Datasheet
4ch White LED Driver Built-in Current Driver
Buck-Boost and Boost DC/DC Converter
for Automotive
BD81A74EFV-M
BD81A74MUV-M
General Description
BD81A74EFV-M / BD81A74MUV-M is a white LED
driver with the capability of withstanding high input
voltage (maximum 35 V). This driver has 4ch constantcurrent 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.
Light modulation (10,000:1@100 Hz dimming
function) is possible by PWM input.
Features
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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)
*1 Grade 1
Key Specifications
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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
LED Maximum Output Current
120 mA/ch
LED Maximum Dimming Ratio
10,000:1@100 Hz
PWM Minimum Pulse Width
1.0 µs
Packages
VQFN28SV5050
HTSSOP-B28
VQFN28SV5050
BD81A74MUV-M
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
HTSSOP-B28
BD81A74EFV-M
Applications
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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
Function
1
LEDEN1
Enable pin 1 for LED output
2
LEDEN2
Enable pin 2 for LED output
3
LED1
LED output pin 1
4
LED2
LED output pin 2
5
LED3
LED output pin 3
6
LED4
LED output pin 4
7
OVP
Over voltage detection pin
8
ISET
LED output current setting pin
9
PGND
LED output GND pin
10
OUTL
Low side FET gate pin
11
DGND
DC/DC converter output GND pin
12
VDISC
Output voltage discharge pin
13
SW
14
OUTH
High side FET source pin
High side FET gate pin
15
BOOT
High side FET driver power supply pin
16
VREG
Internal constant voltage
17
EN
Enable pin
18
CS
DC/DC converter current sense pin
19
VCC
20
SS
21
COMP
Input power supply pin
“Soft Start” capacitor connection
Error Amp output
22
RT
23
SYNC
External synchronization input pin
24
SSCG
Spread spectrum setting capacitor pin
25
GND
Small signal GND pin
26
PWM
PWM light modulation signal input pin
27
FAIL1
“Failure” signal output pin 1
28
FAIL2
“Failure” signal output pin 2
-
EXP-PAD
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Oscillation frequency setting resistor connect
Back side thermal PAD (Connect to GND)
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Pin Configuration
HTSSOP-B28 (TOP VIEW)
Pin Description
Pin No.
Pin Name
1
VCC
2
SS
3
COMP
Function
Input power supply pin
“Soft Start” capacitor connection
Error Amp output
4
RT
5
SYNC
Oscillation frequency setting resistor connect
External synchronization input pin
6
SSCG
Spread spectrum setting capacitor pin
7
GND
Small signal GND pin
8
PWM
PWM light modulation signal input pin
9
FAIL1
“Failure” signal output pin 1
10
FAIL2
“Failure” signal output pin 2
11
LEDEN1
Enable pin 1 for LED output
12
LEDEN2
Enable pin 2 for LED output
13
LED1
LED output pin 1
14
LED2
LED output pin 2
15
LED3
LED output pin 3
16
LED4
LED output pin 4
17
OVP
Over voltage detection pin
18
ISET
LED output current setting pin
19
PGND
LED output GND pin
20
OUTL
Low side FET gate pin
21
DGND
DC/DC converter output GND pin
22
VDISC
Output voltage discharge pin
23
SW
24
OUTH
High side FET gate pin
25
BOOT
High side FET driver power supply pin
26
VREG
Internal constant voltage
27
EN
Enable pin
28
CS
DC/DC converter current sense pin
-
EXP-PAD
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High side FET source pin
Back side thermal PAD (Connect to GND)
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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 VVREG
≥ 3.5 V and stops when at VCC ≤ 3.5 V or VVREG ≤ 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 (CVREG) to the VREG pin for
phase margin. CVREG range is 1.0 µF to 4.7 µF and recommended value is 2.2 µF. If the CVREG is 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
ILED [mA]
and LEDEN2 pins are not switchable during these in operation.
(1) Output Current Setting (RISET)
120
110
100
90
80
70
60
50
40
30
20
40
60
80
100 120 140 160 180 200 220 240
RISET [kΩ]
Figure 1. ILED vs RISET
The Output Current ILED can be obtained by the following equation:
𝐼𝐿𝐸𝐷 = 5000/𝑅𝐼𝑆𝐸𝑇
[A]
The operating range of the RISET value is from 41 kΩ to 250 kΩ. Additionally, the RISET value 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 RISET value is 4.7 kΩ or less, the IC
detects ISET-GND short condition and LED current is turned off.
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2.
