MIC33153 [MICREL]
4MHz PWM 1.2A Internal Inductor Buck Regulator with HyperLight Load and Power Good; 4MHz的PWM 1.2A内部电感的降压型稳压器的HyperLight负载和电源良好
| 型号： | MIC33153 |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | 4MHz PWM 1.2A Internal Inductor Buck Regulator with HyperLight Load and Power Good |
| 文件： | 总17页 (文件大小：919K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC33153
4MHz PWM 1.2A Internal Inductor
Buck Regulator with HyperLight Load™
and Power Good
General Description
Features
• Internal inductor
The MIC33153 is
a
high-efficiency 4MHz 1.2A
synchronous buck regulator with an internal inductor,
HyperLight Load™ mode, Power Good (PG) output
indicator, and programmable soft start. HyperLight Load™
provides very high efficiency at light loads and ultra-fast
transient response which makes the MIC33153 perfectly
suited for supplying processor core voltages. An additional
benefit of this proprietary architecture is very low output
ripple voltage throughout the entire load range with the use
of small output capacitors.
− Simplifies design to two external capacitors
• Input voltage: 2.7V to 5.5V
• Output voltage: fixed or adjustable (0.62V to 3.6V)
• Up to 1.2 A output current
• Up to 93% peak efficiency
• 85% typical efficiency at 1mA
• Power Good (PG) output
• Programmable soft start
• 22µA typical quiescent current
• 4MHz PWM operation in continuous mode
• Ultra-fast transient response
• Low ripple output voltage
The MIC33153 is designed so that only two external
capacitors as small as 2.2µF are needed for stability. This
gives the MIC33153 the ease of use of an LDO with the
efficiency of a HyperLight Load™ DC converter. The
MIC33153 achieves efficiency in HyperLight LoadTM mode
as high as 85% at 1mA, with a very low quiescent current
of 22µA. At higher loads, the MIC33153 provides a
constant switching frequency up to 4MHz.
− 35mVpp ripple in HyperLight Load™ mode
− 7mV output voltage ripple in full PWM mode
• 0.01µA shutdown current
• Thermal shutdown and current limit protection
• 14-pin 3.0 x 3.5 x 1.1mm MLF® package
The MIC33153 is available in 14-pin 3.0mm x 3.5mm
MLF® package with an operating junction temperature
range from –40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
• –40°C to +125°C junction temperature range
Applications
• Solid State Drives (SSD)
• Mobile handsets
• Portable media/MP3 players
• Portable navigation devices (GPS)
• WiFi/WiMax/WiBro modules
• Wireless LAN cards
• Portable applications
____________________________________________________________________________________________________________
Typical Application
Fixed Output Voltage
Adjustable Output Voltage
HyperLight Load is a trademark of Micrel, Inc.
MLF and MicroLeadFrame are registered trademark Amkor Technology Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-01200 • fax + 1 (408) 474-1000 • http://www.micrel.com
M9999-092910-A
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Micrel Inc.
MIC33153
Ordering Information
Nominal Output
Voltage
Junction Temperature
Range
Part Number1
Marking Code
Package2
−4
MIC33153-4YHJ
1.2V
–40°C to +125°C
–40°C to +125°C
14-pin 3.0 x 3.5 x 1.1mm MLF®
14-pin 3.0 x 3.5 x 1.1mm MLF®
33153
MIC
MIC33153YHJ
Adjustable
33153
Notes:
1. Other options available (1V - 3.3V). Contact Micrel Marketing for details.
2. MLF® is GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
14- Pin 3.0mm x 3.5mm MLF® (HJ)
14- Pin 3.0mm x 3.5mm MLF® (HJ)
Fixed Output Voltage
(Top View)
Adjustable Output Voltage
(Top View)
Pin Description
Pin
Number
(Fixed)
Pin
Number
(Adjustable)
Pin
Name
Pin Function
Soft Start: Place a capacitor from this pin to ground to program the soft start time.
Do not leave floating, 100pF minimum CSS is required.
1
2
1
2
SS
Analog Ground: Connect to central ground point where all high current paths meet
(CIN, COUT, PGND) for best operation.
AGND
VIN
3
4
3
4
Input Voltage: Connect a capacitor to ground to decouple the noise.
PGND Power Ground.
Output Voltage: The output of the regulator. Connect to SNS pin. For adjustable option,
connect to feedback resistor network.
