MIC68400YMLTR - Micrel, Inc.

MIC68400

4A Sequencing LDO with Tracking and

Ramp Control™

Ramp Control is a trademark of Micrel, Inc.

MLF and MicroLeadFrame is a registered trademark of Amkor Technology, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

August 2009

M9999-081809-C

General Description

The MIC68400 is a high peak current LDO regulator

designed specifically for powering applications such as

FPGA core voltages that require high start up current with

lower nominal operating current. Capable of sourcing 4A of

current for start-up, the MIC68400 provides high power

from a small MLF® leadless package. The MIC68400 can

also implement a variety of power-up and power-down

protocols such as sequencing, tracking, and ratiometric

tracking.

The MIC68400 operates from a wide input range of 1.65V

to 5.5V, which includes all of the main supply voltages

commonly available today. It is designed to drive digital

circuits requiring low voltage at high currents (i.e. PLDs,

DSP, microcontroller, etc.). The MIC68400 incorporates a

delay pin (Delay) for control of power on reset output

(POR) at turn-on and power-down delay at turn-off. In

addition there is a ramp control pin (RC) for either tracking

applications or output voltage slew rate adjustment at turn-

on and turn-off. This is important in applications where the

load is highly capacitive and in-rush currents can cause

supply voltages to fail and microprocessors or other

complex logic chips to hang up.

Multiple MIC68400s can be daisy chained in two modes.

In tracking mode the output voltage of the Master drives

the RC pin of a Slave so that the Slave tracks the main

regulator during turn-on and turn-off. In sequencing mode

the POR of the Master drives the enable (EN) of the Slave

so that it turns on after the Master and turns off before (or

after) the Master. This behavior is critical for power-up and

power-down control in multi-output power supplies. The

MIC68400 is fully protected offering both thermal, current

limit protection, and reverse current protection.

The MIC68400 has a junction temperature range of

–40°C to +125°C and is available in fixed as well as an

adjustable option. The MIC68400 is offered in the tiny

16-pin 4mm x 4mm MLF® package.

Features

• Stable with 10µF ceramic capacitor

• Input voltage range: 1.65V to 5.5V

• 0.5V reference

• ±2.0% output tolerance over temperature

• 4A maximum output current – peak start up

• 3A continuous operating current

• Tracking on turn-on and turn-off with pin strapping

• Timing controlled sequencing on/off

• Programmable Ramp Control™ for in-rush current

limiting and slew rate control of the output voltage

during turn-on and turn-off

• Power-on reset (POR) supervisor with programmable

delay time

• Single master can control multiple slave regulators

with tracking output voltages

• Tiny 4mm x 4mm MLF® package

• Maximum dropout (VIN – VOUT) of 500mV over

temperature at 3A output current

• Fixed and adjustable output voltages

• Excellent line and load regulation specifications

• Logic controlled shutdown

• Thermal shutdown and current limit protection

Applications

• FPGA/PLD power supply

• Networking/telecom equipment

• Microprocessor core voltage

• High efficiency linear post regulator

• Sequenced or tracked power supply

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Typical Application

Sequenced Dual Power Supply for I/O and Core Voltage of µProcessor

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Tracking Dual Power Supply for I/O and Core Voltage of µProcessor

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Block Diagram

Bandgap

Reference

Output Error

Holdoff

Thermal

Shutdown

Low Voltage

Holdoff

Sequencing

Timer/Controller

BGStart

BGDis

Ramp

Control

RCDis

DLY BGStart: BandGap Startup

BGDis: BandGap Shutdown

RCDis: Ramp Control Discharge

GND

POR

SNS

OUT

Buffer

Error

Amp

Current

Driver

Current

Limit

External on

Adjustable Part

AMP

MIN

Ordering Information

Part Number Output

Current

Voltage Junction

Temperature Range

Package

MIC68400-1.8YML 4.0A 1.8V –40°C to +125°C PB-Free 16-Pin 4x4 MLF®

MIC68400YML 4.0A ADJ –40°C to +125°C PB-Free 16-Pin 4x4 MLF®

NOTE:

For additional voltage options, contact Micrel Marketing.

MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.

