BL8091

BL8091
18V (30V spike) 2A Synchronous PFM/PWM Buck Converter
DESCRIPTION
FEATURES
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The BL8091 is a high efficiency current-mode
synchronous, 18V/2A buck converter. Its input
voltage ranges from 4.5V to 18V and it provides
an adjustable regulated output voltage from
0.923V to 15V while delivering up to 2A of output
current.
The internal synchronous switches increase
efficiency and eliminate the need for an external
Schottky diode. The switching frequency is set to
340KHz. And the BL8091 will automatically switch
between PFM and PWM mode based on the load
current, thus to enhance the converter efficiency
at light load.
Adjustable Output Voltage, Vfb=0.923V
Maximum output current is 2A
Range of operation input voltage: Max 18V
Withstand input voltage spike >30V
Standby current: 1mA (typ.)
Operating current at zero load: 1.2mA (typ.)
Line regulation: 0.1%/V (typ.)
Load regulation: 10mV (typ.)
High efficiency, up to 95%
Environment Temperature: -20C~85C
APPLICATIONS
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BL8091 consists of many protection block such as
UVLO, input voltage over voltage protection to
stand much higher input voltage spike, thermal
protection and output short circuit protection.
The BL8091 is available in the SOP8 and ESOP8
(with exposed pad for heat dissipation) package
Set-top-box
Consumer Electronic Device for automobile
LCD Monitor and LCD TV
Portable DVD
ADSL Modem, WLAN router
Other 12V or double cell Li-ion battery
powered device
TYPICAL APPLICATION
10uH
BST
SS
VIN
EN
LC2321
BL8091
SW
COMP
GND
FB
0.1uF
BST
SS
VIN
EN
VOUT
3.3V/2A
10nF
100K
VIN
LC2321
BL8091
10uF
SW
3.3nF
*Cc optional
GND
FB
10K
PFM at Light Load
5.6K
COMP
22uF
x2
26.1K
* When Vin is as low as 5V, Cc is recommended to
be 100pf, but not needed when Vin larger than 5V.
PIN OUT
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SOP8 and ESOP8
1
BL8091
MARK and ORDERING INFORMATION
Mark Explanation
Ordering Information
HH|: Product Code
LL: Lot No.
U: Fab code
YW: Date code
HH |
LLUYW
SOP8
2500pcs/reel
BL8091CD8TR
ESOP8
2500pcs/reel
BL8091CS8TR
PINOUT DESCRIPTION
PIN #
1
2
3
4
5
NAME
BST
VIN
SW
GND
FB
6
COMP
7
EN
8
SS
DESCRIPTION
High side power transistor gate drive boost input
Power input, the input capacitor should be placed as close to VIN and GND pin as possible
Power switching node to connect inductor
Ground.
Feedback input with reference voltage set to 0.923
Compensation node. A serial RC connected to this pin is required to maintain the Buck
converter control loop stable.
Enable input. Setting it to high level or connecting to Vin via a resistor may turn on the chip,
while setting it to ground level will turn off the chip.
Soft-start node. Connecting a 0.1uF capacitor to ground make the Buck converter output rise
smoothly.
BLOCK DIAGRAM
SS
VIN
UVLO &
Thermal
shutdown
0.923V Ref
+
ISense
5V
BST
-
+
+
-
Σ
Comp
Network
-
EA
EN
PWM
Logic
Anti-ShootThrough
Driver
SW
Slope Comp
+
OSC
Vcomp
-
FB
COMP
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2
GND
BL8091
ABSOLUTE MAXIMUM RATING
Parameter
Value
Max Input Voltage
Max Operating Junction Temperature(Tj)
Ambient Temperature(Ta)
SOP-8L
Package Thermal Resistance (jc)
ESOP-8L
Storage Temperature(Ts)
Lead Temperature & Time
ESD (HBM)
30V
125C
-20C – 85C
45C / W
10C / W
-40C - 150C
260C, 10S
>2000V
Note: Exceed these limits to damage to the device. Exposure to absolute maximum
rating conditions may affect device reliability.