5,6,7
8,9,10
11
5,6,7
8,9,10
11
OUT
SW
EN
Switch: Internal power MOSFET output switches before Inductor
Enable: Logic high enables operation of the regulator. Logic low will shut down the device.
Do not leave floating.
12
12
SNS
PG
Sense: Connect to VOUT as close to output capacitor as possible to sense output voltage.
Power Good: Open drain output for the Power Good (PG) indicator. Use a pull up resistor
from this pin to a voltage source to detect a power good condition.
13
13
14
NC
FB
Not Internally Connected.
−
14
Feedback: Connect a resistor divider from the output to ground to set the output voltage.
−
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MIC33153
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN)... …………………………..2.7V to 5.5V
Enable Input Voltage (VEN) .. ……………………….0V to VIN
Sense Voltage (VSNS) ..................................... 0.62V to 3.6V
Junction Temperature Range (TJ).. ….−40°C ≤ TJ ≤ +125°C
Thermal Resistance
Supply Voltage (VIN).......................................... −0.3V to 6V
Sense Voltage (VSNS) ........................................−0.3V to VIN
Output Switch Voltage (VSW).............................−0.3V to VIN
Enable Input Voltage (VEN)................................−0.3V to VIN
Power Good (PG) Voltage (VPG) .......................−0.3V to VIN
Storage Temperature Range ..……………−65°C to +150°C
Lead Temperature (soldering, 10 sec.)......................260°C
ESD Rating(3).................................................ESD Sensitive
3.0mm x 3.5mm MLF®-14 (θJA)..........................55°C/W
Electrical Characteristics(4)
TA = 25°C; VIN = VEN = 3.6V; COUT = 4.7µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
2.7
Typ.
Max.
5.5
Units
V
Supply Voltage Range
Under-Voltage Lockout Threshold
Under-Voltage Lockout Hysteresis
Quiescent Current
(Turn-On)
2.45
2.55
75
2.65
V
mV
µA
µA
IOUT = 0mA , SNS > 1.2 * VOUT Nominal
22
45
5
Shutdown Current
VEN = 0V; VIN = 5.5V
0.01
VIN = 3.6V if VOUTNOM < 2.5V, ILOAD = 20mA
VIN = 4.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA
Output Voltage Accuracy
+2.5
%
−2.5
Feedback Regulation Voltage
Current Limit
ILOAD = 20mA
0.6045
0.62
3.3
0.6355
V
A
SNS = 0.9*VOUTNOM
2.2
VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, ILOAD = 20mA
VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA
Output Voltage Line Regulation
Output Voltage Load Regulation
0.3
%/V
%/A
1mA < ILOAD < 1A, VIN = 3.6V if VOUTNOM < 2.5V
1mA < ILOAD < 1A, VIN = 5.0V if VOUTNOM ≥ 2.5V
ISW = 100mA PMOS
0.8
0.85
0.2
0.19
4
PWM Switch ON-Resistance
Ω
ISW = −100mA NMOS
Maximum Switching Frequency
Soft Start Time
IOUT = 300mA
MHz
µs
µA
%
VOUT = 90%, CSS = 470pF
VSS = 0V
320
2.7
92
Soft Start Current
PG Threshold (Rising)
PG Threshold Hysteresis
PG Delay Time
86
96
7
%
Rising
68
µs
V
Enable Threshold
Turn-On
0.5
0.9
0.1
160
1.2
2
Enable Input Current
Over-Temperature Shutdown
µA
°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. Human body model, 1.5kΩ in series with 100pF.
