SMM150 datasheet(2/22 Pages) SUMMIT

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SMM150

Preliminary Information

Summit Microelectronics, Inc

2075 2.6 05/13/05

GENERAL DESCRIPTION

The SMM150 is capable of margining the DC output

voltage of LDOs or DC/DC converters that use a

trim/adjust pin. The Margin function is programmable

over a standard 2-wire I

2C serial data interface and is

used to set the margin low/high DC output voltages.

In margining mode the user communicates with the

SMM150 via the I

2C serial data bus to select the

desired values for margining. This allows the part to

margin the supplies up or down to these set values

either through asserting the MUP and MDN pins or by

writing to the margin register directly. The margin high

and margin low voltage settings can range from 0.3V

to VDD around the converter’s nominal output voltage

setting depending on the specified margin range of the

DC-DC converter and/or system components, usually

±10%.

When the SMM150 receives the command to margin,

the TRIM output will begin adjusting the supply to the

selected margin voltage.

This is accomplished by

incrementing (or decrementing) an internal counter

based on the digital comparison between the voltage

margin target value and that read by the ADC from the

VM input. This operation is repeated until the 2 values

are equal, after which the SMM150 holds the TRIM

output pin at the voltage required to maintain the

margin setting. An I

2C command or de-assertion of the

MUP/MDN pin will return the TRIM output pin to a high

impedance state thus allowing the converter to return

to its nominal operating voltage.

The SMM150 has two additional input pins and one

additional output pin. The input pins, COMP1 and

COMP2, are high impedance inputs, each connected

to a comparator and compared against the internal

reference (VREF, 0.5V or 1.25V). Each comparator

can be independently programmed to monitor for UV

or OV. When either of the COMP1 or COMP2 inputs

are in fault the open-drain FAULT# output will be

pulled low. A configuration option exists to disable the

FAULT# output during margining.

Programming of the SMM150 is performed over the

industry standard I

2C 2-wire serial data interface. A

status register is available to read the state of the part

and a Write Protect (WP) pin is available to prevent

writing to the configuration registers and EE memory.

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