LM27241 datasheet(21/27 Pages) NSC

21 / 27 page

Application Information (Continued)

Z1 < FZ2 and FZ1 < FP-COMPLEX

DESIGN EXAMPLE

IN = 15V

OUT = 1.5V

BW = 300kHz

BW = = 30kHz

OUT = 2.2µH

OUT = 2x100µF Tantalum + 2x47µF Ceramic

ESR Tantalum = 100m

Ω

ESR Ceramic = 15m

Ω

OUT total = 294µF

ESR total = 13m

Ω

Notice that F-zero due to the R

ESR is greater than the

cross-over frequency (F

SW). TYPE III Compensation is re-

quired.

MAX 45˚

Pick C

2 to be 4700pF, and calculate R2.C2 = 4700 pF, & R2=

5.6 k

Ω

1 = 190p F (use 220pF).

3 sets FBW:

3 =1k

Ω

1 =5k

Ω

Set output voltage:

4 = 3.32k

Ω

EVALUATION BOARD DETAILS

The Bill of Materials (BOM) is now provided for the LM27241

evaluation board. The schematic is the typical application

circuit. See Layout Guidelines for more guidance on pre-

ferred layout practices and also refer to Application Note

AN-1229. Note that a dual FET pack has been chosen for

the evaluation board.

The evaluation board has its output set to 1.5V. The rated

load 6A continuous, and 7A peak. A minimum load of 0.1mA

should be maintained on each output in SKIP mode, to

ensure regulation.

LM27241 Datasheet(PDF) 21 Page - National Semiconductor (TI)

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