4. Specification for packaged product only.
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MIC33153
Typical Characteristics
Efficiency (VOUT = 3.3V)
Efficiency (VOUT = 2.5V)
Efficiency (VOUT = 1.8V)
100
90
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
VIN = 4.2V
V
IN = 4.2V
V
IN = 3.6V
V
IN = 5.0V
VIN = 3.6V
VIN = 5.5V
VIN = 3.0V
VIN = 5.5V
VIN = 4.2V
COUT = 4.7µF
1000
COUT = 4.7µF
1000
COUT = 4.7µF
1000
1
10
100
10000
1
10
100
10000
10000
5.7
1
10
100
10000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Efficiency (VOUT = 1.5V)
Efficiency (VOUT = 1.2V)
Efficiency (VOUT = 1.0V)
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
IN = 3.0V
V
IN = 3.0V
VIN = 3.0V
V
IN = 4.2V
V
IN = 3.6V
V
IN = 4.2V
VIN = 3.6V
VIN = 3.6V
V
IN = 4.2V
COUT = 4.7µF
1000
COUT = 4.7µF
COUT = 4.7µF
1
10
100
10000
1
10
100
1000
1
10
100
1000
10000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
Quiescent Current
vs. Input Voltage
Current Limit
vs. Input Voltage
Shutdown Current
vs. Input Voltage
40
35
30
25
20
15
10
5
5.00
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
30
25
20
15
10
5
T = 20°C
T = 125°C
T = - 45°C
No Switching
SNS > 1.2 * VOUTNOM
COUT = 4.7µF
0
0
2.7
3.2
3.7
4.2
4.7
5.2
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.7
3.2
3.7
4.2
4.7
5.2
5.7
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Line Regulation
(Light Load)
Line Regulation
(Heavy Load)
Load Regulation
1.900
1.880
1.860
1.840
1.820
1.800
1.780
1.760
1.740
1.720
1.700
1.900
1.880
1.860
1.840
1.820
1.800
1.780
1.760
1.740
1.720
1.700
1.300
1.250
1.200
1.150
1.100
VOUTNOM = 1.8V
IOUT = 40mA
C
OUT = 4.7µF
V
IN = 4.2V
IOUT = 160mA
IOUT = 300mA
VIN = 3.6V
IOUT = 1mA
VIN = 3.0V
IOUT = 1000mA
IOUT = 500mA
VOUTNOM = 1.2V
OUT = 4.7µF
VOUTNOM = 1.8V
COUT = 4.7µF
C
2.5
3
3.5
4
4.5
5
5.5
0
200 400 600 800 1000 1200
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
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MIC33153
Typical Characteristics
Enable Threshold
vs. Temperature
Feedback Voltage
vs. Temperature
0.65
UVLO Threshold
vs. Temperature
2
1.8
1.6
1.4
1.2
1
2.56
2.55
2.54
2.53
2.52
2.51
2.50
2.49
2.48
2.47
2.46
ON
0.64
0.63
0.62
0.61
0.60
Turn ON
0.8
0.6
0.4
0.2
0
Turn OFF
OFF
VOUT = 3.6V
VIN = 3.6V
0.59
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (%)
SW Frequency
vs. Temperature
Enable Voltage
VOUT Rise Time
vs. CSS
vs. Input Voltage
Enable ON
6
5.5
5
2
1.8
1.6
1.4
1.2
1
1000000
100000
10000
1000
100
4.5
4
3.5
3
2.5
2
0.8
0.6
0.4
0.2
0
1.5
1
Enable OFF
V
IN = 3.6V
COUT = 4.7µF
OUT = 150mA
C
OUT = 4.7µF
10
I
0.5
0
Load = 400mA
1
2.7
3.2
3.7
4.2
4.7
5.2
5.7
-40 -20
0
20 40 60 80 100 120
100
1000
10000
100000 1000000
INPUT VOLTAGE (V)
CSS (pF)
TEMPERATURE (°C)
Switching Frequency
vs. Output Current
5
4.5
4
VIN = 3.6V
3.5
3
VIN = 4.2V
2.5
2
1.5
1
0.5
0
0.1
1
10
100
1000 10000
OUTPUT CURRENT (mA)
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Micrel Inc.
MIC33153
Functional Characteristics
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Micrel Inc.
MIC33153
Functional Characteristics (Continued)
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Micrel Inc.
MIC33153
Functional Characteristics (Continued)
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Micrel Inc.
MIC33153
Functional Diagram
Figure 1. Simplified MIC33153 Functional Block Diagram – Fixed Output Voltage
Figure 2. Simplified MIC33153 Functional Block Diagram – Adjustable Output Voltage
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MIC33153
Functional Description
Power Good PG
VIN
The Power Good (PG) pin is an open drain output which
indicates logic high when the output voltage is typically
above 92% of its steady state voltage. When the output
voltage is below 86%, the PG pin indicates logic low. A
pull up resistor of more than 10kꢀ should be connected
The input supply (VIN) provides power to the internal
MOSFETs for the switch mode regulator along with the
internal control circuitry. The VIN operating range is 2.7V
to 5.5V so an input capacitor, with a minimum voltage
rating of 6.3V, is recommended. Due to the high
switching speed, a minimum 2.2µF bypass capacitor
placed close to VIN and the power ground (PGND) pin is
required. Refer to the layout recommendations for
details.
from PG to VOUT
.
