MAX1664 Ver la hoja de datos (PDF) - Maxim Integrated

Número de pieza

componentes Descripción

Fabricante

MAX1664

Active-Matrix Liquid Crystal Display (AMLCD) Supply

Maxim Integrated 

Active-Matrix Liquid Crystal Display

(AMLCD) Supply

VOUT2-

-5V

0.47µF

0.22µF

VOUT2+

15V

33Ω

REF

0.47µF

R5

49.9k

IN

INP

FB2-

LX1

R6

200k

D2

L2

4.7µH

LX2P

FB1

MAX1664

PGND1

LX2N

R7 D3

549k

FB2+

BPVDD

R8

49.9k

PGND2

BPDRV

2.2nF

100k

22nF

PLLC

BPCLK

RDY

GND

FPLL

BPVSS

SHDN

REF

2.2µF 10µF

3.3µH

VSUPPLY

2.8V TO 5.5V

2.2µF

3 x 10µF

R1

301k

50pF

R2

100k

10µF

2 x 10µF

R3

100k

BACKPLANE

DRIVER

R4

100k

ON

OFF

0.22µF

VOUT1

5.5V

Figure 4. Detailed Typical Operating Circuit

Inductor Selection

The optimum inductor value for L1 is 3.3µH, as shown

in Figure 4. Inductors with less than 300mΩ DC series

resistance are recommended to achieve the highest

efficiency. Using a larger value for L1 (e.g., 4.7µH)

increases the output current capability of DC-DC 1 (by

reducing the peak ripple current) at the expense of size

and the additional output filter capacitance needed for

loop stability.

For DC-DC 2, at large input voltages (i.e., 5V) and low

switching frequencies (i.e., ≤400kHz), the value of L2

should be increased (e.g., 6.8µH or 10µH) to limit the

peak current. In some cases it may be necessary to

reduce the value of L2 to increase the output current

capability of DC-DC 2 (Table 2). The relationship between

input voltage, output voltage, switching frequency, induc-

tor value, and maximum load current for DC-DC 2 is com-

plex and nonlinear. This relationship is summarized in

Table 2. The L2 equation is as follows:

[ ] VINP - RON(LX2P) + RON(LX2N) + RL2

L2 >

( ) IPEAK x 2 fDC-DC 1

(IPEAK )

2

where:

Internal MOSFET on-resistance:

RON(LX2P) = RON(LX2N) = 0.9Ω typical

External inductor DC resistance:

RL2 = 0.3Ω typical

Inductor peak current:

IPEAK = 700mA (750mA absolute maximum)

Due to the MAX1664’s high switching frequency, induc-

tors with a high-frequency core material such as ferrite

are recommended. Powdered iron compounds are not

recommended due to their higher core losses. Typical

small-size, low-profile inductors include the ILS-3825

(Dale Electronics-Vishay) and the CLQ61B (Sumida).

These inductors are primarily used for DC-DC

converters with low height requirements. See Table 3

for more information on manufacturers who provide

low-profile inductors.

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