푓

is the DC/DC oscillation frequency.

is the LED parallel number.

ꢇ푆ꢊ

푀

LED intensity may drop when a coil which does not satisfy the above is chosen.

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Selection of Components Externally Connected - continued

4. Selection of Voltage/Current Ratings of Coil (L), Diode (D1, D2), FET (M1, M2), R_CS,and C_OUT

Current Rating

Voltage Rating

-

Heat Loss

Coil L

Diode D1

Diode D2

FET M1

FET M2

R_CS

> I_{L_MAX}

> I_OCP

-

> VCC_{_MAX}

> V_{OVP_MAX}

> VCC_{_MAX}

> V_{OVP_MAX}

-

> I_OCP²x R_CS

C_OUT

-

> V_{OVP_MAX}

-

Consider deviation of external parts and set with enough margins.

In order to achieve fast switching, choose the FET’s with smaller gate-capacitance.

5. Setting of Output Capacitor

Select the output capacitor C_OUTbased on the requirements of the ripple voltage VOUTpp.

2ꢖ×ꢀ

×ꢜ

ꢢꢣꢚ

푉푂푈ꢆ푝푝 =

_×ꢥ+ ∆퐼_퐿× 푅_퐸푆ꢍ[V]

ꢔ

×ꢊ

ꢤꢕꢙꢒ

ꢕꢎꢏ

where:

푉푂푈ꢆ푝푝

퐼_퐿퐸퐷

is the VOUT ripple voltage.

is the LED current per channel.

is the LED parallel number.

푀

푓

is the DC/DC oscillation frequency.

is the VOUT capacity.

ꢇ푆ꢊ

퐶_ꢈꢇꢘ푇

휂

is the efficiency.

∆퐼_퐿

is the coil current amplification.

is the equivalent series resistance of output capacitor C_OUT.

푅_퐸푆ꢍ

The actual VOUT ripple voltage is affected by PCB layout and external components characteristics. Therefore,

check with the actual machine, and design a capacity with enough margins to fit in allowable ripple voltage.

The maximum value of C_OUTthat can be set is 500 µF.

6. Selection of Input Capacitor

An input capacitor which is 10 μF or more with low ESR ceramic capacitor is recommended. An input capacitor

which is not recommended may cause large ripple voltage at the input and hence lead to malfunction of the

IC.

7. Selection of BOOT - SW Capacitor

When using the Buck-Boost application or Buck application, insert 0.1 μF capacitor between the BOOT pin and

the SW pin.

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Selection of Components Externally Connected - continued

8. Setting of Phase Compensation Circuit

COMP Pin Application Schematic(n = 1 to 4)

Stability Condition of Application

The stability in LED voltage feedback system is achieved when the following conditions are met.

(1) When gain is 1 (0 dB), the phase delay is 150° or less (or simply, phase margin is 30° or more).

(2) When gain is 1 (0 dB), the frequency (Unity Gain Frequency) is 1/10 or less of switching frequency.

To assure stability based on phase margin adjustment is setting the Phase-lead fz close to unity gain frequency.

In addition, the Phase-lag fp1 is decided based on C_OUTand output impedance R_L.

The respective formulas are as follows.

Phase-lead

Phase-lag

푓푧 = ꢋ/(ꢉ휋푅_푃ꢊ퐶_푃ꢊ)

푓푝ꢋ = ꢋ/(ꢉ휋푅_퐿퐶_ꢇꢘ푇

[Hz]

)

* The output impedance that is calculated in 푅_퐿= 푉푂푈ꢆ/퐼_ꢇꢘ푇

To make a good result, set fz between 1 kHz to 10 kHz. Substitute the value in the maximum load for R_L.

Further, this setting is easily obtained, and the adjustment with the actual machine may be necessary because

it is not strictly calculated. In case of mass production design, thorough confirmation with the actual machine

is necessary because these characteristics can change based on board layout, load condition and etc.

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Selection of Components Externally Connected - continued

9. Setting of Over Voltage Protection (OVP)

Over voltage protection (OVP) is set from the external resistance R_OVP1, R_OVP2

.

The setting described below is important in the either boost, buck and buck-boost applications.

