MIC22200 DATA SHEET (11/05/2015) DOWNLOAD

MIC22200
2A Integrated Switch Synchronous
Buck Regulator with Frequency
Programmable from 800kHz to 4MHz
General Description
Features
The Micrel MIC22200 is a high-efficiency, 2A integrated
switch synchronous buck (step-down) regulator. The
MIC22200 switching frequency is programmable from
800kHz to 4MHz, allowing the customer to optimize their
designs either for efficiency or for the smallest footprint.
The regulator achieves efficiencies as high as 95% while
still switching at 1MHz over a broad load range.
The ultra high-speed control loops keep the output voltage
within regulation even under the 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 MIC22200 offers a full range of sequencing and
tracking options. The EN/DLY pin, combined with the
Power-On-Reset (POR) pin, allows multiple outputs to be
sequenced in many ways during turn on and turn off. The
RC (ramp control) pin allows the device to be connected to
another device in the MIC22X00 family of products to keep
the output voltages within a certain delta V on start up.
®
The MIC22200 is available in a 3mm × 3mm 12-pin MLF
package 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.
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•
•
•
•
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•
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Input voltage range: 2.6V to 5.5V
Adjustable output voltage option down to 0.7V
Output load current to 2A
Full sequencing and tracking capability
Easy RC compensation
Power-On-Reset (POR) output
Efficiency >90% across a broad load range
Operating frequency: Programmable from 800 kHz up to
4MHz
Ultra-fast transient response
100% maximum duty cycle
Fully integrated MOSFET switches
Micropower shutdown
Thermal-shutdown and current-limit protection
Available in Pb-free 3mm × 3mm MLF-12-pin MLF®
Package
–40°C to +125°C junction temperature range
Applications
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High power density point-of-load conversion
Servers/routers
DVD recorders and multimedia players
Computing peripherals
Base stations
FPGAs, DSP and low voltage ASIC devices
_________________________________________________________________________________________________________________________
Typical Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
December 2010
M9999-120310-C
Micrel, Inc.
MIC22200
Ordering Information
Part Number
Nominal Output Voltage
MIC22200YML
Adjustable
Junction Temperature Range(1)
−40°C to +125°C
Package
Lead Finish
®
3mm × 3mm 12-Pin MLF
Lead Free(1)
Note:
®
MLF is a green RoHS-compliant package. Lead finish is NiPdAu. Mold compound is halogen free.
Pin Configuration
12-Pin MLF® (ML)
Pin Description
Pin Number
Pin Name
Pin Function
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.
1
POR
2
RC
Ramp Control. Capacitor to GND from this pin determines the slew rate of output voltage during
start-up. This can be used for tracking capability as well as for soft start.
3
CF
External capacitor to adjust switching frequency.
4
SGND
Signal Ground (signal): Ground (GND)
5
COMP
Compensation Pin (input): Placing an RC to GND will compensate the device. See Applications
section.
6
FB
7
SVIN
Signal Power Supply Voltage (input): Requires bypass capacitor to GND.
8
PVIN
Power Supply Voltage (input): Requires bypass capacitor to GND.
9
SW
10
PGND
Power Ground (power): Ground (GND)
11
DELAY
Delay (input)
12
EN/DLY
Enable (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.
ePad
GND
Exposed Pad (Power): You must make a full connection to a GND plane for full output power to be
released.
December 2010
Feedback (input): Input to the error amplifier; connected to the external resistor divider network to
set the output voltage.
Switch (output): From internal power MOSFET output switches.
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MIC22200
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (PVIN, SVIN ) ............................................+6V
Output Switch (SW)..........................................................6V
Logic Voltage (EN/DLY, POR, DELAY) ............VIN to -0.3V
Control Voltage (CF, RC, COMP, FB) ..............VIN to -0.3V
Lead Temperature (soldering 10s)............................. 260°C
Storage Temperature Range (Ts) .............−65°C to +150°C
EDS Rating(3) .................................................................. 2kV
Supply Voltage (VIN)..................................... +2.6V to +5.5V
Junction Temperature Range (TJ).......−40°C ≤ TJ ≤ +125°C
Thermal Resistance
3mm × 3mm MLF-12L (θJA) ...............................40°C/W
Electrical Characteristics(4)
TA = 25°C with VIN = VEN = 3.3V, unless otherwise specified. Bold values indicate −40°C ≤ TJ ≤ +125°C
Parameter
Condition
Min.
Supply Voltage Range
Under-Voltage Lockout Threshold
Typ.
2.6
(turn-on)
2.4
UVLO Hysteresis
2.5
Max.
