MIC22600YMLTR - Micrel, Inc.

MIC22600

1MHz, 6A Integrated Switch

Synchronous Buck Regulator

NOT RECOMMENDED FOR NEW DESIGNS

SEE MIC22705

95131 • US 408

Ramp Control is a trademark of Micrel, Inc.

MLF and MicroLeadFrame are registered trademarks of Amkor Tec

Micrel Inc. • 2180 Fortune Drive • San Jose, CA

hnology, Inc.

A • tel +1 (408) 944-0800 • fax + 1 ( ) 474-1000 • http://www.micrel.com

June 2011 M9999-062411-D

General Description

The Micrel MIC22600 is a high-efficiency, 6A, integrated

switch, synchronous buck (step-down) regulator. The

MIC22600 is optimized for highest efficiency and achieves

more than 90% efficiency, while still switching at 1MHz

over a broad load range with only 1µH inductor and down

to 47µF output capacitor. The ultra-high-speed control loop

keeps the output voltage within regulation even under

extreme transient load swings commonly found in FPGAs

and low voltage ASICs. The output voltage can be

adjusted down to 0.7V to address all low voltage power

needs. The MIC22600 offers a full range of sequencing

and tracking options. The EN/DLY pin combined with the

Power Good/Power-on-Reset (PG/POR) pin allows

multiple outputs to be sequenced in any way during turn-

on and turn-off. The RC (Ramp Control™) pin allows the

device to be connected to another product in the

MIC22xxx and/or MIC68xxx family, to keep the output

voltages within a certain V on start-up.

The MIC22600 is available in a 24-pin 4mm x 4mm MLF®

and thermally-enhanced 24-pin ePad TSSOP with a

junction operating range from –40°C to +125°C.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• Input voltage range: 2.6V to 5.5V

• Output voltage adjustable down to 0.7V

• Output current up to 6A

• Full sequencing and tracking ability

• Power-on-Reset/Power Good

• Efficiency > 90% across a broad load range

• Ultra-fast transient response, easy RC compensation

• 100% maximum duty cycle

• Fully-integrated MOSFET switches

• Micropower shutdown

• Thermal-shutdown and current-limit protection

• 24-pin 4mm x 4mm MLF®

• 24-pin ePad TSSOP

• –40°C to +125°C junction temperature range

Applications

• High power density point-of-load conversion

• Servers and routers

• DVD recorders

• Computing peripherals

• Base stations

• FPGAs, DSP and low-voltage ASIC power

Typical Application

MIC22600 6A 1MHz Synchronou s Ou tp ut Converter Sequencing & Tracking

Note:

1. Using a free-wheeling Schottky diode improves efficiency.

Micrel, Inc. MIC22600

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Ordering Information

Part Number Voltage Junction Temperature Range Package Lead Finish

MIC22600YML Adjustable –40° to +125°C 24-Pin 4mm x 4mm MLF® Pb-Free

MIC22600YTSE Adjustable –40° to +125°C 24-pin ePad TSSOP Pb-Free

Note:

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

Pin Configur ation

PVIN

EN/DLY

DELAY

POR/PG

PVIN

SVIN

SGND

COMP

PVIN

PGND

24-Pin 4mm x 4mm MLF (ML) 24-pin ePad TSSOP

Micrel, Inc. MIC22600

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Pin Description

Pin Number

MLF-24

Pin Number

TSSOP-24 Pin Name Description

1, 6, 13, 18 3, 10, 15, 22 PVIN Power Supply Voltage (Input): Requires bypass capacitor to GND.

17 2 SVIN Signal Power Supply Voltage (Input): Requires bypass capacitor to GND.

2 11 EN/DLY

EN/DLY (Input): When this pin is pulled higher than the enable threshold, the

part will start up. Below this voltage the device is in its low quiescent current

mode. The pin has a 1µA current source charging it to VIN. By adding a

capacitor to this pin a delay may easily be generated. The enable function will

not operate with an input voltage lower than the min specified voltage.

4 13 RC

Ramp Control: Capacitor to ground from this pin determines slew rate of output

voltage during start-up. This can be used for tracking capability as well as soft

start. RC pin cannot be left floating. Use a minimum capacitor value of 220pF or

larger.

14 23 FB

Feedback: Input to the error amplifier, connect to the external resistor divider

network to set the output voltage.

15 24 COMP

Compensation pin (Input): Place a RC network to GND to compensate the

device, see applications section.

5 14 POR/PG

Power On Reset (Output): Open-drain output device indicates when the output

is out of regulation and is active after the delay set by the DELAY pin.

7, 12, 19, 24 4, 9, 16, 21 PGND Power Ground (Signal): Ground

16 1 SGND Signal Ground (Signal): Ground

3 12 DELAY

DELAY (Input): Capacitor to ground sets internal delay timer. Timer delays

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

8, 9, 10, 11,

20, 21, 22, 23

5, 6, 7, 8,

17, 18 19, 20 SW Switch (Output): Internal power MOSFET output switches.