Micrel, Inc. MIC68400

August 2009 5 M9999-081809-C

Pin Configur ation

16-Pin 4mm × 4mm MLF® (ML)

Fixed Voltages 16-Pin 4mm × 4mm MLF® (ML)

Adjustable Voltages

Pin Description (Pin Numbering may change depending on layout considerations)

Pin Number

MIC68400YML Pin Name Pin Function

1, 2, 15, 16 VIN Input: Input voltage supply pin. Place a capacitor to ground to bypass the

input supply.

3 Delay

Delay: Capacitor to ground sets internal delay timer. Timer delays power-on

reset (POR) output at turn-on, and ramp down at turn-off.

4 RC

Ramp Control: May be voltage driven for tracking applications or a capacitor

to ground will set the slew rate of output voltage during start-up.

5 EN

Enable (Input): CMOS compatible input. Logic high = enable, logic low =

shutdown.

6, 14 NC Not internally connected.

7, 8, Tab GND Ground.

9 POR

Power-on Reset: Open-drain output device indicates when the output is in

regulation. High (open) means device is regulating within 10%. POR onset

can be delayed using a single capacitor from Delay to ground.

10 (Fixed) SNS Output Voltage Sense Pin: Connect directly to output pin.

10 (ADJ) ADJ Adjustable regulators: Feedback input. Connect to resistor voltage divider.

11, 12, 13 VOUT Output Voltage: Output of voltage regulator. Place capacitor to ground to

bypass the output voltage. Minimum load current is 100µA. Nominal bypass

capacitor is 10µF.

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Absolute Maximum Ratings(1)

Supply Voltage (VIN).........................................................6V

Enable Input Voltage (VEN)...............................................6V

POR (VPOR)........................................................... VIN + 0.3V

RC .......................................................................VIN + 0.3V

Power Dissipation .................................. Internally Limited(3)

Junction Temperature .........................–40°C ≤ TJ ≤ +125°C

Storage Temperature (TS)...................–65°C ≤ TJ ≤ +150°C

ESD Rating(4) ................................................................. 2kV

Operating Ratings(2)

Supply voltage (VIN) ....................................... 1.65V to 5.5V

Enable Input Voltage (VEN)..................................... 0V to VIN

Ramp Control (VRC)............................................. 0V to 5.5V

Junction Temperature Range ............–40°C ≤ TJ ≤ +125°C

Package Thermal Resistance

4x4 MLF-16 (θJA) ..............................................30°C/W

Electrical Characteristics(5)

TA = 25°C with VIN = VOUT + 1V; VEN = VIN; IOUT = 10mA; bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.

Parameter Conditions Min Typ Max Units

Output Voltage Accuracy 10mA < IOUT < IL(max), VOUT + 1 ≤ VIN ≤ 5.5V -2 +2 %

Feedback Voltage Adjustable version only 0.49 0.50 0.51 V

Feedback Current Adjustable version only 20 nA

Output Voltage Line Regulation VIN = VOUT + 1V to 5.0V 0.06 0.5 %

Output Voltage Load Regulation IL = 10mA to 3A 0.5 1 %

VIN – VO; Dropout Voltage IL = 1.5A

IL = 3.0A

IL = 4.0A

300

360

400

500

800

Ground Pin Current IL = 10mA

IL = 1.5A

IL = 3.0A

IL = 4.0A

1.2

130

Shutdown Current VEN = 0V; VOUT = 0V 0.01 10 µA

Current Limit VOUT = 0V; VIN = 3.0V 4.0 6.0 A

Start-up Time VEN = VIN; CRC = Open 35 150 µs

Enable Input

Enable Input Threshold Regulator enable

Regulator shutdown

0.2

Enable Hysteresis 20 120 200 mV

Enable Input Current VIL ≤ 0.2V (Regulator shutdown)

VIH ≥ 1V (Regulator enable)

0.02

µA

POR Output

IPOR(LEAK) V

POR = 5.5V; POR = High 1

µA

VPOR(LO) Output Logic-Low Voltage (undervoltage condition),

IPOR = 1mA

90 mV

7.5 10 12.5 %

Threshold, % of VOUT below nominal 10 12.5 15 %

VPOR: VOUT Ramping Up

VOUT Ramping Down

Hysteresis 3 %

Delay Current VDELAY = 0.75V 0.7 1 1.3 µA

Delay Voltage (Note 6) VPOR = High 1.185 1.235 1.285 V

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Parameter Conditions Min Typ Max Units

