Datasheet
4.5V to 42V Input Voltage Range 3.5A Output Current Integrated FET
1ch Buck Converter
BD9G401EFJ-M
General Description
BD9G401EFJ is a buck converter with built-in high side
MOSFET. It has an input voltage range of 4.5V to 42V.
Current mode architecture provides fast transient
response and a simple phase compensation setup.
The IC is mainly used as a secondary side power
supply: for example, a step-down output of 3.3V/5V can
be produced from voltage power supply such as 12V or
24V. In addition, it has a synchronization function with
an external CLK that provides noise management.
Key Specifications
4.5V to 42V
Input Voltage：
Precision Reference voltage
(Ta= 25°C) ±1.5%
(Ta= -40 to +105°C) ±2.0%
Max Output Current：
3.5A(Max)
-40°C to +105°C
Operating Temperature：
Package W (Typ) x D (Typ) x H (Max)
HTSOP-J8ES
4.90mm x 6.00mm x 1.00mm
Features
AEC-Q100 Qualified
Integrated Nch MOSFET
Synchronizes to external clock 250kHz to 500kHz
ON/OFF Control through EN Terminal
(Standby current of 0µA)
Small package(HTSOP-J8ES)
LowDrop Out operation
(Note1: Grade 2)
(Note 1)
Applications
Consumer devices in general that has 12V / 24V lines
Automotive applications
(Audio system, Navigation system, etc)
Industrial distributed-power applications
Entertainment equipment
HTSOP-J8ES
Typical Application Circuit
0.1µF
5V / 3.5A
L1: 22µH
VOUT
COUT
: 47µF / 16V
D1
LX
VCC
CVCC
: 10µF / 50V
VCC
GND
BST
R4
EN
VC
160kΩ
0.01μF
EN
R5
FB
30kΩ
4.7kΩ
SYNC
SYNC
Figure 1. Typical Application Circuit
〇Product
structure : Silicon monolithic integrated circuit
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BD9G401EFJ-M
Pin Configuration
(TOP_VIEW)
LX 1
GND 2
VC 3
FB 4
8 VCC
7 BST
6 EN
5 SYNC
THERMAL
PAD
Figure 2. Pin Configuration
Pin Description
Pin No.
1
2
3
4
5
6
7
8
-
Pin Name
LX
GND
VC
FB
SYNC
EN
BST
VCC
THERMAL PAD
Switching terminal
Ground terminal
Error amplifier output terminal
Feedback input terminal
External clock input terminal
Enable terminal
Terminal for boot-strap capacitor
Input voltage terminal
PAD for heat dissipation. Always connect to GND.
Description
Block Diagram
ON/OFF
EN
VCC
10μA
TSD
1.8V
UVLO
REF
REG
CHG
+
-
ENUVLO
shutdown
Current
Sense
OCP
Current
Sense AMP
R Q
S
Nch FET SW
140mΩ
BST
FB
0.8V
-
+
+
Error
AMP
Σ
+
-
LX
VOUT
Soft
Start
Oscillator
Maxduty
Logic
10Ω
GND
VC
SYNC
Figure 3. Block Diagram
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Description of Blocks
1.
REF
This block generates the reference voltage.
REG
Regulator for internal circuit power supply.
CHG
Regulator for bootstrap capacitor charging.
TSD
Thermal Shutdown Protection Circuit
When it detects the temperature exceeding Maximum Junction Temperature (Tj= 150°C), it turns off the output FET,
and resets SoftStart circuit. It has a hysteresis function. When the temperature is decreased, the chip automatically
returns to normal operation.
UVLO
Under Voltage Lock-Out Circuit
This prevents internal circuit error during increase and decrease of power supply voltage.
It monitors VCC terminal voltage. When VCC voltage becomes 4.0V (Typ) and below, it turns OFF output FET.
SoftStart circuit also resets during this time. This circuit has a hysteresis of 200mV (Typ).
ENUVLO
If the voltage from this terminal is below 0.3V, IC operation is OFF. If it is between 0.3V and 1.4V, internal REG circuit
turns ON. If it is greater than 1.8V(Typ), the IC is operational and a hysteresis generation current of 10 μA (Typ) is
sourced from the EN terminal. To turn off the IC, source current should be removed.
When the situation without a signal to control EN terminal at the time of start up is assumed, pull down EN terminal by
pull down resistor to prevent becoming the high impedance.
Arbitrary UVLO is possible by connecting EN terminal to a voltage divider from the input voltage.
See Detailed Description below.
ErrorAMP
This is an error amplifier circuit that detects the output signal, and outputs PWM control signal.
Internal reference voltage is set to 0.8V(Typ).
SoftStart
This is a circuit that gently raises the output voltage of the DC / DC converter to prevent in-rush current during start-up.
