MICREL MIC22600

MIC22600
1MHz, 6A Integrated Switch
Synchronous Buck Regulator
NOT RECOMMENDED FOR NEW DESIGNS
SEE MIC22705
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 turnon 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 Synchronous Output Converter
Sequencing & Tracking
Note:
1. Using a free-wheeling Schottky diode improves efficiency.
Ramp Control is a trademark of Micrel, Inc.
MLF and MicroLeadFrame are registered trademarks 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
June 2011
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Micrel, Inc.
MIC22600
Ordering Information
Part Number
Voltage
Junction Temperature Range
Package
MIC22600YML
Adjustable
–40° to +125°C
24-Pin 4mm x 4mm MLF
MIC22600YTSE
Adjustable
–40° to +125°C
24-pin ePad TSSOP
Lead Finish
®
Pb-Free
Pb-Free
Note:
®
MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
PGND
SW
SW
SW
SW
PGND
Pin Configuration
PVIN
PVIN
EN/DLY
SVIN
DELAY
SGND
EP
RC
COMP
FB
POR/PG
PVIN
PGND
SW
SW
SW
SW
PGND
PVIN
24-Pin 4mm x 4mm MLF (ML)
June 2011
24-pin ePad TSSOP
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MIC22600
Pin Description
Pin Number
Pin Number
MLF-24
TSSOP-24
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
Pin Name
EN/DLY
Description
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
5
14
POR/PG
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
EP
EP
GND
June 2011
Compensation pin (Input): Place a RC network to GND to compensate the
device, see applications section.
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.
Switch (Output): Internal power MOSFET output switches.
Exposed Pad (Power): Must make a full connection to a GND plane for full
output power to be realized.
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MIC22600
Absolute Maximum Ratings(1)
Operating Ratings(2)
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
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
Supply Voltage Range
VIN Turn-On Voltage Threshold
UVLO Hysteresis
Quiescent Current, PWM Mode
Shutdown Current
Feedback Voltage
FB Pin Input Current
Current Limit in PWM Mode
Output Voltage Line Regulation
Output Voltage Load Regulation
Maximum Duty Cycle
Switch ON-Resistance PFET
Switch ON-Resistance NFET
Oscillator Frequency
EN/DLY Threshold Voltage
EN/DLY Source Current
RC Pin IRAMP
Condition
Min.
2.6
2.4
VIN rising
VEN ≥1.34V; VFB = 0.9V (not switching)
VEN = 0V
± 1%
± 2% (over temperature)
VFB = 0.5*VNOM
VOUT 1.8V, VIN = 2.6 to 5.5V, ILOAD= 100mA
100mA < ILOAD < 6000mA, VIN = 3.3V
VFB ≤ 0.5V
ISW = 1000mA; VFB=0.5V
ISW = 1000mA; VFB=0.9V
6.5
2.5
280
850
5
0.7
1
9
0.2
0.2
Max.
Units
5.5
2.6
V
V
mV
µA
µA
1300
10
0.707
0.714
100
11.5
100
V
nA
A
%
%
%
VIN = 2.6 to VIN = 5.5V
0.8
1.14
0.7
0.03
0.025
1
1.24
1
1.2
1.34
1.3
MHz
V
µA
Ramp Control Current
0.7
1
1.3
µA
1
2
µA
Power-on-Reset IPG(LEAK)
VPORH = 5.5V; POR = High
Power-on-Reset VPG(LO)
Output Logic-Low Voltage (undervoltage condition),
IPOR = 5mA
Power-on-Reset VPG
0.693
0.686
Typ.
Threshold, % of VOUT below nominal
Hysteresis
Over-Temperature Shutdown
Over-Temperature Shutdown
Hysteresis
Ω
130
7.5
10
mV
12.5
%
2
%
160
°C
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.
