BL8035CB6TR [BELLING]
500KHz, 18V, 2A Synchronous Step-Down Converter;
| 型号： | BL8035CB6TR |
| 厂家： | 
BELLING |
| 描述： | 500KHz, 18V, 2A Synchronous Step-Down Converter |
| 文件： | 总8页 (文件大小：1374K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
500KHz, 18V, 2A Synchronous Step-Down Converter
FEATURES
DESCRIPTION
High Efficiency: Up to 96%
Fixed 500kHz Switching Frequency
2A Output Current
No Schottky Diode Required
4.2V to 18V Input Voltage Range
0.8V Reference
The BL8035 is a fully integrated, high-efficiency 2A
synchronous rectified step-down converter. The
BL8035 operates at high efficiency over a wide
output current load range.
This device offers PWM switching control, which
allows a high efficiency over the wider range of the
load.
Forced PWM
Slope Compensated Current Mode Control for
Excellent Line and Load Transient Response
Integrated internal compensation
Stable with Low ESR Ceramic Output Capacitors
Over Current Protection with Hiccup-Mode
Thermal Shutdown
Inrush Current Limit and Soft Start
Available in SOT23-6
-40°C to +85°C Temperature Range
The BL8035 requires a minimum number of readily
available standard external components and is
available in a 6-pin SOT23 ROHS compliant package.
APPLICATIONS
Distributed Power Systems
Digital Set Top Boxes
Flat Panel Television and Monitors
Wireless and DSL Modems
Notebook Computer
TYPICAL APPLICATION
C3
1uF
C3
1uF
VIN
VIN
L
L
4.7uH
4.7uH
VIN
BST
VOUT
VIN
BST
VOUT
3.3V/2A
3.3V/2A
Ren
100k
Ren
100k
C1
22uF
C1
22uF
SW
FB
SW
FB
R1
40.2k
R1
300k
BL8035
R3
10k
EN
EN
BL8035
C2
22uF
C2
22uF
GND
GND
R2
13k
R2
96k
Figure 1.
Figure 2.
Note: 1) C1 and C2 recommended using 22uF ceramic capacitors. If the electrolytic capacitor is used, it is
recommended that the ceramic capacitor in parallel with a capacitance value of 0.1uF or more.
2) The resistance R3 in Figure 1 makes the loop more stable. If it isn’t used, the resistance R1、R2 should be
adjusted(See Figure2.). The value of R1 is recommended to be about 300kΩ.
3) C3 can be valued as 1uF, 0.1uF.
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BL8035
ORDERING INFORMATION
BST EN
FB
4
Mark Explanation
Ordering Information
6
5
Product ID
Package
BL8035CB6TR
SOT23-6
GR: Product Code
YW: Date code (Year & Week)
GRYW
Devices per reel
3000
1
2
3
GND
VIN
SW
ABSOLUTE MAXIMUM RATING
Parameter
Supply Voltage VIN
Value
-0.3V to 19V
Switch Node Voltage VSW
Boost Voltage VBST
Enable Voltage VEN
-0.3V to (VIN+0.5V)
VSW-0.3V to VSW+5V
-0.3V to 19V
All Other Pins
-0.3V to 6V
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10s)
-40C to 85C
-65C to 150C
300C
ELECTRICAL CHARACTERISTICS
(VIN=12V, VOUT=5V, TA=25C, unless otherwise stated)
Parameter
Input Voltage Range
Conditions
Min
4.2
Typ
Max
18
Unit
V
UVLO Threshold
4.1
0.5
5
0.8
150
70
V
Supply Current in Operation
Supply Current in Shutdown
Regulated Feedback Voltage
High-side Switch On Resistance
Low-side Switch On Resistance
VEN = 2.0V, VFB = 1.1V
VEN = 0V or VEN = GND
4.2V≤VIN ≤18V
mA
uA
V
m Ω
m Ω
uA
A
KHz
%
ns
10
0.816
0.784
High-side Switch Leakage Current VEN = 0V, VSW = 0V
0
10
Upper Switch Current Limit
Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
Minimum Duty Cycle
3.8
500
92
VFB = 0.7V
100
EN Input Voltage “H”
EN Input Voltage “L”
Thermal Shutdown
1.5
V
V
°C
0.6
160
PIN DESCRIPTION
PIN #
NAME
GND
SW
DESCRIPTION
1
2
3
Ground
Switching Pin
Power supply Pin
VIN
Adjustable version feedback input. Connect FB to the center point of the external resistor
divider.
