BL8092
18V (30V spike)2.5A Synchronous PFM/PWM Buck Converter
DESCRIPTION
The BL8092 is a high efficiency current-mode
synchronous, 18V/2.5A buck converter. Its input
voltage ranges from 3.5V 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 BL8092 will automatically switch
between PFM and PWM mode based on the load
current, thus to enhance the converter efficiency
at light load.
BL8092 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 BL8092 is available in the SOP8 and ESOP8
(with exposed pad for heat dissipation) package.
FEATURES
Adjustable Output Voltage, Vfb=0.923V
Maximum output current is 2.5A
Range of operation input voltage: Max 18V
UVLO: 3.4V (typ.)
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: -20C~85C
APPLICATIONS
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
PIN OUT
BST
SS
VIN
EN
SW
LC2321
LC2322
BL8092
COMP
0.1uF
BST
10nF
VIN
VIN
EN
100K
SS
VOUT
3.3V/2A
GND
FB
SOP8 and ESOP8
LC2321
LC2322
BL8092
10uF
SW
COMP
GND
FB
3.3nF
5.6K
22uF
x2
PFM at Light Load
Zero Load Operating Current vs. Vin
7
6
*Cc optional
10K
26.1K
Iq(mA)
* When Vin is as low as 5V, Cc is recommended to
be 100pf, but not needed when Vin larger than 5V.
5
4
3
2
1
0
0
5
10
15
20
Vin(V)
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BL8092
MARK and ORDERING INFORMATION
Mark Explanation
HH: Product Code
LL: Lot No.
U: Fab code
YW: Date code
SOP8
2500pcs/reel
ESOP8
2500pcs/reel
Ordering Information
BL8092CD8TR
BL8092CS8TR
PINOUT DESCRIPTION
PIN #
1
2
3
4
5
6
7
8
NAME
BST
VIN
SW
GND
FB
COMP
EN
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
0.923V Ref
UVLO &
Thermal
shutdown
5V
+
ISense
-
BST
+
EA
EN
Comp
Network
Σ
Slope Comp
OSC
FB
COMP
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-
-
+
PWM
Logic
Anti-Shoot-
Through
Driver
SW
+
Vcomp
-
GND
2
BL8092
ABSOLUTE MAXIMUM RATING
Parameter
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)
Value
30V
125C
-20C – 85C
45C / W
10C / W
-40C - 150C
260C, 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
Input Voltage Range
Operating Junction Temperature(Tj)
Value
Max. 18V
-20C –125C
ELECTRICAL CHARACTERISTICS
(VIN=12V, T
A
=25
C)
Symbol
VDD
Vref
V
UVLO
Ifb
Iq
LnReg
LdReg
Fsoc
RdsonP
RdsonN
Ilimit
Venh
Venl
Vovp
TSD
Parameter
Input Voltage Range
Feedback Voltage
UVLO Voltage
Feedback Leakage current
Quiescent Current
Line Regulation
Load Regulation
Switching Frequency
PMOS Rdson
NMOS Rdson
Peak Current Limit
EN High Threshold
EN Low Threshold
Input Over-Voltage Protection
Over Temperature Proection
Ven=2V
Conditions
Vin=12V, Ven=5V
Vin H-->L, Iout=0.5A
Active, Vfb=1V, No Switching
Shutdown, Vin=8V
Vin=5V to 12V
Iout=0.1 to 2A
Ven=2V, Vin=12V
Min
3.5
0.900
Typ
0.923
3.4
0.1
1.1
6
0.1
0.02
340
130
110
3.8
Max
18
0.946
0.4
1.5
10
Unit
V
V
V
uA
mA
uA
%/V
%/A
KHz
mohm
mohm
A
1
19
1.5
2
0.5
V
V
V
160
C
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BL8092
TYPICAL PERFORMANCE CHARACTERISTICS
(Vin=12V, Vout=3.3V, L=10uH, Cin=10uF, Cout=22uF,
T
A
=25
C,
unless otherwise stated)
Efficiency(Vout=3.3V)
100
80
3.5
3.0
2.5
Vout vs. Iout
Efficiency(%)
60
40
20
0
0.001
Vin=5V
Vin=3.6V
Vin=12V
0.01
0.1
1
10
Vout(V)
2.0
1.5
1.0
0.5
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Vin=5V
Vin=3.6V
Vin=12V
Iout (A)
Iout(A)
Vout vs. Iout
3.5
3.0
2.5
7
6
Zero Load Operating Current
vs. Vin
Vout(V)
5
Iq(mA)
Iout=300mA
2
4
6
8
10
12
14
16
18
20
2.0
1.5
1.0
0.5
0.0
4
3
2
1
0
0
5
10
15
20
Vin(V)
Vin(V)
Switching waveform Vin=18V, Iout=0
(CH1=Vin, CH2=Vout, CH3=SW, CH4=Isw)
Switching waveform Vin=18V, Iout=2A
(CH1=Vin, CH2=Vout, CH3=SW, CH4=Isw)
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BL8092
Switching waveform Vin=5V, Iout=0
(CH1=Vin, CH2=Vout, CH3=SW, CH4=Isw)
Switching waveform Vin=5V, Iout=2A
(CH1=Vin, CH2=Vout, CH3=SW, CH4=Isw)
FUNCTIONAL DECRIPTIONS
Loop Operation
The BL8092 is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to
2.5A 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 3.8A (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. BL8092 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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