SoftStart Time is 8ms (Typ) when the IC operates with the 300 kHz (Typ) internal clock.
When the IC operates with an external clock, SoftStart Time is changed according to the oscillator frequency.
See Detailed Description below.
Oscillator
This is a oscillation circuit with an operating frequency fixed to 300 kHz(Typ).
By inputting external CLK to the SYNC terminal, synchronous operation of 250 kHz to 500 kHz can be achieved.
See Detailed Description below for synchronous operation.
When used in self-running mode, please connect SYNC terminal to GND.
2.
3.
4.
5.
6.
7.
8.
9.
10. Current Sense AMP
This is a voltage - pulse width converter.
It compares the voltage depending on the current of FET SW through the sum of the error amplifier output voltage and
the slope ripple. The output then controls the width of the output pulse and outputs it to the driver.
11. Nch FET SW
This is a Power Nch MOSFET.
It should be used within OCP threshold 4.0A(Min) including the DC current and ripple current of the inductor.
See the Application Components Selection Method below for the calculation of FET maximum current.
12. OCP
The IC has a pulse-by-pulse over current protection function to protect the FET from over current. When OCP is
detected twice sequentially, the device will turn off and restart.
See the Detailed Description below for OCP function.
13. MaxDuty logic
When Nch FET SW continues being turned ON in eight successive cycles, the high side FET will be turned off forcibly.
See the later Detailed Description for LowDrop Out operation.
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BD9G401EFJ-M
Absolute Maximum Ratings (Ta= 25°C)
Parameter
VCC-GND Voltage
BST-GND Voltage
BST-LX Voltage
EN-GND Voltage
LX-GND Voltage
FB-GND Voltage
VC-GND Voltage
SYNC-GND Voltage
Operating Temperature
Storage Temperature
Junction Temperature
Symbol
VCC
VBST
VBST-LX
VEN
VLX
VFB
VVC
VSYNC
Topr
Tstg
Tjmax
Limit Rating
45
50
7
45
45
7
7
7
-40 to +105
-55 to +150
150
Unit
V
V
V
V
V
V
V
V
°C
°C
°C
Caution: Operating the IC over the absolute maximum ratings may damage the IC. The damage can either be a short circuit between pins or an
open circuit between pins and the internal circuitry. Therefore, it is important to consider circuit protection measures, such as adding a fuse, in
case the IC is operated over the absolute maximum ratings
Thermal Resistance
(Note 1)
Parameter
HTSOP-J8ES
Junction to Ambient
Junction to Top Characterization Parameter
(Note 2)
Symbol
Thermal Resistance (Typ)
1s
(Note 3)
2s2p
(Note 4)
Unit
θ
JA
Ψ
JT
206.4
21
45.2
13
°C/W
°C/W
(Note 1)Based on JESD51-2A(Still-Air)
(Note 2)The thermal characterization parameter to report the difference between junction temperature and the temperature at the top center of the outside
surface of the component package.
(Note 3)Using a PCB board based on JESD51-3.
Layer Number of
Measurement Board
Single
Top
Copper Pattern
Footprints and Traces
Layer Number of
Measurement Board
4 Layers
Top
Copper Pattern
Footprints and Traces
Material
FR-4
Board Size
114.3mm x 76.2mm x 1.57mmt
Thickness
70μm
(Note 4)Using a PCB board based on JESD51-7.
Material
FR-4
Board Size
114.3mm x 76.2mm x 1.6mmt
2 Internal Layers
Thermal Via
(Note 5)
Pitch
1.20mm
Bottom
Copper Pattern
74.2mm x 74.2mm
Thickness
70μm
35μm
Diameter
Φ0.30mm
Thickness
70μm
Copper Pattern
74.2mm x 74.2mm
Thickness
(Note 5) This thermal via connects with the copper pattern of all layers..
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BD9G401EFJ-M
Recommended Operating Ratings (Ta= -40°C to +105°C)
Parameter
Power Supply Voltage
Output Voltage
Output Current
SYNC Terminal Input Frequency
Input Capacitance
Inductance
L
Symbol
VCC
VOUT
IOUT
f
SYNC
C
IN
(Note 9)
(Note 10)
Rating
Min
4.5
0.8
(Note 6)
(Note 7)
Typ
-
-
-
-
-
-
Max
42
VCC
(Note 8)
Unit
V
V
A
kHz
µF
µH
-
250
2.2
11
3.5
500
-
-
(Note 6) Voltage more than 4.65V is necessary for IC start. The IC can work to 4.5V after start.
(Note 7) Restricted by Min On Time 200ns(Max).
(Note 8)Upper limit restricted by MaxDuty.
(Note 9) The capacitance is selected in the range including temperature characteristics and bias voltage effect. Refer to P18.
(Note10)Restricted by output voltage setting. Refer to P17.
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