EP EP GND

Exposed Pad (Power): Must make a full connection to a GND plane for full

output power to be realized.

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Absolute Maximum Ratings(1)

Supply Voltage (PVIN, SVIN)............................ –0.3V to 6V

Output Switch Voltage (SW) ............................. –0.3V to 6V

Output Switch Current (ISW).......................Internally Limited

Logic Input Voltage (EN, POR, DELAY) ........... –0.3V to VIN

Control Voltage (RC, COMP, FB) ..................... –0.3V to VIN

Lead Temperature (soldering 10sec.)........................ 260°C

Storage Temperature (Ts) .........................–65°C to +150°C

ESD Rating(3).................................................................. 2kV

Operating Ratings(2)

Supply Voltage (VIN)......................................... 2.6V to 5.5V

Junction Temperature (TJ) ..................–40°C  TJ  +125°C

Thermal Resistance

4x4 MLF-24 (θJC) ...............................................14°C/W

4x4 MLF-24 (θJA) ...............................................40°C/W

24-pin ePad TSSOP (θJC)...............................12.9°C/W

24-pin ePad TSSOP (θJA) ...............................32.2°C/W

Electrical Characteristics(4)

TA = 25°C with VIN = VEN = 3.3V; VOUT = 1.8V, unless otherwise specified. Bold values indicate –40°C< TJ < +125°C.

Parameter Condition Min. Typ. Max. Units

Supply Voltage Range 2.6 5.5 V

VIN Turn-On Voltage Threshold VIN rising 2.4 2.5 2.6 V

UVLO Hysteresis 280 mV

Quiescent Current, PWM Mode VEN 1.34V; VFB = 0.9V (not switching) 850 1300 µA

Shutdown Current VEN = 0V 5 10 µA

Feedback Voltage ± 1%

± 2% (over temperature)

0.693

0.686 0.7 0.707

0.714 V

FB Pin Input Current 1 100 nA

Current Limit in PWM Mode VFB = 0.5*VNOM 6.5 9 11.5 A

Output Voltage Line Regulation VOUT 1.8V, VIN = 2.6 to 5.5V, ILOAD= 100mA 0.2 %

Output Voltage Load Regulation 100mA < ILOAD < 6000mA, VIN = 3.3V 0.2 %

Maximum Duty Cycle VFB ≤ 0.5V 100 %

Switch ON-Resistance PFET

Switch ON-Resistance NFET

ISW = 1000mA; VFB=0.5V

ISW = 1000mA; VFB=0.9V 0.03

0.025 

Oscillator Frequency 0.8 1 1.2 MHz

EN/DLY Threshold Voltage 1.14 1.24 1.34 V

EN/DLY Source Current VIN = 2.6 to VIN = 5.5V 0.7 1 1.3 µA

RC Pin IRAMP Ramp Control Current 0.7 1 1.3 µA

Power-on-Reset IPG(LEAK) V

PORH = 5.5V; POR = High 1

2 µA

Power-on-Reset VPG(LO) Output Logic-Low Voltage (undervoltage condition),

IPOR = 5mA 130 mV

Threshold, % of VOUT below nominal 7.5 10 12.5 %

Power-on-Reset VPG Hysteresis 2 %

Over-Temperature Shutdown 160 °C

Over-Temperature Shutdown

Hysteresis 20 °C

Notes:

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

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

3. Devices are ESD sensitive. Handling precautions recommended.

4. Specification for packaged product only.

Micrel, Inc. MIC22600

Typical Characteristics

June 2011 5 M9999-062411-D

Micrel, Inc. MIC22600

Typical Characteristics (Continued)

June 2011 6 M9999-062411-D

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Functional Characteristics

Start-Up/Shutdown

(

CRC = 10nF

)

ENABLE VO LTAGE

(2mV/div)

OUTPU T CURREN T

(2A/div)

Time (2ms/div)

RAMP CONTRO L VOLTAGE

(500mV/div)

VIN = 3V

VO = 1.8V

OUTPU T VOLTAGE

(1V/div)

Transient Response

T VOLTAGE

(500mV/div)

OUTPUT CURREN T

(2A/div)

INPU

Time (200µs/div)

OUTPUT VOLTAGE

(50mV/div)

VIN = 3V

VO = 1.8V

IO = 0.6A to 6A

Transient Response

OUTPUT CURREN T

(2A/div)

INPUT VOLTAGE

(1V/div)

Time (200µs/div)

High DC Operation

SWITCH VO LTAGE

(2V/div)

Time (200ns/div)

VIN = 5V

VO = 1.8V

IO = 0.6A to 6A

OUTPUT VOLTAGE

(50mV/div)

OUTPU T VOLTAGE

(10mV/div)