Ramp Control

IRC Ramp Control Current (VRC = 0.75V) 0.7 1 1.3 µA

IDISCHARGE(OUTPUT) (Note 7) VOUT = 0.5VNOM, VRAMP =0V 25 45 70 mA

Tracking Accuracy: Fixed

(Note 8)

200mV < VRC < VTARGET ; Measure (VOUT – VRC) -50 25 100 mV

Tracking Accuracy: Adjustable

(Note 8)

Measure (VOUT - VRC x (VTARGET / 500mV)) -10 15 50 mV

Notes:

1. Exceeding the absolute maximum rating may damage the device.

2. The device is not guaranteed to function outside its operating rating.

3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = TJ(max) – TA) / θJA. Exceeding the maximum

allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.

4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.

5. Specification for packaged product only.

6. Timer High Voltage along with Delay pin current (1µA nom) determines the delay per µF of capacitance. Typical delay is 1.1sec/µF.

7. Discharge current is the current drawn from the output to ground to actively discharge the output capacitor during the shutdown process.

8. VTARGET is the output voltage of an adjustable with customer resistor divider installed between VOUT and Adj/Sns pin, or the rated output

voltage of a fixed device.

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Typical Characteristics

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Functional Characteristics

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Applications Information

Enable Input

The MIC68400 features a TTL/CMOS compatible

positive logic enable input for on/off control of the

device. High (>1V) enables the regulator while low

(<.2V) disables the regulator. In shutdown the

regulator consumes very little current (only a few

microamperes of leakage). For simple applications the

enable (EN) can be connected to VIN (IN). While

MIC68400 only requires a few µA’s of enable current

to turn on, actual enable pin current will depend on the

overdrive (enable voltage exceeding 1V) in each

particular application.

Control Logic

High > 1V

Enable Connections for Logic Driven Input

Enable Connection for VIN-Driven

and/or Slow Rise-Time Inputs

Input Capacitor

An input capacitor of 0.1µF or greater is

recommended when the device is more than 4 inches

away from the bulk supply capacitance, or when the

supply is a battery. Small, surface mount chip capac-

itors can be used for the bypassing. The capacitor

should be place within 1 inch of the device for optimal

performance. Larger values will help to improve ripple

rejection by bypassing the regulator input, further

improving the integrity of the output voltage.

Output Capacitor

The MIC68400 requires an output capacitor for stable

operation. As a µCap LDO, the MIC68220 can

operate with ceramic output capacitors of 10µF or

greater with ESR’s ranging from a 3mΩ to over

300mΩ. Values of greater than 10µF improve trans-

ient response and noise reduction at high frequency.

X7R/X5R dielectric-type ceramic capacitors are

recommended because of their superior temperature

performance. X7R-type capacitors change capaci-

tance by 15% over their operating temperature range

and are the most stable type of ceramic capacitors.

Larger output capacitances can be achieved by

placing tantalum or aluminum electrolytics in parallel

with the ceramic capacitor. For example, a 100µF

electrolytic in parallel with a 10µF ceramic can provide

the transient and high frequency noise performance of

a 100µF ceramic at a significantly lower cost. Specific

undershoot/overshoot performance will depend on

both the values and ESR/ESL of the capacitors.

Micrel, Inc. MIC68400

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Adjustable Regulator Design

Adjustable Regulator with Resistors

The adjustable MIC68400 output voltage can be

programmed from 0.5V to 5.5V using a resistor divider

from output to the SNS pin. Resistors can be quite

large, up to 1MΩ because of the very high input

impedance and low bias current of the sense

amplifier. Typical sense input currents are less than

30nA which causes less than 0.3% error with R1 and

R2 less than or equal to 100KΩ. For large value

resistors (>50KΩ) R1 should be bypassed by a small

capacitor (CFF = 0.1µF bypass capacitor) to avoid

instability due to phase lag at the ADJ/SNS input.

