FN6439 Rev 6.00 Page 1 of 9
July 19, 2012
FN6439
Rev 6.00
July 19, 2012
ISL97656
Step-Up Regulator with 4A Integrated Switch
DATASHEET
The ISL97656 is a high frequency, high efficiency current
mode control non-synchronous step-up voltage regulator
operated at constant PMW switching frequency. It has an
internal 4.0A, 120mΩ Low side MOSFET and can deliver high
output current and efficiency over 90%. The selectable 640kHz
and 1.22MHz switching frequency allows use of smaller
inductor and faster transient response. An external
compensation pin gives the user flexibility in setting frequency
compensation allowing the use of low ESR ceramic output
capacitors.
When in shut down mode, ISL97656 draws current <1µA and
can operate at as low as 2.2V input. These features along with
higher switching frequency allows use of tiny external
components and makes it an ideal device for portable
equipment and TFT-LCD displays.
The ISL97656 is available in a 10 Ld TDFN package with a
maximum height of 1.1mm. The device is specified for
operation over the full -40°C to +85°C temperature range.
Features
•4.0A, Low r
DS(ON) Integrated Low Side MOSFET
• +2.2V to +6.0V Operating Input Voltage Range
• +1.1*VIN to +24V Output Voltage Range
• 640kHz or 1.22MHz Switching Frequency
• Higher Efficiency and Better Thermal Performance
• Adjustable Soft-Start
• Internal Thermal Protection
• 0.8mm Maximum Height 10 Ld TDFN Package
• Pb-Free (RoHS Compliant)
•Halogen Free
Applications
• Portable Equipment, Digital Cameras
• TFT-LCD Displays, DSL Modems
• PCMCIA Cards, GSM/CDMA Phones
Pin Configuration
ISL97656
(10 LD TDFN)
TOP VIEW
Ordering Information
PART
NUMBER
(Notes 1, 2, 3)
PART
MARKING
PACKAGE
(Pb-Free)
PKG.
DWG. #
ISL97656IRTZ 656Z 10 Ld TDFN L10.3x3B
NOTES:
1. Add “-T*” suffix for tape and reel. Please refer to TB347 for details
on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special
Pb-free material sets, molding compounds/die attach materials,
and 100% matte tin plate plus anneal (e3 termination finish, which
is RoHS compliant and compatible with both SnPb and Pb-free
soldering operations). Intersil Pb-free products are MSL classified
at Pb-free peak reflow temperatures that meet or exceed the
Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see device information
page for ISL97656. For more information on MSL please see
techbrief TB363.
2
3
4
1
9
8
7
10
COMP
FB
EN
GND
SS
FREQ
VIN
LX
56LX
GND
FIGURE 1. TYPICAL APPLICATION CIRCUIT
1
2
3
4
10
9
8
7
COMP
FB
EN
GND
SS
FREQ
VIN
LX
5GND 6
LX
12V
2.2V TO 6V
INPUT
OUTPUT
D1
C2
22µF
C3
27nF
C4
0.1µF
C3
22µF
10µH
C5
4.7nF
R3
3.9kR1 86.6k
R2
10k
ISL97656
FN6439 Rev 6.00 Page 2 of 9
July 19, 2012
Absolute Maximum Ratings (TA = +25°C) Thermal Information
Temperature Under Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +85°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Terminal Voltage with Respect to GND:
VIN to GND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.5V
LX to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26V
COMP, FB, EN, SS, FREQ to GND. . . . . . . . . . . . . . . . .-0.3V to (VIN +0.3V)
Maximum Continuous Junction Temperature . . . . . . . . . . . . . . . . . .+135°C
ESD Rating (JEDEC)
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2kV
Machine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200V
Charged Device Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2kV
Thermal Resistance (Typical) JA (°C/W) JC (°C/W)
10 Ld TDFN Package (Notes 4, 5) . . . . . . . 53 3
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product
reliability and result in failures not covered by warranty.
NOTES:
4. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
5. For JC, the “case temp” location is the center of the exposed metal pad on the package underside.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise
noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications VIN = 3V, VOUT = 12V, IOUT = 0mA, FREQ = GND, TA = -40°C to +85°C, unless otherwise specified. Boldface
limits apply over the operating temperature range, -40°C to +85°C.
