Rohm BD60A00NUX Specification sheet

BD60A00NUX
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LED Drivers for LCD Backlights
White Backlight LED Drivers
for Small to Medium LCD Panels
(Switching Regulator Type)
BD60A00NUX, BD60A60NUX
●Description
This IC is boost DC/DC converter that can drive white LED with constant current. More stabled white LED lighting can be
achieved by direct current connection without electric tolerance and High-speed response by current mode. Moreover,
separating IC power supply (2.7V~5.5V) and coil power supply (2.3V~20V) makes it possible to widen input range, which
will be helpful to be applied to various kinds of applications. Over voltage setting can be selected corresponding to the
number of LED lightings. BD60A00NUX is for max 11 lightings, BD60A60NUX is for max 6 lightings.
●Features
1) Boost DC/DC converter
2) Drive LED 11 lightings (VOUT=3.6V×11+0.7V=40.3V <Vf MAX=3.7V>) BD60A00NUX
3) Brightness control by outside PWM signal (PWM frequency =100Hz~30kHz, 25kHz 1% dimming application)
4) Brightness control by DC input
5) Soft start function (1ms typ.)
6) Over voltage protection 42V typ. ( BD60A00NUX), 28Vtyp.( BD60A60NUX)
7) SBD open protection and output short protection
8) Over current protection
9) LED terminal over voltage protection
10) UVLO
11) VSON008x2030 package (2.0mm × 3.0mm × 0.6mm MAX)
●Applications
Digital video cameras, digital single-lens reflexes, digital still cameras, digital photo frames, personal navigations (PND),
mobile phones, smart phones, MID, PDA, hand-held computers, MP3 players, GPS, digital media players, etc.
●Absolute maximum ratings
Parameter Symbol Ratings Unit Condition
Maximum applied voltage 1 VMAX1 7 V Vin, EN, PWM, ISET terminals
Maximum applied voltage 2 VMAX2 45 V FB, SW, Vout terminals
BD60A00NUX
Maximum applied voltage 2 VMAX3 31 V FB, SW, Vout terminals
BD60A60NUX
Operating temperature range Topr -40 ~ +85 ℃
Storage temperature range Tstg -55 ~ +150 ℃
Power dissipation 1 Pd1 2000 mW *1
*1 4 layer (ROHM Standard board) has been mounted. When it’s used by more than Ta=25℃, it’s reduced by 20mW/˚C.
●Recommended operating range (Ta=-40℃~ +85℃)
Parameter Symbol Ratings Unit Conditions
Operating power supply voltage VIN 2.7 ~ 5.5 * V Vin terminal
Operating coil voltage Vcoil 2.3 ~ 20 V Coil voltage
*When the operating supply voltage is over 4.61V for BD60A00NUX, please refer the application P.17
No.11040EAT42

Technical Note
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●Electrical characteristics (Unless otherwise specified, Ta=25℃, Vin=3.6V)
Parameter Symbol
Limits Unit Conditions
Min. Typ. Max.
Quiescent Current Iq - 0.1 1.0 A EN=0V
Current Consumption
(No Boost) IddNB - 1.5 3.0 mA EN=2.8 V, PWM=0V
Current Consumption (Boost) IddB - 2.5 5.0. mA EN=2.8 V, PWM=2.8 V
[EN, PWM Terminal]
Low Input Voltage range VthL - - 0.5 V
High Input Voltage range VthH 1.4 - - V
Pull down register Rcnt 65 100 135 k
[Switching Regulator]
FB Terminal Control Voltage FB 0.56 0.70 0.84 V
Switching Frequency fSW - 600 - kHz
Max Duty Duty 90 95 - % FB=0V
SW Transistor ON Resistor Ronn - 0.5 - Isw=80mA
SW Transistor Leak Current IqSW - 0.1 2.0 A EN=0V
[Protection]
Over Current Limit Icoil - 750 - mA *1
Over Voltage Limit
BD60A00NUX OVP1 40 42 44 V Detect voltage of VOUT terminal
Over Voltage Limit
BD60A60NUX OVP2 26 28 30 V Detect Voltage of VOUT terminal
Over Voltage Limit Hysteresis OVPhy - 1 - V
VOUT Terminal Leak Current IqVOUT - 0.1 1.0 A EN=0V
Shot key Diode Open Protection Sop - 0.2 - V Detect Voltage of VOUT terminal
LED Terminal
Over Voltage Protection LEDOVP 4.4 5.9 6.4 V PWM=2.8V
Detect Voltage of Low Voltage UVLO - 2.2 - V Vin falling edge
[Current Driver]
LED Maximum Current ILMAX - - 30 mA VIN=4V, Cout=1µF
LED Current Accuracy ILACCU - - ±3.0 % ILED=20mA
LED Current Limit ILOCP - 0 0.1 mA Current Limit Value at
ISET Resistor 1kSetting
LED Leak Current IqLED - 0.1 2.0 A EN=0V
ISET Terminal Voltage Iset - 0.6 - V
*1 This parameter is tested with DC measurement.

