English

BL8331
Non-isolated Buck Off
Offline LED Driver
Features
Description
The BL8331 is a high precision buck
k constant current
LED driver. It is suitable for 85Vac~
~265Vac universal
low power offline LED lighting.
The BL8331 integrates a 500V power
er MOSFET.
It doesn’t need the auxiliary windiing for supplying
the chip. It can achieve excellent constant current
performance with very few exterrnal components,
so the system cost and size are miniimized.
The BL8331 utilizes patent pending
ng current control
method. It can achieve ± 3% LED
ED output current
acccuracy The output current does
oes not change with
the inductance and LED output voltage.
age.







Internal 500V Power M
MOSFET
± 3% LED Output Curreent Accuracy
Ultra Low Operating
ng Cu
Current
No Auxiliary Winding
Critical Conduction Mode Operation
LED Short Protection
Available in SOP-8 Pack
ackage
Applications



LED Candle Light
LED Bulb
Other LED Lighting
The BL8331 offers rich protection functions
func
to
improve the system reliability, includ
uding LED open
circuit protection, LED short circuit protection, VCC
under voltage protection, CS resisstor short circuit
protection and thermal regulation func
unction.
Typical Application
BL8331 Datasheet V1.0
1
BL8331
Non-isolated Buck Off
Offline LED Driver
ORDERING INFORMATION
Device
Package
BL8333S
SOP8
Shipping
Rail/2500pcs
Mark
PIN ASSIGNMENT and DESCRIPTION
PIN NO
SYMBOL
1
2
3
4
5,6
7,8
GND
RADJ
NC
VDD
DRN
ISEN
DESCRIPTION
Ground
Over Voltage Protection SettingPin.Connect
n.Connect a resistor.
No Connection.
Power Supply Pin.
Internal MOSFET Drain.
Current Sense Pin.Connect a resistor
sistor between this pin and GND.
Absolute Maximum Ratin
ngs (note1)
Symbol
Parameters
Range
Units
VDD
Power Supply
-0.3~20
V
Vdrn
Drain Voltage
-0.3~500
500
V
CS
Current sense pin input
i
voltage
-0.3~6
V
5
IDDMAX
Maximum sink curr
rrent
VRADNJ
Over-voltage setting
ng pin
p voltage
-0.3~6
V
Power dissipation
450
mW
θJA
Thermal resistance
ance (Junction to Ambient)
145
℃/W
TJ
Operating junction
on temperature
-40 too 150
℃
TSTG
Storage temperaturre range
-55 too 150
℃
2000
V
PDMAX
ESD
ESD
mV
Note 1: Stresses beyond those listed under “absol
olute maximum ratings” may cause permanent damage to the device.
BL8331 Datasheet V1.0
2
BL8331
Non-isolated Buck Off
Offline LED Driver
Recommended Operation
n Conditions
Symbol
Para
Parameter
Range
Unit
ILED1
Input
put LED current Voltage
[email protected] VOUT =80V
mA
ILED2
Input LED
ED current Voltage
[email protected] VOUT =36V
mA
VMIN
Minimum LED
L
Loading Voltage
>15
V
Electrical Characteristics
Symbol
VDD_CLP
IDD
VST
Parameter
er
VCC Clamp Vo
oltage
VCC Operating Current
C
VCC Turn On Th
hreshold
VCC Startup Cu
urrent
IST
VUVLO
VCC Turn off Threshold
Thre
Current Sense Section
Threshold Voltage for
VISEN
Peak Current Lim
mit
Threshold Voltage
age for
VISEN-SHT
Peak Current Limiit When
TLEB
TDELAY
MOSFET Section
BVDSS
RSW
VRADJ
Range
15.8~17.2
Units
V
≤135
135
12.8~14.2
2.8~14.2
VDD= VST - 1V
≤195
195
8.1~9.1
uA
V
uA
V
392~408
mV
198
mV
500
ns
150
ns
VGS=0V/IDS=250uA
500
V
VGS=15V/IDS=0.4A
16
Ω
VGS=0V/VDS=500V
0.5
uA
0.55
55
45
255
55
5
V
us
us
us
155
℃
VCC Falling
Output Short
Output Shorrt
Leading Edge Blanking
B
Time for Current
ent Sense
Switch Off Delay
ay Time
Drain-Source Breakdo
akdown
Voltage
Static Drain-source
source Onresistance
Power MOSFET
ET
Drain Leakage
eakage
Current
Internal Time Control Section
IDSS
Conditions
0.8mA
FSYS=65KHz
VCC Rising
ROVP Pin Voltage
age
Maximum ON Time
T
Maximum
OFF
Time
TOFF_MAX
Minimum OFF Time
TOFF_MIN
Thermal Regulation Section
TREG
Thermal Regulation Temperature
TON_MAX
BL8331 Datasheet V1.0
3
BL8331
Non-isolated Buck Off
Offline LED Driver
Application Information
The BL8331 is a high performance non-isolated
non
Buck
converter specially designed for LED
LE lighting. The
device integrates a 500V power MOS
SFET. It achieves
excellent line regulation
lation and load regulation.with
regulation.w very
MOSFET can be calculated bby the equation:
=
400
;
=
×
−
few external components
Where, I P is peak currentt of the inductor, L is the
inductance value, VIN is the
he DC bus voltage after the
rectifier bridge,VLED is the vvoltage on the LED.
Start Up
After the power MOSFET
ET is switched off, the
current in the inductor decre
reases. When the inductor
After system powered up, the VDD
DD pin capacitor is
charged up by the start up resistor. When the VDD
pin voltage reaches the turn on thresshold, the internal
