SC1462(2000) Ver la hoja de datos (PDF) - Semtech Corporation

Número de pieza

componentes Descripción

Fabricante

SC1462
(Rev.:2000)

HIGH OUTPUT CURRENT CHARGE PUMP DOUBLER

Semtech Corporation 

HIGH OUTPUT CURRENT

CHARGE PUMP DOUBLER

SC1462

October 20, 2000

TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com

CAPACITOR SELECTION

Capacitor selection is based on both the maximum

acceptable ripple voltage and the maximum tolerable

drop at the output.

Ripple

The peak to peak output ripple voltage is dependent

on the following factors:

1- Oscillator Frequency

2- ESR of COUT

3- Capacitance value of Cout

Item 1 is fixed and depend on the charge pump de-

vice used. Item 2, and 3 can be optimized for best

performance and reduction of the output ripple.

The following formula could be used for an approxi-

mation for Vout_ripple.

Vout_ripple =

Iout

2 x Fosc x Cout

+ 2 x Iout

x ESR_ Cout

Vout Drop

The voltage drop at the output is specified with the

following equation:

Vout_drop = Iout * Rout

Rout is dependent on the following factors:

1- Oscillator Frequency

2- ESR of COUT & Cbucket

3- Capacitance value of COUT & Cbucket

4- Internal switch resistance (Rsw = Total of all 4

switch resistances).

A good approximation for calculating the output resis-

tance is shown below.

LAYOUT CONSIDERATION

Standard power board layout should followed to en-

sure proper operation. Any stray inductance should

be minimized, this can be achieved by using large

power planes or traces, and reducing the distances

between input, output and the load. All components

should be placed as close as possible to the SC1462.

Following tables show typical capacitor characteris-

tics, and capacitor manufactures.

Component

0.1 uF Ceramic 0603 package

1.0 uF Ceramic 1206 package

10 uF Ceramic 1206 package

47 uF, 16V Tantalum D case

330 uF, 6.3V “OSCON”

330 uF, 16V Al Electrolytic

820 uF, 4.0V “OSCON”

1000 uF, 10V Al Electrolytic

ESR ESL

(Ohms) (nH)

0.050 1.60

0.040 0.47

0.075 0.5

0.100 0.60

0.025 2.5

0.143 2.37

0.012 2.5

0.053 5

Capacitor Manufacturers

AVX Corp.

VISHAY

Nichicon Corp.

muRata

TOKIN

Taiyo Yuden

Sanyo

Phone

(803)-448-9411

(207)-324-4140

(708)-843-7500

(800)-831-9172

(408)-432-8020

(800)-348-2496

(619)-661-6835

R out ≅

1

Fosc x Cbucket

+ 2 × R SW + 4 × ESR_ Cbucket + ESR_ Cout

This equation can be used to calculate Cbucket for a

specific Vout when Vin and Iout are known. The

maximum value for the Rsw from the Electrical Char-

acteristics section on page 2 should be used in order

to find a worst case number.

© 2000 SEMTECH CORP.

7

652 MITCHELL ROAD NEWBURY PARK CA 91320

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