VIN = 5V

IO = 1A

Output Noise & Ripple

SWITCH VO LTAGE

(2V/div)

Time (400ns/div)

Start-Up (CRC = 0nF)

ENABLE VO LTAGE

(1V/div)

OUTPUT CURREN T

(2A/div)

Time (20µs/div)

RAMP CONTRO L VOLTAGE

(500mV/div)

VIN = 5V

VO = 3.3V

IO = 6A

OUTPUT VOLTAGE

(10mV/div)

OUTPUT VOLTAGE

(500mV/div)

VIN = 3V

VO = 1V

IO = 6A

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Functional Characteristics (Continued)

Start-Up into Short

ENABLE VO LTAGE

(2V/div)

SWITCH VO LTAGE

(2V/div)

Time (20µs/div)

VIN = 3V

INPUT CURREN T

(2A/div)

OUTPUT VOLTAGE

(100mV/div)

Current Limit Behavior

OUTPU T VOLTAGE

(500mV/div)

OUTPU T CURREN T

(2A/div)

Time (200µs/div)

INPUT VOLTAGE

(500mV/div)

VIN = 3V

VO = 1.8V

IOSET = 12A

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Typical Circuits and Waveforms

Sequencing Circuit and Waveform

Tracking Circuit and Waveform

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Functional Diagram

Figure 1. MIC22600 Block Diagram

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Functional Description

PVIN, SVIN

PVIN is the input supply to the internal 30m P-Channel

Power MOSFET. This should be connected externally to

the SVIN pin. The supply voltage range is from 2.6V to

5.5V. A 10µF ceramic is recommended for bypassing

each PVIN supply.

EN/DLY

This pin is internally fed with a 1µA current source from

VIN. A delayed turn on is implemented by adding a

capacitor to this pin. The delay is proportional to the

capacitor value. The internal circuits are held off until

EN/DLY reaches the enable threshold of 1.24V.

RC allows the slew rate of the output voltage to be

programmed by the addition of a capacitor from RC to

ground. RC is internally fed with a 1µA current source

and VOUT slew rate is proportional to the capacitor and

the 1µA source. RC pin cannot be left floating. Use a

minimum capacitor value of 220pF or larger.

DELAY

Adding a capacitor to this pin allows the delay of the

POR signal.

When VOUT reaches 90% of its nominal voltage, the

DELAY pin current source (1µA) starts to charge the

external capacitor. At 1.24V, POR is asserted high.

COMP

The MIC22600 uses an internal compensation network

containing a fixed frequency zero (phase lead response)

and pole (phase lag response) which allows the external

compensation network to be much simplified for stability.

The addition of a single capacitor and resistor will add

the necessary pole and zero for voltage mode loop

stability using low value, low ESR ceramic capacitors.

The feedback pin provides the control path to control the

output. A resistor divider connecting the feedback to the

output is used to adjust the desired output voltage. Refer

to the feedback section in the “Applications Information”

for more detail.

POR

This is an open drain output. A 47k resistor can be used

for a pull up to this pin. POR is asserted high when

output voltage reaches 90% of nominal set voltage and

after the delay set by CDELAY. POR is asserted low

without delay when enable is set low or when the output

goes below the -10% threshold. For a Power Good (PG)

function, the delay can be set to a minimum. This can be

done by removing the DELAY capacitor.

This is the connection to the source of the internal P-

Channel MOSFET and drain of the N-Channel MOSFET.

This is a high frequency high power connection;

therefore traces should be kept as short and as wide as

practical.

SGND

Internal signal ground for all low power sections.

PGND

Internal ground connection to the source of the internal

N-Channel MOSFETs.

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Application Information

The MIC22600 is a 6A Synchronous step down regulator

IC with a fixed 1 MHz, voltage mode PWM control

scheme. The other features include tracking and

sequencing control for controlling multiple output power

systems, power on reset.

Component Selection

Input Capacitor

A minimum 10µF ceramic is recommended on each of

the PVIN pins for bypassing. X5R or X7R dielectrics are

recommended for the input capacitor. Y5V dielectrics is

not recommended.

Output Capacitor

The MIC22600 was designed specifically for the use of

ceramic output capacitors and 22µF is optimum output

capacitor. 22µF can be increased to 100µF to improve

transient performance. Since the MIC22600 is a voltage

mode controller, the control loop relies on the inductor

and output capacitor for compensation. For this reason,

do not use excessively large output capacitors. The

output capacitor requires either an X7R or X5R

dielectric. Y5V and Z5U dielectric capacitors, aside from

the undesirable effect of their wide variation in

capacitance over temperature, become resistive at high

frequencies. Using Y5V or Z5U capacitors can cause

instability in the MIC22600.

Inductor Selection

Inductor selection is determined by the following (not

necessarily in the order of importance):

• Inductance

• Rated current value

• Size requirements

• DC resistance (DCR)

The MIC22600 is designed to use a 0.47µH to 4.7µH

inductor.