Drive this pin to a logic-high to enable the IC. Drive to a logic-low to disable the IC and
enter micro-power shutdown mode.
Boostrap. A capacitor connected between SW and BST pins is required to form a floating
supply across the high-side switch driver.
4
5
6
FB
EN
BST
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BL8035
ELECTRICAL PERFORMANCE
Tested under, L=4.7uH, TA=25C, unless otherwise specified
Efficiency vs. Iout
Efficiency vs. Iout
(Vout=1.2V)
(Vout=3.3V)
100%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
90%
80%
70%
60%
50%
40%
30%
20%
Vin=5V
Vin=6V
Vin=12V
Vin=18V
Vin=5V
Vin=12V
10%
0%
0.0
0.5
1.0
1.5
2.0
0.0
0.5
1.0
1.5
2.0
Iout (A)
Iout (A)
Efficiency vs. Iout
Vout vs. Iout
(Vout=1.2V)
(Vout=5.0V)
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Vin=6V
Vin=12V
Vin=18V
Vin=5V
Vin=12V
0.0
0.5
1.0
1.5
2.0
0.0
0.5
1.0
1.5
2.0
Iout (A)
Iout (A)
Vout vs. Iout
(Vout=3.3V)
Vout vs. Iout
(Vout=5.0V)
3.50
3.45
3.40
3.35
3.30
3.25
3.20
3.15
3.10
3.05
3.00
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4.0
Vin=5V
Vin=6V
Vin=12V
Vin=18V
Vin=6V
Vin=12V
Vin=18V
0.0
0.5
1.0
1.5
2.0
0.0
0.5
1.0
1.5
2.0
Iout (A)
Iout (A)
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BL8035
Efficiency vs. Vin
Vout vs. Vin
Iout=1A
Iout=1A
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
Vout=1.2V
6
8
10
12
14
16
18
6
8
10
12
Vin(V)
14
16
18
Vin (V)
Load Transient
Vin=12V, Vout=3.3V, Iout=0.01~2A
Load Transient
Vin=12V, Vout=3.3V, Iout=0.5~1A
Ch2—Vout, Ch4--IL
Ch2—Vout, Ch4--IL
BLOCK DIAGRAM
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BL8035
DETAILED DESCRIPTION
starts first, generating stable reference voltage and
currents, and then the internal regulator is enabled.
The regulator provides stable supply for the
remaining circuitries. Three events can shut down
the chip: EN low, VIN low and thermal shutdown.
In the shutdown procedure, the signaling path is
first blocked to avoid any fault triggering. The
COMP voltage and the internal supply rail are then
pulled down. The floating driver is not subject to
this shutdown command.
Internal Regulator
The BL8035 is a current mode step down DC/DC
converter that provides excellent transient
response with no extra external compensation
components. This device contains an internal, low
resistance, high voltage power MOSFET, and
operates at a high 500K operating frequency to
ensure a compact, high efficiency design with
excellent AC and DC performance.
Error Amplifier
APPLICATIONS INFORMATION
The error amplifier compares the FB pin voltage
with the internal FB reference (VFB) and outputs a
current proportional to the difference between
the two. This output current is then used to
charge or discharge the internal compensation
network to form the COMP voltage, which is used
to control the power MOSFET current. The
optimized internal compensation network
minimizes the external component counts and
simplifies the control loop design.
Setting Output Voltages
The external resistor divider is used to set the
output voltage (see Typical Application on page 1).
The feedback resistor R1 also sets the feedback
loop bandwidth with the internal compensation
capacitor. Choose R1 to be around 300kΩ for
optimal transient response. R2 is then given by:
ꢂ
ꢁ
ꢀ
ꢃꢄꢅꢆꢇꢃꢈꢉ ꢊ ꢋ
Internal Soft-Start
The soft-start is important for many applications
because it eliminates power-up initialization
problems. The controlled voltage ramp of the
output also reduces peak inrush current during
start-up, minimizing start-up transient events to
the input power bus.
Selecting the Inductor
Over-Current-Protection and Hiccup
Use a 2.2μH-to-10μH inductor with a DC current
rating of at least 25% percent higher than the
maximum load current for most applications. For
highest efficiency, select an inductor with a DC
resistance less than 15mΩ. For most designs,
derive the inductance value from the following
equation.