PARAMETER DESCRIPTION CONDITIONS
MIN
(Note 6) TYP
MAX
(Note 6) UNIT
IDD-SHDN Shutdown Supply Current EN = 0V 0.1 5µA
IDD-STDBY Standby Supply Current EN = VIN, FB = 1.3V 0.7 mA
IDD-ACTIVE Active Supply Current EN = VIN, FB = 1.0V 3 5 mA
VFB Feedback Voltage 1.22 1.24 1.26 V
IDD-FB Feedback Input Bias Current 0.01 0.5 µA
VIN Input Voltage Range 2.2 6.0 V
DMAX - 640kHz Maximum Duty Cycle FREQ = 0V 85 92 %
DMAX - 1.2MHz Maximum Duty Cycle FREQ = VIN 85 90 %
ILIM Current Limit - Max Peak Input Current 3.8 4.0 5.1 A
IEN EN pin Input Bias Current EN = 0V 0.01 0.5 µA
rDS(ON) Switch ON Resistance VIN = 2.7V, ILX = 1A 0.12 Ω
ILX-LEAK Switch Leakage Current VSW = 26V 0.01 3 µA
VOUT/VIN Line Regulation 2.2V < VIN < 5.5V, VOUT = 12V 0.2 %
VOUT/IOUT Load Regulation VIN = 3.3V, VOUT = 12V, IO = 30mA to 200mA 0.3 %
FOSC1 Switching Frequency Accuracy FREQ = 0V 500 640 740 kHz
FOSC2 Switching Frequency Accuracy FREQ = VIN 1000 1220 1500 kHz
VIL EN, FREQ pin Input Low Level 0.5 V
VIH EN, FREQ pin Input High Level 1.5 V
gMError Amp Tranconductance 70 130 250 µA/V
VINUVLO VIN UVLO Threshold rising 2.00 2.10 2.20 V
VINUVLO-HYST VIN UVLO Hysteresis 50 mV
ISS Soft-Start Charge Current 2.5 4.5 7.5 µA
TOTP Over-Temperature Protection 150 °C
NOTE:
6. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization
and are not production tested.
ISL97656
FN6439 Rev 6.00 Page 3 of 9
July 19, 2012
Block Diagram
gM
AMPLIFIER
COMPARATOR
OSCILLATOR
SHUTDOWN
AND START-UP
CONTROL
LX
VIN
FREQ EN SS
REFERENCE
GENERATOR
PWM LOGIC
CONTROLLER
FET
DRIVER
CURRENT
SENSE GND
FB
COMP
Pin Descriptions
PIN NUMBER PIN NAME DESCRIPTION
1 COMP Compensation pin. Output of the internal error amplifier. Capacitor and resistor from COMP pin to ground.
2 FB Voltage feedback pin. Internal reference is 1.24V nominal. Connect a resistor divider from VOUT.
VOUT = 1.24V (1 + R1/R2). See “Typical Application Circuit” on page 1.
3 EN Enable control pin. Pull the pin high to turn the device ON.
4, 5 GND Power Ground.
6, 7 LX Power switch pin. Connected to the drain of the internal power MOSFET.
8 VIN Analog power supply input pin.
9 FREQ Frequency select pin. When FREQ pin is set low, switching frequency is set to 640kHz when set high switching
frequency is set to 1.22MHz.