VOUT

R_OVP2

Internal IC

2.0 V / 1.94 V

OVP

R_OVP1

1.0 V / 0.57 V

OVP Application Circuit

The OVP pin detects the over voltage when it is 2.0 V (Typ) or more and stops the DC/DC switching. In

addition, it detects the open condition when the OVP pin is at 2.0 V (Typ) or more and the LED1 to LED4 pins

voltage is at 0.3 V (Typ) or less, and the circuit is latched to OFF (Refer to Protection Feature). In preventing

error in detection of OPEN, it is necessary that the resistor divide voltage of the maximum value of output

voltage shall be less than the minimum value of OPEN detection voltage.

Set the R_OVP1, R_OVP2in such a way the formula shown below can be met.

ꢍ

ꢕꢤꢞꢦ

(

)

푉푂푈ꢆ 푀푎푥 × ₍

< 푉_{ꢇꢈ푃ꢩꢪꢫꢬ}(푀ꢅ푛)……………………………………………………(1)

)

ꢍ

ꢧꢍ

ꢕꢤꢞꢨ

ꢕꢤꢞꢦ

where:

푉푂푈ꢆ

is the DC/DC output voltage.

푉_{ꢇꢈ푃ꢩꢪꢫꢬ}

is the OVP pin open detection voltage.

Example 1: When Vf = 3.2 V±0.3 V LED is used in 8 series

(

)

(

)

(

)

푉푂푈ꢆ 푀푎푥 = ꢋ.ꢋ ꢁꢂꢃ 푐표푛푡푟표푙 푣표푙푡푎푔푒 푀푎푥 + ꢭ.ꢉ + 0.ꢭ × 8 = ꢉ9.ꢋ [V]

( )

푉_{ꢇꢈ푃ꢩꢪꢫꢬ}푀ꢅ푛 = ꢋ.9 [V]

Open Detection OVP Pin Voltage

If R_OVP1= 20 kΩ, set by R_OVP2> 286.3 kΩ from (1).

Example 2: When Vf = 3.2 V±0.3 V LED is used in 3series

(

)

(

)

(

)

푉푂푈ꢆ 푀푎푥 = ꢋ.ꢋ ꢁꢂꢃ 푐표푛푡푟표푙 푣표푙푡푎푔푒 푀푎푥 + ꢭ.ꢉ + 0.ꢭ × ꢭ = ꢋꢋ.ꢮ [V]

( )

푉_{ꢇꢈ푃ꢩꢪꢫꢬ}푀ꢅ푛 = ꢋ.9 [V]

Open Detection OVP Pin Voltage

If R_OVP1= 20 kΩ, set by R_OVP2> 102.1 kΩ from (1).

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Selection of Components Externally Connected - continued

10. Setting of Soft Start Time

The soft start circuit is necessary to prevent increase of the coil current and overshoot of the output during

the start-up. A capacitance in the range of 0.047 µF to 0.47 µF is recommended. A capacitance less than

0.047 µF may cause overshoot at the output voltage. On the other hand, a capacitance more than 0.47 µF

may cause massive reverse current through the parasitic elements when power supply is OFF and may

damage the IC.

Soft start time t_SS(Typ).

푡_푆푆= 퐶_푆푆× ꢭ.ꢭ ∕ (5 × ꢋ0^ꢯꢡ

)

[s]

where:

퐶_푆푆is the Capacitance at the SS pin.

11. Confirmation of Start-up Time

If the PWM duty is smaller at start-up, the start-up time becomes longer. It is effective to reduce the C_PCvalue

to shorten start-up time, however, confirmation of the phase margin is necessary. PWM duty and data of start-

up time in typical 2 conditions are shown below.

Condition 1 (Boost)

VCC = 12 V, VOUT = 30 V (assume 8 LED’s series), R_RT= 27 kΩ (f_OSC= 300 kHz), R_ISET= 100 kΩ (I_LED

50 mA), C_PC= 0.01 µF, R_PC= 5.1 kΩ, C_SS= 0.1 µF, R_OVP1=2 0 kΩ, R_OVP2= 360 kΩ

=

1000

900

800

700

600

500

400

300

200

100

0

1000

900

800

700

600

500

400

300

200

100

0

0.2

0.4

0.6

0.8

1

0

20

40

60

80

100

PWM Duty [%]

Figure 21. Start-up Time(Boost) vs PWM Duty

Condition 2 (Buck-Boost)

VCC = 12 V, VOUT = 20 V (assume 5 LED’s series), R_RT= 27 kΩ (f_OSC= 300 kHz), R_ISET= 100 kΩ (I_LED