Units
5.5
V
2.6
V
280
mV
Quiescent Current, PWM mode
VEN ≥ 1.34V; VFB = 0.9V
1.2
2
mA
Shutdown Current
VEN = 0V
3.7
10
µA
Feedback Voltage
± 2% (over temperature)
0.686
0.7
0.714
V
0.8
1
1.2
MHz
Oscillator Frequency
FB Pin Input Current
1
nA
Current Limit
VFB = 0.9*VNOM
Output Voltage Line Regulation
VIN = 2.6V to 5.5V
0.2
%
Output Voltage Load Regulation
100mA < ILOAD < 2A, VIN = 3.3V
0.2
%
Maximum Duty Cycle
VFB ≤ 0.5V
Switch ON-Resistance PFET
Switch ON-Resistance NFET
ISW = 1000mA VFB=0.5V
ISW = -1000mA VFB=0.9V
EN/DLY Threshold Voltage
VIN=3.3V
2
5.5
8
100
%
0.18
0.10
1.14
EN/DLY Hysteresis
A
1.24
Ω
1.34
12
V
mV
VIN=3.3V
1.14
EN/DLY Source Current
VIN = 2.6 to VIN = 5.5V
0.7
1
1.3
µA
RC Source Current
Ramp Control Current
0.7
1
1.3
µA
POR IPG(LEAK)
VPORH = 5.5V; POR = High
POR VPG(LO)
Output Logic-Low Voltage
(undervoltage condition), IPOR = 5mA
DELAY Threshold Voltage
DELAY Hysteresis
1.24
1.34
6
mV
1
2
135
V
µA
mV
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. Specification for packaged product only.
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MIC22200
Electrical Characteristics(4) (Continued)
TA = 25°C with VIN = VEN = 3.3V, unless otherwise specified. Bold values indicate −40°C ≤ TJ ≤ +125°C
Parameter
POR VPG
Condition
Threshold, % of VOUT below nominal
Typ.
Max.
Units
7.5
10
12.5
%
1
%
Over-Temperature Shutdown
160
°C
Over-Temperature Shutdown
Hysteresis
25
°C
December 2010
Hysteresis
Min.
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MIC22200
Typical Characteristics
10
Shutdown Current
vs. Input Voltage
10
8
8
6
6
4
4
2
2
Shutdown Current
vs. Temperature
1600
Quiescent Current
vs. Input Voltage
1500
1400
1300
0
2.5
1300
1200
TA = 25°C
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
5.5
Quiscent Current
vs. Temperature
0
0.71
No Switching
FB = 0.9V
TA = 25°C
1100
02 55 07 5 100 125
TEMPERATURE (°C)
Reference Voltage
vs. Input Voltage
1000
2.5
0.71
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
5.5
Reference Voltage
vs. Temperature
1250
0.705
0.705
1200
0.7
1150
1100
VIN = 3.3V
No Switching
FB = 0.9V
TA = 25°C
1050
1000
1.3
0.7
TA = 25°C
02 55 07 5 100 125
TEMPERATURE (°C)
Enable Voltage
vs. Temperature
0.695
0.69
2.5
16
0.695
VIN = 3.3V
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
5.5
Enable Hysterisis
vs. Temperature
15
1.26
1100
02 55 07 5 100 125
TEMPERATURE (°C)
Frequency
vs. Temperature
1075
14
1050
13
1.22
1025
12
1.18
11
1000
10
1.14
1.1
0.69
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
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975
9
8
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
5
950
CF = 220pF
VIN = 3.3V
02 55 07 5 100 125
TEMPERATURE (°C)
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Micrel, Inc.
MIC22200
Typical Characteristics (Continued)
Channel RDSON
vs. Temperature
225
215
205
140
100
135
130
95
125
90
195
120
185
115
110
175
Efficiency VOUT=3.3V
Channel RDSON
vs. Temperature
85
80
105
165
155
100
95
75
145
90
70
0
02 55 07 5 100 125
TEMPERATURE (°C)
Frequency
vs. CF
5
4.5
Efficiency VOUT=1.8V
95
90
3
85
2.5
80
2
75
75
70
70
65
65
1
0.5
60
0
50
0
CF CAPICITOR (pF)
December 2010
2
100
VIN = 3.3V
90
1.5
0.5
1
1.5
OUTPUT CURRENT (A)
Efficiency VOUT=1.2V
100
95
4
3.5
02 55 07 5 100 125
TEMPERATURE (°C)
VIN = 5V
VIN = 3.3V
85
VIN = 5.0V
80
0.5
1
1.5
OUTPUT CURRENT (A)
6
2
60
0
VIN = 5.0V
0.5
1
1.5
OUTPUT CURRENT (A)
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MIC22200
Functional Characteristics
December 2010
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MIC22200
Functional Diagram
Figure 1. MIC22200 Functional Diagram
December 2010
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MIC22200
Functional Description
PVIN, SVIN
PVIN is the input supply to the internal 180mΩ
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 the PVIN supply.