10 SS Soft-start control pin. Connect a capacitor to control the converter output slew rate.
ISL97656
FN6439 Rev 6.00 Page 4 of 9
July 19, 2012
Performance Curves
FIGURE 2. VOUT = 5V EFFICIENCY FIGURE 3. VOUT = 5V EFFICIENCY
FIGURE 4. VOUT = 9V EFFICIENCY FIGURE 5. VOUT = 9V EFFICIENCY
FIGURE 6. VOUT = 12.3V EFFICIENCY FIGURE 7. VOUT = 12.3V EFFICIENCY
85
86
87
88
89
90
91
92
93
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
EFFICIENCY (%)
LOAD (A)
VIN = 3.0V
VIN = 3.3V
VIN = 4.5V
VIN = 3.7V
VIN = 4.0VVOUT = 5V, fSW = 640kHz
85
86
87
88
89
90
91
92
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
EFFICIENCY (%)
LOAD (A)
VOUT = 5V, fSW = 1220kHz
VIN = 3.0V
VIN = 3.3V
VIN = 4.5V
VIN = 3.7V
VIN = 4.0V
79
81
83
85
87
89
91
93
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
EFFICIENCY (%)
LOAD (A)
fSW = 1220kHz
fSW = 640kHz
VIN = 3.3V, VOUT = 9V
90
91
92
93
94
0 0.2 0.4 0.6 0.8 1.0 1.2
EFFICIENCY (%)
LOAD (A)
VIN = 5V, VOUT = 9V
fSW = 1220kHz
fSW = 640kHz
82
83
84
85
86
87
88
89
90
91
92
93
94
95
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
EFFICIENCY (%)
LOAD (A)
fSW = 1220kHz
fSW = 640kHz
VIN = 5V, VOUT = 12.3V
ISL97656
FN6439 Rev 6.00 Page 5 of 9
July 19, 2012
FIGURE 8. VIN = 5V, LOAD REGULATION FIGURE 9. VIN = 3.3V, LOAD REGULATION
FIGURE 10. LINE REGULATION FIGURE 11. VIN = 3.3V, VO = 12V, fSW = 640kHz, TRANSIENT RESPONSE
FIGURE 12. VIN = 3.3V, VO = 12V, fSW = 1.22MHz, TRANSIENT RESPONSE
Performance Curves (Continued)
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD REGULATION (%)
LOAD (A)
VIN 5, VO = 12V, fSW = 1.22MHz
VIN 5, VO = 9V, fSW = 640kHz
VIN 5, VO = 9V, fSW = 1.22MHz
VIN 5, VO = 12V, fSW = 640kHz
LOAD (A)
LOAD REGULATION (%)
0
0.05
0.10
0.15
0.20
0.25
0.30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
VIN 3.3V, VO = 5V, fSW = 1.22MHz
VIN 3.3V, VO = 9V, fSW = 1.22MHz
VIN 3.3V, VO = 9V, fSW = 640kHz
VIN 3.3V, VO = 12V, fSW = 640kHz
VIN 3.3V, VO = 5V
fSW = 640kHz
VIN 3.3V, VO = 12V
fSW = 1.22MHz
VIN (V)
LINE REGULATION (%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
VO = 5V
fSW = 1.22MHz
VO = 12V
fSW = 1.22MHz
VO = 9V
fSW = 1.22MHz
VO = 5V, fSW = 640kHz
VO = 9V, fSW = 640kHz
VO = 12V
fSW = 640kHz
IO = 50mA TO 300mA
IO = 50mA TO 300mA
ISL97656
FN6439 Rev 6.00 Page 6 of 9
July 19, 2012
Applications Information
The ISL97656 is a high frequency, high efficiency boost regulator
operated at constant frequency PWM mode. The boost converter
stores energy from an input voltage source and delivers higher
output voltage. The input voltage range is 2.2V to 6.0V and the
output voltage range is 5V to 25V. The switching frequency can be
selected between 640kHz and 1.22MHz. The higher switching
frequency allows use of smaller inductors and faster transient
response. An external compensation pin gives the user greater
flexibility in setting output transient response and tighter load
regulation. The converter soft-start characteristic can be
controlled by the external CSS capacitor. The EN pin allows the
user to shut down the device.
Boost Converter Operations
Figure 13 shows a boost converter with all the key components.
In steady state and continuous conduction mode, the boost
converter operates in two cycles. During the first cycle, as shown
in Figure 14, the internal power FET turns on and the Schottky
diode is reverse biased and cuts off the current flow to the
output. The output current is supplied from the output capacitor.
The voltage across the inductor is VIN and the inductor current
ramps up with a rate of VIN/L, where L is the inductance. The
inductor is magnetized and energy is stored in the inductor. The
change in inductor current is shown in Equation 1:
During the second cycle, the power FET turns off and the
Schottky diode is forward biased, (see Figure 15). The energy
stored in the inductor is supplied to the output. This energy is
used to charge the output capacitor and supply output current. In
this cycle switching node (LX) is held to VOUT + Schottky diode
drop. Voltage drop across the inductor is VIN - VOUT (ignoring
diode drop across Schottky diode). The change in inductor
current during the second cycle is shown in Equation 2:
In steady state operation, the change in the inductor current
must be equal as shown in Equation 3.
.