The output resistor divider values are calculated by:

⎟

⎠

⎞

⎜

⎝

⎛+= 1

0.5VVOUT

Power on Reset (POR) and Delay (DLY)

The power-on reset output (POR) is an open-drain

N-Channel device requiring a pull-up resistor to either

the input voltage or output voltage for proper voltage

levels. POR is driven by the internal timer so that the

release of POR at turn-on can be delayed for as much

as 1 second. POR is always pulled low when enable

(EN) is pulled low or the output goes out of regulation

by more than 10% due to loading conditions.

The internal timer is controlled by the DLY pin which

has a bidirectional current source and two limiting

comparators. A capacitor connected from DLY to

GND sets the delay time for two functions. On start

up, DLY sets the time from the nominal output voltage

is reached to the release of the POR. At shut down,

the delay sets the time from disable (EN pin driven

low) to actual ramp down of the output voltage. The

current source is ±1µA, which charges the capacitor

from ~150mV (nominal disabled DLY voltage) to

~1.25V. At turn on, the DLY cap begins to charge

when the output voltage reaches 90% of the target

value. When the capacitor reaches 1.25V, the output

of the POR is released to go high. At turn off, the DLY

cap begins to discharge when the EN is driven low.

When the cap reaches ~150mV the output is ramped

down. Both delays are nominally the same, and are

calculated by the same formula:

()

⎟

⎠

⎞

⎜

⎝

⎛

=A1

1.1T DLY

DLY μ

Scale Factor is:

1.1 seconds/microfarad,

1.1 milliseconds/nanofarad, or

1.1 microseconds/picofarad.

TDLYOFF is the time from lowering of EN to the start of

ramp down on the off cycle. TPOR is the time from the

rising of EN to the release (low to high edge) of the

POR. This behavior means that a µP or other complex

logic system is guaranteed that the nominal output

voltage is stable for a known time before the POR is

released, and they are further guaranteed that once

POR is pulled low, they have a known time to ‘tidy up’

memory or other registers for a well controlled

shutdown. In Master/Slave configurations the timers

can be used to assure that the Master is always

accurately regulating when the Slave is on.

Ramp Control

The ramp control (RC) has a bidirectional current

source and a sense amplifier, which together are used

to control the voltage at the output. When RC is below

the target voltage (nominal output voltage for fixed

voltage parts, 0.5V for adjustable parts) the RC pin

controls the output voltage. When RC is at or above

the target voltage, the output is controlled by the

internal regulator.

Tracking Applications: Driving RC from a Voltage

Source

Fixed Parts: If RC is driven from another (Master)

regulator the two outputs will track each other until the

Master exceeds the target voltage of the Slave

regulator. Typically the output of the MIC68400 will

track above the RC input by 30mV to 70mV. This

offset is designed to allow Master/Slave tracking of

same-voltage regulators. Without the offset, same-

voltage Master/Slave configurations could suffer poor

regulation.

Adjustable Parts: The RC pin on adjustable versions

operates from 0V to 0.5V. To implement tracking on

an adjustable version, an external resistor divider

must be used. This divider is the nearly same ratio as

the voltage setting divider used to drive the

Sense/Adjustable pin. It is recommended that the ratio

be adjusted to track ~50mV (2% to 3%) above the

target voltage if the Master and Slave are operating at

the same target voltage.

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Ramp Up: Cap Controlled Slew Rate

If a capacitor is connected to RC, the bidirectional

current source will charge the cap during startup and

discharge the cap during shutdown. The size of the

capacitor and the RC current (1µA nom) control the

slew rate of the output voltage during startup. For

example, to ramp up a 1.8V regulator from zero to full

output in 10mSec requires a 5.6nF capacitor.

For Fixed Versions:

⎟

⎠

⎞

⎜

⎝

⎛

=A1

VT RC

OUTRC

⎟

⎠

⎞

⎜

⎝

⎛

ON C

Similarly, to slew an adjustable (any output voltage)

from 0 to full output in 10mSec requires a 20nF cap.

For Adjustable Versions:

⎟

⎠

⎞

⎜

⎝

⎛

=A1

V 5.0T RC

⎟

⎠

⎞

⎜

⎝

⎛

OUTON C

2VSR

Ramp Down: Turn Off Slew Rate

When EN is lowered and the DLY pin has discharged,

the RC pin and the OUT pin slew toward zero. For

fixed voltage devices, the RC pin slew rate is 2 to 3

times the SRON defined above. For adjustable voltage

devices the RC pin slew is much higher. In both

cases, turn off slew rate may be determined by the

RC pin for low values of output capacitor, or by the

maximum discharge current available at the output for

large values of output capacitor. Turn off slew rate is

not a specified characteristic of the MIC68400.