circuits start operating.
Due to the ultra-low operating curreent, the auxiliary
winding is not needed to supply the IC.
C.
Constant Current Control
The BL8331 works under CRM mode with a internal
400mV reference voltage and the voltage
age on CS pin is
compared with the peak inductor current
ent
The peak inductor current is given by:
=
400
2
current reaches zero, the power MOSFET is turned
on again by IC internal llogic. The off time of the
MOSFET is given by:
=
×
The inductance can be calcu
culated by the equation:
=
× (
×
−
×
)
The F is the system swittching frequency, which is
proportional to the input
nput voltage. So the minimum
switching frequency is seet at lowest input voltage,
and the maximum switching
ng frequency is set at highest
input voltage.
The minimum and maximuum off time of BL8331 is set
at 50KHZ and 120KHZ, resspectively. Referring to the
Where, ILED is driving current, RISEN is the current
sense resistor value.
Inductor Selection
The BL8331 works under CRM mode.
m
When the
power MOFET is switched on, the
he current
cu
in the
inductor rises up from zero, the on time of the
BL8331 Datasheet V1.0
4
BL8331
Non-isolated Buck Off
Offline LED Driver
small, the tOFF may be smaller than the
he minimum off
time, system will operate in
n discontinuous
conduction mode and the output current
cu
will be
smaller than the designed value. If the
he inductance is
too large, the tOFF may be larger than
han the maximum
off time, the system will operate in continuous
conduction mode and the output current
cu
will be
higher than the designed value. So itt is important to
choose a proper inductance.
Over Voltage Protection
When the LED is open circuit, the
he output voltage
increases gradually, and the demagne
agnetization time
gets shorter. The over voltage pro
otection can be
programmed by the RADJ resistor
≈
× × 15
× 10 ( ohm)
×
Where,
V
is the ISEN turn off threshold (400mV)
L is the inductance value
RISEN is the current sense resistor value.
ue.
Vovp is the open circuit protection voltage.
voltage
Protection Function
The BL8331 offers rich protection
on functions to
improve the system reliability, including LED
open/short protection, ISEN resistor short protection,
VDD under/over voltage protection, the
hermal regulation.
When the LED is open circuit, the
t
system will
trigger the over voltage protec
ection and stop
switching.
When the LED short circuit is detec
ected, the system
works at low frequency (5kHz), So the
he system power
consumption is very low. At some
so
catastrophic
fault condition, such as ISEN resisstor shorted or
inductor saturated, the internal fastt fault detection
circuit will be triggered, the system
m stops
s
switching
immediately.
BL8331 Datasheet V1.0
After the system enters intoo fault condition, the VCC
voltage will decrease unti
til it reaches the UVLO
threshold, then the system will re-start again. If the
fault condition is removed, tthe system will recover to
normal operation.
The BL8331 integrates thermal regulation function.
When the system is over temperature, the output
current is gradually reduced; th
the output power and
thermal dissipation are also reduced. The system
temperature is regulated and the system reliability is
improved. The thermal regulation temperature is set
to 155℃ internally.
PCB Layout
The following rules should be followed in BL8331 PCB
layout:
The bypass capacitor on VDD pin should be as close as
possible to the VDD Pin and GN
GND pin.
The area of main current loop should be as small as
possible to reduce EMI radiation, such as the
inductor, the power MOSFET, the output diode and the
bus capacitor loop.
The power ground path for current sense should be short,
and the power ground path should be separated from
small signal ground path before connecting to the
negative node of the bulk capacitor.
The RADJ resistor should bee as close as possible to the
RADJ Pin.
The NC pin should be conneccted to GND (pin1).
To increase the copper area of DRAIN pin for better
thermal dissipation. However too large copper area may
compromise EMI performance.
5
BL8331
Non-isolated Buck Off
Offline LED Driver
PACKAGE OUTLINE
BL8331: SOP8
L
E
E1
?
TYPICAL
MAX
A
1.350
1.10
1.750
A1
0.100
---
0.250
A2
1.350
1.10
1.550
b
0.330
0.40
0.510
c
0.170
0.125
0.250
D
4.700
2.90
5.100
E
3.800
1.60
4.000
E1
5.800
e
---
1.90(typ)
---
L
0.400
---
1.270
θ
0°
5°
8°
6.200
A
A2
A1
e
BL8331 Datasheet V1.0
MIN
c
D
b
SIZE(
(mm)
SYMBOL
6