MIC22602
1MHz, 6A Integrated Switch High
Efficiency Synchronous Buck Regulator
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
October 2009 M9999-102809-A
General Description
The Micrel MIC22602 is a high efficiency 6A Integrated
switch synchronous buck (step-down) regulator. The
MIC22602 is optimized for highest efficiency, achieving
more than 95% efficiency while still switching at 1MHz
over a broad range. The device works with a small 1µH
inductor and 100µF 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 MIC22602 offers a full range of
sequencing and tracking options. The EN/DLY pin
combined with the Power Good/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 MIC22602 is available in a 24-pin 4mm x 4mm MLF®
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 load current up to 6A
• Full sequencing and tracking capability
• Power on Reset/Power Good output
• Efficiency > 95% across a broad load range
• Ultra fast transient response−Easy RC compensation
• 100% maximum duty cycle
• Fully integrated MOSFET switches
• Hic-cup mode current limiting
• Micropower shutdown
• Thermal shutdown and current limit protection
• 24-pin 4mm x 4mm MLF®
• –40°C to +125°C junction temperature range
Applications
• High power density point of load conversion
• Servers and routers
• DVD recorders / Blu-Ray players
• Computing peripherals
• Base stations
• FPGAs, DSP and low voltage ASIC power
Typical Application
MIC22602 6A 1MHz Synchronous Output Converter
50
55
60
65
70
75
80
85
90
95
100
0123456
OUTPUT CURRENT (A)
Efficiency @ 3.3VOUT
VIN = 5.5V
Sequencing & Tracking
Micrel, Inc. MIC22602
October 2009 2 M9999-102809-A
Ordering Information
Part Number Voltage Junction Temp. Range Package Lead Finish
MIC22602YML Adj. –40° to +125°C 24-Pin 4x4 MLF® Pb-Free
Note: MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
PVIN
EN/DLY
DELAY
RC
POR/PG
PVIN
PVIN
SVIN
SGND
COMP
FB
PVIN
SW
SW
SW
PGND
SW
PGND
SW
SW
SW
PGND
SW
PGND
EP
24-Pin 4mm x 4mm MLF® (ML)
Pin Description
Pin Number Pin Name Description
1, 6, 13, 18 PVIN Power Supply Voltage (Input): Requires bypass capacitor to GND.
17 SVIN Signal Power Supply Voltage (Input): Requires bypass capacitor to GND.
2 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 minimum voltage specified.
4 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. The RC pin cannot be left floating. Use a minimum capacitor value of 470pF
or larger.
14 FB
Feedback: Input to the error amplifier, connect to the external resistor divider
network to set the output voltage.
15 COMP
Compensation pin (Input): Place a RC network to GND to compensate the device,
see applications section.
5 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 PGND Power Ground: Ground
16 SGND Signal Ground: Ground
3 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
SW Switch (Output): Internal power MOSFET output switches.
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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October 2009 3 M9999-102809-A
Absolute Maximum Ratings(1)
Supply Voltage (PVIN, SVIN) .............................. –0.3V to 6V
Output Switch Voltage (VSW) ............................. –0.3V to 6V
Output Switch Current (ISW).......................Internally Limited
Logic Input Voltage (EN, POR, DLY) ................ –0.3V to VIN
Control Voltage (RC, COMP, FB) ..................... –0.3V to VIN
Storage Temperature (Ts) .........................–65°C to +150°C
ESD Rating(3).................................................................. 2kV
Lead Temperature (Soldering 10sec) ........................ 260°C
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
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 ± 2% (over temperature) 0.686 0.7 0.714 V
FB Pin Input Current 1 nA
Current Limit VFB = 0.5 6 10 14 A
Output Voltage Line Regulation VOUT 1.8V, VIN = 2.6 to 5.5V, ILOAD= 100mA 0.2 %
Output Voltage Load Regulation 100mA < ILOAD < 6A, 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 Threshold Voltage 1.14 1.24 1.34 V
EN 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
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.