Technical Note
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●Block Diagram and Application
Fig.1 Block Diagram and Application
・Pin assignment table
PIN No. PIN Name In/Out Function Terminal Diagram
1 EN In Enable Control B
2 VIN In Battery Input C
3 PWM In PWM Input B
4 ISET In LED Current Setting Terminal A
5 FB In Feedback Voltage Input B
6 VOUT In Over Voltage Protection Input B
7 GND - GND C
8 SW Out Switching Terminal B
●Terminal Diagram
Fig.2 Terminal Diagram
GND
C
Vin
GND
PIN
B
GND
PIN
A
Vin
L1
10H
+
+
-
OSC
Control +
-
S
Q R
TSD
SW
EN
GND
PWMcomp ERRAMP FB
Vin
Th
erma
l
Shutdown
C
urrent
Sense
Over Current
protect
Cbat
4.7F
Cout
2.2.F
Coil Power
2.3V to 20
V
D1
Q1
VOUT
+
-
Over & under Voltage Protect
Cin
1F
11 LEDs
PWM
PWM control
IC Power
2.7V to 5.5V
Current
Driver
ISET
UVLO
Enable control

Technical Note
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●Main characteristics examples
1) Efficiency
●BD60A60NUX <efficiency – ILED>
LED 6series, coil : VLF302512MT-100M
●BD60A00NUX <efficiency – ILED>
LED 10series, coil : VLF302512MT-100M coil : VLF302512MT-100M

Technical Note
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IC Power=5.0V, Coil Power=4V to 16V
・BD60A00NUX
IC Power=5.0V, Coil Power=2.7V to 20V, LED 8serial, LED current =25mA,
coil 1094AS-10M(TOKO), SBD RB060M-60TR(ROHM)
・BD60A60NUX
IC Power=5.0V, Coil Power=2.7V to 20V, LED 6serial, LED current =25mA,
coil 1094AS-10M(TOKO), SBD RB521A-40TR(ROHM)
BD60A00NUX Vcoil vs efficiency
VIN=5V Ta=25℃
LED 8灯(26V)
coil 1094AS-10M(TOKO)
SBD RB060M-60TR(ROHM)
LED電流設定 2 5 mA
PWM=100%
eff1=(Vout*ILED)/(Vcoil*Icoil)*100
eff2=(Vout*ILED)/(Vcoil*Icoil+VIN+IVIN)*100
70
75
80
85
90
95
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Vcoil (V)
efficiency (%)
eff1
eff2
BD60A60 Vcoil vs efficiency
VIN=5V Ta=25℃
LED 6灯(20V)
coil 1094AS-10M(TOKO)
SBD RB521S-40(Rohm) for BD60A60
LED電流設定 25mA
PWM=100%
eff=(Vout*ILED)/(Vcoil*Icoil+VINI*VIN)*100
70
75
80
85
90
95
234567891011121314
Vcoil (V)
efficiency (%)