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
section for more detail.
EN/DLY
This pin is internally fed with a 1µA current source to
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.
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 pin capacitor.
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.
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.
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.
CF
Adding a capacitor to this pin can adjust switching
frequency from 800kHz to 4MHz. The CF capacitor must
be connected between the CF pin and power ground.
COMP
The MIC22200 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.
December 2010
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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MIC22200
in a fault condition. For best electrical performance, the
inductor should be placed very close to the SW nodes of
the IC. For this reason, the heat of the inductor is
somewhat coupled to the IC, so it offers some level of
protection if the inductor gets too hot. 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.
DC resistance is also important. While DCR is inversely
proportional to size, DCR can represent a significant
efficiency loss. Refer to the Efficiency Considerations
below for a more detailed description.
Application Information
The MIC22200 is a 2A Synchronous step-down regulator
IC with an adjustable switching frequency from 800kHz
to 4MHz, voltage mode PWM control scheme. The other
features include tracking and sequencing control for
controlling multiple output power systems, POR.
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,
aside from losing most of their capacitance over
temperature, they also become resistive at high
frequencies. This reduces their ability to filter out highfrequency noise.
EN/DLY Capacitor
EN/DLY pin 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 CEN/DLY to 1.25V. Therefore:
Output Capacitor
The MIC22200 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 MIC22200 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 MIC22200.
TEN/DLY =
1.24 × CEN/DLY
1.10 − 6
CF Capacitor
Adding a capacitor to this pin can adjust switching
frequency from 800kHz to 4MHz. CF sources 400µA out
of the IC to charge the CF capacitor to set up the
switching frequency. The switch period is simply the time
it takes 400µA to charge CF to 1.0V (±2%). Therefore:
Inductor Selection
Inductor selection will be determined by the following
(not necessarily in the order of importance):
Capacitor CF
Frequency
56pF
4.4MHz
68pF
4MHz
Size requirements
82pF
3.4MHz
DC resistance (DCR)
100pF
2.8MHz
150pF
2.1MHz
180pF
1.7MHz
220pF
1.4MHz
270pF
1.2MHz
330pF
1.1MHz
390pF
1.05MHz
470pF
1MHz
•
Inductance
•
Rated current value
•
•
The MIC22200 is designed for use with 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 MIC22200 to prevent overheating
December 2010
Table 1. CF vs. Frequency
It is necessary to connect the CF capacitor between the
CF pin and power ground.
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MIC22200
The region, 0.2A to 2A, efficiency loss is dominated by
MOSFET RDSON and inductor DC losses. Higher input
supply voltages will increase the gate-to-source voltage
on the internal MOSFETs, reducing the internal RDSON.
This improves efficiency by reducing DC losses in the
device. All but the inductor losses are inherent to the
device. 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:
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power consumed:
⎛ VOUT × IOUT ⎞
Efficiency % = ⎜
⎟ × 100
⎝ VIN × IIN ⎠
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 draw
from a battery increases the devices operating time,
critical in hand held devices.
There are mainly two loss terms in switching converters:
static losses and switching losses. Static 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. 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 current required to
drive the gates on and in the frequency range from
800kHz to 4MHz and the switching transitions make up
the switching losses.
Figure 2 shows an efficiency curve. The portion, from 0A
to 0.2A, 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.
LPD = IOUT 2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
⎡ ⎛
⎞⎤
VOUT × IOUT
⎟⎟⎥ × 100
Efficiency % = ⎢1 − ⎜⎜
⎣ ⎝ (VOUT × IOUT ) + LPD ⎠⎦
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 due
to the inductance becomes a significant factor. When
light load efficiencies become more critical, a larger
inductor value may be desired. Larger inductances
reduce 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:
94
92
Efficiency
vs. Inductance
4.7µH
90
88
1µH
86
84
82
80
78
76
0
0.2 0.4 0.6 0.8
1
1.2
OUTPUT CURRENT (A)
Figure 3. Efficiency vs. Inductance
Figure 2. Efficiency Curve
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MIC22200
The resistor divider network for a desired VOUT is given
by:
Compensation
The MIC22200 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 MIC22200 is capable of
extremely fast transient responses.