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MIC22600
Typical Characteristics
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MIC22600
Typical Characteristics (Continued)
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VIN = 5V
VO = 3.3V
IO = 6A
Output Noise & Ripple
Time (400ns/div)
7
ENABLE VO LTAGE
(1V/div)
VIN = 5V
VO = 1.8V
IO = 0.6A to 6A
SWITCH VO LTAGE
(2V/div)
INPUT VOLTAGE
(1V/div)
OUTPU T CURREN T
(2A/div)
OUTPU T VOLTAGE
(10mV/div)
OUTPU T VOLTAGE
(50mV/div)
OUTPU T CURREN T OUTPU T VOLTAGE
(50mV/div)
(2A/div)
INPU T VOLTAGE
(500mV/div)
ENABLE VO LTAGE
(2mV/div)
RAMP CONTRO L VOLTAGE
(500mV/div)
OUTPU T CURREN T
(2A/div)
OUTPU T VOLTAGE
(1V/div)
VIN = 3V
VO = 1.8V
RO
OUTPU T CURREN T
(2A/div)
OUTPU T VOLTAGE
(500mV/div)
OUTPU T VOLTAGE
(10mV/div)
RAMP CONTRO L VOLTAGE
(500mV/div)
SWITCH VO LTAGE
(2V/div)
Micrel, Inc.
MIC22600
Functional Characteristics
Start-Up/Shutdown (CRC = 10nF)
Transient Response
Transient Response
Time (200µs/div)
VIN = 3V
VO = 1.8V
IO = 0.6A to 6A
Time (2ms/div)
Time (200µs/div)
High DC Operation
VIN = 5V
IO = 1A
Time (200ns/div)
Start-Up (CRC = 0nF)
VIN = 3V
VO = 1V
IO = 6A
Time (20µs/div)
M9999-062411-D
Micrel, Inc.
MIC22600
June 2011
VIN = 3V
Time (20µs/div)
OUTPU T CURREN T OUTPU T VOLTAGE
(2A/div)
(500mV/div)
Current Limit Behavior
INPUT VOLTAGE
(500mV/div)
ENABLE VO LTAGE
(2V/div)
Start-Up into Short
SWITCH VO LTAGE
(2V/div)
OUTPU T VOLTAGE
(100mV/div)
INPUT CURREN T
(2A/div)
Functional Characteristics (Continued)
VIN = 3V
VO = 1.8V
IOSET = 12A
Time (200µs/div)
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MIC22600
Typical Circuits and Waveforms
Sequencing Circuit and Waveform
Tracking Circuit and Waveform
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MIC22600
Functional Diagram
Figure 1. MIC22600 Block Diagram
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MIC22600
Functional Description
FB
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.
PVIN, SVIN
PVIN is the input supply to the internal 30mΩ 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.
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.
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
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.
SW
This is the connection to the source of the internal PChannel 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.
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.
SGND
Internal signal ground for all low power sections.
PGND
Internal ground connection to the source of the internal
N-Channel MOSFETs.
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.
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MIC22600
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.
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.
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:
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.
TDLY =
Inductance
•
Rated current value
•
Size requirements
•
DC resistance (DCR)
⎛V
×I
Efficiency % = ⎜⎜ OUT OUT
⎝ VIN × IIN
⎞
⎟⎟ × 100
⎠
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 (ISW2). 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.
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.
June 2011
1.10 −6
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power consumed.
Inductor Selection
Inductor selection is determined by the following (not
necessarily in the order of importance):
•
1.24 × C DLY
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MIC22600
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.
95
Efficiency
vs. Inductance
90
85
80
75
L = 1µH
L = 4.7µH
70
65
60
55
50
0
200
400
600
800
OUTPUT CURRENT (mA)
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.
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:
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
1
) ideally less than 26 kHz to ensure
(
LPD = IOUT2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
Efficiency Loss =
⎡ ⎛
VOUT × IOUT
⎢1 − ⎜⎜
⎢⎣ ⎝ (VOUT × IOUT ) + L PD
June 2011
⎞⎤
⎟⎥ × 100
⎟
⎠⎥⎦
2×Π ×
L ⋅C
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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MIC22600
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.
