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PDF BD9428 Data sheet ( Hoja de datos )
| Número de pieza | BD9428 | |
| Descripción | White LED Driver | |
| Fabricantes | ROHM Semiconductor | |
| Logotipo |  |
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Datasheet
LED Drivers for LCD Backlights
White LED Driver for large LCD
Panels (DCDC Converter type)
BD9428
●General Description
BD9428 is a high efficiency driver for white LEDs and
designed for large LCDs. This IC is built-in a boost
DCDC converters that employ an array of LEDs as the
light source. BD9428 has some protect function against
fault conditions, such as the over-voltage protection
(OVP), the over current limit protection of DCDC (OCP),
the short circuit protection (SCP), the open detection of
LED string. Therefore BD9428 is available for the
fail-safe design over a wide range output voltage.
●Key Specifications
Operating power supply voltage range: 9.0V to 35.0V
LED minimum current
30mA
LED maximum current:
250mA
Oscillator frequency:
150kHz (RT=100kΩ)
Operating Current:
4.5mA (Typ.)
Operating temperature range:
-40°C to +85°C
●Applications
TV, Computer Display, Notebook, LCD Backlighting
●Features
4ch LED constant current driver and DC/DC converter
Maximum LED Current: 250mA
LED Feedback Voltage: 0.40V (@ILED=100mA),
so lower heat. Adjustable Feed Back Voltage
by following LED Current setting.
2% LED current accuracy
(when each LED is set to 100mA)
LED pin rating 80V
Individual detection and individual LED OFF for both
open and short circuits
Built-in ISET pin short-circuit protection circuit
Set Soft-Start time by external capacitor (SSFB pin).
FET’s Gate (N pin) is driven by 10V swing
Built-in Vout overvoltage protection (OVP) /
Short circuit protection (SCP)
DIP16 package
●Package
DIP16
W(Typ.) x D(Typ.) x H(Max.)
19.40mm x 6.50mm x 7.95mm
● Typical Application Circuit (4 light with PWM)
VIN
VIN
Inductor
Diode
CIN
FET
PGND
AGND
COUT
REG100
CREG
RN2
RCS DN RN1
RRT
ROVP1
ROVP2
COVP
RFB CFB1
REG100
RISET
RFAIL
REG100
N
GND
CS
RT
OVP
SSFB
ISET
FAIL
STB
VCC
LED4
LED3
LED2
LED1
PWM
ON/OFF
RVCC
CVCC
CLED4
CLED3
CLED2
CLED1
PWM
DIP16
Figure 1. Typical Application Circuit
○Product structure：Silicon monolithic integrated circuit
.www.rohm.com
© 2013 ROHM Co., Ltd. All rights reserved.
TSZ22111・14・001
○This product is not designed protection against radioactive rays
1/25
TSZ02201-0F1F0C100290-1-2
16.Oct.2013 Rev.001
1 page  
BD9428
●Pin Descriptions
Pin No
Pin Name
1 FAIL
2 REG100
3N
4 GND
5 CS
6 OVP
7 LED1
8 LED2
9 LED3
10 LED4
11 PWM
12 ISET
13 SSFB
14 RT
15 STB
16 VCC
In/Out
Out
Out
Out
-
In
In
Out
Out
Out
Out
In
Out
In/Out
Out
In
In
Function
Error detection output pin.
Power supply for N pin
DC/DC switching output pin
Ground pin
DC/DC output current detection and OCP detection pin
Overvoltage protection detection pin
Output pin 1 for LED (If unused, connect LED1 to GND)
Output pin 2 for LED (If unused, connect LED2 to GND)
Output pin 3 for LED (If unused, connect LED3 to GND)
Output pin 4 for LED (If unused, connect LED4 to GND)
External PWM light modulation signal input pin for LED1-4
LED current setting resistor connection pin
Soft start setting, Loop compensation setting pin
DC/DC drive frequency setting resistor connection pin.
Enable pin
Power supply pin
Datasheet
Rating [V]
-0.3 ~ 36
-0.3 ~ 13
-0.3 ~ 13
-
-0.3 ~ 7
-0.3 ~ 36
-0.3 ~ 80
-0.3 ~ 80
-0.3 ~ 80
-0.3 ~ 80
-0.3 ~ 36
-0.3 ~ 7
-0.3 ~ 7
-0.3 ~ 7
-0.3 ~ 36
-0.3 ~ 36
www.rohm.com
© 2013 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
5/25
TSZ02201-0F1F0C100290-1-2
16.Oct.2013 Rev.001
5 Page 
BD9428
Datasheet
●Startup operation and soft start capacitance setting
The following section describes the sequence for the startup of this IC.
①
5V
STB
Soft-St art(ISS=8uA)
IFB(Sink, Source)=±100uA)
OSC
SSFB
QD
PWM
COMP
OSC
DRIVER
N
CS
VOUT
PWM
N
②
SSFB
LE D_OK
LED
VOUT
ILED
LED_OK
③
④
⑤
⑥
RS SFB
CS SFB
0.4V
LED_DRIVER
PWM
Figure 10. Timing Chart at start up
Description of startup sequence
(1) Set the STB and PWM pin to “ON”.
(2) Set all systems to “ON”, SSFB charge will be initiated.
(3) Since the SSFB pin reach the lower limit of the internal sawtooth wave of the IC, the DC/DC converter operates to
start VOUT voltage rising.
(4) The Vout voltage continues rising to reach a voltage at which LED current starts flowing.
(5) When the LED current reaches the set amount of current, the startup operation is completed.
(6) After that, conduct normal operation following the feedback operation sequence with the LED pins.
If the SSFB pin sink/source current is ±100uA, the LED protection function will be activated.
SSFB capacitance setting procedure
As aforementioned, this IC stops DC/DC converter when the PWM pin is set to Low level and conducts step-up operation
only in the section in which the PWM pin is maintained at High level. Consequently, setting the PWM duty cycle to the
minimum will extend the startup time. The startup time also varies with application settings of output capacitance, LED
current, output voltage, and others.
Startup time at minimum duty cycle can be approximated according to the following method:
Make maeasurement of VOUT startup time with a 100% duty cycle, first. Take this value as “Trise100”.
The startup time “Trise_min” for the relevant application with the minimum duty cycle is given by the following equation.
Trise_ min
Trise_100[Sec]
Min_ Duty[ratio]
[Sec]
However, since this calculation method is just for approximation, use it only as a guide.
Make setting of time during which the SSFB pin voltage reaches the feedback voltage longer than this startup time.
Assuming that the SSFB pin voltage is VSSFB, the time is given by the following equation:
TSS
CSSFB[F]VSSFB[V ]
8[A]
[sec]
As a result, it is recommended to make SSFB capacitance setting so that “TSSFB” will be greater than “Trise_min”
www.rohm.com
© 2013 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
11/25
TSZ02201-0F1F0C100290-1-2
16.Oct.2013 Rev.001
11 Page | ||
| Páginas | Total 29 Páginas | |
| PDF Descargar | [ Datasheet BD9428.PDF ] | |
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