BD81A74MUV-M
Current Driver – continued
During PWM dimming, the LED pin voltage (VLED) rises when PWM = Low because LED current doesn't flow,
and controls VLED to 1 V when PWM = High. When PWM rise up, VLED undershoot 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
VLED
ILED
Undershoot
(ΔVdrop)
(a) Timing Chart of VLED, ILED at PWM Dimming
(b) Temperature(Ta) vs LED Current(ILED)
Figure 2. Relation Between Undershoot of VLED and LED Current
(2) PWM Dimming Control
1 ms/Div
500 ns/Div
PWM
(2 V/Div)
PWM
(2 V/Div)
ILED
(50 mA/Div)
ILED
(50 mA/Div)
(a) PWM = 150 Hz, Duty = 0.02 %, ILED Waveform
(b) PWM = 150 Hz, Duty = 50.0 %, ILED Waveform
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 ILED. 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.
𝐿𝐸𝐷 𝑆𝑒𝑟𝑖𝑒𝑠 𝑁𝑢𝑚𝑏𝑒𝑟 × 𝑉𝑓 𝑉𝑎𝑟𝑖𝑎𝑡𝑖𝑜𝑛
< 𝑆ℎ𝑜𝑟𝑡 𝐷𝑒𝑡𝑒𝑐𝑡𝑖𝑜𝑛 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 (𝑀𝑖𝑛)－ 𝐿𝐸𝐷 𝐶𝑜𝑛𝑡𝑟𝑜𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒(𝑀𝑎𝑥)
(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.
𝑉𝑂𝑈𝑇 ≥ {(𝑅𝑂𝑉𝑃1 + 𝑅𝑂𝑉𝑃2 ) ∕ 𝑅𝑂𝑉𝑃1 } × 2.0
where:
𝑉𝑂𝑈𝑇 is the Output voltage.
𝑅𝑂𝑉𝑃1 is the GND side OVP resistance.
𝑅𝑂𝑉𝑃2 is the Output voltage side OVP resistance.
For example, OVP is active when VOUT ≥ 32 V if ROVP1 = 22 kΩ and ROVP2 = 330 kΩ.
(3) Buck-Boost DC/DC Converter Oscillation Frequency (fOSC)
fOSC [kHz]
1000
100
1
10
100
RRT [kΩ]
Figure 4. fOSC vs RRT
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 RRT using the above data and the equation below.
𝑓𝑂𝑆𝐶 = (81 × 105 ⁄𝑅𝑅𝑇 )
[kHz]
81 x 105 is 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 (fSSCG) decided in the SSCG pin capacity CSSCG. 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
fSSCG can be calculated by the following equation.
𝑓𝑆𝑆𝐶𝐺 =
3
4×𝐶𝑆𝑆𝐶𝐺 ×𝑅𝑅𝑇
[Hz]
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.
𝑆 = −10 × 𝑙𝑜𝑔 (𝑓
𝑓𝑆𝑆𝐶𝐺
𝑂𝑆𝐶
) [dB]
×0.2
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 (CSS) 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 lightsout 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
ILED
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VOUT keep
Stable LED current output
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Description of Blocks – continued
4.
Protection Feature
Table 2. Detect Condition of Each Protection Feature and Operation during Detection
Function
Detect Condition
[Detection]
[Release/Cancellation]
VCC ≥ 4.0 V and
Operation During Detection
UVLO
VCC ≤ 3.5 V or VVREG ≤ 2.0 V
TSD
Ta ≥ 175 °C
Ta ≤ 150 °C
All blocks shut down except VREG
OVP
VOVP ≥ 2.0 V
VOVP ≤ 1.94 V
DC/DC switching OFF
OCP
VCS ≤ VCC-0.2 V
VCS > VCC-0.2 V
DC/DC switching OFF
EN Reset
or
UVLO Reset
After SCP delay time,
all blocks latch OFF except VREG
EN Reset
or
UVLO Reset
Only detected channel
LED current latches OFF
SCP
LED Open
Protection
VOVP ≤ 0.57 V
or
Any of VLED1 to VLED4 is
0.3 V or less
(100 ms delay @300 kHz)
Any of VLED1 to VLED4 is
0.3 V or less
and
VOVP ≥ 2.0 V
VVREG ≥ 3.5 V
All blocks shut down except VREG
LED
Any of VLED1 to VLED4 is
EN Reset
After LED Short delay time,
Short
4.5 V and more
or
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.
BD81A74MUV-M
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 VVREG ≤ 2.0 V. And UVLO
is released by VCC ≥ 4.0 V and VVREG ≥ 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 VCS
≤ VCC-0.2 V. When the OCP is activated, the switching operation of the DC/DC converter turns off. And VCS
> 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 VOVP ≤ 0.57 V, the built-in counter operation starts. The clock
frequency of counter is the oscillation frequency (fOSC), which is determined by RRT. 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 VOVP 2.0 V or more, LED open is detected and latches
off the open LED channel only.
(7) LED Short Protection
If any of VLED1 to VLED4 is 4.5 V or more, the built-in counter operation starts. The clock frequency of counter
is the oscillation frequency (fOSC), which is determined by RRT. 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 (fOSC), which is determined by RRT. It stops the operation of circuits
except VREG at 32768 counts. When fOSC = 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.