50 mA), C_PC= 0.01 µF, R_PC= 5.1 kΩ, C_SS= 0.1 µF, R_OVP1= 30 kΩ, R_OVP2= 360 kΩ

=

1000

900

800

700

600

500

400

300

200

100

0

900

800

700

600

500

400

300

200

100

0

20

40

60

80

100

0

0.2

0.4

0.6

0.8

1

PWM Duty [%]

Figure 22. Start-up Time(Buck-Boost) vs PWM Duty

The above are reference data. Always confirm by machine operation because the actual start-up time depends

on layout pattern, component constant, and component characteristics.

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Selection of Components Externally Connected - continued

12. Confirmation of Actual Operation

Set up the external components value by procedures and attentions mentioned above. However, those settings

above are not guaranteed because these are theoretically calculated and it does not include the external parts'

variation or characteristics changing. The overall characteristics may change depend on power supply voltage,

LED current, LED number, inductance, output capacitance, switching frequency, and PCB layout. We strongly

recommend verifying your design by taking the actual measurements.

Additional parts for EMC

The example of EMC countermeasure components is shown in the chart below.

1. The resistance for adjusting Slew Rate of high side FET

2. The capacitor for reducing current loop noise of high side FET.

3. The capacitor for reducing noise of high frequency on power line.

4. The low pass filter for reducing noise of power line.

5. The common mode filter for reducing noise of power line.

6. The snubber circuit for reducing noise of high frequency of low side FET.

7. The snubber circuit for reducing ringing of low side FET switching.

Application Circuit Reference Example (Including EMC Countermeasure Components)

It is basically non-recommended to connect a capacitor to the LED1 to LED4 pins. Please refer to PCB

Application Circuit. When the connection of the capacitor is necessary for noise measures, please refer to us.

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Precautions on PCB Layout

The layout pattern greatly affects the efficiency and ripple characteristics. Therefore, it is necessary to examine

carefully when designing. As show in the figure below, Buck-Boost DC/DC converter has two loops; “Loop1” and

“Loop2”. The parts in each loop have to be set as near as possible to each other. (For example, GND of C_OUTand

DGND should be very near, GND of C_INand GND of D1 should be very near and so on.)

Moreover, the wirings of each loop should be as low impedance as possible.

Figure 23. Circuit of DC/DC Block

Figure 24. BD81A74MUV-M PCB TOP-layer

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Calculation Example of Power Consumption (Case of Buck-Boost application)

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I/O Equivalence Circuit

*All values are Typ value

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Operational Notes

1. Reverse Connection of Power Supply

Connecting the power supply in reverse polarity can damage the IC. Take precautions against reverse polarity

when connecting the power supply, such as mounting an external diode between the power supply and the

IC’s power supply pins.

2. Power Supply Lines

Design the PCB layout pattern to provide low impedance supply lines. Furthermore, connect a capacitor to

ground at all power supply pins. Consider the effect of temperature and aging on the capacitance value when

using electrolytic capacitors.

3. Ground Voltage

Except for pins the output and the input of which were designed to go below ground, ensure that no pins are

at a voltage below that of the ground pin at any time, even during transient condition.

4. Ground Wiring Pattern

When using both small-signal and large-current ground traces, the two ground traces should be routed

separately but connected to a single ground at the reference point of the application board to avoid fluctuations

in the small-signal ground caused by large currents. Also ensure that the ground traces of external

components do not cause variations on the ground voltage. The ground lines must be as short and thick as

possible to reduce line impedance.

5. Recommended Operating Conditions

The function and operation of the IC are guaranteed within the range specified by the recommended operating

conditions. The characteristic values are guaranteed only under the conditions of each item specified by the

electrical characteristics.

6. Inrush Current

When power is first supplied to the IC, it is possible that the internal logic may be unstable and inrush current

may flow instantaneously due to the internal powering sequence and delays, especially if the IC has more

than one power supply. Therefore, give special consideration to power coupling capacitance, power wiring,

width of ground wiring, and routing of connections.

7. Testing on Application Boards

When testing the IC on an application board, connecting a capacitor directly to a low-impedance output pin

may subject the IC to stress. Always discharge capacitors completely after each process or step. The IC’s

power supply should always be turned off completely before connecting or removing it from the test setup

during the inspection process. To prevent damage from static discharge, ground the IC during assembly and

use similar precautions during transport and storage.