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October 2009 4 M9999-102809-A
Typical Characteristics
0
2
4
6
8
10
-40
-25
-10
5
20
35
50
65
80
95
110
125
SHUTDOWN CURRENT (µA)
TEMPERATURE (°C)
Shutdown Current
vs. Temperature
EN = 0V
VIN = 3.3V
800
810
820
830
840
850
860
870
880
890
900
-40
-25
-10
5
20
35
50
65
80
95
110
125
QUIESCENT CURRENT (µA)
TEMPERATURE (°C)
Quiescent Current
vs. Temperature
EN > 1.34V
VFB = 0.9V
VIN = 3.3V
No Switching
0.6980
0.6981
0.6982
0.6983
0.6984
0.6985
0.6986
0.6987
0.6988
0.6989
0.6990
2.533.544.555.5
FEEDBACK VOLTAGE (V)
INPUT VOLTAGE (V)
Feedback Voltage
vs. Input Voltag e
EN = VIN
VIN = 3.3V
AMB = 25°C
0.695
0.696
0.697
0.698
0.699
0.700
0.701
-40
-25
-10
5
20
35
50
65
80
95
110
125
FEEDBACK VOLTAGE (V)
TEMPERATURE (°C)
Feedback Voltage
vs. Temperature
VIN = 3.3V
EN = VIN
1.235
1.236
1.237
1.238
1.239
1.24
1.241
1.242
1.243
1.244
1.245
-40
-25
-10
5
20
35
50
65
80
95
110
125
ENABLE VOLTAGE (V)
TEMPERATURE (C)
Enable Voltage
vs. Temperature
VIN = 3.3V
0.0050
0.0055
0.0060
0.0065
0.0070
0.0075
0.0080
0.0085
0.0090
0.0095
0.0100
-40
-25
-10
5
20
35
50
65
80
95
110
125
ENABLE HYSTERESIS (V)
TEMPERATURE (°C)
Enable Hysteresis
vs. Temperature
VIN = 3.3V
980
985
990
995
1000
1005
1010
1015
1020
-40
-25
-10
5
20
35
50
65
80
95
110
125
FREQUENCY (kHz)
TEMPERATURE (°C)
Frequency
vs. Temperature
VIN = 3.3V
EN = VIN
980
990
1000
1010
1020
1030
1040
2.5 3 3.5 4 4.5 5 5.5
FREQUENCY (kHz)
INPUT VOLTAGE (V)
Frequency
vs. Input Voltage
EN = VIN
20
22
24
26
28
30
32
34
36
38
40
2.533.544.555.5
RDSON (mOhm)
INPUT VOLTAGE (V)
P-Channel RDSON
vs. Input Voltag e
EN = VIN
600
700
800
900
1000
1100
1200
2.5 3 3.5 4 4.5 5 5.5
QUIESCENT CURRENT (µA)
INPUT VOLTAGE (V)
Quiescent Current
vs. Input Voltage
EN > 1.34V
VFB = 0.9V
No Switching
4.0
4.5
5.0
5.5
6.0
6.5
7.0
2.5 3 3.5 4 4.5 5 5.5
SHUTDOWN CURRENT (µA)
INPUT VOLTAGE (V)
Shutdown Current
vs. Input Voltage
EN = 0V
Micrel, Inc. MIC22602
October 2009 5 M9999-102809-A
Typical Characteristics (c ontinued)
50
55
60
65
70
75
80
85
90
95
100
0123456
OUTPUT CURRENT (A)
Efficiency @ 1.2VOUT
2.6VIN
5.5VIN
3.3VIN
50
55
60
65
70
75
80
85
90
95
100
0123456
OUTPUT CURRENT (A)
Efficiency @ 1.8VOUT
2.6VIN
5.5VIN
3.3VIN
50
55
60
65
70
75
80
85
90
95
100
0123456
OUTPUT CURRENT (A)
Efficiency @ 3.3VOUT
VIN = 5.5V
100 1k 10k 100k 1M
FREQUENCY (Hz)
250
200
150
100
50
0
-50
-100
-150
-200
-250
100
80
60
40
20
0
-20
-40
-60
-80
-100
Bode Plot
(VIN - 3.6V, VO - 1.8V)
100 1k 10k 100k 1M
FREQUENCY (Hz)
Bode Plot
(VIN - 5.5V, VO - 1.8V) 250
200
150
100
50
0
-50
-100
-150
-200
-250
100
80
60
40
20
0
-20
-40
-60
-80
-100
100 1k 10k 100k 1M
FREQUENCY (Hz)
Bode Plot
(VIN - 5.0V, VO - 3.3V) 250
200
150
100
50
0
-50
-100
-150
-200
-250
100
80
60
40
20
0
-20
-40
-60
-80
-100
Micrel, Inc. MIC22602
October 2009 6 M9999-102809-A
Functional Characteristics
Micrel, Inc. MIC22602
October 2009 7 M9999-102809-A
Functional Characteristics (continued)
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October 2009 8 M9999-102809-A
Typical Circuits and Waveforms
Sequencing Circuit and Waveform
Tracking Circuit and Waveform
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October 2009 9 M9999-102809-A
Functional Diagram
Figure 1. MIC22602 Block Diag ram
Micrel, Inc. MIC22602
October 2009 10 M9999-102809-A
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 22µF 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
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. The RC pin cannot be left floating. Use
a minimum capacitor value of 470pF 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 MIC22602 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.
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.
POR
This is an open drain output. A 47.5k 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.
SW
This is the connection to the drain 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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October 2009 11 M9999-102809-A
Application Information
The MIC22602 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 22µF ceramic is recommended on each of
the PVIN pins for bypassing. X5R or X7R dielectrics are
recommended for the input capacitor. Y5V dielectric is
not recommended.