Technical Note
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PWM 20kHz Dut
y
50%
VOUT
LED current
PWM
VOUT
LED current
PWM
PWM 20kHz Dut
y
1%
100mV/div
100mV/div
40µs/div
200ns/div

Technical Note
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・BD60A00NUX PWM duty – LED current
IC Power=5.0V, LED 8serial, LED current =25mA, PWM frequency = 20kHz, Ta=25deg
coil 1094AS-10M(TOKO), SBD RB060M-60TR(ROHM)
BD60A00NUX Vcoil vs efficiency
VIN=5V Ta=25℃
LED 8 灯(26V)
coil 1094AS-10M(TOKO)
SBD RB060M-60TR(ROHM)
LED current 25mA
PWM frequency 20kHz
0.01
0.10
1.00
10.00
100.00
0.1 1.0 10.0 100.0
PWM duty (%)
LED current (mA)
Possible to Duty 0.4% at PWM=20kHz
0.4%

Technical Note
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●Functional Descriptions
1) PWM current mode DC/DC converter
This IC keeps output voltage invariably by setting PWM duty to make FB terminal 0.7V when the power is on. As for the
inputs of the PWM comparator as the feature of the PWM current mode, one is overlapped with error components from
the error amplifier, and the other is overlapped with a current sense signal that controls the inductor current into Slope
waveform to prevent sub harmonic oscillation. This output controls internal Nch Tr via the RS latch. In the period where
internal Nch Tr gate is ON, energy is accumulated in the external inductor, and in the period where internal Nch Tr gate
is OFF, energy is transferred to the output capacitor via external SBD.
This IC has many safety functions, and their detection signals stop switching operation at once.
2) Soft Start
This IC has soft start function, which prevents rush current at turning on.
After EN and PWM are changed LH, soft start becomes effective within 1ms. Soft start doesn't become effective
even if Enable is changed LH, after that. By changing EN and PWM LH, soft start can become effective.
Since a soft start function stops working at the time of following PWM=H when EN=H is held with PWM=L
After EN=H should input a PWM signal within 10ms.
PWM
OFF ON ONOFF OFF OFF ON
OFFOFF
EN
Soft Star
t
Soft Star
t
Rese
t
Reset Reset
Soft start time Finish
PWM
EN Within 10ms
Fig.3Softstart