SS
The soft start (SS) pin is used to control the output
voltage ramp up time. The approximate equation for the
ramp time in milliseconds is:
EN
T(ms) = 270x103 x ln (10) x CSS
A logic high signal on the enable pin activates the output
voltage of the device. A logic low signal on the enable
pin deactivates the output and reduces supply current to
0.01µA. MIC33153 features external soft start circuitry
via the soft start (SS) pin that reduces in rush current
and prevents the output voltage from overshooting at
start up. Do not leave the EN pin floating.
where:
T is the time in milliseconds and CSS is the external soft
start capacitance (in Farads).
For example, for a CSS = 470pF, Trise ~ 0.3ms or 300µs.
See the Typical Characteristics curve for a graphical
guide. The minimum recommended value for CSS is
100pF.
SW
The switch (SW) connects directly to one end of the
inductor and provides the current path during switching
cycles. The other end of the inductor is connected to the
load, SNS pin and output capacitor. Due to the high
speed switching on this pin, the switch node should be
routed away from sensitive nodes whenever possible.
FB
The feedback (FB) pin is provided for the adjustable
voltage option (no internal connection for fixed options).
This is the control input for programming the output
voltage. A resistor divider network is connected to this
pin from the output and is compared to the internal
0.62V reference within the regulation loop.
SNS
The sense (SNS) pin is connected to the output of the
device to provide feedback to the control circuitry. The
SNS connection should be placed close to the output
capacitor. Refer to the layout recommendations for more
details.
The output voltage can be programmed between 0.65V
and 3.6V using the following equation:
R1
R2
⎛
⎞
⎟
AGND
VOUT = VREF × 1+
⎜
⎝
⎠
The analog ground (AGND) is the ground path for the
biasing and control circuitry. The current loop for the
signal ground should be separate from the power ground
(PGND) loop. Refer to the layout recommendations for
more details.
where:
R1 is the top resistor, R2 is the bottom resistor.
PGND
Example feedback resistor values:
The power ground pin is the ground path for the high
current in PWM mode. The current loop for the power
ground should be as small as possible and separate
from the analog ground (AGND) loop as applicable.
Refer to the layout recommendations for more details.
VOUT
1.2V
1.5V
1.8V
2.5V
3.3V
R1
R2
274k
316k
301k
324k
309k
294k
221k
158k
107k
71.5k
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MIC33153
Maintaining high efficiency serves two purposes. It
reduces power dissipation in the power supply, reducing
the need for heat sinks and thermal design
considerations and it reduces consumption of current for
battery powered applications. Reduced current draw
from a battery increases the devices operating time and
is critical in hand held devices.
Application Information
The MIC33153 is a high performance DC-to-DC step
down regulator offering a small solution size. With the
HyperLight Load™ switching scheme, the MIC33153 is
able to maintain high efficiency throughout the entire
load range while providing ultra-fast load transient
response. The following sections provide additional
device application information.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I2R. Power is dissipated in the
high side switch during the on cycle. Power loss is equal
to the high side MOSFET RDSON multiplied by the Switch
Current squared. During the off cycle, the low side N-
channel MOSFET conducts, also dissipating power.
Device operating current also reduces efficiency. The
product of the quiescent (operating) current and the
supply voltage represents another DC loss. The current
required driving the gates on and off at a constant 4MHz
frequency and the switching transitions make up the
switching losses.
Input Capacitor
A 2.2µF ceramic capacitor or greater should be placed
close to the VIN pin and PGND pin for bypassing. A
Murata GRM188R60J475ME84D, size 0603, 4.7µF
ceramic capacitor is recommended based upon
performance, size, and cost. A X5R or X7R temperature
rating is recommended for the input capacitor. Y5V
temperature rating capacitors, aside from losing most of
their capacitance over temperature, can also become
resistive at high frequencies. This reduces their ability to
filter out high frequency noise.