BD81A74MUV-M
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.
𝑡𝐷𝐼𝑆𝐶 =
3×𝑉𝑂𝑈𝑇×𝐶𝑂𝑈𝑇
[s]
4×𝐼𝐷𝐼𝑆𝐶
where:
𝑡𝐷𝐼𝑆𝐶
is the DC/DC converter output discharge time.
𝐶𝑂𝑈𝑇
is the VOUT capacity.
𝑉𝑂𝑈𝑇
is the DC/DC converter output voltage.
𝐼𝐷𝐼𝑆𝐶
is the discharge current.
From the graph below, find the IDISC value in 25 % VOUT voltage, and substitute it in the above equation.
For example, substitute IDISC value 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 DISC or
more long.
Always check with actual machine because the tDISC found here is a reference level.
0.12
0.10
IDISC [A]
0.08
0.06
0.04
0.02
0.00
0
5
10
15
20
25
30
35
40
VOUT [V]
Figure 7. IDISC vs VOUT
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Absolute Maximum Ratings (Ta = 25 °C)
Parameter
Symbol
Rating
Unit
VCC
40
V
VBOOT, VOUTH
45
V
SW, CS Pin Voltage
VSW, VCS
40
V
BOOT-SW Pin Voltage
VBOOT-SW
7
V
40
V
-0.3 to +7
V
-0.3 to +7 < VCC
V
-0.3 to +7 < VVREG
V
Tjmax
150
°C
Storage Temperature Range
Tstg
-55 to +150
°C
LED Maximum Output Current
ILED
120*1
mA
Power Supply Voltage
BOOT, OUTH Pin Voltage
LED1 to LED4, VDISC Pin Voltage
VLEDn
PWM, SYNC, EN Pin Voltage
(n = 1 to 4),
VVDISC
VPWM, VSYNC, VEN
VREG, OVP, FAIL1, FAIL2,
VVREG, VOVP, VFAIL1, VFAIL2,
SS, RT, SSCG Pin Voltage
VSS, VRT, VSSCG
LEDEN1, LEDEN2, ISET,
VLEDEN1, VLEDEN2, VISET
COMP, OUTL Pin Voltage
VCOMP, VOUTL
Maximum Junction Temperature
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
Parameter
Symbol
Thermal Resistance (Typ)
1s*3
2s2p*4
Unit
VQFN28SV5050
Junction to Ambient
θJA
128.50
31.50
°C/W
Junction to Top Characterization Parameter*2
ΨJT
12
9
°C/W
Junction to Ambient
θJA
107.00
25.10
°C/W
Junction to Top Characterization Parameter*2
ΨJT
6
3
°C/W
HTSSOP-B28
Layer Number of
Measurement Board
Single
Material
Board Size
FR-4
114.3 mm x 76.2 mm x 1.57 mmt
Top
Copper Pattern
Thickness
Footprints and Traces
70 μm
Layer Number of
Measurement Board
4 Layers
Material
Board Size
FR-4
114.3 mm x 76.2 mm x 1.6 mmt
Top
2 Internal Layers
Thermal Via*5
Pitch
Diameter
1.20 mm
Φ0.30 mm
Bottom
Copper Pattern
Thickness
Copper Pattern
Thickness
Copper Pattern
Thickness
Footprints and Traces
70 μm
74.2 mm x 74.2 mm
35 μm
74.2 mm x 74.2 mm
70 μm
*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
Power Supply Voltage
*1
Symbol
Min
Typ
Max
Unit
VCC
4.5
12
35
V
Operating Temperature
Topr
-40
+25
+125
°C
DC/DC Oscillation Frequency
fOSC
200
300
2200
kHz
fSYNC
Higher of 200
or fOSC x 0.8
300
Lower of 2200
or fOSC x 1.2
kHz
DSYNC
40
50
60
%
Max
Unit
External Synchronized Frequency
*2
*3
External Synchronized Pulse Duty
*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
Symbol
Min
VREG Capacity
CVREG
1.0
2.2
4.7
μF
LED Current Setting Resistance
Oscillation Frequency Setting
Resistance
Soft Start Capacity Setting
RISET
41
100
250
kΩ
RRT
3.6
27
41
kΩ
CSS
0.047
0.1
0.47
μF
Spread Spectrum Setting Capacity
CSSCG
4.7
10
47
nF
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Typ
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8.Oct.2021 Rev.007
BD81A74EFV-M
BD81A74MUV-M
Electrical Characteristics(Unless otherwise specified, VCC = 12 V, Ta = -40 °C to +125 °C)
Parameter
Symbol
Min
Typ
Max
Unit
Conditions
EN = High, SYNC = High,
RT = OPEN, PWM = Low,
ISET = OPEN, CIN = 10 μF
EN = Low, VDISC = OPEN
Circuit Current
ICC
-
-
10
mA
Standby Current
IST
-
-
10
μA
VVREG
4.5
5.0
5.5
V
IVREG = -5 mA, CVREG = 2.2 μF
RONHH
1.5
3.5
7.0
Ω
IOUTH = -10 mA
0.8
2.5
5.5
Ω
IOUTH = 10 mA
[VREG]
Reference Voltage
[OUTH]