Technical Note
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●Protection
・Over voltage protection
At such an error of output open as the output DC/DC and the LED is not connected to IC, the DC/DC boosts too much
and the VOUT terminal exceeds the absolute maximum ratings, and may destruct the IC. Therefore, when the VOUT
becomes sensing voltage or higher, the over voltage limit protection works, turns off the switching Tr, DC/DC will be
stopped, and the output voltage goes down slowly. When output voltage becomes below the hysteresis voltage of Over
voltage protection, A boost function works and output voltage reaches detection voltage again.
This operation is repeated unless the abnormalities in application are recovered.
・Schottky Diode open protection
In the case of external SBD is not connected to IC, or VOUT is shorted to GND, the coil or internal Tr may be destructed.
Therefore, at such an error as VOUT becoming 0.2V or below, turns off the output Tr, and prevents the coil and the IC
from being destructed.
And the IC changes from activation into non-activation, and current does not flow to the coil (0mA).
・Thermal shut down
This IC has thermal shut down function.
The thermal shut down works at 175C or higher, and the IC changes from activation into non-activation.
・Over Current Protection
Over current flows the current detection resistor that is connected to between internal switching transistor source and
GND. Current sense voltage turns more than detection voltage, over current protection is operating and it is prevented
from flowing more than detection current by reducing ON duty of switching Tr without stopping boost.
As over current detector of This IC is detected peak current, current more than over current setting value does not flow.
< The estimate of the current value which need for the normal operation>
As over current detector of This IC is detected the peak current, it has to estimate peak current to flow to the coil by
operating condition.
In case of, Switching frequency = fsw Typ=0.6MHz
Supply voltage of coil = VIN Inductance value of coil = L
Output voltage = VOUT Total LED current = IOUT
Average current of coil = Iave Peak current of coil = Ipeak
Efficiency = eff
ON time of switching transistor = Ton
Ipeak = (VIN / L) × (1 / fsw) × (1-(VIN / VOUT))
Iave=(VOUT × IOUT / VIN) / eff
Ton=(Iave × (1-VIN/VOUT) × (1/fsw) × (L/VIN) × 2)1/2
As peak current varies according to whether there is the direct current superposed, the next is decided.
(1-VIN/VOUT) × (1/fsw) < Tonpeak current = Ipeak /2 + Iave (continuous mode CCM)
(1-VIN/VOUT) × (1/fsw) > Tonpeak current = (VIN / L)×Ton (discontinuous mode DCM)
(Example 1)
In case of, VIN=6.0V, L=10µH, fsw=0.6MHz, VOUT=32.5V, IOUT=25mA, current =85%
Ipeak = (6.0V / 10µH) × (1 / 0.6MHz) × (1-(6.0V / 32.5V)) =0.82 A
Iave = (32.5V × 25mA / 6.0V) / 85% = 0.16A
Ton = (0.16A × (1-6.0V / 32.5V) × (1 / 0.75MHz) × (10µH /6.0V) × 2)1/2 = 0.85µs
(1- VIN/VOUT) × (1/fsw)=1.36µs > Ton
peak current = (6.0V / 10µH)×0.85µs =0.51A
+
-
SW

Technical Note
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・LED terminal over voltage protection
When FB terminal becomes higher than 5.9V(typ), IC senses the situation trouble after 100us and then stops constant
current driver and DC/DC. Therefore IC becomes never heated, even if output and FB are both shorted. Moreover, if FB
terminal becomes lower than 5.9V(typ), IC senses normal condition and activates constant current driver.
・Prevention of LED terminal over voltage protection malfunction
As the below diagrams show, voltage drop of FB terminal becomes slow when PWM operates by connecting capacitor on
a parallel with LED and decreasing LED current. At that time, LED terminal voltage protection works after condition of FB
terminal > 5.9V keeps more than 100us. LED terminal voltage protection might stop current driver and DC/DC and also
turns off LEDs, so that please set up coil selection and LED current setting less than 100us until FB terminal < 5.9V.
・Low voltage detect protection (UVLO)
Supply voltage(VIN) becomes lower than low voltage detect voltage 2.2V(typ), IC stops DC/DC and constant current
driver. Moreover, this function can be off by boosting supply voltage up to more than hysteresis voltage.
DC/DC
Current Driver
VIN
reset
2.20 V 5%
0V
A
ctive
A
ctive
2.32 V
Current Driver
FB
reset
5.9 V
0V
A
ctive
A
ctive
DC/DC
A
ctive
A
ctive
A
ctive
FB
VOU
T
Current Driver
FB
reset
5.9 V
A
ctive
DC/DC
A
ctive
100us
reset
reset
reset
PWM L H
EN L H

Technical Note
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●Operating of the application deficiency
1) When 1 LED or 1string OPEN during the operating
Since FB terminal is set to 0V when set to OPEN, Output boosts up to the over voltage protection voltage. When over
voltage is detected, the boosting operation stops and then output voltage goes down slowly. Later, if output voltage
becomes less than hysteresis of over current protection, output voltage keeps boosting up to over voltage protection
voltage again.
Fig. 8 LED open detect
2) When LED short-circuited in the plural
Even if one LED short-circuits during boost operation, it usually passes along LED and it is turned on. By making LED
shorted, FB terminal voltage increases by LED VF. Therefore output voltage becomes lower by LED VF, and the
condition turns to be normal.
Fig. 9 One LED shorted
Fig.10 FB terminal – VOUT terminal shorted
FB
FB
output
Vout
FB voltage
LED
connection normal Open
LED current 20mA 0mA
Hysteresis voltage
0.7V+VF of LED
F
B
VOU
T
LED curren
t
20mA
0.7V
LED short
VF of LED
VF of LED
FB
VOU
T
F
B
VOU
T
LED curren
t
20mA
0.7V
LED short VIN
5.9V
0.1mA
100uS

