HE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver11 Feb 242016 Page 1
Features
 2V to 24V Input Voltage
 Up to 28V Output Voltage
 Integrated 80mΩ Power MOSFET
 12MHz Fixed Switching Frequency
 Internal 4A Switch Current Limit
 Internal Compensation
 Thermal Shutdown
 Output Adjustable from 06V
 Available in a 6pin SOT23 package
Applications
 Digital Settop Box (STB)
 Tablet Personal Computer (Pad)
 LCD Bias Supply
 BatteryPowered Equipment
 Portable Media Player (PMP)
 General Purposes
General Description
inrush current and extends battery life
The HE9710 includes undervoltage lockout current
limiting and thermal overload protection to prevent
damage in the event of an output overload The
HE9710 is available in a small 6pin SOT23 package
The HE9710 is a constant frequency current mode
stepup converter intended for small low power
applications The HE9710 switches at 12MHz and
allows the use of tiny low cost capacitors and inductors
2mm or less in height Internal softstart results in small
Typical Application
Figure1 Basic Application CircuitHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver11 Feb 242016 Page 2
Functional Block Diagram
Figure 1 HE9710 Block Diagram
Pin Description
PINNAMEFUNCTION
1 LX
Power Switch Output LX is the drain of the internal MOSFET switch
Connect the power inductor and output rectifier to LX LX can swing
between GND and 28V
2 GND Ground Pin
3 FB Feedback Input The FB voltage is 06V Connect a resistor divider
to FB
4 EN
Regulator OnOff Control Input A high input at EN turns on the
converter and a low input turns it off When not used connect EN to
the input supply for automatic startup
5 IN Input Supply Pin Must be locally bypassed
6 NC Not ConnectionHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver11 Feb 242016 Page 3
Packageorder Information
(SOT236)
Absolute Maximum Ratings (Note 1)
PARAMETER ABSOLUTE MAXIMUM RATINGS UNIT
VINVEN03 to 26 V
VSW03 to 26 V
All Other Pins 03 to 6 V
Continuous Power Dissipation(TA+25℃) 06 W
Junction Temperature 150 °C
Operating Temperature Range 40 to 85
Lead Temperature 260 °C
Storage Temperature 65 to 150 °C
Thermal ResistanceθJA 250 °C W
Thermal ResistanceθJC 130 °C W
Recommended Operating Conditions
PARAMETERRECOMMENDEDUNIT
Supply Voltage VIN 2 to 24 V
Output Voltage VOUT VIN to 28 V
Operating Junction Temp(TJ) 40 to 125 °CHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver11 Feb 242016 Page 4
Electrical Charcteristics (Note 3)
PARAMETERSYMBOL TEST CONDITIONS MINTYPMAXUNIT
Supply
Current(Shutdown)
IIN VEN0V 01 1 µA
Quiescent Current
(PFM)
VFB07VNo
switch 50 100 µA
Quiescent Current
(PWM) VFB05Vswitch 02 04 mA
SW Leakage VSW 20V 1 µA
SW On Resistance 80 150 mΩ
Operating Input
Voltage 2 24 V
Current Limit ILIMIT VIN 5VDuty
cycle50 4 A
Oscillator
Frequency
fSW VFB075V 12 MHz
Maximum Duty
Cycle
DMAX VFB07V 90
Feedback Voltage VFB 588 600 612 mV
FB Input Bias
Current VFB06V 50 10 nA
EN Threshold VEN 1 V
Thermal Shutdown 160 °CHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver11 Feb 242016 Page 5
Marking Information
The major marks：B6282
Remark If there are other requirementsplease contact our sales office
Operation
The HE9710 uses a fixed frequency peak current
mode boost regulator architecture to regulate voltage
at the feedback pin The operation of the HE9710 can
be understood by referring to the block diagram of
Figure 3 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 06V
band gap 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
HE9710 has internal soft start to limit the amount of
input current at startup and to also limit the amount of
overshoot on the output
SOT236
Pin1 sign
MARKHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver10 Feb 242016 Page 6
Applications Information
Setting the Output Voltage
HE9710 are internally compensated and do not require
external components to achieve stable operation The
output voltage can be programmed by resistor divider
Inductor Selection
The HE9710 boost converter can utilize small surface
mount and chip inductors due to the fast 12MHz
switching frequency Inductor values between 22µH and
10µH are suitable for most applications Larger values of
inductance will allow slightly greater output current
capability by reducing the inductor ripple current
Increasing the inductance above 10µH will increase size
while providing little improvement in output current
capability The minimum boost inductance value is given
by
Where
• IRIPPLE：PeaktoPeak inductor current
• VIN：Input voltage
•VOUT：Output voltage
•VDIODE：Output diode Forward Voltage
•FS：Switching frequency Hertz
The inductor current ripple is typically set for 20 to40
of the maximum inductor current High frequency ferrite
core inductor materials reduce frequency dependent
power losses compared to cheaper powdered iron types