8. Inter-pin Short and Mounting Errors

Ensure that the direction and position are correct when mounting the IC on the PCB. Incorrect mounting may

result in damaging the IC. Avoid nearby pins being shorted to each other especially to ground, power supply

and output pin. Inter-pin shorts could be due to many reasons such as metal particles, water droplets (in very

humid environment) and unintentional solder bridge deposited in between pins during assembly to name a

few.

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Operational Notes - continued

9. Unused Input Pins

Input pins of an IC are often connected to the gate of a MOS transistor. The gate has extremely high impedance

and extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it.

The small charge acquired in this way is enough to produce a significant effect on the conduction through the

transistor and cause unexpected operation of the IC. So unless otherwise specified, unused input pins should

be connected to the power supply or ground line.

10. Regarding the Input Pin of the IC

This monolithic IC contains P+ isolation and P substrate layers between adjacent elements in order to keep

them isolated. P-N junctions are formed at the intersection of the P layers with the N layers of other elements,

creating a parasitic diode or transistor. For example (refer to figure below):

When GND > Pin A and GND > Pin B, the P-N junction operates as a parasitic diode.

When GND > Pin B, the P-N junction operates as a parasitic transistor.

Parasitic diodes inevitably occur in the structure of the IC. The operation of parasitic diodes can result in

mutual interference among circuits, operational faults, or physical damage. Therefore, conditions that cause

Resistor

Transistor (NPN)

Pin A

Pin B

B

E

C

Pin A

B

C

E

P

P⁺

N

P⁺

P

P⁺

N

Parasitic

Elements

Parasitic

Elements

P Substrate

GND GND

P Substrate

GND

Parasitic

Elements

Parasitic

Elements

N Region

close-by

these diodes to operate, such as applying a voltage lower than the GND voltage to an input pin (and thus to

the P substrate) should be avoided.

Figure 25. Example of monolithic IC structure

11. Ceramic Capacitor

When using a ceramic capacitor, determine a capacitance value considering the change of capacitance with

temperature and the decrease in nominal capacitance due to DC bias and others.

12. Thermal Shutdown Circuit (TSD)

This IC has a built-in thermal shutdown circuit that prevents heat damage to the IC. Normal operation should

always be within the IC’s maximum junction temperature rating. If however the rating is exceeded for a

continued period, the junction temperature (Tj) will rise which will activate the TSD circuit that will turn OFF

power output pins. When the Tj falls below the TSD threshold, the circuits are automatically restored to normal

operation.

Note that the TSD circuit operates in a situation that exceeds the absolute maximum ratings and therefore,

under no circumstances, should the TSD circuit be used in a set design or for any purpose other than protecting

the IC from heat damage.

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Operational Notes - continued

13. Over Current Protection Circuit (OCP)

This IC incorporates an integrated overcurrent protection circuit that is activated when the load is shorted.

This protection circuit is effective in preventing damage due to sudden and unexpected incidents. However,

the IC should not be used in applications characterized by continuous operation or transitioning of the

protection circuit.

Ordering Information

B

D

8

1

A

7

4

E

F

V

-

M E 2

Package

EFV: HTSSOP-B28

Product Rank

M: for Automotive

Packaging and forming specification

E2: Embossed carrier tape

B

D

8

1

7

4

M

U

V

- M E 2

Package

Product Rank

MUV: VQFN28SV5050

M: for Automotive

Packaging and forming specification

E2: Embossed carrier tape

Marking Diagram

HTSSOP-B28 (TOP VIEW)

VQFN28SV5050 (TOP VIEW)

Part Number Marking

LOT Number

Part Number Marking

LOT Number

BD81A74EFV

B D 8 1 A

7 4 M U V

Pin 1 Mark

Package

HTSSOP-B28

VQFN28SV5050

Orderable Part Number

BD81A74EFV-ME2

Marking

BD81A74EFV

BD81A74MUV

BD81A74MUV-ME2

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Physical Dimension and Packing Information

Package Name

HTSSOP-B28

Packing Information

Packing Form

Quantity

Embossed carrier tape

2500 pcs

E2

Direction of feed

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Physical Dimension and Packing Information - continued

Package Name

VQFN28SV5050

Packing Information

Packing Form

Quantity

Embossed carrier tape

2500 pcs

E2

Direction of feed

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Revision History

Date

Revision

001

Details

25.Sep.2017

New Release

P.1 General Description

Change to “Light modulation (10,000:1@100Hz dimming function) is possible by PWM

input.”

