MAX1940(2002) Ver la hoja de datos (PDF) - Maxim Integrated

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Fabricante

MAX1940
(Rev.:2002)

Triple USB Switch with Autoreset and Fault Blanking

Maxim Integrated 

Triple USB Switch with Autoreset and

Fault Blanking

IN_

ONA

SWITCH A

CHARGE

(EXPANDED)

PUMP

IN2

IN1

FAULTA

SEL

THERMAL

SHUTDOWN

ILIM

25mA

OUTA

MAX1940

FAULT LOGIC

20ms TIMERS

UVLO

OSC

25kHz

SWITCH B

(SEE SWITCH A)

OUTB

FAULTB

OUTC

SWITCH C

BIAS

(SEE SWITCH A)

FAULTC

ONB

REF

ONC

GND

IN2 IN3

IN4 IN5

Figure 1. Functional Diagram

Detailed Description

The MAX1940 triple current-limited USB power switch

provides three independent switches, each with its own

enable-control input and fault indicator (see Figure 1).

A logic input sets the active polarity of the enable con-

trol inputs. The fault indicators notify the system when

the current-limit, short-circuit, undervoltage lockout, or

thermal-shutdown threshold is exceeded.

The MAX1940 operates from a 4V to 5.5V input supply

and supplies a minimum output current of 700mA per

channel. A built-in current limit of 0.9A (typ) limits the

output current in the event of an overload condition.

Built-in short-circuit detection pulses the output current if

the output voltage falls below 1V, resulting in lower RMS

output current and reduced power dissipation in the

device. Independent thermal shutdown allows normal

operation to continue if one channel experiences a pro-

longed overload or short-circuit condition.

Low-RON NMOS switches enable the MAX1940 to pro-

vide three switches in the space-saving 16-pin QSOP

package. An internal micropower charge pump gener-

ates the high-side supply needed for driving the gates

of these high-side switches. Separate current-limiting

and thermal-shutdown circuitry permits each switch to

operate independently, improving system robustness.

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