MAX652ESA データシートの表示（PDF） - Maxim Integrated

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MAX652ESA

5V/3.3V/3V or Adjustable, High-Efficiency, Low IQ, Step-Down DC-DC Controllers

Maxim Integrated 

5V/3.3V/3V or Adjustable, High-Efficiency,

Low IQ, Step-Down DC-DC Controllers

1.5A

1A

0A

2µs/div

V+ = 10V, ILOAD = 1.3A

CIRCUIT OF FIGURE 1, R1 = 150mΩ

Figure 3a. MAX649 Continuous-Conduction Mode, Heavy

Load-Current Waveform (500mA/div)

2.5A

2.0A

1.5A

1.0A

0.5A

0A

5µs/div

V+ = 10V, ILOAD = 1.4A

CIRCUIT OF FIGURE 1, R1 = 100mΩ

Figure 3b. MAX649 Light/Medium Load-Current Waveform

(500mA/div)

inductor, and the control circuit adjusts the switch duty

cycle to maintain regulation without exceeding the

switch current capability (Figure 3a). This provides

excellent load-transient response and high efficiency.

In discontinuous-conduction mode (DCM), current

through the inductor starts at zero, rises to a peak

value, then ramps down to zero. Although efficiency is

still excellent, the output ripple increases slightly, and

the switch waveforms exhibit ringing (the self-resonant

frequency of the inductor). This ringing is to be expect-

ed and poses no operational problems.

Dropout

The MAX649/MAX651/MAX652 are said to be in

dropout when the input voltage (V+) is low enough

that the output drops below the minimum output

voltage specification (see Electrical Characteristics).

The dropout voltage is the difference between the

input and output voltage when dropout occurs.

See the Typical Operating Characteristics for the

Dropout Voltage vs. Load Current and Dropout Voltage

vs. Temperature graphs.

VIN

V+ 5

MAX649

MAX651

MAX652

R1

0.1Ω

6

CS

3

SHDN

7

EXT

C4

C1

0.1µF 100µF

P1

Si9430 L1

22µH

OUTPUT

@ 1.5A

4 REF

C3

0.1µF

OUT 1

2

GND

FB

8

( ) R2 = R3 VOUT – 1

VREF

VREF = 1.5V

D1

1N5820

R2

C2

330µF

R3

150k

Figure 4. Adjustable-Output Operation

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