MP2358 – 2A, 23V, 370KHz STEP-DOWN CONVERTER

MP2358 Rev. 1.3

www.MonolithicPower.com

3

3/23/2006

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© 2006 MPS. All Rights Reserved.

TM

Parameter

Symbol Condition

Min

Typ

Max

Units

Maximum Duty Cycle

90

%

Minimum On Time

100

ns

EN Shutdown Threshold

0.7

1.0

1.3

V

Enable Pull Up Current

1.0

µA

EN UVLO Threshold Rising

2.37

2.50

2.62

V

EN UVLO Threshold Hysteresis

210

mV

Supply Current (Shutdown)

23

36

µA

Supply Current (Quiescent)

1.1

1.3

mA

Thermal Shutdown

160

°C

Note:

4) Slope compensation changes current limit above 40% duty cycle.

PIN FUNCTIONS

QFN10

Pin #

SOIC8

Pin #

Name Description

1

NC

No Connect.

2

1

BS

Bootstrap. This capacitor (C5) is needed to drive the power switch’s gate above the

supply voltage. It is connected between the SW and BS pins to form a floating supply

across the power switch driver. The voltage across C5 is about 5V and is supplied by

the internal +5V supply when the SW pin voltage is low.

3

NC

No Connect.

4

2

IN

Supply Voltage. The MP2358 operates from a +4.75V to +23V unregulated input. C1

is needed to prevent large voltage spikes from appearing at the input.

5

3

SW

Switch. This connects the inductor to either IN through M1 or to GND through M2.

6

4

GND

Ground. This pin is the voltage reference for the regulated output voltage. For this

reason care must be taken in its layout. This node should be placed outside of the D1

to C1 ground path to prevent switching current spikes from inducing voltage noise

into the part.

7

5

FB

Feedback. An external resistor divider from the output to GND, tapped to the FB pin,

sets the output voltage. To prevent current limit runaway during a short circuit fault

condition the frequency foldback comparator lowers the oscillator frequency when the

FB voltage is below 400mV.

8

6

COMP Compensation. This node is the output of the transconductance error amplifier and the input

to the current comparator. Frequency compensation is done at this node by connecting a

series R-C to ground. See the compensation section for exact details.

9

7

EN

Enable/UVLO. A voltage greater than 2.62V enables operation. Leave EN

unconnected if unused. An Under Voltage Lockout (UVLO) function can be

current shutdown the EN pin voltage needs to be less than 700mV.

10

8

SS

Soft-Start. Connect SS to an external capacitor to program the soft-start. If unused,

leave it open.