MIC2250YML datasheet(8/14 Pages) MICREL

8 / 14 page

Micrel, Inc.

MIC2250

April 2011

M9999-041811-B

Functional Description

VIN

The input supply (VIN) provides power to the internal

MOSFETs and control circuitry for the switch mode

regulator. The operating input voltage range is from 2.5V

to 5.5V. An input capacitor with a minimum voltage

rating of 6.3V is recommended. Refer to the layout

recommendations for details.

A logic level input of 1.5V or higher enables the

regulator. A logic input of 0.4V or less places the

regulator in shutdown mode which reduces the supply

current to less than 1µA. The MIC2250 features built-in

soft start circuitry that reduces in-rush current and

prevents the output voltage from overshooting during

startup. Do not leave the Enable pin floating.

The MIC2250 has an internal MOSFET switch that

connects directly to one end of the inductor (SW pin) and

provides a current path to ground during switching

cycles. The source of the internal MOSFET connects

through a current sense resistor to ground.

PGND

The power ground pin is the high current path to ground.

The current loop for the power ground should be as

small as possible and separate from the analog ground

(AGND). Refer to the layout recommendations for more

details.

AGND

Analog ground (AGND) is the ground path for the biasing

and control circuitry. The current loop for the signal

ground should be separate from the power ground

(PGND) loop. Refer to the layout recommendations for

more details.

DITH

The DITH function is a frequency dithering technique

that reduces EMI noise by spreading the boost

regulators’ noise spectrum. This technique reduces the

EMI peaks by distributing the switching frequency across

a wider spectrum. Connect this pin high to enable the

pseudo-random on-time dithering. Connect this pin to

ground to disable this function.

The feedback pin (FB) allows the regulated output

voltage to be set by applying an external resistor divider

network. The internal reference voltage is 1.24V. The

output voltage is calculated from the following equation:

⎟

⎠

⎞

⎜

⎝

⎛ +

1.24V

VOUT

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