Technical Note
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3) When Schottky diode(SBD) remove
In the situation that connection is opened and also DC/DC is activated, SW terminal voltage becomes more than rated
voltage due to a lack of parts that can accept the current accumulated inside the coil. Consequently IC might be
destroyed. To prevent the IC destruction, SBD open protection is functioned. SW terminal is never destroyed as
boosting operation is stopped after VOUT terminal detects less than 0.2V.
4) When resistance linked to an ISET terminal short-circuits
Since Resistor connected to ISET terminal becomes 0Ω, LED current setting value becomes more than rating. In order
to avoid this trouble, this IC has LED current limit protection. By using this function, setting current of rating current
driver becomes 0mA, and the current flow of LED is almost same as leak current.
●Control signal input timing
When input control signals such as Enable and PWM without completing the standup of supply voltage (VIN), be
careful of the following points.
① Input each control signal after VIN exceeds 2.2V and UVLO is off.
② When input Enable and PWM, the standup time should be placed as Min.100µs from 2.2V to stable voltage for
VIN.
③ Since a soft start function stops working at the time of following PWM=H when EN=H is held with PWM=L.
After EN=H should input a PWM signal within 10ms.
●Start control (EN) and select LED current driver (PWM)
This IC can control the IC system by EN terminal and also turns off compulsorily by setting “L” level input voltage 0.4V or
below. It also powers on when EN becomes more than “H” level input voltage 1.4V. In the case of EN=H, LED current fixed
by ISET resistor with PWM=H flows. When it is selected at PWM=L, LED current stop to flow.
EN PWM IC LED current
L L Off Off
H L On Off
L H Off Off
H H On Current fixed by ISET
●LED current setting range
LED current sets up normal current by resister (RISET) connected to ISET voltage.
Each setting current is shown as below.
Normal current = 600/RISET [A]
Normal current setting range is 10mA~30mA, and also LED current at off setting is MAX 2µA of leak current.
ISET Normal current setting example
RISET LED current
20.0k(E96) 30.0mA
24.0k(E24) 25.0mA
30.0k(E24) 20.0mA
56.0k(E24) 10.7mA
VIN
①
2.2V
EN
②
Min. 100µs
PWM
DC/DC VOUT
Fig.11 Control signal input timing
VIN
EN
③
Min. 10ms
PWM
DC/DC VOUT

Technical Note
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●Brightness control
There are two dimming method available; the first method is analog dimming that applies analog voltage to ISET terminal,
and the second method is digital dimming that inputs PWM to PWM terminal. Since each method has the different merits,
please choose a suitable method for the application of use.
1) Current driver PWM control is controlled by providing PWM signal to PWM, as it is shown Fig.12.
The current set up with ISET is chosen as the H section of PWM and the current is off as the L section. Therefore, the
average LED current increases in proportion to duty cycle of PWM signal. This method that internal circuit and DC/DC
work, because it becomes to switch the driver, the current tolerance is a few when the PWM brightness is adjusted, so
it makes it possible to brightness control until 0.4µs (MIN1% at 25kHz). And, don't use for the brightness control,
because effect of ISET changeover is big under 0.4µs ON time and under 3µs OFF time. Typical PWM frequency is
100Hz~25kHz.
2) Analog dimming can be operated by applying voltage to ISET terminal via resistor as the below figure shows. ISET
terminal voltage works to become 0.6V regardless of the connected resistor. LED current increases ISET terminal
current 600 times, so that LED current can be minimized by decreasing flow current into ISET terminal using external
DC input
LED current = 1000 x 0.6V
470k+22k
1000 0.6V - DAC output
PWM
LED current
Coil current
IC’s active current
ON OFF
ON OFF
ON OFF
ON
Fig.12 PWM sequence
SW Vin
Cin
4.7F
R1
24k
Cout
2.2F
25mA
Vin
2.7V to 4.6
V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM Input
0
5
10
15
20
25
30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
DC Voltage [V]
LED Current [mA]
0
5
10
15
20
25
30
0 20406080100
PWM Hi duty [%]
LED Current [mA]
SW Vin
Cin
4.7F
R1
470k
Cout
2.2F
Vin
2.7V to 4.6V
Vout
FB
L1
10H
ISET
GND
EN
PWM
LED ON/OFF
RESET
DC
R2 22k