OUTH High Side ON-Resistor
OUTH Low Side ON-Resistor
RONHL
OCP Detection Voltage
VOLIMIT
この行は削除してください
tOLIMIT
-
30
-
ns
VCS = VCC-0.5V
OUTL High Side ON-Resistor
RONLH
1.5
3.5
10.0
Ω
IOUTL = -10 mA
OUTL Low Side ON-Resistor
RONLL
0.8
2.5
5.5
Ω
IOUTL = 10 mA
RON_SW
4.0
10.0
25.0
Ω
ISW = 10 mA
LED Control Voltage
VLED
0.9
1.0
1.1
V
COMP Sink Current
ICOMPSINK
35
80
145
μA
ICOMPSOUCE
-145
-80
-35
μA
VCC-0.22 VCC-0.20 VCC-0.18
V
[OUTL]
[SW]
SW ON-Resistor
[ERRAMP]
COMP Source Current
VLEDn = 2 V (n = 1 to 4),
VCOMP = 1 V
VLEDn = 0.5 V (n = 1 to 4),
VCOMP = 1 V
[Oscillator]
Oscillation Frequency 1
fOSC1
285
300
315
kHz
RRT = 27 kΩ
Oscillation Frequency 2
fOSC2
1800
2000
2200
kHz
RRT = 3.9 kΩ
[OVP]
OVP Detection Voltage
VOVP1
1.9
2.0
2.1
V
VOVP: Sweep up
OVP Hysteresis Width
VOVPHYS1
0.02
0.06
0.10
V
VOVP: 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 Detection Voltage
VUVLO
3.2
3.5
3.8
V
VCC: Sweep down
UVLO Hysteresis Width
VUHYS
0.25
0.50
0.75
V
VCC: Sweep up,
VVREG > 3.5 V
-3
-
+3
%
-5
-
+5
%
-3
-
+3
%
-5
-
+5
%
[UVLO]
[LED Output]
LED Current Relative
Dispersion
LED Current Absolute
Dispersion
ILED1
ILED2
ILED = 50 mA, Ta = 25 °C
ΔILED1 = (ILEDn/ILEDn_AVG-1)x 100
(n = 1 to 4)
ILED = 50 mA,
Ta = -40 °C to +125 °C
ΔILED1 = (ILEDn/ILEDn_AVG-1)x 100
(n = 1 to 4)
ILED = 50 mA, Ta = 25 °C
ΔILED2 = (ILEDn/50mA-1) x 100
(n = 1 to 4)
ILED = 50 mA,
Ta = -40 °C to +125 °C
ΔILED2 = (ILEDn/50mA-1) x 100
(n = 1 to 4)
ISET Voltage
VISET
0.9
1.0
1.1
V
RISET = 100 kΩ
PWM Minimum Pulse Width
tMIN
1
-
-
μs
fPWM = 100 Hz to 20 kHz,
ILED = 20 mA to 100 mA
PWM Frequency
fPWM
0.1
-
20
kHz
LED Open Detection Voltage
VOPEN
0.2
0.3
0.4
V
VLEDn :(n = 1 to 4)
Sweep down
LED Short Detection Voltage
VSHORT
4.2
4.5
4.8
V
VLEDn :(n = 1 to 4)
Sweep up
LED Short Detection Latch OFF
Delay Time
tSHORT
70
100
130
ms
RRT = 27 kΩ
SCP Latch OFF Delay Time
tSCP
70
100
130
ms
RRT = 27 kΩ
PWM Latch OFF Delay Time
tPWM
70
100
130
ms
RRT = 27 kΩ
ISET-GND Short Protection
Impedance
ISETPROT
-
-
4.7
kΩ
VLSDET
-
1.24
-
V
Input High Voltage
VINH
2.1
-
VVREG
V
EN, SYNC, PWM,
LEDEN1, LEDEN2
Input Low Voltage
VINL
GND
-
0.8
V
EN, SYNC, PWM,
LEDEN1, LEDEN2
IIN
15
50
100
μA
VOL
-
0.1
0.2
V
[Protection Circuit]
LSDET Detection Voltage
[Logic Input Voltage]
Input Current
VIN = 5 V (EN, SYNC,
PWM, LEDEN1, LEDEN2)
[FAIL Output (Open Drain)]
FAIL Low Voltage
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IFAIL = 0.1 mA
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BD81A74EFV-M
BD81A74MUV-M
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, VEN = 3.3 V, VPWM = 0 V)
Figure 9. Reference Voltage vs Temperature
(VCC = 12 V, VEN = 3.3 V, VPWM = 0 V)
Figure 10. Oscillation Frequency 1 vs Temperature
(@300 kHz, VCC = 12 V, VEN = 3.3 V, RRT = 27 kΩ)
Figure 11. Oscillation Frequency 2 vs Temperature
(@2000 kHz, VCC = 12 V, VEN = 3.3 V, RRT = 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, VEN = 3.3 V,
VLEDn = sweep (n = 1 to 4))
Figure 13. LED Current vs Temperature
(VCC = 12 V, VEN = 3.3 V,
VLEDn = 2 V (n = 1 to 4), VPWM = VVREG)
Figure 14. Efficiency vs LED Current(n = 1 to 4)
(Buck-Boost Application)
(Ta = 25 °C, VCC = 12 V,VEN = 3.3 V, VPWM = VVREG,
4 LED loads per channel, all channels have loads)
Figure 15. Efficiency vs LED Current(n = 1 to 4)
(Boost Application)
(Ta = 25 °C, VCC = 12 V,VEN = 3.3 V, VPWM = VVREG,
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
*2
The count time of 32770 clk x 1/fOSC. In case of fosc=300 kHz, the count time is 100 ms(typ).