P.1 Key Specifications

Change to “LED Maximum Dimming Ratio 10,000:1@100Hz”.

25.Oct.2017

002

P.14 PWM Minimum Pulse Width, Conditions

Change to “fPWM = 100Hz to 20kHz”.

P.14 PWM Frequency, Min

Change to “0.1kHz”.

P.1 Add words

〇This product is protected by U.S. Patent No.7,235,954, No.7,541,785, No.7,944,189.

5.Dec.2018

2.Sep.2019

003

004

P.8 Add “(8) DC/DC switching control at over voltage output (LSDET)” and " (9) PWM

pulse and DC/DC switching"

P.5 Add <Caution of Large LED Current Setting>

Format update

Change the sentence about "Spread Spectrum Function"

(Before) The band of the switching frequency becomes 90 %±10 % of …

(After) The band of the switching frequency becomes 100 % to 80 % …

Change the calculation of noise reduction S.

Added Figure19, Figure20 and calculation.

Added the following sentence to the description of "PCB Application Circuit Diagram"

When PWM min pulse width satisfies the following formula, please do not connect a

capacitor to LED1 to LED4 pins. It might misdetect LED short protection. When the

connection of the capacitor is necessary for noise measures, please refer to us.

10.Apr.2020

005

t_MIN≤ 10/f_OSC

t_MIN: PWM min pulse width

f_OSC: DCDC frequency target

Added

the

following

sentence

to

"Selection

of

Components

Externally

Connected"/"Confirmation of Actual Operation"

It is basically non-recommended to connect a capacitor to the LED1 to LED4 pins. Please

refer to PCB Application Circuit. When the connection of the capacitor is necessary for

noise measures, please refer to us.

P.7 Figure 4 X axis name

Before：R_RT[Ω]

After：R_RT[kΩ]

12.Feb.2021

8.Oct.2021

006

007

P.1 Typical Application Circuit

Modified the right side of the figure broke off.

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Notice

Precaution on using ROHM Products

(Note 1)

1. If you intend to use our Products in devices requiring extremely high reliability (such as medical equipment

,

aircraft/spacecraft, nuclear power controllers, etc.) and whose malfunction or failure may cause loss of human life,

bodily injury or serious damage to property (“Specific Applications”), please consult with the ROHM sales

representative in advance. Unless otherwise agreed in writing by ROHM in advance, ROHM shall not be in any way

responsible or liable for any damages, expenses or losses incurred by you or third parties arising from the use of any

ROHM’s Products for Specific Applications.

(Note1) Medical Equipment Classification of the Specific Applications

JAPAN

USA

EU

CHINA

CLASSⅢ

CLASSⅣ

CLASSⅡb

CLASSⅢ

2. ROHM designs and manufactures its Products subject to strict quality control system. However, semiconductor

products can fail or malfunction at a certain rate. Please be sure to implement, at your own responsibilities, adequate

safety measures including but not limited to fail-safe design against the physical injury, damage to any property, which

a failure or malfunction of our Products may cause. The following are examples of safety measures:

[a] Installation of protection circuits or other protective devices to improve system safety

[b] Installation of redundant circuits to reduce the impact of single or multiple circuit failure

3. Our Products are not designed under any special or extraordinary environments or conditions, as exemplified below.

Accordingly, ROHM shall not be in any way responsible or liable for any damages, expenses or losses arising from the

use of any ROHM’s Products under any special or extraordinary environments or conditions. If you intend to use our

Products under any special or extraordinary environments or conditions (as exemplified below), your independent

verification and confirmation of product performance, reliability, etc, prior to use, must be necessary:

[a] Use of our Products in any types of liquid, including water, oils, chemicals, and organic solvents

[b] Use of our Products outdoors or in places where the Products are exposed to direct sunlight or dust

[c] Use of our Products in places where the Products are exposed to sea wind or corrosive gases, including Cl2,

H2S, NH3, SO2, and NO2

[d] Use of our Products in places where the Products are exposed to static electricity or electromagnetic waves

[e] Use of our Products in proximity to heat-producing components, plastic cords, or other flammable items

[f] Sealing or coating our Products with resin or other coating materials

[g] Use of our Products without cleaning residue of flux (Exclude cases where no-clean type fluxes is used.