Output Voltage
An external feedback resistor divider is required to divide the
output voltage down to the nominal 1.24V reference voltage. The
current drawn by the resistor network should be limited to
maintain the overall converter efficiency. The maximum value of
the resistor network is limited by the feedback input bias current
and the potential for noise being coupled into the feedback pin. A
resistor network less than 100k is recommended. The boost
converter output voltage is determined by the relationship as
shown in Equation 4. The nominal VFB voltage is 1.24V.
IL1 T1
VIN
L
---------
=
T1 D
fSW
----------
=
D Duty Cycle=
VO
IOUT
COUT
----------------T1
=(EQ. 1)
ILT2
VIN VOUT
–
L
--------------------------------
=
T2 1D–
fSW
-------------
=(EQ. 2)
I1 I2+0=
D
fSW
---------- VIN
L
--------- 1D–
fSW
------------- VIN VOUT
–
L
--------------------------------
+0=
VOUT
VIN
----------------1
1D–
-------------
=(EQ. 3)
ISL97656
COUT
CIN
LD
VIN VOUT
FIGURE 13. BOOST CONVERTER
ISL97656
COUT
CIN
L
VIN VOUT
T1
VO
ILIL1
FIGURE 14. BOOST CONVERTER - CYCLE 1, POWER SWITCH CLOSED
ISL97656
COUT
CIN
LD
VIN VOUT
T2
VO
IL2 IL
FIGURE 15. BOOST CONVERTER - CYCLE 2, POWER SWITCH OPEN
VOUT VFB 1
R1
R2
-------
+



=(EQ. 4)
ISL97656
FN6439 Rev 6.00 Page 7 of 9
July 19, 2012
Inductor Selection
The inductor selection determines the output ripple voltage,
transient response, output current capability and efficiency. Its
selection depends on the input voltage, output voltage, switching
frequency and maximum output current. For most applications,
the inductance should be in the range of 2µH to 33µH. The
inductor maximum DC current specification must be greater than
the peak inductor current required by the regulator. The peak
inductor current can be calculated using Equation 5:
Output Capacitor
Low ESR capacitors should be used to minimize the output
voltage ripple. Multilayer ceramic capacitors (X5R and X7R) are
preferred for the output capacitors because of their lower ESR
and small packages. Tantalum capacitors with higher ESR can
also be used. The output ripple can be calculated using
Equation 6:
For noise sensitive applications, a 0.1µF placed in parallel with
the larger output capacitor is recommended to reduce the
switching noise coupled from the LX switching node.
Schottky Diode
In selecting the Schottky diode, the reverse break-down voltage,
forward current and forward voltage drop must be considered for
optimum converter performance. The diode must be rated to
handle 4.0A, the current limit of the ISL97656. The breakdown
voltage must exceed the maximum output voltage. Low forward
voltage drop, low leakage current, and fast reverse recovery will
help the converter to achieve the maximum efficiency.
Input Capacitor
The value of the input capacitor depends on the input and the
output voltages, maximum output current, inductor value and
maximum permissible noise fed back in the input line. For most
applications, a minimum 10µF is required. For applications that
run close to the maximum output current limit, an input
capacitor in the range of 22µF to 47µF is recommended.
The ISL97656 is powered from the VIN. A High frequency 0.1µF
bypass capacitor is recommended to be close to the VIN pin to
reduce supply line noise and ensure stable operation.
Loop Compensation
The ISL97656 incorporates a transconductance amplifier in its
feedback path to allow the user some adjustment on the
transient response and better regulation. The ISL97656 uses
current mode control architecture, which has a fast current sense
loop and a slow voltage feedback loop. The fast current feedback
loop does not require any compensation. The slow voltage loop
must be compensated for stable operation. The compensation
network is a series RC network from the COMP pin to ground. The
resistor sets the high frequency integrator gain for fast transient
response and the capacitor sets the integrator zero to ensure
loop stability. For most applications, the compensation resistor in
the range of 0k to 2.0k and the compensation capacitor in the
range of 3nF to 10nF.
Soft-Start
The regulator goes through the soft-start sequence after EN is
pulled high. The soft-start is provided by an internal 4.5µA
current source. This internal current source is used to charge the
external CSS capacitor. The peak MOSFET current is limited by
the voltage on the capacitor. As the voltage at the CSS capacitor
increases, this results in ramping up of the current limit from 0A
to full scale. This in turn controls the rising rate of the output
voltage.
