High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

_______________________________________________________________________________________

7

0

2

6

4

8

10

010

5

15202530

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (PWM MODE)

INPUT VOLTAGE (V)

0.8

0.6

0.4

0.2

0

015

510

20

25

30

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE (SKIP MODE)

INPUT VOLTAGE (V)

20

µs/div

LOAD-TRANSIENT RESPONSE

(PWM MODE)

INDUCTOR

CURRENT

2A/div

AC COUPLED

100mV/div

DL

5V/div

MAX1844 toc12A

20

µs/div

LOAD-TRANSIENT RESPONSE

(SKIP MODE)

INDUCTOR

CURRENT

2A/div

AC COUPLED

100mV/div

DL

5V/div

MAX1844 toc12B

500

µs/div

STARTUP WAVEFORM

INDUCTOR

CURRENT

5A/div

1V/div

MAX1844 toc14

SHDN

5V/div

DL

5V/div

40

µs/div

OUTPUT OVERLOAD WAVEFORM

(UVP = GND)

1V/div

DL

5V/div

INDUCTOR

CURRENT

5A/div

MAX1844 toc13A

Ω

40

µs/div

OUTPUT OVERLOAD WAVEFORM

1V/div

DL

5V/div

INDUCTOR

CURRENT

5A/div

MAX1844 toc13B

Ω

100

µs/div

SHUTDOWN WAVEFORM

(OVP = GND)

1V/div

DL

5V/div

INDUCTOR

CURRENT

5A/div

MAX1844 toc15A

Ω

100

µs/div

SHUTDOWN WAVEFORM

1V/div

DL

5V/div

INDUCTOR

CURRENT

5A/div

MAX1844 toc15B

Ω

Typical Operating Characteristics (continued)