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PDF A7642 Fiche technique - AiT Semiconductor

Numéro de référence A7642
Description DC-DC CONVERTER/BOOST
Fabricant AiT Semiconductor 
Logo AiT Semiconductor Logo 



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A7642 Datasheet, Description
AiT Semiconductor Inc.
www.ait-ic.com
A7642
DC-DC CONVERTER/BOOST (STEP-UP)
1MHz, 2A PWM REGULATOR
DESCRIPTION
A7642 is an asynchronous PWM boost converter
using a constant frequency peak current mode. An
external Schottky diode is needed. At light load,
A7642 works in the light load mode. The supply
current during the light mode is 100uA , together
with the 200mΩ internal NMOS power transistor
guarantees high efficiency in the whole output load
current range. Up to 2A peak current, Let A7642
can provide 1A output load current, which is
suitable to use as MID and mobile power supply.
The input voltage 3V~25V.The operating frequency
is internally set at 1MHz.
The A7642 is available in SOT-26 package.
FEATURES
High Efficiency: Up to 92%
1.0MHz Constant Switching Frequency
Switch current up to 2A
Low RDS(ON): 0.2Ω
Accurate Reference:0.6V
Tiny External Components
Available in SOT-26 Package
APPLICATION
WLED Drivers
Networking cards powered from PCI or PCI-express
slots
MID and Mobile Power
TYPICAL APPLICATION
ORDERING INFORMATION
Package Type
Part Number
SOT-26
A7642E6R
E6
A7642E6VR
V: Halogen free Package
Note
R: Tape & Reel
SPQ: 3,000/pcs
AiT provides all RoHS products
Suffix V means Halogen free Package
Figure 1. Basic Application Circuit with A7642
REV1.0
- JUN 2014 RELEASED -
-1-
A7642 Fiche technique
AiT Semiconductor Inc.
www.ait-ic.com
A7642
DC-DC CONVERTER/BOOST (STEP-UP)
1MHz, 2A PWM REGULATOR
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage
-0.3V~+26V
SW, SHDN Voltage
-0.3V~+26V
FB Voltages
-0.3V~+6V
Package Thermal ResistanceNOTE1
θJA 220°C/W
θJC 110°C/W
Operating Temperature Range
-40°C ~+85°C
Storage Temperature Range
-65°C~150°C
Lead Temperature (Soldering, 10s)
+260°C
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: Thermal Resistance is specified with approximately 1 square of 1oz copper.
ELECTRICAL CHARACTERISTICSNOTE2
VOUT=12V, TA = 25°C, Test Circuit of Figure 1, unless otherwise noted.
Parameter
Symbol
Conditions
Min. Typ. Max. Unit
Input Voltage Range
VIN
3 25 V
Quiescent Current
IQ FB=0.66V,No switch
100 μA
Shutdown Current
ISHDN
SHDN=0
3 μA
Low Side Main FET RON
RDS(ON)
200
Main FET Current Limit
ILIM1
2 2.6 A
Switching Frequency
FSW VIN=3V,IO=300mA
0.8 1 1.2 MHz
Feedback Reference Voltage
VREF
VIN=3V,IO=10mA
0.588 0.6 0.612 V
IN UVLO rising threshold
VUVLO
VIN Rising
2.7 V
UVLO hysteresis
UVLO.HYS
0.1 V
Thermal Shutdown Temperature
TSD
150 °C
NOTE2: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
REV1.0
- JUN 2014 RELEASED -
-3-

3 Page

A7642 pdf
AiT Semiconductor Inc.
www.ait-ic.com
A7642
DC-DC CONVERTER/BOOST (STEP-UP)
1MHz, 2A PWM REGULATOR
DETAILED INFORMATION
Operation
The A7642 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the
feedback pin. The operation of the A7642 can be understood by referring to the block diagram of BLOCK
DIAGRAM. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry. To
prevent subharmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the
output of the current sense amplifier and the result is fed into the negative input of the PWM comparator.
When this voltage equals the output voltage of the error amplifier the power MOSFET is turned off. The
voltage at the output of the error amplifier is an amplified version of the difference between the 0.6V bandgap
reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation.
If the feedback voltage starts to drop, the output of the error amplifier increases. These results in more current
to flow through the power MOSFET, thus increasing the power delivered to the output. The A7642 has
internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the
output.
Application Information
Setting the Output Voltage
The internal reference VREF is 0.6V (Typical).The output voltage is divided by a resistor divider, R1 and R2 to
the FB pin. The output voltage is given by
Inductor Selection
The recommended values of inductor are 3.3 to 10μH. Small size and better efficiency are the major concerns
for portable device, such as A7642 used for mobile phone. The inductor should have low core loss at 1.0MHz
and low DCR for better efficiency. To avoid inductor saturation current rating should be considered.
Capacitor Selection
Input ceramic capacitor of 10μF is recommended for A7642 applications. For better voltage filtering, ceramic
capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage
and temperature ranges.
REV1.0
- JUN 2014 RELEASED -
-6-

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