Fremont Micro Devices FT484 Datasheet

Fremont Micro Devices FT484 Preliminary

2A, 18V, 340KHz Synchronous Rectified

Step-Down Converter

FEATURES

¾ 2A Continuous Output Current
¾ Wide 4.75V to 18V Operating Input Range
¾ Integrated 130mΩ Power MOSFET Switches
¾ Output Adjustable from 0.925V to 15V
¾ Up to 93% Efficiency
¾ Programmable Soft-Start
¾ Stable with Low ESR Ceramic Output Capacitors
¾ Fixed 340KHz Frequency
¾ Cycle-by-Cycle Over Current Protection
¾ Input Under Voltage Lockout

DESCRIPTION

The FT484 is a monolithic synchronous buck

regulator. The device integrates top and bottom

130mΩ MOSFETS that provide 2A of continuous

load current over a wide operating input voltage of

4.75V to 18V. Current mode control provides fast

transient response and cycle-by-cycle current limit.

An adjustable soft-start prevents inrush current at

turn-on and in shutdown mode, the supply current

drops below 1µA. The FT484 is PIN compatible to

the MP1482 2A/18V/Synchronous Step-Down

TYPICAL APPLICATION

Converter.

¾ 　 Distributed Power Systems
¾ 　 FPGA,ASIC, DSP Power Supplies
¾ 　 Networking Systems
¾ 　 Green Electronics/Appliances
¾ 　 Notebook Computers

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Fremont Micro Devices FT484 Preliminary

TYPICAL APPLICATION CIRCUIT

Figure 1: Typical Application Circuit

ABSOLUTE MAXIMUM RATINGS

Supply Voltage VIN………..........................................................................................………………-0.3V to +20V

Switch voltage V

Boost Voltage V

All Other Pins………………………...............................................................................................….-0.3V to +6V

Junction Temperature………………….............................................................................................…….…. 150 ℃

Lead Temperature………………….............................................................................................……………260 ℃

Storage Temperature………...........................................................................................……….….-65 to +150℃℃

Recommended Operating Conditions

Supply Voltage V

Output voltage V

Ambient Operating Temp............................................................................................................…...-40 to +85℃℃

NOTES:

1) Exceeding these ratings may damage the device.

2) The device is not guaran teed to function outside of its operating conditions.

………………………..……........................................................................................……21V

SW

…………..........................................................................................…VSW -0.3V to VSW +6V

BS

……………...........................................................................................…………4.75V to 18V

IN

……................................................................................................……………0.925V to 15V

OUT

(1)

(2)

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Fremont Micro Devices FT484 Preliminary

PIN CONFIGURATION

Part Number* Package Temperature

FT484 SOIC8 -40 to +℃ 85 ℃

Table 1

TERMINAL DEFINITION

Pin Name Description

High-Side Gate Drive Boost Input. BS supplies the drive for the high-Side N-Channel

1 BS

2 IN

3 SW

4 GND Ground (Connect the exposed pad to Pin 4).

5 FB

6 COMP

7 EN

8 SS

MOSFET Switch. Connect a 0.01µF or greater capacitor from SW to BS to power the

high side switch.

Power Input. IN supplies the power to the IC, as well as the step-down converter

switches. Drive IN with a 4.75V to 18V power source. See Input Capacitor.

Power Switching Output. SW is the switching node that supplies power to the output.

Connect the output LC filter from SW to the output load. Note that a capacitor is required

from SW to BS to power the high-side switch.

Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive

Voltage divider connected to it from the output voltage. The feedback threshold is

0.925V. See Setting the output Voltage.

Compensation Node. COMP is used to compensate the regulation control loop. Connect a

series RC network from COMP to GND. In some cases, and additional capacitor form

COMP to GND is required. See Compensation Components.

Enable input. En is a digital input that turns the regulator on or off. Drive EN high to turn

on the regulator; low to turn it off. Attach to IN with a 100K Ω pull up resistor for

automatic startup.

Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to

GND to set the soft-start period. A 0.1µF capacitor sets the soft-start period to 15ms. To

disable the soft-start feature, leave SS unconnected.

Table 2

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Fremont Micro Devices FT484 Preliminary

APPENDIX A：REVISION HISTORY

Version A0: Original data sheet for the FT484 Series.

* Information furnished is believed to be accurate and reliable. However, Fremont Micro Devices,
Incorporated (BVI) assumes no responsibility for the consequences of use of such information or for any
infringement of patents of other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent rights of Fremont Micro Devices, Incorporated
(BVI). Specifications mentioned in this publication are subject to change without notice. This publication
supersedes and replaces all information previously supplied. Fremont Micro Devices, Incorporated (BVI)
products are not authorized for use as critical components in life support devices or systems without
express written approval of Fremont Micro Devices, Incorporated (BVI). The FMD logo is a registered
trademark of Fremont Micro Devices, Incorporated (BVI). All other names are the property of their
respective owners.

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