Low at VEN is 0.8 V or less and as High at VEN is 2.1 V or more. Do not use this IC in the condition of VEN is between 0.8 V and 2.1 V.
*3
The above timing chart is when the FAIL1 and FAIL2 pins are pulled up to the VREG pin.
① When VOVP is less than 1.0 V, regardless of PWM input, the DC/DC switching operation is active (Pre-Boost
function). And if VOVP reaches 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 VLED2 is 0.3 V or less and VOVP is 2.0 V or more, LED Open Protect is active and LED2 is turned OFF.
Then FAIL2 becomes Low.
③ If the condition of VLED3 is 4.5 V or more and passes 100 ms (@fOSC = 300 kHz), LED3 is turned OFF. Then
FAIL2 becomes Low.
④ When VLED4 is shorted to GND, increase the VOUT voltage. Then VOVP rises 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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BD81A74MUV-M
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 VIN cannot 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 RCS.
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 RRT resistor near the RT pin and do not attach capacitor.
Arrange RISET resistor near the ISET pin and do not attach capacitor.
Attach the decoupling capacitor of CIN and CVREG to 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.
・
・
・
・
・
・
・
・
・
𝑡𝑀𝐼𝑁 ≤
10
𝑓𝑂𝑆𝐶
𝑡𝑀𝐼𝑁 ：PWM min pulse width
𝑓𝑂𝑆𝐶 ：DCDC frequency target
・ Wire both ends of RCS1 and RCS2 (Red line of below figure) most shortly. If a wiring is long, it may lead to false
detection of OCP by an inductance.
VCC
RCS2
CCS
RCS2
RCS3
CS
Figure 19. The Case of RCS Parallel
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RCS3
RCS1
CS
RCS1
CCS
VCC
Figure 20. The case of RCS Series
TSZ02201-0T2T0C600300-1-2
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BD81A74EFV-M
BD81A74MUV-M
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 IL_MAX
VIN
Internal IC
IL
RCS
CS
OUTH
M1
L
SW
D2
D1
VOUT
COUT
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
𝑉𝑂𝑈𝑇_𝑀𝐴𝑋 = (𝑉𝑓 + ∆𝑉𝑓) × 𝑁 + 1.1
where:
𝑉𝑂𝑈𝑇_𝑀𝐴𝑋
is the maximum output voltage.
𝑉𝑓
is the LED Vf voltage.
∆𝑉𝑓
is the LED Vf voltage variation.
𝑁
is the LED series number.
(2) Maximum Output Current IOUT_MAX Computation
𝐼𝑂𝑈𝑇_𝑀𝐴𝑋 = 𝐼𝐿𝐸𝐷 × 1.05 × 𝑀
where:
𝐼𝑂𝑈𝑇_𝑀𝐴𝑋
is the maximum output current.
𝐼𝐿𝐸𝐷
is the output current per channel.
𝑀
is the LED parallel number.
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1. Derivation of Maximum Input Leak Current IL_MAX - continued
(3) Maximum Input Peak Current IL_MAX Computation
1
𝐼𝐿_𝑀𝐴𝑋 = 𝐼𝐿_𝐴𝑉𝐺 + ∆𝐼𝐿
2
where:
𝐼𝐿_𝑀𝐴𝑋
is the maximum input current.
𝐼𝐿_𝐴𝑉𝐺
is the maximum input average current.
∆𝐼𝐿
is the coil current amplification.