However, recommend sufficiently about the residue.); or Washing our Products by using water or water-soluble

cleaning agents for cleaning residue after soldering

[h] Use of the Products in places subject to dew condensation

4. The Products are not subject to radiation-proof design.

5. Please verify and confirm characteristics of the final or mounted products in using the Products.

6. In particular, if a transient load (a large amount of load applied in a short period of time, such as pulse, is applied,

confirmation of performance characteristics after on-board mounting is strongly recommended. Avoid applying power

exceeding normal rated power; exceeding the power rating under steady-state loading condition may negatively affect

product performance and reliability.

7. De-rate Power Dissipation depending on ambient temperature. When used in sealed area, confirm that it is the use in

the range that does not exceed the maximum junction temperature.

8. Confirm that operation temperature is within the specified range described in the product specification.

9. ROHM shall not be in any way responsible or liable for failure induced under deviant condition from what is defined in

this document.

Precaution for Mounting / Circuit board design

1. When a highly active halogenous (chlorine, bromine, etc.) flux is used, the residue of flux may negatively affect product

performance and reliability.

2. In principle, the reflow soldering method must be used on a surface-mount products, the flow soldering method must

be used on a through hole mount products. If the flow soldering method is preferred on a surface-mount products,

please consult with the ROHM representative in advance.

For details, please refer to ROHM Mounting specification

Notice-PAA-E

Rev.004

Precautions Regarding Application Examples and External Circuits

1. If change is made to the constant of an external circuit, please allow a sufficient margin considering variations of the

characteristics of the Products and external components, including transient characteristics, as well as static

characteristics.

2. You agree that application notes, reference designs, and associated data and information contained in this document

are presented only as guidance for Products use. Therefore, in case you use such information, you are solely

responsible for it and you must exercise your own independent verification and judgment in the use of such information

contained in this document. ROHM shall not be in any way responsible or liable for any damages, expenses or losses

incurred by you or third parties arising from the use of such information.

Precaution for Electrostatic

This Product is electrostatic sensitive product, which may be damaged due to electrostatic discharge. Please take proper

caution in your manufacturing process and storage so that voltage exceeding the Products maximum rating will not be

applied to Products. Please take special care under dry condition (e.g. Grounding of human body / equipment / solder iron,

isolation from charged objects, setting of Ionizer, friction prevention and temperature / humidity control).

Precaution for Storage / Transportation

1. Product performance and soldered connections may deteriorate if the Products are stored in the places where:

[a] the Products are exposed to sea winds or corrosive gases, including Cl₂, H₂S, NH₃, SO₂, and NO₂

[b] the temperature or humidity exceeds those recommended by ROHM

[c] the Products are exposed to direct sunshine or condensation

[d] the Products are exposed to high Electrostatic

2. Even under ROHM recommended storage condition, solderability of products out of recommended storage time period

may be degraded. It is strongly recommended to confirm solderability before using Products of which storage time is

exceeding the recommended storage time period.

3. Store / transport cartons in the correct direction, which is indicated on a carton with a symbol. Otherwise bent leads

may occur due to excessive stress applied when dropping of a carton.

4. Use Products within the specified time after opening a humidity barrier bag. Baking is required before using Products of

which storage time is exceeding the recommended storage time period.

Precaution for Product Label

A two-dimensional barcode printed on ROHM Products label is for ROHM’s internal use only.

Precaution for Disposition

When disposing Products please dispose them properly using an authorized industry waste company.

Precaution for Foreign Exchange and Foreign Trade act

Since concerned goods might be fallen under listed items of export control prescribed by Foreign exchange and Foreign

trade act, please consult with ROHM in case of export.

Precaution Regarding Intellectual Property Rights

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Notice-PAA-E

Rev.004


型号：	BD81A74MUV-M
厂家：	ROHM
描述：	BD81A74MUV-M是35V高耐压的白色LED驱动器。1chip中内置4ch恒流输出，高达120mA/ch，适合高亮度LED驱动。内置对应升降压电流模式的DC/DC控制器，对于电源电压变动，可实现稳定的动作。可通过PWM输入进行调光控制（10,000:1）。驱动控制器驱动器
文件：	总44页 (文件大小：3143K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

BD81A74MUV-M [ROHM]

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