The BL8035 has a cycle-by-cycle over-current limit
for when the inductor current peak value exceeds
the set current-limit threshold. First, when the
output voltage drops until FB falls below the
Under-Voltage (UV) threshold (typically 140mV) to
trigger a UV event, the BL8035 enters hiccup
mode to periodically restart the part. This
protection mode is especially useful when the
output is dead-shorted to ground. This greatly
reduces the average short-circuit current to
alleviate thermal issues and to protect the
regulator. The BL8035 exits hiccup mode once the
overcurrent condition is removed.
ꢃꢍꢎꢏ ꢐ ꢑꢃ ꢊ ꢃꢍꢎꢏ
ꢔ
ꢒꢓ
ꢌ ꢁ
ꢃ ꢐ ꢕꢖꢗ ꢐ ꢘ
ꢒꢓ
ꢄꢙꢚ
Where ΔIL is the inductor ripple current. Choose
an inductor current approximately 30% of the
maximum load current. The maximum inductor
peak current is:
ꢕꢖꢗ
ꢖꢗꢑꢛꢜꢝꢔ ꢁ ꢖꢗꢍꢜꢞ
ꢟ
Startup and Shutdown
If both VIN and EN are higher than their appropriate
thresholds, the chip starts. The reference block
ꢠ
Under light-load conditions (below 100mA), use
a larger inductor to improve efficiency.
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BL8035
1) Keep the connection between the input
ground and GND pin as short and wide as
possible.
2) Keep the connection between the input
capacitor and VIN pin as short and wide as
possible.
Selecting the Output Capacitor
The output capacitor (C2) maintains the DC
output voltage. Use ceramic, tantalum, or low-
ESR electrolytic capacitors. Use low ESR
capacitors to limit the output voltage ripple.
Estimate the output voltage ripple with:
3) Use short and direct feedback connections.
Place the feedback resistors and compensation
components as close to the chip as possible.
4) Route SW away from sensitive analog areas
such as FB.
ꢃꢍꢎꢏ
ꢃ
ꢋ
ꢕꢃꢍꢎꢏ
ꢁ
ꢐ ꢢꢋ ꢊ ꢍꢎꢏꢣ ꢐ ꢢ ꢤꢡꢥ ꢟ
ꢣ
ꢘ ꢐ ꢌ
ꢡ
ꢃ
ꢦ ꢐ ꢘ ꢐ ꢧꢀ
ꢒꢓ
ꢡ
Where L is the inductor value and RESR is the
equivalent series resistance (ESR) of the output
capacitor.
For ceramic capacitors, the capacitance
dominates the impedance at the switching
frequency and causes most of the output voltage
ripple. For simplification, estimate the output
voltage ripple with:
ꢃꢍꢎꢏ
ꢃ
ꢕꢃꢍꢎꢏ
ꢁ
ꢐ ꢢꢋ ꢊ ꢍꢎꢏꢣ
ꢦ ꢐ ꢘꢀ ꢐ ꢌ ꢐ ꢧꢀ
ꢃ
ꢒꢓ
ꢙ
For tantalum or electrolytic capacitors, the ESR
dominates the impedance at the switching
frequency. For simplification, the output ripple
can be approximated with:
ꢃꢍꢎꢏ
ꢃ
ꢕꢃꢍꢎꢏ
ꢁ
ꢐ ꢢꢋ ꢊ ꢍꢎꢏꢣ ꢐ
ꢤꢡꢥ
ꢘ ꢐ ꢌ
ꢃ
ꢡ
ꢒꢓ
The characteristics of the output capacitor also
affect the stability of the regulation system. The
BL8035 can be optimized for a wide range of
capacitance and ESR values.
PC BOARD LAYOUT
PCB layout is very important to achieve stable
operation. For best results, use the following
guidelines and figures as reference.
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BL8035
TYPICAL APPLICATION CIRCUITS
BL8035
Figure3. 12V VIN, 5V/2A
BL8035
Figure4. 12V VIN, 3.3V/2A
BL8035
Figure5. 12V VIN, 2.5V/2A
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BL8035
BL8035
Figure6. 12V VIN, 1.8V/2A
BL8035
Figure7. 12V VIN, 1.2V/2A
PACKAGE OUTLINE
Package
SOT23-6
Devices per reel
3000
Unit
mm
Package specification：
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