Page 1
AiT Semiconductor Inc.
www.ait-ic.com
A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
DESCRIPTION
FEATURES
The A7406 is a current mode monolithic buck
switching regulator. Operating with an input range of
4.7V~40V, the A7406 delivers 600mA of continuous
output current with two integrated N-Channel
MOSFETs. The internal synchronous power switches
provide high efficiency without the use of an external
Schottky diode. At light loads, the regulator operates
in low frequency to maintain high efficiency and low
output ripple. Current mode control provides tight load
transient response and cycle-by-cycle current limit.
The A7406 guarantees robustness with short-circuit
protection, thermal protection, current run-away
protection, and input under voltage lockout.
The A7406 is available in SOT-26 package.
ORDERING INFORMATION
Package Type
Part Number
SOT-26
E6
A7406E6R
A7406E6VR
Note
V: Halogen free Package
R: Tape & Reel
AiT provides all RoHS products
Suffix “ V “ means Halogen free Package
4.7V to 40V operating input range
600mA output current
Up to 93% efficiency
High efficiency (>78%) at light load
Internal Soft-Start
2MHz switching frequency
Input under voltage lockout
Current run-away protection
Short circuit protection
Thermal protection
Available in SOT-26 Package
APPLICATION
Distributed Power Systems
Automotive Systems
High Voltage Power Conversion
Industrial Power Systems
Battery Powered Systems
TYPICAL APPLICATION
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
PIN DESCRIPTION
Top View
Pin #
Symbol
Function
1
BST
Bootstrap pin for top switch. A 0.1uF or larger capacitor should be connected between
this pin and the SW pin to supply current to the top switch and top switch driver.
2
GND
Ground
3
FB
Output feedback pin. FB senses the output voltage and is regulated by the control
loop to 800mV. Connect a resistive divider at FB.
4
EN
Drive EN pin high to turn on the regulator and low to turn off the regulator.
5
VIN
Input voltage pin. VIN supplies power to the IC. Connect a 4.7V to 40V supply to VIN
and bypass VIN to GND with a suitably large capacitor to eliminate noise on the input
to the IC.
6
SW
SW is the switching node that supplies power to the output. Connect the output LC
filter from SW to the output load.
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
ABSOLUTE MAXIMUM RATINGS
VIN, EN, SW Pin
-0.3V~44V
BST Pin
SW-0.3V~SW+5V
All other Pins
-0.3V~6V
Junction Temperature
NOTE1,2
150ºC
Lead Temperature
260ºC
Storage Temperature
－65ºC~+150ºC
Recommended Operating Conditions
VIN, Input Voltage
4.7V~40V
V
OUT
, Output Voltage
0.8V~37V
Operating Junction Temperature
-40ºC~125ºC
Thermal resistance
NOTE3
θJA
220ºC/W
θJC
130ºC/W
Stress beyond above listed “Absolute Maximum Ratings” may lead permanent damage to the device. These are stress ratings only and
operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
NOTE1: The A7406 guarantees robust performance from -40°C to 150°C junction temperature. The junction temperature range
specification is assured by design, characterization and correlation with statistical process controls.
NOTE2: The A7406 includes thermal protection that is intended to protect the device in overload conditions. Thermal protection is active
when junction temperature exceeds the maximum operating junction temperature. Continuous operation over the specified
absolute maximum operating junction temperature may damage the device.
NOTE3: Measured on JESD51-7, 4-layer PCB.
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
VIN Undervoltage Lockout Thershold
V
IN_MIN
VIN falling
4.2 V
VIN Undervoltage Lockout Hysteresis
V
IN_MIN_HYST
VIN rising
160 mV
Shutdown Supply Current
ISD
VEN=0V
0.07 1 μA
Supply Current
IQ
VEN=5V, VFB=1V
50 μA
Feedback Voltage
VFB
4.7V<VIN<40V
776
800
824
mV
Top Switch Resistance
R
DS(ON)T
500 mΩ
Bottom Switch Resistance
R
DS(ON)B
220 mΩ
Top Switch Leakage Current
I
LEAK_TOP
VIN=40V, VEN=0V,
VSW=0V
1 μA
Bottom Switch Leakage Current
I
LEAK_BOT
VIN=VSW=40V,
VEN=0V
1 μA
Top Switch Current Limit
I
LIM_TOP
Minimum Duty Cycle
1 A
Switch Frequency
fSW
2 MHz
Minimum On Time
T
ON_MIN
80 ns
Minimum Off Time
T
OFF_MIN
VFB=0V
100 ns
EN Shut Down Threshold Voltage
V
EN_TH
VEN falling, FB=0V
1.2 V
EN Shut Down Hysteresis
V
EN_HYST
VEN rising, FB=0V
40 mV
Thermal Shutdown
T
TSD
135 °C
Thermal Shutdown Hysteresis
T
TSD_HYST
15 °C
VIN=24V, TA=25ºC, unless otherwise stated.
