STMicroelectronics 0.7A/1.2V synchronous buck converter STEVAL-ISA055V1 STEVAL-ISA055V1 Data Sheet

For further information contact your local STMicroelectronics sales office.

September 2008

  Rev 1

1/4

4

0.7 A / 1.2 V synchronous buck converter

with enable function based on the ST1S12XX

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Step-down current mode PWM (1.7 MHz) DC-
DC converter

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Fixed output voltage of 1.2 V

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0.7 A output current capability

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3% DC output voltage tolerance

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Synchronous rectification

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Enable function

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Internal soft-start

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Typical efficiency: > 90%

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Not switching quiescent current: max 600 µA 
over temperature range

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R

DS(on)

 typ. 250 m

Ω and 400 mΩ

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Uses tiny capacitors and inductors

This demonstration board is based on the 
ST1S12 family of synchronous step-down DC-DC 
converters optimized for powering low-voltage 
digital cores in HDD (hard disk drive) applications 
and is generally used to replace high-current 
linear solutions when power dissipation may 
cause high heating of the application 
environment.

It provides up to 0.7 A over an input voltage range 
of 2.5 V to 5.5 V. A high switching frequency of 1.7 
MHz allows the use of tiny surface-mount 
components. For the adjustable version, a resistor 
divider to set the output voltage value, an 
inductor, and two capacitors are required. Only an 
inductor and 2 capacitors are needed for the 1.2 V 
and 1.8 V fixed version. A low output ripple is 
guaranteed by the current mode PWM topology 
and by the use of low ESR surface-mount ceramic 
capacitors.

The ST1S12 device is thermal protected and 
current limited to prevent damage due to 

accidental short-circuit. This family of products is 
available in the TSOT23-5L package.