Technical Note
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3) The brightness control to set large current over IC max setting current is made by giving DC control voltage to VFB pin
of IC via a series resistor as shown in under figure. LED luminance (current) changed by giving DC voltage to VFB
directly. DC voltage is given from filtered one of DAC signal, or PWM signal shown in under figure.
LED current (ILED) is next expression.
ILED = [[(FB-DC) / R1] * R2 + FB ] / RFB
SWVin
Cin
4.7F
Cout
2.2F
Vin
2.7V to 4.6V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
DC
RFB
6.49
R2
6.8k
3s7p
R1
22k
SW Vin
Cin
4.7F
Cout
2.2F
Vin
2.7V to 4.6V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM
5
33k
3s7p
47k
100k
47nF
0 - 3.3V
BD60A60NUX 3LEDx7pararel
ILED
tota
l
(
mA
)
DC (V)

Technical Note
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●The coil selection
The DC/DC is designed by more than 4.7µH. When L value sets to a lower value, it is possibility that the specific
sub-harmonic oscillation of current mode DC / DC will be happened.
Please do not let L value to 3.3µH or below.
And, L value increases, the phase margin of DC / DC becomes to zero. Please enlarge the output capacitor value when you
increase L value.
●Output capacitor selection
Output Capacitor smoothly keeps output voltage and supplies LED current.
If LED current is set more than 20mA with Vcoil=2.3V～5.5V, please make output capacitor more than 2.2µF. Otherwise
phase margin of DC/DC decreases and might oscillate.
Output Voltage consists of Charge (FET ON) and Discharge (LED current). So Output voltage has Output ripple Voltage
every FET switching.
Output ripple voltage is calculated as following.
Output ripple Voltage
- Switching cycle = T - Total LED current = ILED
- Switching ON duty = D - Output ripple Voltage = Vripple
- Output Capacitor = COUT - Output Capacitor (real value) = Creal
- Decreasing ratio of Capacitor = Cerror
Creal = COUT × Cerror (Capacitor value is decreased by Bias, so)
Creal = ILED × (1-D) × T / Vripple
COUT = ILED × (1-D) × T / Vripple / Cerror
(Example 1)
In case of, VIN=5.0V, fsw = 0.6MHz, VOUT =32.5V, ILED =20mA, COUT = 2.2µF, Cerror = 50%
T = 1 / 0.6MHz
D = 1 – VIN / VOUT = 1 – 5/32.5
Vripple = ILED × (1-D) × T / (COUT×Cerror) = 20mA × (5/32.5) ×(1 / 0.6MHz) / (2.2µF×0.5)
= 4.7mV
●LED selection
Please select LED VF that input voltage is smaller than output voltage (VOUT).
0V 35V 50V
Output voltage
Capa [µF]
Cout
Creal