(In case of Boost Application)
𝐼𝐿_𝐴𝑉𝐺 = 𝑉𝑂𝑈𝑇_𝑀𝐴𝑋 ×
∆𝐼𝐿 =
𝐼𝑂𝑈𝑇_𝑀𝐴𝑋
𝜂 × 𝑉𝐶𝐶
𝑉𝐶𝐶
1
𝑉𝑂𝑈𝑇_𝑀𝐴𝑋 − 𝑉𝐶𝐶
×
×
𝐿
𝑓𝑂𝑆𝐶
𝑉𝑂𝑈𝑇_𝑀𝐴𝑋
(In case of Buck-Boost application)
𝐼𝐿_𝐴𝑉𝐺 = (𝑉𝐶𝐶 + 𝑉𝑂𝑈𝑇_𝑀𝐴𝑋 ) ×
∆𝐼𝐿 =
𝐼𝑂𝑈𝑇_𝑀𝐴𝑋
𝜂 × 𝑉𝐶𝐶
𝑉𝐶𝐶
1
𝑉𝑂𝑈𝑇_𝑀𝐴𝑋
×
×
𝐿
𝑓𝑂𝑆𝐶 𝑉𝐶𝐶 + 𝑉𝑂𝑈𝑇_𝑀𝐴𝑋
(In case of Buck application)
𝐼𝐿_𝐴𝑉𝐺 = 𝐼𝑂𝑈𝑇_𝑀𝐴𝑋 ∕ 𝜂
∆𝐼𝐿 =
𝑉𝑂𝑈𝑇
1
𝑉𝐶𝐶 − 𝑉𝑂𝑈𝑇_𝑀𝐴𝑋
×
×
𝐿
𝑓𝑂𝑆𝐶
𝑉𝐶𝐶
where:
𝑉𝐶𝐶
is the supply voltage.
𝜂
is the efficiency.
𝑓𝑂𝑆𝐶
is the DC/DC oscillation frequency.
𝐿
is the coil value.
•
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 (IOCP)
𝐼𝑂𝐶𝑃 =
𝑉𝑂𝐶𝑃_𝑀𝐼𝑁
𝑅𝐶𝑆
> 𝐼𝐿_𝑀𝐴𝑋
[A]
where:
𝐼𝑂𝐶𝑃_𝑀𝐼𝑁
is the overcurrent protection detect voltage.
𝑉𝑂𝐶𝑃_𝑀𝐼𝑁 is the overcurrent protection detect voltage (0.18 V).
𝑅𝐶𝑆
is the current detect resistance.
𝐼𝐿_𝑀𝐴𝑋
is the maximum input peak current.
RCS should 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.
0.05 <
𝑉𝑂𝑈𝑇×𝑅𝐶𝑆
𝐿×106
<
0.63×𝑓𝑂𝑆𝐶
[V/μs]
106
where:
𝑉𝑂𝑈𝑇
is the DC/DC converter output voltage.
𝑅𝐶𝑆
is the current detect resistance.
𝐿
is the coil value.
𝑓𝑂𝑆𝐶
is the DC/DC oscillation frequency.
Consider the deviation of L value and set with enough margins.
It is more stable by reducing the value of
𝑉𝑂𝑈𝑇×𝑅𝐶𝑆
𝐿×106
, however it slows down the response time.
Also, the following equation should be satisfied during coil selection in case it is used in VCC = 5 V or less.
𝐿 <
12 × 𝑉𝐶𝐶 × 𝑉𝐶𝐶 × 𝜂
𝑉𝑂𝑈𝑇 × 𝐼𝐿𝐸𝐷 × 𝑀 × 𝑓𝑂𝑆𝐶
where:
𝐿
is the coil value.
𝑉𝐶𝐶
is the supply voltage.
𝜂
is the efficiency.
𝑉𝑂𝑈𝑇 is the DC/DC converter output voltage.
𝐼𝐿𝐸𝐷
is the LED current per channel.
𝑓𝑂𝑆𝐶
is the DC/DC oscillation frequency.
𝑀
is the LED parallel number.
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), RCS, and COUT
Current Rating
Voltage Rating
Heat Loss
Coil L
> IL_MAX
-
-
Diode D1
> IOCP
> VCC_MAX
-
Diode D2
> IOCP
> VOVP_MAX
-
FET M1
> IOCP
> VCC_MAX
-
FET M2
> IOCP
> VOVP_MAX
-
RCS
-
-
> IOCP2 x RCS
COUT
-
> VOVP_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 COUT based on the requirements of the ripple voltage VOUTpp.
𝑉𝑂𝑈𝑇𝑝𝑝 =
20×𝐼𝐿𝐸𝐷 ×𝑀
𝑓𝑂𝑆𝐶 ×𝐶𝑉𝑂𝑈𝑇 ×𝜂
+ ∆𝐼𝐿 × 𝑅𝐸𝑆𝑅
[V]
where:
𝑉𝑂𝑈𝑇𝑝𝑝
is the VOUT ripple voltage.
