________________________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

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

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.

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

High-Efficiency, Step-Down DC-DC Controllers

______________________________________________________________________________________

13

MAX1627

C5

0.47

µF

P

D1

0.15

Ω

U1

LOGIC-LEVEL MOSFET

C4

0.1

µF

OUT

N.C.

SHDN

REF

V+

EXT

CS

GND

FB

INPUT

L1

22

µH, 3A

R3

R2

C1

220

µF

LOW-ESR

TANTALUM

C2

68

µF LOW-ESR

TANTALUM

C3

68

µF LOW-ESR

TANTALUM

L1: SUMIDA CDRH125-220

D1: NIHON NSQ03A03

U1: MOTOROLA MMSF3P02HD

ADJUSTABLE

OUTPUT

Figure 8. MAX1627 Typical Operating Circuit

MAX1626

C3

0.47

µF

P

D1

0.15

Ω

U1

LOGIC-LEVEL MOSFET

C4

0.1

µF

3/5

SHDN

REF

V+

EXT

CS

GND

OUT

INPUT

L1

68

µH, 0.7A

OUTPUT

C1

100

µF

LOW-ESR

TANTALUM

C2

68

µF LOW-ESR

TANTALUM

L1: SUMIDA CDR1053-680

D1: MOTOROLA MBRS130T3

U1: MOTOROLA MMSF3P02HD

Figure 9. 0.5A Step-Down Converter

MAX1627

P

OUTPUT

2.5V, 6A

R3

21.5k, 1%

R2

20k, 1%

D1

220pF

Q1

LOGIC-LEVEL MOSFET

C10

0.1

µF

OUT

3V TO 6V

SHDN

N.C.

REF

V+

EXT

CS

GND

FB

INPUT

L1

2.7

µH >8A

C4

100

µF

C5

100

µF

C9

1.0

µF

0.025

Ω

C8

1.0

µF

C7

0.1

µF

C3

220

µF

C2

220

µF

C1

220

µF

C6

0.1

µF

C1–C3: SANYO OS-CON 220

µF, 6.3V

C4, C5: SANYO OS-CON 100

µF,20V

RCS1, RCS2: 0.025

Ω DALE WSL-2512

Q1: MOTOROLA MTB50PO3HDL

D1: NIEC C10T04Q

L1: SUMIDA CDRH127-2R7NC

Figure 10. 6A Step-Down Converter