MIC2505 datasheet(14/24 Pages) MICROCHIP

14 / 24 page

MIC2505/6

DS20005579A-page 14

 2016 Microchip Technology Inc.

6.0

APPLICATION INFORMATION

6.1

Supply Filtering

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

located at the device is strongly recommended to

control supply transients. Without a bypass capacitor,

an output short may cause sufficient ringing on the

input (from supply lead inductance) to destroy the

internal control circuitry.

Input transients must not exceed the absolute

maximum supply voltage (VIN(MAX) = 7.5V) even for a

short duration.

FIGURE 6-1:

Supply Bypassing.

The bypass capacitor may be omitted only if board

design precautions are followed, such as using

extremely short supply leads or power and ground

planes.

6.2

Control Input

CTL must be driven logic high or logic low, or be pulled

high or low for a clearly defined input. Floating the input

may cause unpredictable operation. Add a diode clamp

if negative spikes may occur. See Figure 6-2.

6.3

Open-Load Detection

Refer

the

Typical

Application

Schematics.

Open-load detection is available only on the MIC2505

and MIC2506. For USB power distribution applications,

the open-load detection feature is not included in the

MIC2505-1 or -2 versions.

The optional open-load detection resistor supplies a

small pull-up current to the load when the output switch

is off. A 100 kΩ resistor will draw 50 μA from a 5V

supply. Normally, the load dominates, pulling OUT low.

If the load is absent, the optional resistor pulls OUT

high, activating the fault flag if CTL is off.

When a load is switched off with CTL, capacitance on

the output may cause the open-load function to pull the

flag low until the capacitor is discharged below

approximately 2.4V.

Omit the pull-up resistor when open load detection is

not required and for minimum off-state supply current.

6.4

Power Bus Switch

The MIC2505/6 family features a MOSFET reverse

current flow prevention circuit. This prevents current

from flowing backwards (from OUT to IN) when CTL is

disabled as long as VIN is above UVLO minimum. In

Figure 6-2, when U1 is on and U2 is off, this feature

prevents current flow from the load (5V) backward

through U2 to the 3.3V supply. If a discrete MOSFET

and driver were used, the MOSFET’s internal body

diode would short the 5V load to the 3.3V supply.

FLG will be active (low) on any switch that is off

whenever the load voltage is greater than the open

load

threshold

(approximately

1V)

except

for

MIC2505-1 and MIC2505-2.

FIGURE 6-2:

5V/3.3V Switch Concept.

This circuit’s function would otherwise require a dual

driver, two MOSFETs, plus two diodes (or a dual driver

plus four MOSFETs).

6.5

Hot Plug-In Applications

(Soft-Start)

The MIC2505/6 family can be used to protect the

socket-side and card-side of a supply circuit from

transients caused when a capacitive load is connected

to an active supply.

The switch presents a high impedance when off, and

slowly becomes a low impedance as it turns on. This

reduces the inrush current and related voltage drop

that result from charging a capacitive load.

FIGURE 6-3:

Hot Pulg-In Concept.

OFF

MIC2505YM

CTL

OUT

FLG

GND

OUT

GATE

0.1μF to 1μF

3.0V to 7.5V

Logic-High = 5V Output

Logic-Low = 3.3V Output

MIC2505YM

CTL

OUT

FLG

GND

OUT

GATE

+5V

0.1μF

MIC2505YM

CTL

OUT

FLG

GND

OUT

GATE

+3.3V

0.1μF

1N4148

(optional)

MIC2505YM

CTL

OUT

FLG

GND

OUT

GATE

0.1μF

Capacitive

Load

3.3V

Power Control

Circuitry

GND

Card

Socket

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