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
1. Steady State Test
VIN=12V, V
OUT
=5V, I
OUT
=600mA
2. Startup through Enable
VIN=12V, V
OUT
=5V, I
OUT
=600mA(Resistive load)
3. Shutdown through Enable
VIN=12V, V
OUT
=5V, I
OUT
=600mA(Resistive load)
4. Heavy Load Operation
600mA LOAD
5. Medium Load Operation
300mA LOAD
6. Light Load Operation
0A LOAD
VIN=12V, V
=5V, L=10μH, C
OUT
=10μF, TA=+25°C, unless otherwise noted
OUT
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
7. Short Circuit Protection
VIN=12V, V
OUT
=5V, I
OUT
=600mA-Short
8. Short Circuit Recovery
VIN=12V, V
OUT
=5V, I
OUT
=Short-600mA
9. Load Transient
300mA LOAD→600mA LOAD→300mA LOAD
10. Efficiency @ V
OUT
=5V
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
BLOCK DIAGRAM
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
DETAILED INFORMATION
FUNCTIONAL DESCRIPTION
The A7406 is a synchronous, current-mode, step-down regulator. It regulates input voltages from 4.7V to 40V
down to an output voltage as low as 0.8V, and is capable of supplying up to 600mA of load current.
Current-Mode Control
The A7406 utilizes current-mode control to regulate the output voltage. The output voltage is measured at the
FB pin through a resistive voltage divider and the error is amplified by the internal transconductance error
amplifier.
Output of the internal error amplifier is compared with the switch current measured internally to control the
output current.
PFM Mode
The A7406 operates in PFM mode at light load. In PFM mode, switch frequency decreases when load current
drops to boost power efficiency at light load by reducing switch-loss, while switch frequency increases when
load current rises, minimizing output voltage ripples.
Shut-Down Mode
The A7406 shuts down when voltage at EN pin is below 1.2V. The entire regulator is off and the supply
current consumed by the A7406 drops below 0.1uA when voltage at EN pin is below 0.3V.
Power Switch
N-Channel MOSFET switches are integrated on the A7406 to down convert the input voltage to the regulated
output voltage. Since the top MOSFET needs a gate voltage great than the input voltage, a boost capacitor
connected between BST and SW pins is required to drive the gate of the top switch. The boost capacitor is
charged by the internal 3.3V rail when SW is low.
VIN Under-Voltage Protection
A resistive divider can be connected between VIN and ground, with the central tap connected to EN, so that
when VIN drops to the pre-set value, EN drops below 1.2V to trigger input under voltage lockout protection.
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
Output Current Run-Away Protection
At start-up, due to the high voltage at input and low voltage at output, current inertia of the output inductance
can be easily built up, resulting in a large start-up output current. A valley current limit is designed in the
A7406 so that only when output current drops below the valley current limit can the top power switch be
turned on. By such control mechanism, the output current at start-up is well controlled.
Output Short Protection
When output is shorted to ground, output current rapidly reaches its peak current limit and the top power
switch is turned off. Right after the top power switch is turned off, the bottom power switch is turned on and
stay on until the output current falls below the valley current limit. When output current is below the valley
current limit, the top power switch will be turned on again and if the output short is still present, the top power
switch is turned off when the peak current limit is reached and the bottom power switch is turned on. This
cycle goes on until the output short is removed and the regulator comes into normal operation again.
Thermal Protection
When the temperature of the A7406 rises above 135°C, it is forced into thermal shut-down. Only when core
temperature drops below 120°C can the regulator becomes active again.
PCB Layout Note
1. Place the input decoupling capacitor as close to A7406 (V
at the input pin.
2. Put the feedback trace as far away from the inductor and noisy power traces as possible.
3. The ground plane on the PCB should be as large as possible for better heat dissipation.
pin and PGND) as possible to eliminate noise
IN
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
REFERENCE DESIGN
Reference 1：
VIN :
V
OUT
:
I
OUT
:
5.1V~40V
3.3V
0~600mA
Reference 2：
VIN :
V
OUT
:
I
OUT
:
7V~40V
5V
0~600mA
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
PACKAGE INFORMATION
Dimension in SOT-26 Package (Unit: mm)
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AiT Semiconductor Inc.
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A7406
DC-DC CONVERTER/BUCK (STEP-DOWN)
600mA, 40V SYNCHRONOUS STEP-DOWN CONVERTER
IMPORTANT NOTICE
AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to
discontinue any integrated circuit product or service without notice, and advises its customers to obtain the
latest version of relevant information to verify, before placing orders, that the information being relied on is
current.
AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to
be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT
products in such applications is understood to be fully at the risk of the customer. As used herein may involve
potential risks of death, personal injury, or servere property, or environmental damage. In order to minimize
risks associated with the customer's applications, the customer should provide adequate design and
operating safeguards.
AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT
warrants the performance of its products of the specifications applicable at the time of sale.
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