Frequency Selection
The ISL97656 switching frequency can be user selectable. The
ISL97656 operates at either constant 640KHz or 1.22MHz
switching frequency. Connecting the FREQ pin to ground sets the
PWM switching frequency to 640kHz. When connecting FREQ
high or VIN, the switching frequency is set to 1.22MHz.
Shutdown Control
When the EN pin is pulled low, the ISL97656 is in shutdown
mode, reducing the supply current to <1µA.
Maximum Output Current
The MOSFET current limit is nominally 4.0A and guaranteed
3.8A. This restricts the maximum output current, IOMAX, based
on Equation 7:
where:
IL = MOSFET current limit
IL(AVG) = average inductor current
IL = inductor ripple current
VDIODE = Schottky diode forward voltage, typically, 0.6V
fSW = switching frequency, 640kHz or 1.22MHz
D = MOSFET turn-on ratio:
IL PEAK
IOUT VOUT
VIN
------------------------------------12VIN VOUT VIN
–
LV
OUT FREQ
-----------------------------------------------------
+=
(EQ. 5)
VO
IOUT D
fSW CO
------------------------- IOUT ESR+= (EQ. 6)
ILILAVG
12IL
+= (EQ. 7)
IL
VIN VOVDIODE
+VIN
–
LV
O
VDIODEfSW
+
------------------------------------------------------------------------------
=(EQ. 8)
IL-AVG
IOUT
1D–
-------------
=(EQ. 9)
D1
VIN
VOUT VDIODE
+
--------------------------------------------
–= (EQ. 10)
FN6439 Rev 6.00 Page 8 of 9
July 19, 2012
ISL97656
Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted
in the quality certifications found at www.intersil.com/en/support/qualandreliability.html
Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such
modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are
current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its
subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
For additional products, see www.intersil.com/en/products.html
© Copyright Intersil Americas LLC 2007-2012. All Rights Reserved.
All trademarks and registered trademarks are the property of their respective owners.
Cascaded MOSFET Application
A 24V N-Channel MOSFET is integrated in the boost regulator. For
the applications where the output voltage is greater than 24V, an
external cascaded MOSFET is needed as shown in Figure 16. The
voltage rating of the external MOSFET should be greater than
VIN.
DC PATH BLOCK APPLICATION
There is a DC path in the boost converter from the input to the
output through the inductor and diode. In the non-synchronous
topology, although the system is still in shutdown mode, the
output voltage will be the input voltage minus the forward
voltage diode drop of the Schottky diode. If this voltage is not
desired, the following circuit (see Figure 17) can be used between
input and inductor to disconnect the DC path when the ISL97656
is in shutdown mode.
FIGURE 16. CASCADED MOSFET TOPOLOGY FOR HIGH OUTPUT
VOLTAGE APPLICATIONS
INTERSIL
ISL97656
LX
FB
VOUT
VIN
FIGURE 17. CIRCUIT TO DISCONNECT THE DC PATH OF BOOST
CONVERTER
INPUT
EN
TO INDUCTOR
ISL97656
FN6439 Rev 6.00 Page 9 of 9
July 19, 2012
Package Outline Drawing
L10.3x3B
10 LEAD THIN DUAL FLAT PACKAGE (TDFN) WITH E-PAD
Rev 3, 10/11
located within the zone indicated. The pin #1 identifier may be
Unless otherwise specified, tolerance : Decimal ± 0.05
Tiebar shown (if present) is a non-functional feature.
The configuration of the pin #1 identifier is optional, but must be
Dimensions in ( ) for Reference Only.
Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
5.
either a mold or mark feature.
3.
4.
2.
Dimensions are in millimeters.1.
NOTES:
BOTTOM VIEW
DETAIL "X"
SIDE VIEW
TYPICAL RECOMMENDED LAND PATTERN
TOP VIEW
(4X) 0.15
INDEX AREA
PIN 1
PIN #1 INDEX AREA
C
SEATING PLANE
0.08
SEE DETAIL "X"
C
C4
5
5
A
B
0.10 C
2
6
10 1
0.75
0.05
0.50
2.38 +0.1/ - 0.15
3.00
(10X0.25)
(8x 0.50)
2.38
1.64
(10x0.60)
3.00
0.05
0.20 REF
0.25 +0.05/ - 0.07
10x 0.40 +/- 0.1
1.64 +0.1/ -0.15
2.80 TYP