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.
C
L
22-47µF
47µF100µF
100µF470µF
0.47µH
0*-10pF
22pF
33pF
1µH
0†-15pF
15-22pF
33pF
15-33pF
33-47pF
100-220pF
2.2µH
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
1.24 × C DLY
matched at TPOR =
1.10 −6
†
* 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:
R2 =
R1
⎞
⎛ VOUT
⎜⎜
− 1⎟⎟
V
⎠
⎝ REF
where VREF is 0.7V and VOUT is the desired output
voltage. A 10kΩ 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 NChannel MOSFET provides the current during the off
cycle, a freewheeling Schottky diode from the switch
node-to-ground is not required.
June 2011
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 ratiometric 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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MIC22600
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
0.7 ⋅ C RC
where TRAMP is the time
is given by TRAMP =
1.10 − 6
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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MIC22600
Sequencing:
Normal Tracking:
Figure 4. Sequencing MIC22600 Circuit
Figure 7. Normal Tracking Circuit
Figure 5. Window Sequencing Example
Figure 8. Normal Tracking Example
Figure 6. Delayed Sequencing Example
June 2011
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Micrel, Inc.
MIC22600
DDR Memory VDD and VTT Tracking
Ratio Metric Tracking:
Figure 11. DDR Memory Tracking Circuit
Figure 9. Ratio Metric Tracking Circuit
Figure 10. Ratio Metric Tracking Example
Figure 12. DDR Memory 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.
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
Where
Current Limit
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.
The circuit in Figure 4 describes the operation of the
current-limit circuit. Since the actual RDSON of the PChannel 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.
•
PDISS 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.
•
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.
•
TAMB 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:
VOUT
@6A
VIN
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
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
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.
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
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.
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.
IC
•
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.
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.
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 overvoltage spike seen on the input supply with power is
suddenly applied.
June 2011
Diode
20
•
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.
M9999-062411-D
Micrel, Inc.
MIC22600
MIC22600YML Schematic
Bill of Materials
Item
C1, C2,
C3, C4,
C5
C6
C7
C8
C9
C10, C11
C12
D1
L1
Part Number
C2012X5R0J226M
08056D2226MAT
TDK
AVX(2)
C1608X7R1H221K
Open (VJ0603Y102KQCW1BC)
Open (GRM188R71H102KA01D)
TDK
Vishay(4)
Murata(3)
GRM1555C1H390JZ01D
VJ0402A390KXQCW1BC
Murata(3)
Vishay(4)
GRM31CC80G476ME19L
VJ0402A101KXQCW1BC
GRM15551H101JZ01D
DFLS220L-7
CDRH8D43NP-1R2NC
FP3-1R0-R
Qty.
22µF/6.3V, 0805 Ceramic Capacitor
5
Open, 0603 Ceramic Capacitor
1
220pF, 0603 Ceramic Capacitor
1
1nF, 0603 Ceramic Capacitor
1
39pF, 0402 Ceramic Capacitor
1
47µF/6V, 1206 Ceramic Capacitor
2
100pF, 0402 Ceramic Capacitor
1
2A, 20V Schottky Diode
1
1µH, 6A Inductor
1
(3)
Murata
C3216X5R0J476M
12066D476KAT
Description
(1)
GRM21BR60J226ME39L
OPEN
GRM188R71H221KA01D
VJ0603Y221KXACW1BC
SPM6530T-1R0M120
June 2011
Manufacturer
Murata(3)
Vishay(4)
(1)
TDK(1)
AVX(2)
(3)
Murata
Vishay(4)
Murata(3)
Diodes Inc(5)
Sumida(6)
Coiltronics(7)
TDK
(1)
21
M9999-062411-D
Micrel, Inc.
MIC22600
Bill of Materials (Continued)
Item
R1
R2
R3
R4
Rx
Q1
U1
Part Number
CRCW06031101FKEYE3.