𝐼𝐿𝐸𝐷
is the LED current per channel.
𝑀
is the LED parallel number.
𝑓𝑂𝑆𝐶
is the DC/DC oscillation frequency.
𝐶𝑉𝑂𝑈𝑇
is the VOUT capacity.
𝜂
is the efficiency.
∆𝐼𝐿
is the coil current amplification.
𝑅𝐸𝑆𝑅
is the equivalent series resistance of output capacitor COUT.
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 COUT that 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 COUT and output impedance RL.
The respective formulas are as follows.
Phase-lead
𝑓𝑧 = 1/(2𝜋𝑅𝑃𝐶 𝐶𝑃𝐶 )
[Hz]
Phase-lag
𝑓𝑝1 = 1/(2𝜋𝑅𝐿 𝐶𝑂𝑈𝑇 )
[Hz]
* The output impedance that is calculated in
𝑅𝐿 = 𝑉𝑂𝑈𝑇/𝐼𝑂𝑈𝑇
To make a good result, set fz between 1 kHz to 10 kHz. Substitute the value in the maximum load for RL.
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 ROVP1, ROVP2.
The setting described below is important in the either boost, buck and buck-boost applications.
VOUT
Internal IC
ROVP2
2.0 V / 1.94 V
OVP
ROVP1
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 ROVP1, ROVP2 in such a way the formula shown below can be met.
𝑉𝑂𝑈𝑇(𝑀𝑎𝑥) × (𝑅
𝑅𝑂𝑉𝑃1
𝑂𝑉𝑃1 +𝑅𝑂𝑉𝑃2 )
< 𝑉𝑂𝑉𝑃𝑜𝑝𝑒𝑛 (𝑀𝑖𝑛)……………………………………………………(1)
where:
𝑉𝑂𝑈𝑇
is the DC/DC output voltage.
𝑉𝑂𝑉𝑃𝑜𝑝𝑒𝑛
is the OVP pin open detection voltage.
Example 1: When Vf = 3.2 V±0.3 V LED is used in 8 series
𝑉𝑂𝑈𝑇(𝑀𝑎𝑥) = 1.1(𝐿𝐸𝐷 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑀𝑎𝑥) + (3.2 + 0.3) × 8 = 29.1 [V]
Open Detection OVP Pin Voltage
𝑉𝑂𝑉𝑃𝑜𝑝𝑒𝑛 (𝑀𝑖𝑛) = 1.9 [V]
If ROVP1 = 20 kΩ, set by ROVP2 > 286.3 kΩ from (1).
Example 2: When Vf = 3.2 V±0.3 V LED is used in 3series
𝑉𝑂𝑈𝑇(𝑀𝑎𝑥) = 1.1(𝐿𝐸𝐷 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑀𝑎𝑥) + (3.2 + 0.3) × 3 = 11.6 [V]
Open Detection OVP Pin Voltage
𝑉𝑂𝑉𝑃𝑜𝑝𝑒𝑛 (𝑀𝑖𝑛) = 1.9 [V]
If ROVP1 = 20 kΩ, set by ROVP2 > 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 tSS (Typ).
[s]
𝑡𝑆𝑆 = 𝐶𝑆𝑆 × 3.3 ∕ (5 × 10−6 )
where:
𝐶𝑆𝑆 is 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 CPC value
to shorten start-up time, however, confirmation of the phase margin is necessary. PWM duty and data of startup time in typical 2 conditions are shown below.
