MAX1823AEUB 데이터 시트보기 (PDF) - Maxim Integrated

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MAX1823AEUB

Dual USB Switch with Fault Blanking and Autoreset

Maxim Integrated 

Dual USB Switch with Fault

Blanking and Autoreset

After the fault condition is removed, the FAULT_ output

deasserts after a 20ms delay. Ensure that the MAX1823

has adequate input bypass capacitance to prevent

glitches from triggering FAULT_ outputs. Input glitches

greater than 0.2V/µs may cause erroneous FAULT_

indications.

Behavior During Current Limit

and Fault Blanking

The MAX1823 limits switch current in three ways. When

ON_ is deasserted (high for MAX1823/MAX1823A, low

for MAX1823B/MAX1823H), the switch is off and leak-

age dominates the residual output current. When ON_

is asserted (low for MAX1823/MAX1823A, high for

MAX1823B/MAX1823H), the switch supplies a continu-

ous output current of at least 720mA. When the output

current exceeds the 0.9A threshold, the MAX1823 lim-

its the current depending on the output voltage. For

VOUT_ greater than 1V (current-limit mode), the

MAX1823 regulates the output current to 0.9A. For

VOUT_ less than 1V (short-circuit mode), the MAX1823

pulses the switch, decreasing the current to 0.35ARMS

(Table 1). Note that a thermal overload may result from

either of these high-current conditions.

The MAX1823 switches may enter current limit in nor-

mal operation when powering up or driving heavy

capacitive loads. To differentiate these conditions from

short circuits or sustained overloads that may damage

the device, the MAX1823 has an independent fault-

blanking circuit in each switch. When a load transient

causes the device to enter current limit, an internal

counter starts to monitor the duration of the fault. For

load faults exceeding 20ms fault-blanking time, the

switch turns off, the FAULT_ signal asserts low, and the

device enters autoreset mode (see the Autoreset Mode

section). Only current-limit and short-circuit faults are

blanked. Thermal-overload faults and input voltage

drops below the UVLO threshold immediately cause

the switch to turn off and FAULT_ to assert low.

INA

INA

ONA

*(ONA)

CHARGE

PUMP

BIAS

UVLO

THERMAL

SHUTDOWN

FAULTA

ILIM

25mA

OUTA

1µF

4V TO 5.5V

IN_

0.1µF

*(ONB)

ONB

INB

REF

OSC

25kHz

TIMER

20ms

MAX1823/MAX1823A

MAX1823B/MAX1823H

CHARGE

PUMP

FAULT

LOGIC

25mA

ILIM

GND

OUTB

1µF

INB

*( ) ARE FOR THE MAX1823B/MAX1823H.

FAULTB

Figure 2. Functional Diagram

10 ______________________________________________________________________________________

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