Output Capacitor
The MIC33153 is designed for use with a 2.2µF or
greater ceramic output capacitor. Increasing the output
capacitance will lower output ripple and improve load
transient response but could also increase solution size
or cost. A low equivalent series resistance (ESR)
ceramic output capacitor such as the Murata
GRM188R60J475ME84D, size 0603, 4.7µF ceramic
capacitor is recommended based upon performance,
size, and cost. Both the X7R or X5R temperature rating
capacitors are recommended. The Y5V and Z5U
temperature rating capacitors are not recommended due
to their wide variation in capacitance over temperature
and increased resistance at high frequencies.
Compensation
The MIC33153 is designed to be stable with a 4.7µF
ceramic (X5R) output capacitor.
Figure 3. Efficiency Under Load
Figure 3 shows an efficiency curve. From no load to
100mA, efficiency losses are dominated by quiescent
current losses, gate drive and transition losses. By using
the HyperLight Load™ mode, the MIC33153 is able to
maintain high efficiency at low output currents.
Duty Cycle
The typical maximum duty cycle of the MIC33153 is
80%.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied:
⎛
⎜
⎜
⎞
⎟
⎟
VOUT ×IOUT
VIN ×IIN
Efficiency % =
×100
⎝
⎠
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MIC33153
Over 100mA, efficiency loss is dominated by MOSFET
RDSON and inductor losses. Higher input supply voltages
will increase the gate to source threshold on the internal
MOSFETs, thereby 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:
HyperLight Load™ Mode
MIC33153 uses a minimum on and off time proprietary
control loop (patented by Micrel). When the output
voltage falls below the regulation threshold, the error
comparator begins a switching cycle that turns the
PMOS on and keeps it on for the duration of the
minimum on time. This increases the output voltage. If
the output voltage is over the regulation threshold, then
the error comparator turns the PMOS off for a minimum
off time until the output drops below the threshold. The
NMOS acts as an ideal rectifier that conducts when the
PMOS is off. Using a NMOS switch instead of a diode
allows for lower voltage drop across the switching device
when it is on. The asynchronous switching combination
between the PMOS and the NMOS allows the control
loop to work in discontinuous mode for light load
operations. In discontinuous mode, the MIC33153 works
in pulse frequency modulation (PFM) to regulate the
output. As the output current increases, the off time
decreases, thus provides more energy to the output.
This switching scheme improves the efficiency of
MIC33153 during light load currents by only switching
when it is needed. As the load current increases, the
MIC33153 goes into continuous conduction mode (CCM)
and switches at a frequency centered at 4MHz. The
equation to calculate the load when the MIC33153 goes
into continuous conduction mode may be approximated
by the following formula:
PDCR = IOUT2 x DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
⎡
⎤
⎥
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
VOUT ×IOUT
Efficiency Loss = 1−
×100
⎢
VOUT ×IOUT +PDCR
⎢
⎣
⎥
⎦
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.
The effect of MOSFET voltage drops and DCR losses in
conjunction with the maximum duty cycle combine to
limit maximum output voltage for a given input voltage.
The following graph shows this relationship based on the
typical resistive losses in the MIC33153:
(V − V
)×D
⎛
⎞
IN
OUT
I
> ⎜
⎜
⎟
⎟
LOAD
2L×f
⎝
⎠
As shown in the above equation, the load at which
MIC33153 transitions from HyperLight Load™ mode to
PWM mode is a function of the input voltage (VIN), output
voltage (VOUT), duty cycle (D), inductance (L) and
frequency (f). For example, if VIN = 3.6V, VOUT=1.8V,
D=0.5, f=4MHz and the internal inductance of MIC33153
is 0.47μH, then the device will enter HyperLight Load™
mode or PWM mode at approximately 200mA.
VOUTMAX vs. VIN
5
100mA
4.5
4
400mA
3.5
3
2.5
2
1.2A
800mA
1.5
1
0.5
0
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
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Micrel Inc.
MIC33153
As can be seen in the diagram, total thermal resistance
RθJA = RθJC + RθCA. Hence this can also be written:
Power Dissipation Considerations
As with all power devices, the ultimate current rating of
the output is limited by the thermal properties of the
package and the PCB it is mounted on. There is a
simple, Ohm’s law type of relationship between thermal
resistance, power dissipation and temperature which is
analogous to an electrical circuit:
T = P
×
Rθ
)
+ T
J
DISS
JA AMB
Since effectively all of the power loss in the converter is
dissipated within the MIC33153 package, PDISS can be
calculated thus:
1
P
= P
× ( −1)
DISS
OUT
η
Where:
η = Efficiency taken from efficiency curves
RθJC and RθJA are found in the operating ratings section
From this simple circuit, one can calculate VX if one
knows ISOURCE, VZ and the resistor values, RXY and RYZ
using the equation:
of the datasheet.