Technical Note
16/22
BD60A00NUX, BD60A60NUX
www.rohm.com 2011.12 - Rev.
A
© 2011 ROHM Co., Ltd. All rights reserved.
●The separation of the IC power supply and coil power supply
This IC can work in separating the power source in both IC power supply and coil power supply. With this application, it can
obtain that decrease of IC power consumption, and the applied voltage exceeds IC rating 5.5V.
That application is shown in below Fig.14. The coil power supply is connected to high voltage source applied from adapters.
Then the IC power supply is connected to the power supply that should be different from the coil power supply.
Fig.14 Application at the time of power supply separation
Fig.15 Application at the time of power supply common
The number of available LEDs by each power supply voltage condition
SWVin
Cin
1F
R1
24k
Cout
2.2F
25mA
Coil Power
2.3V to 20V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM Input
IC Power
2.7V to 4.6V
Step down
DC/DC
2,3cell Battery
Ccoil
4.7F
SWVin
Cin
4.7F
R1
24k
Cout
2.2F
25mA
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM Input
IC Power
2.3V to 4.6V
１
cell Battery
ＰＷＭ dimming（LED current setting＝25mA)
2.7V 3V ４V 5V 6V 7V 8V 9V 10V 11V 12V 13V 14V 15V 16V 17V 18V 19V 20V
2 C、SC、SC、SC、S×××××××××××××××
3 C、S C、S C、S C、S S S × × × × × × × × × × × × ×
4 C、S C、S C、S C、S S S S S S × × × × × × × × × ×
5 C、S C、S C、S C、S S S S S S S S × × × × × × × ×
6 C、S C、S C、S C、S S S S S S S S S S × × × × × ×
7 C、S C、S C、S C、S S S S S S S S S S S S × × × ×
8 C、SC、SC、SC、SSSSSSSSSSSSS×××
9 C、SC、SC、SC、SSSSSSSSSSSSSSS×
10 C、SC、SC、SC、SSSSSSSSSSSSSSSS
※ C・・・Vcoil-Vin common power supply
S・・・Vcoil-Vin separated power supply
×・・・No use due to LED terminal over voltage protection
VIN
LEDs
3セル
２セル
１セル

Technical Note
17/22
BD60A00NUX, BD60A60NUX
www.rohm.com 2011.12 - Rev.
A
© 2011 ROHM Co., Ltd. All rights reserved.
●About the order of a power supply injection at the time of power supply separation
Even if the IC power supply is 0V, leak channel is blocked as pull down resistor for power off is placed inside the
IC. The resistor intercepts leak channel from coil power supply. Additionally, there is no order for standing up and down of
coil and IC power supply.
・ At the time of starting
It doesn’t matter whether coil Power or IC Power becomes activated first.
・ At the time of power supply OFF
Please turn off after make EN terminal “L”. If power supply voltage of coil power becomes low, coil current increases
due to high boosting, which leads to over current limit. In order to avoid this state, before turning off a power supply
it is necessary to surely set EN to L.
●Input voltage 5V（BD60A00NUX）
The GND noise become big by impedance of PCB boards, so that wake up characteristics might become unstable.
To select input voltage to 5V(input voltage 4.61V over), we recommend under application to insert 4.7Ω
between input voltage line and Vin terminal
SWVin
Cin
4.7F
RISET
24k
Cout
2.2F
25mA
Vin
2.7V to 5.5V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM Input
4.7
IC Power
EN
PWM
VOUT
Coil Power Free