RECOMMENDED WORK CONDITIONS
Parameter
Value
Input Voltage Range
Operating Junction Temperature(Tj)
Max. 18V
-20C –125C
ELECTRICAL CHARACTERISTICS
(VIN=12V, TA=25C)
Symbol
Parameter
VDD
Input Voltage Range
Vref
Feedback Voltage
Ifb
Feedback Leakage current
Iq
Quiescent Current
Conditions
Min
Typ
Max
Unit
18
V
0.946
V
0.1
0.4
uA
1.1
1.5
mA
6
10
uA
4.5
Vin=12V, Ven=5V
0.900
Active, Vfb=1V, No Switching
Shutdown, Vin=8V
0.923
LnReg
Line Regulation
Vin=5V to 12V
0.1
%/V
LdReg
Load Regulation
Iout=0.1 to 2A
0.02
%/A
Switching Frequency
Ven=2V, Vin=12V
340
KHz
Fsoc
RdsonP
PMOS Rdson
130
mohm
RdsonN
NMOS Rdson
110
mohm
Ilimit
Peak Current Limit
2.5
A
Venh
EN High Threshold
Venl
EN Low Threshold
Vovp
Input Over-Voltage Protection
TSD
Over Temperature Proection
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Ven=2V
1.5
18
V
V
V
160
3
2
0.5
C
BL8091
TYPICAL PERFORMANCE CHARACTERISTICS
(Vin=12V, Vout=3.3V, L=10uH, Cin=10uF, Cout=22uF, TA=25C, unless otherwise stated)
Efficiency (Vout=3.3V)
Vout Vs. Iout
100
3.5
3
80
Vout (V)
Eff. (%)
2.5
60
40
Vin=5V
Vin=12V
Vin=4.5V
20
2
1.5
1
Vin=4.5V
Vin=5V
Vin=12V
0.5
0
0
1
10
100
1,000
0
Iout (mA)
1
1.5
2
Iout (A)
Vout Vs. Vin
Zero Load Operating Current Vs. Vin
4
1.4
3.5
1.2
3
1
2.5
Iq (mA)
Vout (V)
0.5
2
1.5
0.8
0.6
0.4
1
IOUT=300mA
0.5
0.2
0
Iq (mA)
0
4
6
8
10
12
14
16
18
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Vin (V)
Vin (V)
Switching waveform Vin=18V, Iout=0
Switching waveform Vin=18V, Iout=2A
VIN
VIN
VOUT
VOUT
I_L
SW
SW
I_L
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BL8091
Switching waveform Vin=5V, Iout=0
Switching waveform Vin=5V, Iout=2A
VOUT
VOUT
VIN
VIN
SW
SW
I_L
I_L
FUNCTIONAL DECRIPTIONS
Loop Operation
The BL8091 is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to
2A of output current, integrated with a 110m synchronous MOSFET, eliminating the need for external diode. It uses a
PWM current-mode control scheme. An error amplifier integrates error between the FB signal and the internal reference
voltage. The output of the integrator is then compared to the sum of a current-sense signal and the slope compensation
ramp. This operation generates a PWM signal that modulates the duty cycle of the power MOSFETs to achieve regulation
for output voltage.
Current Limit
There is a cycle-by-cycle current limit on the high-side MOSFET of 3A(typ). When the current flowing out of SW exceeds
this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. Unlike the traditional method of
current limiting by limiting the voltage at the compensation pin, which usually has large variation due to duty cycle
variance, this type of peak current limiting scheme provides a relatively more accurate limit for output current, thereby
lowering the requirements for system design.
Light Load Operation
Traditionally, a fixed current mode constant frequency PWM DC-DC regulator always switches even when the output
load is small. When energy is shuffling back and forth through the power MOSFETs, power is lost due to the finite
RDSONs of the MOSFETs and parasitic capacitances. At light load, this loss is prominent and efficiency is therefore very
low. BL8091 employs a proprietary control scheme that improves efficiency in this situation by enabling the device into a
power save mode during light load, thereby extending the range of high efficiency operation.
Faster Transient Response
Normally, people use 3.3nF and 5.6Kohm RC for compensation to keep the loop stable. However, if one needs to have
faster load transient response, 3.3nF and 8.5Kohm is recommended.
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BL8091
COMPONENT SELECTRION
When setting up the BL8091 for different output voltage, please use following recommended component value for the
best performance.
VOUT (V)
8
5
3.3
2.5
1.8
1.2
COUT (F)
22x2
22x2
22x2
22x2
22x2
22x2
L (H)
22
15
10
6.8
4.7
3.3
THERMAL CONSIDERATION
BL8091 is high efficiency Buck converter, which means it consumes very few power when converting the high voltage to
low voltage. However, when output power is very large, like 5V/2A, the output power is as high as 10W, a heat
dissipation path is strongly recommended to be routed on PCB. BL8091 has two different SOP8 package. For the normal
SOP8, the heat is conducted out via Pin 4 (GND), so the heat dissipation route on PCB should be connected to the Pin 4
of the chip. If ESOP8 is selected, the heat dissipation copper area should be exposed and connected to the exposed pad
underneath the chip body.
When output power is larger than 10W, the ESOP8 package is recommended.
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BL8091
PACKAGE OUTLINE
Package
SOP8
Devices per reel
2500
Unit
mm
Devices per reel
2500
Unit
mm
Package specification：
Package
ESOP8
Package specification：
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