Maximum current ratings of the inductor are generally

given in two methods: permissible DC current and

saturation current. Permissible DC current can be rated

either for a 40°C temperature rise or a 10% loss in

inductance. Ensure the inductor selected can handle the

maximum operating current. When saturation current is

specified, make sure that there is enough margin that

the peak current will not saturate the inductor. The ripple

can add as much as 1.2A to the output current level. The

RMS rating should be chosen to be equal or greater than

the Current Limit of the MIC22600 to prevent

overheating in a fault condition. For best electrical

performance, the inductor should be placed very close to

the SW nodes of the IC.

It is important to test all operating limits before settling

on the final inductor choice.

The size requirements refer to the area and height

requirements that are necessary to fit a particular

design. Please refer to the inductor dimensions on their

datasheet.

DCR is inversely proportional to size and can represent

a significant efficiency loss. Refer to the “Efficiency

Considerations” below for a more detailed description.

EN/DLY Capacitor

EN/DLY sources 1µA out of the IC to allow a startup

delay to be implemented. The delay time is simply the

time it takes 1µA to charge CDLY to 1.25V. Therefore:

DLY

DLY 1.10

C1.24

T−

Efficiency Considerations

Efficiency is defined as the amount of useful output

power, divided by the amount of power consumed.

Efficiency % = 100

ININ

OUTOUT ×

⎟

⎠

⎞

⎜

⎝

⎛

Maintaining high efficiency serves two purposes. It

decreases power dissipation in the power supply,

reducing the need for heat sinks and thermal design

considerations and it decreases consumption of current

for battery powered applications. Reduced current drawn

from a battery increases the devices operating time,

particularly in hand held devices.

There are mainly two loss terms in switching converters:

conduction losses and switching losses. Conduction

losses are simply the power losses due to VI or I2R. For

example, power is dissipated in the high side switch

during the on cycle. The power loss is equal to the high

side MOSFET RDS(ON) multiplied by the RMS Switch

Current squared (ISW

2). During the off cycle, the low side

N-Channel MOSFET conducts, also dissipating power.

Similarly, the inductor’s DCR and capacitor’s ESR also

contribute to the I2R losses. Device operating current

also reduces efficiency by the product of the quiescent

(operating) current and the supply voltage. The power

consumed at 1MHz frequency and power loss due to

switching transitions add up to switching losses. A free

wheeling schottky diode is recommended to use in

parallel with synchronous N-MOSFET to improve the

efficiency.

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Figure 2 shows an efficiency curve. The portion, from 0A

to 1A, efficiency losses are dominated by quiescent

current losses, gate drive and transition losses. In this

case, lower supply voltages yield greater efficiency in

that they require less current to drive the MOSFETs and

have reduced input power consumption.

0 200 400 600 800

OUTPUT CURRENT (mA)

vs. Inductance

Efficiency

L = 1µH

Figure 2. Efficiency Curve

The region, 1A to 6A, efficiency loss is dominated by

MOSFET RDS(ON) and inductor DC losses. Higher input

supply voltages will increase the Gate-to-Source voltage

on the internal MOSFETs, reducing the internal RDS(ON).

This improves efficiency by decreasing conduction loss

in the device but the inductor DCR loss is inherent to the

device. So inductor selection becomes increasingly

critical in efficiency calculations. As the inductors are

reduced in size, the DC resistance (DCR) can become

quite significant. The DCR losses can be calculated as

follows:

LPD = IOUT

2 × DCR

From that, the loss in efficiency due to inductor

resistance can be calculated as follows:

Efficiency Loss =

()

100

LIV

PDOUTOUT

OUTOUT ×

⎥

⎦

⎤

⎢

⎣

⎡

⎟

⎠

⎞

⎜

⎝

⎛

+×

−×

L = 4.7µH

Figure 3. Efficiency vs. Inductance

Efficiency loss due to DCR is minimal at light loads and

gains significance as the load is increased. Inductor

selection becomes a trade-off between efficiency and

size in this case.

Alternatively, under lighter loads, the ripple current

becomes a significant factor. When light load efficiencies

become more critical, a larger inductor value maybe

desired. Larger inductance reduces the peak-to-peak

inductor ripple current, which minimize losses. The

graph in Figure 3 illustrates the effects of inductance

value at light load.

Compensation

The MIC22600 has a combination of internal and

external stability compensation to simplify the circuit for

small, high efficiency designs. In such designs, voltage

mode conversion is often the optimum solution. Voltage

mode is achieved by creating an internal 1MHz ramp

signal and using the output of the error amplifier to

modulate the pulse width of the switch node, thereby

maintaining output voltage regulation. With a typical gain

bandwidth of 100-200kHz, the MIC22600 is capable of

extremely fast transient responses.

