ADP1621 查看數據表（PDF） - Analog Devices

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ADP1621

Constant-Frequency, Current-Mode Step-Up DC/DC Controller

Analog Devices 

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.

Trademarks and registered trademarks are the property of their respective owners.

TYPICAL APPLICATION CIRCUIT

VIN = 3.3V

L1

4.7µH

D1

C3

C4

1µF 0.1µF

10V 10V

PIN IN

RS

80Ω

CS

R1

35.7kΩ

1%

ADP1621

SDSN

GATE

R2

11.5kΩ

M1

1%

COMP

PGND

C2

120pF

RCOMP

9.09kΩ

CCOMP

1.8nF

FREQ

FB

GND

RFREQ

31.6kΩ

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

10

LOAD CURRENT (A)

Figure 2. Efficiency of Circuit Shown in Figure 1

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.

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