CRCW04026980FKEYE3.
CRCW06034752FKEYE3.
CRCW04022002FKEYE3.
OPEN
OPEN
MIC22600YML
Manufacturer
Vishay(4)
Vishay(4)
Vishay(4)
Vishay(4)
Micrel(8)
Description
Qty.
1.1k, 0603 Resistor
698Ω, 0402 Resistor
47.5k, 0603 Resistor
20k, 0402 Resistor
Open, 0603 Resistor
SOT-23
Integrated 6A Synchronous Buck Regulator
1
1
1
1
1
1
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.
June 2011
22
M9999-062411-D
Micrel, Inc.
MIC22600
PCB Layout Recommendations −YML Package
Top Layer
June 2011
23
M9999-062411-D
Micrel, Inc.
MIC22600
MIC22600YTSE Schematic
Bill of Materials
Item
C1, C2,
C3, C4,
C5
C6
C7
C8
C9
C10, C11
C12
D1
L1
Part Number
C2012X5R0J226M
08056D2226MAT
TDK
AVX(2)
C1608X7R1H221K
Open (VJ0603Y102KQCW1BC)
Open (GRM188R71H102KA01D)
TDK
Vishay(4)
Murata(3)
GRM1555C1H390JZ01D
VJ0402A390KXQCW1BC
Murata(3)
Vishay(4)
GRM31CC80G476ME19L
VJ0402A101KXQCW1BC
GRM15551H101JZ01D
DFLS220L-7
CDRH8D43NP-1R2NC
FP3-1R0-R
Qty
22µF/6.3V, 0805 Ceramic Capacitor
5
Open, 0603 Ceramic Capacitor
1
220pF, 0603 Ceramic Capacitor
1
1nF, 0603 Ceramic Capacitor
1
39pF, 0402 Ceramic Capacitor
1
47µF/6V, 1206 Ceramic Capacitor
2
100pF, 0402 Ceramic Capacitor
1
2A, 20V Schottky Diode
1
1µH, 6A Inductor
1
(3)
Murata
C3216X5R0J476M
12066D476KAT
Description
(1)
GRM21BR60J226ME39L
OPEN
GRM188R71H221KA01D
VJ0603Y221KXACW1BC
SPM6530T-1R0M120
June 2011
Manufacturer
Murata(3)
Vishay(4)
(1)
TDK(1)
AVX(2)
(3)
Murata
Vishay(4)
Murata(3)
Diodes Inc(5)
Sumida(6)
Coiltronics(7)
TDK
(1)
24
M9999-062411-D
Micrel, Inc.
MIC22600
Bill of Materials (Continued)
Item
R1
R2
R3
R4
Rx
Q1
U1
Part Number
CRCW06031101FKEYE3.
CRCW04026980FKEYE3.
CRCW06034752FKEYE3.
CRCW04022002FKEYE3.
OPEN
OPEN
MIC22600YTSE
Manufacturer
Vishay(4)
Vishay(4)
Vishay(4)
Vishay(4)
Micrel(8)
Description
Qty
1.1k, 0603 Resistor
698Ω, 0402 Resistor
47.5k, 0603 Resistor
20k, 0402 Resistor
Open, 0603 Resistor
SOT-23
Integrated 6A Synchronous Buck Regulator
1
1
1
1
1
1
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.
June 2011
25
M9999-062411-D
Micrel, Inc.
MIC22600
PCB Layout Recommendations − YTSE Package
Top Layer
Mid Layer 1
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
PCB Layout Recommendations − YTSE Package (Continued)
Mid Layer 2
Bottom Layer
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
Package Information
24-Pin 4mm x 4mm MLF® (ML)
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
Package Information (Continued)
24-Pin ePad TSSOP
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
Recommended Landing Pattern
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
Recommended Landing Pattern (Continued)
June 2011
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M9999-062411-D
Micrel, Inc.
MIC22600
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.
© 2007 Micrel, Incorporated.
June 2011
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