Technical Note
18/22
BD60A00NUX, BD60A60NUX
www.rohm.com 2011.12 - Rev.
A
© 2011 ROHM Co., Ltd. All rights reserved.
●PCB Layout
In order to make the most of the performance of this IC, its PCB layout is very important. Characteristics such as efficiency
and ripple and the likes change greatly with PCB layout, which please note carefully
<Input capacitor Cin (1F) for coil>
Connect input capacitor Cin (1F) as close as possible between coil L1 and GND.
<Schottky barrier diode SBD>
Connect schottky barrier diode SBD as close as possible between coils L1and SW pin.
<Output capacitor Cout>
Connect output capacitor Cout between cathode of SBD and GND.
Make both GND sides of Cin and Cout as close as possible.
<LED current setting resistor RISET(24kΩ)>>
Connect LED current setting resistor RISET(24kΩ) as close as possible between ISET pin and GND.
There is possibility to oscillate when capacity is added to ISET terminal, So pay attention that capacity isn’t added.
<Heat radiation of back side PAD>
PAD is used for improving the efficiency of IC heat radiation. Solder PAD to GND pin.
Moreover, connect ground plane of board using via as shown in the patterns of next page.
The efficiency of heat radiation improves according to the area of ground plane.
<Others>
When those pins are not connected directly near the chip, influence is give to the performance of BD60A00NUX, and
may limit the current drive performance. As for the wire to the inductor, make its resistance component small so as to
reduce electric power consumption and increase the entire efficiency.
The PCB layout in consideration of these is shown in the next page.
SW Vin
Cin
4.7F
RISET
24k
Cout
2.2F
25mA
Vin
2.7V to 4.6V
Vout
FB
L1
10H
ISET
GND
EN
PWM
RESET
PWM Input

Technical Note
19/22
BD60A00NUX, BD60A60NUX
www.rohm.com 2011.12 - Rev.
A
© 2011 ROHM Co., Ltd. All rights reserved.
●Recommended PCB layout

Technical Note
20/22
BD60A00NUX, BD60A60NUX
www.rohm.com 2011.12 - Rev.
A
© 2011 ROHM Co., Ltd. All rights reserved.
●Selection of external parts
Recommended external parts are as shown below.
When to use other parts than these, select the following equivalent parts.
L1: This coil is for boosting. Recommended capacity value is 10uH. Please use the coil with adequate direct current
capacity and also low direct current resistor.
Value Manufacturer Product number Size DC current
(mA)
DCR
()
Vertical Horizontal Height
10µH TDK VLF4012AT-100MR79 4.0 3.8 1.2 800 0.30
10µH TDK VLF302512MT-100M 3.0 2.5 1.2 690 0.25
10µH TOKO 1094AS-100M 3.5 3.7 1.2 760 0.18
10µH TOKO 1229AS-H-100M 3.5 3.7 1.2 750 0.24
Cin: This is bypath capacitor for power supply, which removes power supply noise occurred instantly and provides stable
power supply for IC. In order to obtain better quality, please use low ESR products such as ceramic capacitors.
Recommended capacity value is more than 1µF.
C0: This is output smoothing capacitor. Recommended capacity value is 2.2µF.
When choosing capacitors such as Cin and C0, please be careful of pressure. The base line of pressure is about 2 times of
actual applying voltage. If pressure margin decreases, it might be happened that capacity value becomes almost a half of
nominal value.
Value Pressur
e
Manufactur
eProduct number Size
Vertical Horizontal Height
[ Cin : Power supply voltage capacitor]
1.0µF 10V. MURATA GRM185B31A105 1.6. 0.8. 0.5.
[ C0 : Output capacitor ]
1.0µF 50V MURATA GRM31MB31H105 3.2 1.6 1.15
2.2µF 50V MURATA GRM31CB31H225 3.2 1.6 1.6
R1: LED current ILED should be decided when activated.
Value Tolerance Manufacturer Product number Size ILED (mA)
Vertical Horizontal Height
[ R1 : Resistor used for deciding LED current]
20k±0.5% ROHM MCR03PZPZD2002 1.6 0.8 0.45 30
24k±0.5% ROHM MCR03PZPZD2402 1.6 0.8 0.45 25
30k±0.5% ROHM MCR03PZPZD3002 1.6 0.8 0.45 20
56k±0.5% ROHM MCR03PZPZD5602 1.6 0.8 0.45 10.7
D1: This schottky diode (SBD) is for output rectification. In order to obtain higher switching efficiency, please use low Vf, low
reverse leak, and high current capacity.
Pressure Manufacturer Product Number Size
Vertical Horizontal Height
60V ROHM RB160M-60 3.5 1.6 0.8
40V ROHM RB521S-40 1.6 0.8 0.6
60V ROHM RB060M-60 3.5 1.6 0.8