MAX1922 データシートの表示（PDF） - Maxim Integrated

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MAX1922

1A Current-Limited Switch for 2 USB Ports

Maxim Integrated 

1A Current-Limited Switch for 2 USB Ports

Pin Description

PACKAGE

TDFN SO

6

1

1, 3, 9 2, 3

5

4

7

5

2, 4, 6, 7,

8, 10

8

—

—

NAME

GND

IN

EN

OC

OUT

EP

FUNCTION

Ground

Input. p-channel MOSFET source—connect all IN pins together and bypass with a 1µF capacitor ground.

Active-Low Switch Enable Input. A logic-low turns on the switch.

Overcurrent-Indicator Output. This open-drain output goes low when the device is in thermal shutdown

or undervoltage lockout, or during a sustained (10ms) current-limit condition.

Switch Output. p-channel MOSFET drain—connect all OUT pins together and bypass with a 0.1µF

capacitor to ground.

TDFN Only. Exposed paddle. Connect to the GND plane for optimum thermal dissipation. This does not

remove the requirement for a proper ground.

IN

OC

N

P

OUT

MAX1922

P

REPLICA

AMPLIFIER

ON

P

ON

10ms

TIMER

HOT

CURRENT-LIMIT

AMPLIFIER

1.24V

GND

EN

CONTROL

CIRCUITRY

Figure 1. Functional Diagram

Detailed Description

The MAX1922 p-channel MOSFET power switch limits

output current to 1.4A min and 2.1A max. When the out-

put current increases beyond the current limit (ILIMIT),

the current also increases through the replica switch

(IOUT / 13000). The current-limit error amplifier com-

pares the voltage to the internal 1.24V reference and

regulates the current back to the ILIMIT (Figure 1).

These switches are not bidirectional; therefore, the

input voltage must be higher than the output voltage.

Continuous Short-Circuit Protection

The MAX1922 is a short-circuit-protected switch. In the

event of an output short-circuit condition, the current

through the switch is foldback-current-limited to 1A

continuous.

Thermal Shutdown

The MAX1922 has a thermal shutdown feature. The

switch turns off and the OC output goes low immediate-

ly (no overcurrent blanking) when the junction tempera-

ture exceeds +165°C. When the MAX1922 cools 20°C,

the switch turns back on. If the fault short-circuit condi-

tion is not removed, the switch cycles on and off, result-

ing in a pulsed output.

OC Indicator

The MAX1922 provides an overcurrent output (OC). A

100kΩ pullup resistor from OC to IN provides a logic

control signal. This open-drain output goes low when

any of the following conditions occur:

• The input voltage is below the 2.4V undervoltage

lockout (UVLO) threshold.

• The die temperature exceeds the thermal shutdown

temperature limit of +165°C.

• The device is in current limit for greater than 10ms.

OC Blanking

The MAX1922 features 10ms overcurrent blanking.

Blanking allows brief current-limit faults, including

momentary short-circuit faults that occur when hot-

swapping a capacitive load, and ensures that no OC is

issued during power-up. When a load transient causes

the device to enter current limit, an internal counter

starts. If the load fault persists beyond the 10ms over-

current blanking timeout, the OC output asserts low.

Ensure that the MAX1922 input is adequately bypassed

to prevent input glitches from triggering spurious OC

6 _______________________________________________________________________________________

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