MAX1627(1996) Просмотр технического описания (PDF) - Maxim Integrated

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MAX1627
(Rev.:1996)

5V/3.3V or Adjustable, 100% Duty-Cycle, High-Efficiency, Step-Down DC-DC Controllers

Maxim Integrated 

5V/3.3V or Adjustable, 100% Duty-Cycle,

High-Efficiency, Step-Down DC-DC Controllers

INPUT

C2

68µF LOW-ESR

TANTALUM

C3

68µF LOW-ESR

TANTALUM

C5

0.47µF

INPUT

C2

68µF LOW-ESR

TANTALUM

C3

0.47µF

N.C.

C4

0.1µF

V+

MAX1627

OUT

CS

SHDN

REF

GND

EXT

FB

R3

R2

RSENSE

0.15Ω

U1

LOGIC-LEVEL MOSFET

P L1

22µH, 3A

ADJUSTABLE

OUTPUT

C1

D1

220µF

LOW-ESR

TANTALUM

L1: SUMIDA CDRH125-220

D1: NIHON NSQ03A03

CR2

U1: MOTOROLA MMSF3P02HD

C4

0.1µF

V+

MAX1626

3/5

CS

SHDN

EXT

REF GND OUT

RSENSE

0.15Ω

U1

LOGIC-LEVEL MOSFET

P

L1

68µH, 0.7A

OUTPUT

C1

D1

100µF

LOW-ESR

TANTALUM

L1: SUMIDA CDR1053-680

D1: MOTOROLA MBRS130T3

U1: MOTOROLA MMSF3P02HD

Figure 8. MAX1627 Typical Operating Circuit

________________________Applications

The MAX1626/MAX1627 typical operating circuits

(Figures 1 and 8) are designed to output 2A at a 5V

output voltage. The following circuits provide examples

and guidance for other applications.

Micropower Step-Down Converter

When designing a low-power, battery-based applica-

tion, choose an external MOSFET with low gate capaci-

tance (to minimize switching losses), and use a low

peak current limit to reduce I2R losses. The circuit in

Figure 9 is optimized for 0.5A.

High-Current Step-Down Converter

The circuit in Figure 10 outputs 6A at 2.5V from a 5V or

3.3V input. High-current design is difficult, and board

layout is critical due to radiated noise, switching tran-

sients, and voltage gradients on the PC board traces.

Figure 11 is a recommended PC board design. Choose

the external MOSFET to minimize RDS(ON). Keep the

gate-charge factor below the MAX1626/MAX1627’s

drive capability (see Ext Rise and Fall Times vs.

Capacitance graph in the Typical Operating

Characteristics). Otherwise, increased MOSFET rise

and fall times will contribute to efficiency losses. For

higher efficiencies, especially at low output voltages,

the MAX796 family of step-down controllers with syn-

chronous rectification is recommended.

Figure 9. 0.5A Step-Down Converter

INPUT 3V TO 6V

C4

100µF

C5

100µF

V+

N.C.

C10

0.1µF

MAX1627

OUT

CS

SHDN

REF

EXT

GND

FB

C6 C7 C8 C9

0.1µF 0.1µF 1.0µF 1.0µF

RCS1, RCS2

0.025Ω

Q1

LOGIC-LEVEL MOSFET

P

L1

2.7µH >8A

D1

OUTPUT

2.5V, 6A

R3

21.5k, 1%

R2

20k, 1%

C1 C2 C3

220µF 220µF 220µF

CR2

220pF

C1–C3: SANYO OS-CON 220µF, 6.3V

C4, C5: SANYO OS-CON 100µF, 20V

RCS1, RCS2: 0.025Ω DALE WSL-2512

Q1: MOTOROLA MTB50PO3HDL

D1: NIEC C10T04Q

L1: SUMIDA CDRH127-2R7NC

Figure 10. 6A Step-Down Converter

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