The MIC22200 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 26kHz to ensure
2×Π× L × C
stability can be achieved. The minimum recommended
inductor value is 0.47µH and minimum recommended
output capacitor value is 22µF. The tradeoff between
changing these values is that 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
in Table 2:
(
R2 =
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.
)
CÆ
LÈ
0.47µH
22-47µF
47µF100µF
100µF470µF
0*-10pF
22pF
33pF
†
1µH
0 -15pF
15-22pF
33pF
2.2µH
15-33pF
33-47pF
100-220pF
PWM Operation
The MIC22200 is a voltage-mode, pulse-width
modulation (PWM) controller. By controlling the ratio of
on-to-off time, or 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 MIC22200 will run at 100% duty
cycle.
The MIC22200 provides constant switching from 800kHz
to 4MHz with synchronous internal MOSFETs. The
internal MOSFETs include a 180mΩ high-side PChannel MOSFET from the input supply to the switch pin
and a 100mΩ N-Channel MOSFET from the switch pinto-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.
Other methods of regulation, such as burst and skip
modes, have frequency spectrums that change with load
that can interfere with sensitive communication
equipment.
* VOUT > 1.2V, † VOUT > 1V
Table 2. Compensation Capacitor Selection
Sequencing and Tracking
The MIC22200 provides additional pins to provide
up/down sequencing and tracking capability for
connecting multiple voltage regulators together.
Note: For compensation values for various output
voltages and inductor values refer to Table 4.
Feedback
The MIC22200 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.
December 2010
R1
⎛ VOUT ⎞
− 1⎟
⎜
⎝ VREF
⎠
EN/DLY Pin
The EN/DLY 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.
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MIC22200
Sequencing:
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 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/DLY pin 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 pin
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 pin continues to charge to a
voltage VDD. When FB falls below 90% of nominal, POR
is asserted low immediately. However, if EN/DLY pin is
driven low, POR will fall immediately to the low state and
DELAY pin will begin to fall as the external capacitor is
discharged by the 1µA current sink. When the threshold
of VDD -1.24V is crossed, 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 × CDELAY
matched at TPOR =
.
1.10 − 6
Figure 4. Sequencing MIC22200 Circuit
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 MIC22200 to be
used in systems requiring voltage tracking or ratio-metric
voltage tracking at startup.
There are two ways of using the RC pin:
•
Externally driven from a voltage source
•
Externally attached capacitor sets output ramp
up/down rate
Figure 5. Window Sequencing Example
In the first case, driving RC with a voltage from 0V to
VREF will program 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 × CRC
is given by TRAMP =
where TRAMP is the time
1.10 − 6
from 0 to 100% nominal output voltage.
Sequencing and Tracking Examples
There are four distinct variations which are easily
implemented using the MIC22200. The two sequencing
variations are Windowed and Delayed. The two tracking
variants are Normal and Ratio Metric. Figures 5 thru 10
illustrate methods for connecting two MIC22200’s to
achieve these requirements.
December 2010
Figure 6. Delayed Sequencing Example
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MIC22200
Normal Tracking:
Radio Metric Tracking:
Figure 7. Normal Tracking Circuit
Figure 9. Radio Metric Tracking Circuit
Figure 8. Normal Tracking Example
Figure 10. Radio Metric Tracking Example
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MIC22200
Figure 13 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 5.5A 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.
An alternative method here shows an example of a VDDQ
and 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.
Figure 11. DDR Memory Tracking Circuit
Figure 13. Current-Limit Detail
Thermal Considerations
The MIC22200 is packaged in the MLF® 3mm x 3mm, 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 = TA + PD × RθJA
Figure 12. DDR Memory Tracking Example
where: PD is the power dissipated within the MLF®
package and is typically 0.8W at 2A for VIN = 5V and
VOUT = 1.8V load. This has been calculated for a 1µH
inductor and details can be found in Table 3.
Current Limit
The MIC22200 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.
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MIC22200
TA is the Operating Ambient temperature.
Example:
To calculate the junction temperature for a 50°C
ambient:
TJ = TA + PDI . RθJA
TJ = 50 + 0.8 x 40
TJ = 82°C
This is below the maximum of 125°C.
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.
