MP1580 – 2A, 380KHz STEP-DOWN CONVERTER

MP1580 Rev. 3.0

www.MonolithicPower.com

3

12/5/2005

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© 2005 MPS. All Rights Reserved.

TM

Parameter

Symbol Condition

Min

Typ

Max

Units

Maximum Duty Cycle

90

%

Minimum Duty Cycle

0

%

EN Shutdown Threshold Voltage

0.7

1.0

1.3

V

Enable Pull-Up Current

1.15

1.46

1.8

µA

EN UVLO Threshold Rising

2.37

2.495

2.62

V

EN UVLO Threshold Hysteresis

210

mV

Supply Current (Shutdown)

23

36

µA

Supply Current (Quiescent)

1.0

1.2

mA

Thermal Shutdown

160

°C

Note:

4) Derate current limit 0.011A/°C.

PIN FUNCTIONS

Pin #

Name

Description

1

BS

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

supply voltage. It is connected between 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.

2

IN

Supply Voltage. The MP1580 operates from a +4.75V to +25V unregulated input. C1 is

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

3

SW

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

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.

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 run away during a short circuit fault condition

the frequency foldback comparator lowers the oscillator frequency when the FB voltage is

below 700mV.

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.

7

EN

Enable/UVLO. A voltage greater than 2.62V enables operation. For complete low current

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

8

SYNC

Synchronization Input. This pin is used to synchronize the internal oscillator frequency to

an external source. There is an internal 11kΩ pull down resistor to GND; therefore leave

SYNC unconnected if unused.