Output Capacitor
The MIC22602 was designed specifically for the use of
ceramic output capacitors. Additional 100µF can improve
transient performance. Since the MIC22602 is in voltage
mode, 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 MIC22602.
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 MIC22602 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 MIC22602 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 represents
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:
6
101
24.1
−
×
⋅
=DLY
DLY C
T
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power consumed.
Efficiency % = 100×
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
×
×
ININ
OUTOUT IV IV
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 critical in hand held devices.
There are mainly two loss terms in switching converters:
conduction losses and switching losses. Conduction loss
is 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
RDSON 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 for
switching at 1MHz frequency and power loss due to
switching transitions add up to switching losses.
Micrel, Inc. MIC22602
October 2009 12 M9999-102809-A
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.
50
55
60
65
70
75
80
85
90
95
100
0 1 2 3 4 5 6
LOAD CURRENT (A)
Efficiency
50
VIN = 3.3V
VOUT = 1.8V
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 loss is inherent to the
converter. In which case, 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 = IOUT2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
Efficiency Loss =
()
1001 ×
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+⋅
⋅
−PDOUTOUT
OUTOUT LIV IV
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
following graph in Figure 3 illustrates the effects of
inductance value at light load.
50
55
60
65
70
75
80
85
90
95
0 200 400 600 800
OUTPUT CURRENT (mA)
vs. Inductance
Efficiency
L = 1µH
L = 4.7µH
Figure 3. Efficiency vs. Inductance
Compensation
The MIC22602 has a combination of internal and
external stability compensation to simplify the circuit for
small size, 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 MIC22602 is capable of
extremely fast transient responses.
The MIC22602 is designed to be stable with a typical
application using a 1µH inductor and a 100µF ceramic
(X5R) output capacitor. These values can be varied
dependant upon the tradeoff between size, cost and
efficiency, keeping the LC natural frequency
(CL ⋅××
π
2
1) ideally less than 26kHz 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.
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.
CÆ
LÈ
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
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October 2009 13 M9999-102809-A
Feedback
The MIC22602 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:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
=
1
1
2
REF
OUT
V
VR
R
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 MIC22602 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
MIC22602 will run at 100% duty cycle.
The MIC22602 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, very low power is dissipated during the off period.
PWM control provides fixed frequency operation. By
maintaining a constant switching frequency, predictable
fundamental and harmonic frequencies are achieved.
Sequencing and tracking
The MIC22602 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
101
24.1
−
×
⋅
=DLY
POR C
T
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 MIC22602
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
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
101
7.0
−
×
⋅
=RC
RAMP C
T where TRAMP is the time
from 0 to 100% nominal output voltage.
The RC pin cannot be left floating. Use a minimum
capacitor value of 470pF or larger.
Micrel, Inc. MIC22602
October 2009 14 M9999-102809-A
Sequencing & Tracking examples
There are four distinct variations which are easily
implemented using the MIC22602. 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
MIC22602’s to achieve these requirements.
Sequencing:
Normal Tracking:
Ratio Metric Tracking:
Micrel, Inc. MIC22602
October 2009 15 M9999-102809-A
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.
Current Limit
The MIC22602 is protected against overload in two
stages. The first is to limit the current in the P-channel
switch; the second is 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 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 nominal value. 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.
Figure 4. Current Limit Detail
Thermal Considerations
The MIC22602 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:
TJ = TAMB + PDISS · RθJA
Where
• 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.
Micrel, Inc. MIC22602
October 2009 16 M9999-102809-A
• 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.
VINÆ
VOUT
@6AÈ
2.6V 3.3V 3.6V 4.5V 5.5V 5.5V
0.7V 1.41 1.269 1.209 1.192 1.198 1.202
1.2V 1.43 1.276 1.220 1.206 1.207 1.214
1.8V 1.48 1.292 1.230 1.221 1.218 1.231
2.5V ------ 1.295 1.228 1.215 1.224 1.230
3.3V ------ ------ 1.216 1.208 1.201 1.224
Table 1. Power Dissipation (W) for 6A output
• 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
This is below the maximum of 125°C.
Micrel, Inc. MIC22602
October 2009 17 M9999-102809-A
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. MIC22602
October 2009 18 M9999-102809-A
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.
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.
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. MIC22602
October 2009 19 M9999-102809-A
Evaluation Board Schematic
PVIN
PVIN
PVIN
PVIN
SVIN
EN
RC
DELAY
SW
SW
SW
SW
SW
SW
SW
SW
FB
COMP
J11
POR
POR/PG
PGND
PGND
PGND
PGND
EP
SGND
C4
22µF
1 8
9
10
11
20
21
22
23
14
15
6
13
18
17
2
4
3
5
7
12
19
24
16
C8
N.U.