The MIC22600 is designed to be stable with a typical

application using a 1µH inductor and a 47µF ceramic

(X5R) output capacitor. These values can be varied

dependant upon the tradeoff between size, cost and

efficiency, keeping the LC natural frequency

(

C⋅L2

×Π×

) ideally less than 26 kHz to ensure

stability can be achieved. The minimum recommended

inductor value is 0.47µH and minimum recommended

output capacitor value is 22µF. With a larger inductor,

there is a reduced peak-to-peak current which yields a

greater efficiency at lighter loads. A larger output

capacitor will improve transient response by providing a

larger hold up reservoir of energy to the output.

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The integration of one pole-zero pair within the control

loop greatly simplifies compensation. The optimum

values for CCOMP (in series with a 20k resistor) are shown

below.

L 22-47µF 47µF-

100µF 100µF-

470µF

0.47µH 0*-10pF 22pF 33pF

1µH 0†-15pF 15-22pF 33pF

2.2µH 15-33pF 33-47pF 100-220pF

* VOUT > 1.2V, † VOUT > 1V

Table1. Compensation Capacitor Selection

Feedback

The MIC22600 provides a feedback pin to adjust the

output voltage to the desired level. This pin connects

internally to an error amplifier. The error amplifier then

compares the voltage at the feedback to the internal

0.7V reference voltage and adjusts the output voltage to

maintain regulation. The resistor divider network for a

desired VOUT is given by:

⎟

⎠

⎞

⎜

⎝

⎛−

REF

OUT

where VREF is 0.7V and VOUT is the desired output

voltage. A 10k or lower resistor value from the output

to the feedback is recommended since large feedback

resistor values increase the impedance at the feedback

pin, making the feedback node more susceptible to

noise pick-up. A small capacitor (50pF – 100pF) across

the lower resistor can reduce noise pick-up by providing

a low impedance path to ground.

PWM Operation

The MIC22600 is a voltage mode, pulse width

modulation (PWM) controller. By controlling the duty

cycle, a regulated DC output voltage is achieved. As

load or supply voltage changes, so does the duty cycle

to maintain a constant output voltage. In cases where

the input supply runs into a dropout condition, the

MIC22600 will run at 100% duty cycle.

The MIC22600 provides constant switching at 1MHz with

synchronous internal MOSFETs. The internal MOSFETs

include a high-side P-Channel MOSFET from the input

supply to the switch pin and an N-Channel MOSFET

from the switch pin-to-ground. Since the low-side N-

Channel MOSFET provides the current during the off

cycle, a freewheeling Schottky diode from the switch

node-to-ground is not required.

PWM control provides fixed-frequency operation. By

maintaining a constant switching frequency, predictable

fundamental and harmonic frequencies are achieved.

Sequencing and Tracking

The MIC22600 provides additional pins to provide

up/down sequencing and tracking capability for

connecting multiple voltage regulators together.

EN/DLY Pin

The EN pin contains a trimmed, 1µA current source

which can be used with a capacitor to implement a fixed

desired delay in some sequenced power systems. The

threshold level for power on is 1.24V with a hysteresis of

20mV.

DELAY Pin

The DELAY pin also has a 1µA trimmed current source

and a 1µA current sink which acts with an external

capacitor to delay the operation of the Power On Reset

(POR) output. This can be used also in sequencing

outputs in a sequenced system, but with the addition of a

conditional delay between supplies; allowing a first up,

last down power sequence.

After EN is driven high, VOUT will start to rise (rate

determined by RC capacitor). As the FB voltage goes

above 90% of its nominal set voltage, DELAY begins to

rise as the 1µA source charges the external capacitor.

When the threshold of 1.24V is crossed, POR is

asserted high and DELAY continues to charge to a

voltage SVIN. When FB falls below 90% of nominal, POR

is asserted low immediately. However, if EN is driven

low, POR will fall immediately to the low state and

DELAY will begin to fall as the external capacitor is

discharged by the 1µA current sink. When the threshold

of ((VTP+1.24V)-1.24V) is crossed (VTP is the internal

voltage clamp, VTP-=0.9V), VOUT will begin to fall at a rate

determined by the RC capacitor. As the voltage change

in both cases is 1.24V, both rising and falling delays are

matched at 6

DLY

POR 1.10

C1.24

−

RC Pin

The RC pin provides a trimmed 1µA current source/sink

similar to the DELAY Pin for accurate ramp up (soft

start) and ramp down control. This allows the MIC22600

to be used in systems requiring voltage tracking or ratio-

metric voltage tracking at startup.

There are two ways of using the RC pin:

1. Externally driven from a voltage source

2. Externally attached capacitor sets output ramp

up/down rate

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In the first case, driving RC with a voltage from 0V to

VREF programs the output voltage between 0 and 100%

of the nominal set voltage.