Example:
A MIC33153 is intended to drive a 1A load at 1.8V and is
placed on a printed circuit board which has a ground
plane area of at least 25mm square. The voltage source
is a Li-ion battery with a lower operating threshold of 3V
and the ambient temperature of the assembly can be up
to 50ºC.
V
= I
×
(
R
+R
)
+ V
X
SOURCE
XY
YZ Z
Thermal circuits can be considered using these same
rules and can be drawn similarly replacing current
sources with power dissipation (in Watts), resistance
Summary of variables:
º
IOUT = 1A
with thermal resistance (in C/W) and voltage sources
with temperature (in ºC):
VOUT = 1.8V
VIN = 3V to 4.2V
TAMB = 50ºC
RθJA = 55ºC/W from Datasheet
η @ 1A = 80% (worst case with VIN=4.2V from the
Typical Characteristics Efficiency vs. Load graphs)
1
PDISS = 1.8⋅1×(
−1) = 0.45W
0.80
The worst case switch and inductor resistance will
increase at higher temperatures, so a margin of 20% can
be added to account for this:
Now replacing the variables in the equation for VX, one
can find the junction temperature (TJ) from power
dissipation, ambient temperature and the known thermal
resistance of the PCB (RθCA) and the package (RθJC):
PDISS = 0.45 x 1.2 = .54W
T = P
×
(
Rθ +Rθ
)
+ T
J
DISS
JC
CA AMB
Therefore:
TJ = 0.54W x (55 ºC/W) + 50ºC
TJ = 79.7ºC
This is well below the maximum 125ºC.
M9999-092910-A
September 2010
13
Micrel Inc.
MIC33153
Typical Application Circuit (Fixed Output)
Bill of Materials
Item
Part Number
Manufacturer Description
Qty.
C1608X5R0J475K
GRM188R60J475KE19D
C1608NPO0J471K
CRCW06031002FKEA
TDK(1)
Murata(2)
TDK(1)
C1, C2
Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603
2
C3
Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603
Resistor, 10k, Size 0603
1
2
R3, R4
Vishay(3)
4MHz 1.2A Buck Regulator with HyperLight Load™ Mode
and Fixed Output Voltage
U1
MIC33153-xYHJ
Micrel, Inc.(4)
1
Notes:
1. TDK: www.tdk.com.
2. Murata: www.murata.com.
3. Vishay: www.vishay.com.
4. Micrel, Inc.: www.micrel.com.
M9999-092910-A
September 2010
14
Micrel Inc.
MIC33153
Typical Application Circuit (Adjustable Output)
Bill of Materials
Item
Part Number
Manufacturer Description
Qty.
C1608X5R0J475K
GRM188R60J475KE19D
C1608NPO0J471K
−
TDK(1)
Murata(2)
TDK(1)
C1, C2
Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603
2
C3
Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603
Not Fitted (NF)
1
0
1
1
2
C4
−
R1
CRCW06033013FKEA
CRCW06031583FKEA
CRCW06031002FKEA
Vishay(3)
Vishay(3)
Vishay(3)
Resistor, 301k, Size 0603
Resistor, 158k, Size 0603
Resistor, 10k, Size 0603
R2
R3, R4
4MHz 1.2A Buck Regulator with HyperLight Load™ Mode
and Adjustable Output Voltage
U1
MIC33153-YHJ
Micrel, Inc.(4)
1
1. TDK: www.tdk.com.
2. Murata : www.murata.com.
3. Vishay: www.vishay.com.
4. Micrel, Inc.: www.micrel.com.
M9999-092910-A
September 2010
15
Micrel Inc.
MIC33153
PCB Layout Recommendations
Top Layer
Bottom Layer
M9999-092910-A
September 2010
16
Micrel Inc.
MIC33153
Package Information
14-Pin 3.0mm x 3.5mm MLF® (HJ)
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.
© 2010 Micrel, Incorporated.
M9999-092910-A
September 2010
17
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