Sequencing Configurations

Sequencing refers to timing based Master/Slave

control between regulators. It allows a Master device

to control the start and stop timing of a single or

multiple Slave devices. In typical sequencing the

Master POR drives the Slave EN. The sequence

begins with the Master EN driven high. The Master

output ramps up and triggers the Master DLY when

the Master output reaches 90%. The Master DLY then

determines when the POR is released to enable the

Slave device. When the Master EN is driven low, the

Master POR is immediately pulled low causing the

Slave to ramp down. However, the Master output will

not ramp down until the Master DLY has fully

discharged. In this way, the Master power can remain

good after the Slave has been ramped down.

In sequencing configurations the Master DLY controls

the turn-on time of the Slave and the Slave DLY

controls the turn-off time of the Slave.

Sequencing Connections

CDlyS > CDlyM [CDlyS=2nF; CDlyM=1nF]

Delayed Sequencing

CDlyS < CDlyM [CDlyS=1nF; CDlyM=2nF]

Windowed Sequencing

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Tracking Configurations

Normal Tracking

In normal tracking the Slave RC pin is driven from the

Master output. The internal control buffering assures

that the output of the Slave is always slightly above

the Master to guarantee that the Slave properly

regulates (based on its own internal reference) if

Master and Slave are both fixed voltage devices of the

same output voltage. The schematic and plot below

show a 1.2 volt device tracking a 1.8 volt device

through the entire turn-on / turn-off sequence. Note

that since the RC pin will overdrive the target voltage

(to assure proper regulation) the ramp down delay is

longer than the POR delay during turn-on.

Fixed Voltage Devices

Fixed voltage versions of MIC68400 have two internal

voltage dividers: one for setting the output voltage and

the other for driving the tracking circuitry. Adjustable

parts have up to two external dividers: one from

output to SNS (to set the output voltage) and one from

the output to the Slave RC pin (in tracking

configurations). Also, the RC pin in fixed parts

operates at the same voltage as the output, whereas

the RC pin in adjustable parts operates at the 0.5V

reference. To setup a normal tracking configuration,

the divider driving the Slave RC pin is the same ratio

(or nearly the same – if both Master and Slave are set

to the same output voltage, the Slave RC divider

should be adjusted 2% to 4% higher) as the divider

driving the Slave SNS pin. This is shown below.

Adjustable Voltage devices

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August 2009 14 M9999-081809-C

Ratiometric Tracking

Ratiometric tracking allows independent ramping

speeds for both regulators so that the regulation

voltage is reached at the same time. This is

accomplished by adding a resistor divider between the

Master output pin and the Slave RC pin. The divider

should be scaled such that the Slave RC pin reaches

or exceeds the target output voltage of the Slave as

the Master reaches its target voltage.

Ratiometric tracking may be used with adjustable

parts by simply connecting the RC pins of the Master

and Slave. Use a single RC capacitor of twice the

normal value (since twice the current is injected into

the single RC cap). Alternatively, fixed parts may use

ratiometric tracking in a manner similar to adjustable

normal tracking, with the tracking divider changed to

the same resistor ratio driving the Master Adj/Sns pin.

Adjustable Voltage Devices

Fixed Voltage Devices

Final Note on Tracking

The MIC68400 does not fully shutdown until the output load is discharged to near zero. If RC is driven from an

external source in a tracking configuration, and the external source does not go to zero on shutdown it may prevent

complete shutdown of the MIC68400. This will cause no damage, but some Q current will remain and may cause

concern in battery operated portable equipment. Also, when RC is driven in tracking mode, pulling EN low will not

cause the output to drop. Maintaining low EN in tracking mode simply means that the MIC68400 will shutdown when

the tracking voltage gets near zero. In no case can the MIC68400 enter the tracking mode unless EN is pulled high.

Micrel, Inc. MIC68400

August 2009 15 M9999-081809-C

Package Information

16-Pin 4mm x 4mm MLF (ML)

MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its

use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product

reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intendedcan

for surgical implant

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