MIC2007YML datasheet(27/30 Pages) MICREL

27 / 30 page

Micrel, Inc.

MIC20xx Family

August 2011

M9999-080211-D

The VUVLO comparator uses no hysteresis. This is

because the VUVLO blanking timer prevents any

chattering that might otherwise occur if VIN varies about

the trigger point. The timer is reset by upward crossings

of the trip point such that VIN must remain below the trip

point for the full 32ms period for load disengagement to

occur.

In selecting a VTRIP voltage, the designer is cautioned to

not make this value less than 2.5V. A minimum of 2.5V

is required for the MIC20X6’s internal circuitry to

operate properly. VUVLO trip points below 2.5V will

result in erratic or unpredictable operation.

Kickstart™

2003

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Only parts in bold have Kickstart™.

(Not available in 5-pin SOT-23 packages).

Kickstart™ allows brief current surges to pass to the

load before the onset of normal current limiting, which

permits dynamic loads to draw bursts of energy without

sacrificing system safety.

Functionally, Kickstart™ is a forced override of the

normal current limiting function provided by the switch.

The Kickstart™ period is governed by an internal timer

which allows current to pass up to the secondary

current limit (ILIMIT_2nd) to the load for 128ms and then

normal (primary) current limiting goes into action.

During Kickstart™, a secondary current-limiting circuit

is monitoring output current to prevent damage to the

switch, as a hard short combined with a robust power

supply can result in currents of many tens of amperes.

This secondary current limit is nominally set at 4A and

reacts immediately and independently of the Kickstart™

period. Once the Kickstart™ timer has finished its count

the primary current limiting circuit takes over and holds

IOUT to its programmed limit for as long as the excessive

load persists.

Once the switch drops out of current limiting the

Kickstart™ timer initiates a lock-out period of 128ms

such that no further bursts of current above the primary

current limit, will be allowed until the lock-out period has

expired.

Kickstart™ may be over-ridden by the thermal

protection circuit and if sufficient internal heating

occurs, Kickstart™ will be terminated and IOUT

0A.

Upon cooling, if the load is still present IOUT

ILIMIT, not

ILIMIT_2nd.

Figure 11. Kickstart™

Automatic Load Discharge

2003

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2005X

2006

2007

2008

2009X

2013

2014

2015

2016

2017

2018

2019X

Only parts in bold have automatic load discharge.

Automatic discharge is a valuable feature when it is

desirable to quickly remove charge from the VOUT pin.

This allows for a quicker power-down of the load. This

also prevents any charge from being presented to a

device being connected to the VOUT pin, for example,

USB, 1394, PCMCIA, and CableCARD™.

Automatic discharge is performed by a shunt MOSFET

from VOUT pin to GND. When the switch is disabled, a

break before make action is performed turning off the

main power MOSFET and then enabling the shunt

MOSFET. The total resistance of the MOSFET and

internal resistances is typically 126Ω.

Supply Filtering

A minimum 1μF bypass capacitor positioned close to

the VIN and GND pins of the switch is both good design

practice and required for proper operation of the switch.

This will control supply transients and ringing. Without a

bypass capacitor, large current surges or a short may

cause sufficient ringing on VIN (from supply lead

inductance) to cause erratic operation of the switch’s

control circuitry. For best-performance good quality,

low-ESR capacitors are recommended, preferably

ceramic.

When bypassing with capacitors of 10μF and up, it is

good practice to place a smaller value capacitor in

parallel with the larger to handle the high frequency

components of any line transients. Values in the range

of 0.01μF to 0.1μF are recommended. Again, good

quality, low-ESR capacitors should be chosen.

MIC2007YML Datasheet(PDF) 27 Page - Micrel Semiconductor

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