In the second case, the external capacitor sets the ramp

up and ramp down time of the output voltage. The time

is given by 6

10.1

7.0

−

=RC

RAMP C⋅

T where TRAMP is the time

from 0 to 100% nominal output voltage.

RC pin cannot be left floating. Use a minimum capacitor

value of 220pF or larger.

Sequencing and Tracking Examples

There are four distinct variations which are easily

implemented using the MIC22600. The two sequencing

variations are Delayed and Windowed. The two tracking

variants are Normal and Ratio Metric. The following

diagrams illustrate methods for connecting two

MIC22600’s to achieve these requirements.

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Sequencing:

Figure 4. Sequencing MIC22600 Circuit

Figure 5. Window Sequencing Examp le

Figure 6. Delayed Sequencing Example

Normal Tracking:

Figure 7. Normal Tracking Circui t

Figure 8. Normal Tracking Example

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Ratio Metric Tracking:

Figure 9. Ratio Metric Tracking Circuit

Figure 10. Ratio Metric Tracking Example

An alternative method here shows an example of a VDDQ

& VTT solution for a DDR memory power supply. Note

that POR is taken from Vo1 as POR2 will not go high.

This is because POR is set high when FB > 0.9⋅VREF. In

this example, FB2 is regulated to ½⋅VREF.

DDR Memory VDD and VTT Tracking

Figure 11. DDR Memory Tracking Circuit

Figure 12. DDR Memory Tracking Example

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Where

Current Limit

• P

DISS is the power dissipated within the MLF®

package and is typically 1.5W at 6A load. This

has been calculated for a 1µH inductor and

details can be found in Table 1 below for

reference.

The MIC22600 is protected against overload in two

stages. The first is to limit the current in the P-channel

switch; the second is by over temperature shutdown.

Current is limited by measuring the current through the

high-side MOSFET during its power stroke and

immediately switching off the driver when the preset limit

is exceeded.

• RθJA is a combination of junction to case thermal

resistance (RθJC) and Case-to-Ambient thermal

resistance (RθCA), since thermal resistance of

the solder connection from the ePAD to the PCB

is negligible; RθCA is the thermal resistance of

the ground plane to ambient, so RθJA = RθJC +

RθCA.

The circuit in Figure 4 describes the operation of the

current-limit circuit. Since the actual RDSON of the P-

Channel MOSFET varies part-to-part, over temperature

and with input voltage, simple IR voltage detection is not

employed. Instead, a smaller copy of the Power

MOSFET (Reference FET) is fed with a constant current

which is a directly proportional to the factory set current

limit. This sets the current limit as a current ratio and

thus, is not dependant upon the RDSON value.Current

limit is set to 9A nominal. Variations in the scale factor K

between the Power PFET and the reference PFET used

to generate the limit threshold account for a relatively

small inaccuracy.

• T

AMB is the Operating Ambient temperature.

Example:

The Evaluation board has two copper planes

contributing to an RθJA of approximately 25°C/W. The

worst case RθJC of the MLF 4x4 is 14oC/W.

RθJA = RθJC + RθCA

RθJA = 14 + 25 = 39oC/W

To calculate the junction temperature for a 50°C

ambient:

TJ = TAMB+PDISS . RθJA

TJ = 50 + (1.5 x 39)

TJ = 109°C

Figure 13. Current-Limit Detail This is below the maximum of 125°C.

Thermal Considerations

The MIC22600 is packaged in the MLF® 4mm x 4mm, a

package that has excellent thermal performance

equaling that of the larger TSSOP packages. This

maximizes heat transfer from the junction to the exposed

pad (ePad) which connects to the ground plane. The

size of the ground plane attached to the exposed pad

determines the overall thermal resistance from the

junction to the ambient air surrounding the printed circuit

board. The junction temperature for a given ambient

temperature can be calculated using:

VIN

VOUT

@6A 3 3.5 4 4.5 5

1 1.47 1.50 1.52 1.54 1.56

1.2 1.45 1.47 1.49 1.51 1.54

1.8 1.46 1.45 1.45 1.47 1.48

2.5 1.61 1.53 1.49 1.47 1.47

3.3 – 1.70 1.62 1.56 1.53

Table 2. Power Dissipation (W) for 6A Output

TJ = TAMB + PDISS · RθJA

Micrel, Inc. MIC22600

June 2011 19 M9999-062411-D

Ripple Measurements

To properly measure ripple on either input or output of a

switching regulator, a proper ring in tip measurement is

required. Standard oscilloscope probes come with a

grounding clip, or a long wire with an alligator clip.

Unfortunately, for high-frequency measurements, this

ground clip can pick-up high frequency noise and

erroneously inject it into the measured output ripple.

The standard evaluation board accommodates a home

made version by providing probe points for both the

input and output supplies and their respective grounds.