C7
470pF
C3
22µF
C2
22µF
C1
22µF
TP2
J2
GND
J1
VIN = 3.3V
J3
EN
J4
SHDN
J5
RC
J6
DELAY
TP3
Q1
N.U.
C5
22µF
6.3V
C6
N.U.
R5
N.U.
R3
47.5k
SVIN
SVIN
SVIN
31
42
31
42
C9
39pF
R4
20k
R2
698 C12
100pF
C13
10nF
R1
1.1k
L1
1.0µH
TP1
C11
47µF
6.3V
C10
47µF
6.3V
D1
DFLS220
31
42
J8
SGND
J7
VOUT 1.8V
U1 MIC22602-YML
Notes:
1. If buck capacitor on input rail is away (4 inches or more) from the MIC22602, install the 470µF buck capacitor near VIN.
2. Source impedance should be as low as 10m.
Micrel, Inc. MIC22602
October 2009 20 M9999-102809-A
Bill of Materials
Item Part Number Manufacturer Description Qty
C2012X5R0J226M TDK(1)
08056D226MAT AVX(2)
C1, C2, C3,
C4, C5
GRM21BR60J226ME39L Murata(3)
22µF/6.3V, 0805, Ceramic Capacitor 5
Open(VJ0603Y102KXQCW1BC) Vishay(4) 1nF, 0603, Ceramic Capacitor
Open(GRM188R71H102KA01D) Murata 1000pF/50V, X7R, 0603, Ceramic Capacitor
C6
Open(C1608C0G1H102J) TDK 1000pF/50V, COG, 0603, Ceramic Capacitor
1
VJ0603Y471KXACW1BC Vishay
C7 C1608X7R1H471M TDK
470pF, 0603, Ceramic Capacitor 1
Open(VJ0603Y102KXQCW1BC) Vishay 1nF, 0603, Ceramic Capacitor,
Open(GRM188R71H102KA01D) Murata 1000pF/50V, X7R, 0603, Ceramic Capacitor
C8
Open(C1608C0G1H102J) TDK 1000pF/50V, COG, 0603, Ceramic Capacitor
1
GRM1555C1H390JZ01D Murata 39pF/50V, COG, 0402, Ceramic Capacitor
C9 VJ0402A390KXQCW1BC BC components(5) 39pF/10V, 0402, Ceramic Capacitor 1
C3216X5R0J476M TDK 47µF/6.3V, X5R, 1206, Ceramic Capacitor
GRM31CR60J476ME19 Murata 47µF/6.3V, X5R, 1206, Ceramic Capacitor
C10, C11
GRM31CC80G476ME19L Murata 47µF/4V, X6S, 1206, Ceramic Capacitor
2
VJ0402A101KXQCW1BC Vishay 100pF, 0603, Ceramic Capacitor
C12 GRM1555C1H101JZ01D Murata 100pF/50V, COG, 0402, Ceramic Capacitor 1
C13 GRM188R71H103KA01D Murata 10nF, 0603, Ceramic Capacitor 1
SS2P2L Vishay
D1 DFLS220 Diodes, Inc.(6) Schottky Diode, 2A, 20V 1
SPM6530T-1R0M120 TDK 1µH, 12A, size 7x6.5x3mm
L1 HCP0704-1R0-R Coiltronics(7) 1µH, 12A, size 6.8x6.8x4.2mm 1
R1 CRCW06031101FKEYE3 Vishay Resistor, 1.1k, 0603, 1% 1
R2 CRCW04026980FKEYE3 Vishay Resistor, 698, 0603, 1% 1
R3 CRCW06034752FKEYE3 Vishay Resistor, 47.5k, 0603, 1% 1
R4 CRCW04022002FKEYE3 Vishay Resistor, 20k, 0402, 1% 1
R5 Open(CRCW06031003FRT1) Vishay Resistor, 100k, 0603, 1% 1
Open(2N7002E) Vishay
Q1
Open(CMDPM7002A)
Central
Semiconductor(8)
Signal MOSFET – SOT-23-6 1
U1 MIC22602YML Micrel(9) 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. BC Components: www.bccomponents.com
6. Diodes, Inc.: www.diodes.com
7. Coiltronics:coiltronics.com
8. Central Semiconductor: www.centralsemi.com
9. Micrel, Inc.: www.micrel.com
Micrel, Inc. MIC22602
October 2009 21 M9999-102809-A
PCB Layout Recommendations
Top Silk
Top Layer
Micrel, Inc. MIC22602
October 2009 22 M9999-102809-A
Mid Layer 1
Mid Layer 2
Micrel, Inc. MIC22602
October 2009 23 M9999-102809-A
Bottom Silk
Bottom Layer
Micrel, Inc. MIC22602
October 2009 24 M9999-102809-A
Package Information
24-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
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.
© 2009 Micrel, Incorporated.
