MIC2524 View Datasheet(PDF) - Micrel

Part Name

Description

Manufacturer

MIC2524

Quad USB Power Control Switch Not Recommended for New Designs

Micrel 

MIC2524/2527

Applications Information

Supply Filtering

A 0.1µF to 1µF bypass capacitor from IN to GND, located at

the device, is strongly recommended to control supply tran-

sients. Without a bypass capacitor, an output short may

cause sufficient ringing on the input (from supply lead induc-

tance) to damage internal control circuitry.

Input or output transients must not exceed the absolute

maximum supply voltage (VIN max = 7V) even for a short

duration.

VIN

2.7V to 5.5V

0.1µF to 1µF

MIC2524/7

FLGA FLGB

ENA ENB

OUTA OUTB

GND

IN

IN

GND

OUTC OUTD

ENC END

FLGC FLGD

0.1µF to 1µF

Figure 1. Supply Bypassing

Enable Input

EN must be driven logic high or logic low for a clearly defined

input. Floating the input may cause unpredictable operation.

EN should not be allowed to go negative with respect to GND.

Soft Start

The MIC2524/7 presents a high impedance when off, and

slowly becomes a low impedance as it turns on. This reduces

inrush current and related voltage drop that results from

charging a capacitive load, satisfying the USB voltage droop

requirements.

Micrel

Transient Overcurrent Filter

When the MIC2524/7 is enabled, large values of capacitance

at the output of the device will cause inrush current to exceed

the short circuit current-limit threshold of the device and

assert the flag. The duration of this time will depend on the

size of the output capacitance. Refer to the “Functional

Characteristics” turn-on and turnoff behaviors for details.

During the capacitance charging time, the device enters into

constant-current mode. As the capacitance is charged, the

current decreases below the short circuit current-limit thresh-

old, and the flag will then be deasserted.

In USB applications, it is required that output bulk capaci-

tance is utilized to support hot-plug events. When the

MIC2524/7 is enabled, the flag may go active for about 1ms

due to inrush current exceeding the current-limit setpoint.

Additionally, during hot-plug events, inrush currents may also

cause the flag to go active for 30µs. Since these conditions

are not valid overcurrent faults, the USB controller must

ignore the flag during these events. To prevent this erroneous

overcurrent reporting, a 1ms RC filter as shown in Figure 2

may be used. Alternatively, a 1ms debounce routine may be

programmed into the USB logic controller, eliminating the

need for the RC filter.

USB Controller

OVERCURRENT

10k

10k

0.1µF

FLGA

FLGB

FLGC

FLGD

Figure 2. Transient Filter

June 1999

9

MIC2524/2527

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