This requires the removing of the oscilloscope probe

sheath and ground clip from a standard oscilloscope

probe and wrapping a non-shielded bus wire around the

oscilloscope probe. If there does not happen to be any

non-shielded bus wire immediately available, the leads

from axial resistors will work. By maintaining the

shortest possible ground lengths on the oscilloscope

probe, true ripple measurements can be obtained.

Micrel, Inc. MIC22600

June 2011 20 M9999-062411-D

PCB Layout Guideline

Warning!!! To minimize EMI and output noise, follow

these layout recommendations.

PCB Layout is critical to achieve reliable, stable and

efficient performance. A ground plane is required to

control EMI and minimize the inductance in power,

signal and return paths.

The following guidelines should be followed to insure

proper operation of the MIC22602 converter.

• Place the IC close to the point of load (POL).

• Use fat traces to route the input and output power

lines.

• The exposed pad (EP) on the bottom of the IC must

be connected to the ground.

• Use several vias to connect the EP to the ground

plane, layer 2.

• Signal and power grounds should be kept separate

and connected at only one location.

Input Capacitor

• Place the input capacitor next.

• Place the input capacitors on the same side of the

board and as close to the IC as possible.

• Place a 22µF/6.3V ceramic bypass capacitor next to

each of the 4 PVIN pins.

• Keep both the VIN and PGND connections short.

• Place several vias to the ground plane close to the

input capacitor ground terminal, but not between the

input capacitors and IC pins.

• Use either X7R or X5R dielectric input capacitors.

Do not use Y5V or Z5U type capacitors.

• Do not replace the ceramic input capacitor with any

other type of capacitor. Any type of capacitor can be

placed in parallel with the input capacitor.

• If a Tantalum input capacitor is placed in parallel

with the input capacitor, it must be recommended for

switching regulator applications and the operating

voltage must be derated by 50%.

• In “Hot-Plug” applications, a Tantalum or Electrolytic

bypass capacitor must be used to limit the over-

voltage spike seen on the input supply with power is

suddenly applied.

Inductor

• Keep the inductor connection to the switch node

(SW) short.

• Do not route any digital lines underneath or close to

the inductor.

• Keep the switch node (SW) away from the feedback

(FB) pin.

• To minimize noise, place a ground plane underneath

the inductor.

Output Capacitor

• Use a wide trace to connect the output capacitor

ground terminal to the input capacitor ground

terminal.

• Phase margin will change as the output capacitor

value and ESR changes. Contact the factory if the

output capacitor is different from what is shown in

the BOM.

• The feedback trace should be separate from the

power trace and connected as close as possible to

the output capacitor. Sensing a long high current

load trace can degrade the DC load regulation.

Diode

• Place the Schottky diode on the same side of the

board as the IC and input capacitor.

• The connection from the Schottky diode’s Anode to

the input capacitors ground terminal must be as

short as possible.

• The diode’s Cathode connection to the switch node

(SW) must be keep as short as possible.

Micrel, Inc. MIC22600

June 2011 21 M9999-062411-D

MIC22600YML Schematic

Bill of Materials

Item Part Number Manufacturer Description Qty.

C2012X5R0J226M TDK(1)

08056D2226MAT AVX(2)

C1, C2,

C3, C4,

C5 GRM21BR60J226ME39L Murata(3)

22µF/6.3V, 0805 Ceramic Capacitor 5

C6 OPEN Open, 0603 Ceramic Capacitor 1

GRM188R71H221KA01D Murata(3)

VJ0603Y221KXACW1BC Vishay(4)

C1608X7R1H221K TDK(1)

220pF, 0603 Ceramic Capacitor 1

Open (VJ0603Y102KQCW1BC) Vishay(4)

C8 Open (GRM188R71H102KA01D) Murata(3) 1nF, 0603 Ceramic Capacitor 1

GRM1555C1H390JZ01D Murata(3)

C9 VJ0402A390KXQCW1BC Vishay(4) 39pF, 0402 Ceramic Capacitor 1

C3216X5R0J476M TDK(1)

12066D476KAT AVX(2)

C10, C11

GRM31CC80G476ME19L Murata(3)

47µF/6V, 1206 Ceramic Capacitor 2

VJ0402A101KXQCW1BC Vishay(4)

C12 GRM15551H101JZ01D Murata(3) 100pF, 0402 Ceramic Capacitor 1

D1 DFLS220L-7 Diodes Inc(5) 2A, 20V Schottky Diode 1

CDRH8D43NP-1R2NC Sumida(6)

FP3-1R0-R Coiltronics(7)

SPM6530T-1R0M120 TDK(1)

1µH, 6A Inductor 1

Micrel, Inc. MIC22600

June 2011 22 M9999-062411-D

Bill of Materials (Continued)

Item Part Number Manufacturer Description Qty.

