CS51412G datasheet(10/16 Pages) ONSEMI

No de pièce	CS51412G

Description	1.5A, 260 kHz AND 520 kHz, LOW VOLTAGE BUCK REGULATORS WITH EXTERNAL BIAS OR SYNCHRONIZATION CAPABILITY

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Fabricant	ONSEMI [ON Semiconductor]

Site Internet	http://www.onsemi.com

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CS51411, CS51412, CS51413, CS51414

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10

IRMS + IO D(1 * D)

where:

D = switching duty cycle which is equal to VO/VIN.

IO = load current.

Figure 10. Input Voltage Ripple in a Buck Converter

To calculate the RMS current, multiply the load current

with the constant given by Figure 11 at each duty cycle. It is

a common practice to select the input capacitor with an RMS

current rating more than half the maximum load current. If

multiple capacitors are paralleled, the RMS current for each

capacitor should be the total current divided by the number

of capacitors.

Figure 11. Input Capacitor RMS Current can be

Calculated by Multiplying Y Value with Maximum Load

Current at any Duty Cycle

0

0.2

0.4

1.0

Duty Cycle

0

0.1

0.3

0.4

0.5

0.6

0.2

0.6

0.8

Selecting the capacitor type is determined by each

design’s

constraint

and

emphasis.

The

aluminum

electrolytic capacitors are widely available at lowest cost.

Their ESR and ESL (equivalent series inductor) are

relatively high. Multiple capacitors are usually paralleled to

achieve lower ESR. In addition, electrolytic capacitors

usually need to be paralleled with a ceramic capacitor for

filtering high frequency noises. The OS–CON are solid

aluminum electrolytic capacitors, and therefore has a much

lower ESR. Recently, the price of the OS–CON capacitors

has dropped significantly so that it is now feasible to use

them for some low cost designs. Electrolytic capacitors are

physically large, and not used in applications where the size,

and especially height is the major concern.

Ceramic capacitors are now available in values over 10

µF.

Since the ceramic capacitor has low ESR and ESL, a single

ceramic capacitor can be adequate for both low frequency

and high frequency noises. The disadvantage of ceramic

capacitors are their high cost. Solid tantalum capacitors can

have low ESR and small size. However, the reliability of the

tantalum capacitor is always a concern in the application

where the capacitor may experience surge current.

Output Capacitor

In a buck converter, the requirements on the output

capacitor are not as critical as those on the input capacitor.

The current to the output capacitor comes from the inductor

and thus is triangular. In most applications, this makes the

RMS ripple current not an issue in selecting output

capacitors.

The output ripple voltage is the sum of a triangular wave

caused by ripple current flowing through ESR, and a square

wave due to ESL. Capacitive reactance is assumed to be

small compared to ESR and ESL. The peak to peak ripple

current of the inductor is:

IP

* P +

VO(VIN * VO)

(VIN)(L)(fS)

VRIPPLE(ESR), the output ripple due to the ESR, is equal

to the product of IP–P and ESR. The voltage developed

across the ESL is proportional to the di/dt of the output

capacitor. It is realized that the di/dt of the output capacitor

is the same as the di/dt of the inductor current. Therefore,

when the switch turns on, the di/dt is equal to (VIN – VO)/L,

and it becomes VO/L when the switch turns off. The total

ripple voltage induced by ESL can then be derived from

VRIPPLE(ESL) + ESL(

VIN

L

)

) ESL(

VIN * VO

L

)

+ ESL(

VIN

L

)

Numéro de pièce similaire - CS51412G

Fabricant	No de pièce	Fiches technique	Description
ON Semiconductor	CS51412G	706Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability September, 2007 - Rev. 18
	CS51412GD8	252Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability February, 2007 ??Rev. 17
	CS51412GD8	706Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability September, 2007 - Rev. 18
	CS51412GD8G	252Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability February, 2007 ??Rev. 17
	CS51412GD8G	706Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability September, 2007 - Rev. 18

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Description similaire - CS51412G

Fabricant	No de pièce	Fiches technique	Description
ON Semiconductor	CS51411	252Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability February, 2007 ??Rev. 17
	CS51411-D	706Kb / 20P	1.5 A, 260 kHz and 520 kHz, Low Voltage Buck Regulators with External Bias or Synchronization Capability September, 2007 - Rev. 18
	CS51411	290Kb / 20P	1.5 A, 260 kHz and 520 kHz Low Voltage Buck Regulators with External Bias or Synchronization Capability November, 2012 ??Rev. 20
	NCV51411	182Kb / 16P	1.5 A, 260 kHz, Low Voltage Buck Regulator with Synchronization Capability May, 2010 ??Rev. 15
	NCV51411	224Kb / 16P	1.5 A, 260 kHz, Low Voltage Buck Regulator with Synchronization Capability May, 2010 ??Rev. 15
	NCV8842	377Kb / 16P	1.5 A, 170 kHz, Buck Regulator with Synchronization Capability July, 2011 ??Rev. 10
	NCV8842	180Kb / 15P	1.5 A, 170 kHz, Buck Regulator with Synchronization Capability October, 2006 ??Rev. 1
	NCV8843	187Kb / 15P	1.5 A, 340 kHz, Buck Regulator with Synchronization Capability October, 2006 ??Rev. 1
	NCP1546	152Kb / 13P	1.5 A, 170 kHz, Buck Regulator with Synchronization Capability March, 2007 ??Rev. 0
	NCV8843	385Kb / 16P	1.5 A, 340 kHz, Buck Regulator with Synchronization Capability May, 2010 ??Rev. 10

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