improving efficiency The inductor should have low
DCR(series resistance of the winding) to reduce the I2R
power losses and must not saturate at peak inductor
current levels Molded chokes and some chip inductors
usually
Capacitor Selection
The internal loop compensation of the HE9710 boost
converter is designed to be stable with output capacitor
values of 10µF or greater Low ESR (equivalent series
resistance) capacitors should be used to minimize the
output voltage ripple Multilayer ceramic capacitors are
an excellent choice as they have extremely low ESR and
are available in small footprints A 10µF to 22µF output
capacitor is sufficient for most fixed frequency
applications For applications where Burst Mode
operation is enabled a minimum value of 22µF is
recommended Larger values may be used to obtain very
low output ripple and to improve transient response X5R
and X7R dielectric materials are preferred for their ability
to maintain capacitance over wide voltage and
temperature ranges Y5V types should not be used
Case sizes smaller than 0805 are not recommended due
to their increased DC bias effect
Low ESR input capacitors reduce input switching noise
and reduce the peak current drawn from the battery It
follows that ceramic capacitors are also a good choice
for input decoupling and should be located as close as
possible to the device A 22µF input capacitor connected
to inductor is sufficient for most applications Larger
values maybe used without limitations For applications
where the power source is more than a few inches away
a larger bulk decoupling capacitor is recommended on
the input to the boost converter
Diode Selection
A Schottky diode should be used for the output diode
The forward current rating of the diode should be higher
than the load current and the reverse voltage rating
must be higher than the output voltage Do not use
ordinary rectifier diodes since slow switching speedsHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver10 Feb 242016 Page 7
and long recovery times cause the efficiency and the
load regulation to suffer
Layout Consideration
PC board layout is an important part of DCDC converter
design Poor board layout can disrupt the performance of
a DCDC converter and surrounding circuitry by
contributing to EMI ground bounce and resistive voltage
loss in the traces These can send erroneous signals to
the DCDC converter resulting in poor regulation or
instability Good layout can be implemented by following
a few simple design rules
1 Minimize area of switched current loops In a buck
regulator there are two loops where currents are
switched rapidly The first loop starts from the CIN input
capacitor to the regulator VIN terminal to the regulator
SW terminal to the inductor then out to the output
capacitor COUT and load The second loop starts from
the output capacitor ground to the regulator GND
terminals to the inductor and then out to COUT and the
load To minimize both loop areas the input capacitor
should be placed as close as possible to the VIN terminal
Grounding for both the input and output capacitors
should consist of a small localized topside plane that
connects to GND The inductor should be placed as
close as possible to the SW pin and output capacitor
2 Minimize the copper area of the switch node The SW
terminals should be directly connected with a trace that
runs on top side directly to the inductor To minimize IR
losses this trace should be as short as possible and with
a sufficient width However a trace that is wider than 100
mils will increase the copper area and cause too much
capacitive loading on the SW terminal The inductors
should be placed as close as possible to the SW
terminals to further minimize the copper area of the
switch node
3 Have a single point ground for all device analog
grounds The ground connections for the feedback
components should be connected together then routed
to the GND pin of the device This prevents any switched
or load currents from flowing in the analog ground plane
If not properly handled poor grounding can result in
degraded load regulation or erratic switching behavior
4 Minimize trace length to the FB terminal The
feedback trace should be routed away from the SW pin
and inductor to avoid contaminating the feedback signal
with switch noise
5 Make input and output bus connections as wide as
possible This reduces any voltage drops on the input or
output of the converter and can improve efficiency If
voltage accuracy at the load is important make sure
feedback voltage sense is made at the load Doing so
will correct for voltage drops at the load and provide the
best output accuracyHE9710 High Efficiency12MHz
28V Output 2A Step Up Regulator
Ver10 Feb 242016 Page 8
Package Description
6pin SOT236 Outline Dimensions

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