R1 CRCW06031101FKEYE3. Vishay(4) 1.1k, 0603 Resistor 1

R2 CRCW04026980FKEYE3. Vishay(4) 698, 0402 Resistor 1

R3 CRCW06034752FKEYE3. Vishay(4) 47.5k, 0603 Resistor 1

R4 CRCW04022002FKEYE3. Vishay(4) 20k, 0402 Resistor 1

Rx OPEN Open, 0603 Resistor 1

Q1 OPEN SOT-23 1

U1 MIC22600YML Micrel(8) Integrated 6A Synchronous Buck Regulator 1

Notes:

1. TDK: www.tdk.com.

2. AVX: www.avx.com.

3. Murata: www.murata.com.

4. Vishay: www.vishay.com.

5. Diodes Inc.: www.diodes.com.

6. Sumida: www.sumida.com.

7. Coiltronics: www.mouser.com/coiltronics.

8. Micrel: www.micrel.com.

Micrel, Inc. MIC22600

June 2011 23 M9999-062411-D

PCB Layout Recommendations −YML Package

Top Layer

Micrel, Inc. MIC22600

June 2011 24 M9999-062411-D

MIC22600YTSE Schematic

Bill of Materials

Item Part Number Manufacturer Description Qty

C2012X5R0J226M TDK(1)

08056D2226MAT AVX(2)

C1, C2,

C3, C4,

C5 GRM21BR60J226ME39L Murata(3)

22µF/6.3V, 0805 Ceramic Capacitor 5

C6 OPEN Open, 0603 Ceramic Capacitor 1

GRM188R71H221KA01D Murata(3)

VJ0603Y221KXACW1BC Vishay(4)

C1608X7R1H221K TDK(1)

220pF, 0603 Ceramic Capacitor 1

Open (VJ0603Y102KQCW1BC) Vishay(4)

C8 Open (GRM188R71H102KA01D) Murata(3) 1nF, 0603 Ceramic Capacitor 1

GRM1555C1H390JZ01D Murata(3)

C9 VJ0402A390KXQCW1BC Vishay(4) 39pF, 0402 Ceramic Capacitor 1

C3216X5R0J476M TDK(1)

12066D476KAT AVX(2)

C10, C11

GRM31CC80G476ME19L Murata(3)

47µF/6V, 1206 Ceramic Capacitor 2

VJ0402A101KXQCW1BC Vishay(4)

C12 GRM15551H101JZ01D Murata(3) 100pF, 0402 Ceramic Capacitor 1

D1 DFLS220L-7 Diodes Inc(5) 2A, 20V Schottky Diode 1

CDRH8D43NP-1R2NC Sumida(6)

FP3-1R0-R Coiltronics(7)

SPM6530T-1R0M120 TDK(1)

1µH, 6A Inductor 1

Micrel, Inc. MIC22600

June 2011 25 M9999-062411-D

Bill of Materials (Continued)

Item Part Number Manufacturer Description Qty

R1 CRCW06031101FKEYE3. Vishay(4) 1.1k, 0603 Resistor 1

R2 CRCW04026980FKEYE3. Vishay(4) 698, 0402 Resistor 1

R3 CRCW06034752FKEYE3. Vishay(4) 47.5k, 0603 Resistor 1

R4 CRCW04022002FKEYE3. Vishay(4) 20k, 0402 Resistor 1

Rx OPEN Open, 0603 Resistor 1

Q1 OPEN SOT-23 1

U1 MIC22600YTSE Micrel(8) Integrated 6A Synchronous Buck Regulator 1

Notes:

1. TDK: www.tdk.com.

2. AVX: www.avx.com.

3. Murata: www.murata.com.

4. Vishay: www.vishay.com.

5. Diodes Inc.: www.diodes.com.

6. Sumida: www.sumida.com.

7. Coiltronics: www.mouser.com/coiltronics.

8. Micrel: www.micrel.com.

Micrel, Inc. MIC22600

June 2011 26 M9999-062411-D

PCB Layout Recommendations − YTSE Package

Top Layer

Mid Layer 1

Micrel, Inc. MIC22600

June 2011 27 M9999-062411-D

PCB Layout Recommendations − YTSE Package (Continued)

Mid Layer 2

Bottom Layer

Micrel, Inc. MIC22600

June 2011 28 M9999-062411-D

Package Information

24-Pin 4mm x 4mm MLF® (ML)

Micrel, Inc. MIC22600

June 2011 29 M9999-062411-D

Package Information (Continued)

24-Pin ePad TSSOP

Micrel, Inc. MIC22600

June 2011 30 M9999-062411-D

Recommended Landing Pattern

Micrel, Inc. MIC22600

June 2011 31 M9999-062411-D

Recommended Landing Pattern (Continued)

Micrel, Inc. MIC22600

June 2011 32 M9999-062411-D

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

Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.

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

can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant

into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A

Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully

indemnify Micrel for any damages resulting from such use or sale.