Condition 1 (Boost)
VCC = 12 V, VOUT = 30 V (assume 8 LED’s series), RRT = 27 kΩ (fOSC = 300 kHz), RISET = 100 kΩ (ILED =
1000
1000
900
900
800
800
Start-up Time [ms]
Start-up Time [ms]
50 mA), CPC = 0.01 µF, RPC = 5.1 kΩ, CSS = 0.1 µF, ROVP1 =2 0 kΩ, ROVP2 = 360 kΩ
700
600
500
400
300
200
600
500
400
300
200
100
100
0
700
0
0
20
40
60
PWM Duty [%]
80
100
0
0.2
0.4
0.6
PWM Duty [%]
0.8
1
Figure 21. Start-up Time(Boost) vs PWM Duty
Condition 2 (Buck-Boost)
VCC = 12 V, VOUT = 20 V (assume 5 LED’s series), RRT= 27 kΩ (fOSC = 300 kHz), RISET = 100 kΩ (ILED =
1000
1000
900
900
800
800
700
Start-up Time [ms]
Start-up Time [ms]
50 mA), CPC = 0.01 µF, RPC = 5.1 kΩ, CSS = 0.1 µF, ROVP1 = 30 kΩ, ROVP2 = 360 kΩ
600
500
400
300
200
100
0
700
600
500
400
300
200
100
0
20
40
60
PWM Duty [%]
80
100
0
0
0.2
0.4
0.6
PWM Duty [%]
0.8
1
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 OUT and
DGND should be very near, GND of CIN and 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
C
Pin A
N
P+
N
P
N
P+
N
Parasitic
Elements
N
P+
GND
E
N P
N
P+
B
N
C
E
Parasitic
Elements
P Substrate
P Substrate
Parasitic
Elements
Pin B
B
Parasitic
Elements
GND
GND
N Region
close-by
GND
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
-
Package
EFV: HTSSOP-B28
B
D
8
1
A
7
4
M
U
M E 2
Product Rank
M: for Automotive
Packaging and forming specification
E2: Embossed carrier tape
V
-
Package
MUV: VQFN28SV5050
M E 2
Product Rank
M: for Automotive
Packaging and forming specification
E2: Embossed carrier tape
Marking Diagram
HTSSOP-B28 (TOP VIEW)
VQFN28SV5050 (TOP VIEW)
Part Number Marking
BD81A74EFV
LOT Number
Part Number Marking
BD81A
LOT Number
74MUV
Pin 1 Mark
Marking
Pin 1 Mark
Package
Orderable Part Number
BD81A74EFV
HTSSOP-B28
BD81A74EFV-ME2
BD81A74MUV
VQFN28SV5050
BD81A74MUV-ME2
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Physical Dimension and Packing Information
Package Name
HTSSOP-B28
Packing Information
Packing Form
Embossed carrier tape
Quantity
2500 pcs
Direction of feed
E2
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Physical Dimension and Packing Information - continued
Package Name
VQFN28SV5050
Packing Information
Packing Form
Embossed carrier tape
Quantity
2500 pcs
Direction of feed
E2
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Revision History
Date
Revision
25.Sep.2017
001
Details
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
25.Oct.2017
002
Change to “LED Maximum Dimming Ratio 10,000:1@100Hz”.
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
003
P.8 Add “(8) DC/DC switching control at over voltage output (LSDET)” and " (9) PWM
pulse and DC/DC switching"
2.Sep.2019
004
P.5 Add
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.
10.Apr.2020
005
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.
tMIN ≤ 10/fOSC
tMIN : PWM min pulse width
fOSC : 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.
12.Feb.2021
006
P.7 Figure 4 X axis name
Before：RRT [Ω]
After：RRT [kΩ]
8.Oct.2021
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
1.
If you intend to use our Products in devices requiring extremely high reliability (such as medical equipment (Note 1),
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
CLASSⅡb
CLASSⅢ
CLASSⅢ
CLASSⅣ
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
© 2015 ROHM Co., Ltd. All rights reserved.
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 Cl 2, 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
1.
All information and data including but not limited to application example contained in this document is for reference
only. ROHM does not warrant that foregoing information or data will not infringe any intellectual property rights or any
other rights of any third party regarding such information or data.
2.
ROHM shall not have any obligations where the claims, actions or demands arising from the combination of the
Products with other articles such as components, circuits, systems or external equipment (including software).
3.
No license, expressly or implied, is granted hereby under any intellectual property rights or other rights of ROHM or any
third parties with respect to the Products or the information contained in this document. Provided, however, that ROHM
will not assert its intellectual property rights or other rights against you or your customers to the extent necessary to
manufacture or sell products containing the Products, subject to the terms and conditions herein.
Other Precaution
1.
This document may not be reprinted or reproduced, in whole or in part, without prior written consent of ROHM.
2.
The Products may not be disassembled, converted, modified, reproduced or otherwise changed without prior written
consent of ROHM.
3.
In no event shall you use in any way whatsoever the Products and the related technical information contained in the
Products or this document for any military purposes, including but not limited to, the development of mass-destruction
weapons.
4.
The proper names of companies or products described in this document are trademarks or registered trademarks of
ROHM, its affiliated companies or third parties.
Notice-PAA-E
© 2015 ROHM Co., Ltd. All rights reserved.
Rev.004
Datasheet
General Precaution
1. Before you use our Products, you are requested to carefully read this document and fully understand its contents.
ROHM shall not be in any way responsible or liable for failure, malfunction or accident arising from the use of any
ROHM’s Products against warning, caution or note contained in this document.
2. All information contained in this document is current as of the issuing date and subject to change without any prior
notice. Before purchasing or using ROHM’s Products, please confirm the latest information with a ROHM sales
representative.
3.
The information contained in this document is provided on an “as is” basis and ROHM does not warrant that all
information contained in this document is accurate and/or error-free. ROHM shall not be in any way responsible or
liable for an y damages, expenses or losses incurred b y you or third parties resulting from inaccuracy or errors of or
concerning such information.
Notice – WE
© 2015 ROHM Co., Ltd. All rights reserved.
Rev.001
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