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BL9641B
42V Input Standoff Voltage, 0.4A Step-Down Converter
FEATURES
DESCRIPTION
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The BL9641B is a wide input range, highefficiency, and high frequency DC-to-DC stepdown switching regulator, capable of delivering
up to 0.4A of output current. With a fixed
switching frequency of 750KHz, this current mode
PWM controlled converter allows the use of small
external components, such as ceramic input and
output caps, as well as small inductors.BL9641B
also employs a proprietary control scheme that
switches the device into a power save mode
during light load, thereby extending the range of
high efficiency operation. An OVP function
protects the IC itself and its downstream system
against input voltage surges. With this OVP
function, the IC can stand off input voltage as
high as 42V, making it an ideal solution for
industrial applications such as smart meters as
well as automotive applications.
In automotive systems, power comes from the
battery, with its voltage typically between 9V and
24V. Including cold crank and double battery
jump-starts, the minimum input voltage may be
as low as 4V and the maximum up to 36V, with
even higher transient voltages. With these high
input voltages, linear regulators cannot be used
for high supply currents without overheating the
regulator. Instead, high efficiency switching
regulators such as BL9641B must be used to
minimize thermal dissipation.
BL9641B is available SOT23-6 Packages.
APPLICATIONS
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Smart Meters
Industrial Applications
Automotive Applications
PIN OUT
TYPICAL APPLICATION
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Wide Input Operating Range from 4V to 38V
Standoff Input Voltage: 42V
High Efficiency at 20V In 12V Out: Up to 95%:
High Efficiency PFM mode at light load
Capable of Delivering 0.4A
No External Compensation Needed
Current Mode control
Logic Control Shutdown
Thermal shutdown and UVLO
Available in SOT23-6 Package
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BL9641B
MARK and ORDERING INFORMATION
Mark Explanation
X2: Type
Y: Year
W: Week
PINOUT DESCRIPTION
PIN #
1
2
3
4
5
6
NAME
BST
GND
FB
EN
IN
SW
DESCRIPTION
Bootstrap pin. Connect a 10nF capacitor from this pin to SW
Ground
Feedback Input. Connect an external resistor divider from the output to FB and GND to set VOUT
Enable pin for the IC. Drive this pin high to enable the part, low to disable.
Supply Voltage. Bypass with a 10μF ceramic capacitor to GND
Inductor Connection. Connect an inductor Between SW and the regulator output.
BLOCK DIAGRAM
EN
BST
IN
+
UVLO &
Thermal
shutdown
REG
&REF
Current
Sense
-
+
EA
+
COMP
network
Σ
-
FB
PWM
Logic
DRIVER
OSC
Slope Comp
GND
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2
SW
BL9641B
ABSOLUTE MAXIMUM RATING
Parameter
Value
Input Voltage Range
Max Operating Junction Temperature(Tj)
SW, EN Voltage
BST Voltage
FB Voltage
SW to ground curren
Operating Temperature(To)
SOT23-6
Package Thermal Resistance (θjc)
Storage Temperature(Ts)
-0.3V-42V
150°C
–0.3V to VIN+0.3V
–0.3V to SW+6V
–0.3V to 6V
Internally limited
-40°C –85°C
110°C / W
-55°C - 150°C
Note: Exceed these limits to damage to the device. Exposure to absolute maximum
rating conditions may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = 12V, unless otherwise specified. Typical values are at TA = 25°C .)
PARAMETER
Input Standoff Voltage
Input Voltage Range
Input UVLO
Input OVP
Input Supply Current
Input Shutdown Current
FB Feedback Voltage
FB Input Current
Switching Frequency
Maximum Duty Cycle
FoldBack Frequency
High side Switch On Resistance
High side Switch Current Limit
SW Leakage Current
EN Input Current
EN Input Low Voltage
Thermal Shutdown
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CONDITIONS
MIN
TYP
42
4
Rising, Hysteresis=140mV
Rising, Hysteresis=1.3V
VFB =0.85V
0.780
MAX
38
3.80
38
0.6
6
0.800
0.01
750
0.820
90
VFB = 0V
ISW =200mA
95
550
0.7
VIN=12V,VSW=0, EN= GND
VIN=12V ,VEN =5V
Rising, Hysteresis=100mV
Hysteresis=40°C
0.8
3
1
1.1
150
10
5
1.4
UNITS
V
V
V
V
mA
μA
V
μA
KHz
%
KHz
mΩ
A
μA
μA
V
°C
BL9641B
TYPICAL PERFORMANCE CHARACTERISTICS
(Typical values are at TA = 25°C unless otherwise specified.)
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4
BL9641B
TYPICAL CHARACTERISTICS
(Typical values are at TA = 25°C unless otherwise specified.)
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BL9641B
FUNCTIONAL DECRIPTIONS
Loop Operation
The BL9641B is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to
0.4A of output current, integrated with a 550mΩ high side MOSFET. 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.
Light Load Operation
Traditionally, a fixed 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. BL9641B
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.
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BL9641B
PACKAGE OUTLINE
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