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Analog Devices Semiconductor Electronic Components Datasheet

ADP1621 Datasheet

Current-Mode Step-Up DC/DC Controller

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ADP1621 pdf
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Constant-Frequency, Current-Mode
Step-Up DC/DC Controller
ADP1621
FEATURES
92% efficiency (no sense resistor required)
±1.0% initial accuracy
IC supply voltage range: 2.9 V to 5.5 V
Power-input voltage as low as 1.0 V
Capable of high supply input voltage (>5.5 V)
with an external NPN or a resistor
VIN UVLO and 35 mA shunt regulator
External slope compensation with 1 resistor
Programmable operating frequency
(100 kHz to 1.5 MHz) with 1 resistor
Lossless current sensing for switch-node voltage <30 V
Resistor current sensing for switch-node voltage >30 V
Synchronizable to external clock
Current-mode operation for excellent line and load transient
responses
10 μA shutdown current
Current limit and thermal overload protection
Soft start in 2048 clock cycles
APPLICATIONS
APD bias
Portable electronic equipment
Isolated dc/dc converter
Step-up/step-down dc/dc converter
LED driver for laptop computer and navigation system
LCD backlighting
GENERAL DESCRIPTION
The ADP1621 is a fixed-frequency, pulse-width modulation
(PWM), current-mode, step-up converter controller. It drives an
external n-channel MOSFET to convert the input voltage to a
higher output voltage. The ADP1621 can also be used to drive
flyback, SEPIC, and forward converter topologies, either isolated
or nonisolated.
The ADP1621 eliminates the use of a current-sense power
resistor by measuring the voltage drop across the on resistance
of the n-channel MOSFET. This technique, allowed up to a
maximum voltage of 30 V at the switch node, maximizes
efficiency and reduces cost. For switch-node voltages higher than
30 V or for more accurate current limiting, the CS pin can be
connected to a current-sense resistor in the source of the MOSFET.
The slope compensation is implemented by an external resistor,
allowing a wide range of external components (inductors and
MOSFETs), and can be chosen for various switching frequencies
and input and output voltages.
The ADP1621 supply input voltage range is 2.9 V to 5.5 V, although
higher input voltages are possible with the use of a small-signal
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
TYPICAL APPLICATION CIRCUIT
VIN = 3.3V
L1
4.7µH
D1
C3 C4
1µF 0.1µF
10V 10V
PIN IN
RS
80
CS
R1
35.7k
1%
ADP1621
SDSN
GATE
R2
11.5k
M1 1%
COMP
PGND
C2
120pF
RCOMP
9.09k
CCOMP
1.8nF
FREQ
FB
GND
RFREQ
31.6k
1%
VOUT = 5V
1A
COUT1
1µF
10V
COUT2
10µF
10V
COUT3
150µF
6.3V
×2
C1
47µF
6.3V
AGND
fOSC = 600kHz
C1 = MURATA GRM31CR60J476M
COUT3 = SANYO POSCAP 6TPE150M
L1 = TOKO FDV0630-4R7M
M1 = VISHAY Si7882DP
D1 = VISHAY SSA33L
Figure 1. High Efficiency Output Boost Converter in Lossless Mode,
3.3 V Input, 5 V Output (Bootstrapped)
100
90
80
70
60
50
40
30
0.01
0.1
1
LOAD CURRENT (A)
Figure 2. Efficiency of Circuit Shown in Figure 1
10
NPN pass transistor or a single resistor. The voltage of the
power input can be as low as 1 V for fuel cell applications. The
switching frequency is set by an external resistor over a range of
100 kHz to 1.5 MHz and can be synchronized to an external
clock by using the SDSN pin. The shutdown quiescent current is
less than 10 μA. The ADP1621 has a thermal shutdown feature
that shuts down the gate driver when the junction temperature
reaches approximately 150°C. The internal soft start circuit limits
inrush current at startup. The ADP1621 is available in the 10-lead
MSOP lead-free package and is specified over the −40°C to +125°C
junction temperature range.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.


Analog Devices Semiconductor Electronic Components Datasheet

ADP1621 Datasheet

Current-Mode Step-Up DC/DC Controller

No Preview Available !

ADP1621 pdf
ADP1621
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Typical Application Circuit ............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Simplified Block Diagram ............................................................... 6
Pin Configuration and Function Descriptions............................. 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 12
Control Loop............................................................................... 12
Current-Sense Configurations.................................................. 12
Current Limit .............................................................................. 13
Undervoltage Lockout ............................................................... 13
Shutdown..................................................................................... 13
Soft Start ...................................................................................... 13
Internal Shunt Regulators.......................................................... 13
Setting the Oscillator Frequency and Synchronization
Frequency .................................................................................... 13
Application Information: Boost Converter................................. 14
Duty Cycle ................................................................................... 14
REVISION HISTORY
12/06—Rev. 0 to Rev. A
Changes to Table 1............................................................................ 3
Changes to Table 2............................................................................ 5
Added Table 3.................................................................................... 5
Changes to Table 5.......................................................................... 19
Changes to Ordering Guide .......................................................... 31
7/06—Revision 0: Initial Version
Setting the Output Voltage........................................................ 14
Inductor Current Ripple............................................................ 14
Inductor Selection ...................................................................... 14
Input Capacitor Selection.......................................................... 15
Output Capacitor Selection....................................................... 15
Diode Selection........................................................................... 15
MOSFET Selection..................................................................... 16
Loop Compensation .................................................................. 16
Slope Compensation .................................................................. 17
Current Limit.............................................................................. 18
Light Load Operation ................................................................ 18
Recommended Component Manufacturers........................... 19
Layout Considerations................................................................... 20
Efficiency Considerations ............................................................. 21
Examples of Application Circuits................................................. 22
Standard Boost Converter—Design Example ........................ 22
Bootstrapped Boost Converter................................................. 23
SEPIC Converter Circuit ........................................................... 27
Low Voltage Power-Input Circuit ............................................ 27
LED Driver Application Circuits ............................................. 28
Related Parts.................................................................................... 30
Outline Dimensions ....................................................................... 31
Ordering Guide .......................................................................... 31
Rev. A | Page 2 of 32


Part Number ADP1621
Description Current-Mode Step-Up DC/DC Controller
Maker Analog Devices
Total Page 30 Pages
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