VOUT
@2A
VIN
3V
VIN
3.5V
VIN
4V
VIN
4.5V
VIN
5V
1
0.86822
0.81512
0.7836
0.77014
0.76194
1.2
0.87796
0.8247
0.79362
0.77956
0.76842
1.8
0.93972
0.86722
0.82568
0.8095
0.80076
2.5
0.91848
0.90504
0.85466
0.83296
0.81846
3.3
—
—
0.8764
0.842
0.8326
Table 3. Power Dissipation (W) for 2A Output
VIN = 5V
VOUT
L
COUT
CCOMP
RCOMP
CFF
RFF
CFB
RFB
1.1V
3.3µH
2 x 47µF
100pF
5k Ω
N.U.
4.7k Ω
100pF
8.2k Ω
1.3V
1.5µH
2 x 47µF
100pF
5k Ω
1nF
4.7k Ω
100pF
5.49k Ω
1.8V
2.2µH
2 x 47µF
100pF
5k Ω
1nF
4.7k Ω
100pF
3.0k Ω
4.2V
1.5µH
2 x 47µF
100pF
20k Ω
1nF
4.7k Ω
100pF
953 Ω
Table 4. Compensation Selection
Figure 14. Table 4 Schematic Reference
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MIC22200
Design Example
MIC22200YML Evaluation Board Schematic
Bill of Materials
Item
Part Number
C2012X5R0J106K
C1
GRM2196R60J106K
C2
C4
C1608X5R0J105K
TDK(1)
Murata(2)
06036D105KAT2A
AVX (3)
C1608C0G1H102J
TDK(1)
GRM1885C1H102JA01D
Murata(2)
AVX
C1608X7R1H332K
TDK(1)
Murata(2)
AVX
C1608C0G1H470J
TDK(1)
Murata(2)
AVX
C1608C0G1H221J
TDK(1)
Murata(2)
AVX
1
Capacitor, 1µF, 6.3V, X5R, Size 0603
1
Capacitor, 1nF, 50V, NPO, Size 0603
3
Capacitor, 3.3nF, 50V, X7R, Size 0603
1
Capacitor, 47pF, 50V, NPO, Size 0603
1
Capacitor, 220pF, 50V, NPO, Size 0603
1
(3)
06035A470JAT2A
06035A221JAT2A
Capacitor, 10µF, 6.3V, X5R, Size 0805
(3)
06035C332KAT2A
GRM1885C1H221JA01D
Qty.
(3)
06035A102KAT2A
GQM1885C1H470JB01D
C6
Murata(2)
AVX(3)
GRM188R71H332KA01D
C5
TDK
Description
(1)
08056D106KAT2A
GRM188R60J105KA01D
C3, C7, C8
Manufacturer
(3)
Notes:
1.
TDK: www.tdk.com.
2.
Murata: www.murata.com.
3.
AVX: www.avx.com.
4.
Vishay: www.vishay.com
5.
Micrel, Inc.: www.micrel.com.
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MIC22200
Bill of Materials (Continued)
Item
Part Number
C3216X5R0J476M
C9, C10
C11
GRM31CR60J476ME19L
Manufacturer
Murata(2)
AVX
C1608C0G1H101J
TDK(1)
06035A101JAT2A
Qty.
Murata(2)
AVX
Capacitor, 47µF, 6.3V, X5R, Size 1206
2
Capacitor, 100pF, 50V, NPO Size 0603
1
(3)
1206D476MAT2A
GRM1885C1H101JA01D
Description
TDK(1)
(3)
Vishay (4)
L1
IHLP1616BZER1R0M11
Inductor , 1µH, 5A
1
R1
CRCW06031602FKEA
AVX (3)
Resistor, 16K, 1%, Size 0603
1
CRCW06031002FKEA
AVX
(3)
Resistor, 10K, 1%, Size 0603
2
AVX
(3)
Resistor, 20K, 1%, Size 0603
1
(3)
R2, R3
R4
CRCW060320K0FKEA
R5
CRCW06032R20FKEA
AVX
R6
CRCW060349R9FKEA
AVX (3)
U1
MIC22200YML
Micrel(5)
Resistor, 2.2Ω, 1%, Size 0603
1
Resistor, 49.9Ω, 1%, Size 0603
1
Integrated 2A Synchronous Buck Regulator
1
Notes:
1.
TDK: www.tdk.com.
2.
Murata: www.murata.com.
3.
AVX: www.avx.com.
4.
Vishay: www.vishay.com
5.
Micrel, Inc.: www.micrel.com.
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MIC22200
PCB Layout Recommendations
Top Silk
Top Layer
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MIC22200
PCB Layout Recommendations (Continued)
Bottom Layer
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MIC22200
Package Information
12-Pin MLF® (ML)
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MIC22200
Recommended Land Pattern for 32-Pin 3mm x 3mm MLF®
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.
© 2008 Micrel, Incorporated.
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