MIC2039 datasheet(13/28 Pages) MICROCHIP

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2018 - 2022 Microchip Technology Inc. and its subsidiaries.

DS20005540B-page 13

MIC2039

4.0

FUNCTIONAL DESCRIPTION

The MIC2039 is a high-side MOSFET power

distribution switch that provides increased system

reliability by using 5% current-limit accuracy. The

MIC2039 is internally current-limited and has thermal

shutdown, which protects the device and system.

The MIC2039 has a soft-start circuit that minimizes

inrush current by slowing the turn-on time. Additionally,

the MIC2039 has an optional kickstart feature, which

momentarily overrides the normal current-limiting

function to allow higher inrush and/or transient

currents.

4.1

Soft-Start

Soft-start reduces the power supply input surge current

at startup by controlling the output voltage rise time.

The input surge appears while the output capacitor is

charged up. A slower output rise time draws a lower

input surge current.

4.2

Kickstart Inrush Overcurrent Filter

The MIC2039EYxx and MIC2039FYxx are equipped

with a secondary current-limit that allows high inrush

current transients to pass for a set period before the

primary current-limit circuitry becomes active. The

FAULT/ status flag does not assert during the kickstart

period (typically 120 ms), which eliminates any false

(FAULT/) assertions. The kickstart function is active

during initial startup or while operating in steady state.

4.3

Input Capacitor

A 1 µF to 100 µF ceramic input capacitor is

recommended for most applications. Place the input

capacitor on the same side of the board and next to the

MIC2039 to minimize the voltage ringing during

transient and short-circuit conditions. Using two vias for

each end of the capacitor to connect to the power and

ground plane is also recommended.

An X7R or X5R dielectric ceramic capacitors is

recommended

because

their

temperature

performance. X7R-type capacitors change capacitance

by 15% over their operating temperature range and are

the most stable type of ceramic capacitors. Z5U and

Y5V dielectric capacitors change value by as much as

50% and 60%, respectively, over their operating

temperature ranges. To use a ceramic chip capacitor

with Y5V dielectric, the value must be much higher than

an X7R ceramic or a tantalum capacitor to ensure the

same capacitance value over the operating

temperature range.

4.4

Output Capacitor

The output capacitor type and placement criteria are

the same as the input capacitor.

The exact amount of capacitance depends upon the

specific application. For example, USB applications will

typically use 150 µF, whereas local consumers, such

as microcontrollers, may require as little as 1 µF.

Care must be taken when choosing the output

capacitance for inductive loads. Without sufficient

capacitance or clamping devices, sudden disconnects

or shorts on VOUT can result in stresses beyond the

device's absolute maximum ratings, even for short

cables, which will damage the device.

4.5

Enable

The MIC2039 offers either an active-high or active-low

enable input (EN) that allows ON/OFF control of the

switch output. The current through the device reduces

to near zero when the device is shut down, with only

microamperes of leakage current. The EN input can be

directly tied to VIN or driven by a voltage that is equal to

or less than VIN. Do not leave this pin floating.

Care should be taken to ensure that the EN pin does

not exceed VIN by more than 500 mV at any time. This

includes at power-up and during load transients.

Whenever possible, it is recommended to tie EN to VIN

through a pull-up resistor and use an open-drain or

open-collector device to change the state.

4.6

Adjustable Current-Limit

The MIC2039 current-limit is adjustable from 0.2A to

2.5A by connecting a resistor from the ILIMIT pin to

GND. The following equation determines the resistor:

EQUATION 4-1:

If the output current exceeds the set current-limit, the

MIC2039 switch enters constant current-limit mode.

The maximum allowable current-limit can be less than

the full specified and/or expected current if the

MIC2039 is not mounted on a circuit board with

sufficiently low thermal resistance. Table 4-1 shows

resistor values (1%) for select current-limit settings.

TABLE 4-1:

RESISTOR SELECTION FOR

ADJUSTABLE

CURRENT-LIMIT

ILIMIT

0.2A

0.5A

1.0A

2.0A

2.5A

RLIMIT 1.45 kΩ 576Ω 287Ω 145Ω

115Ω

RLIMIT

289

ILIMIT

---------------



Where:

ILIMIT

Typical current-limit from

Electrical Characteristics table.

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