MIC2230
Dual Synchronous 800mA/800mA
Step-Down DC/DC Regulator
MLF and MicroLead Frame 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
March 2008
M9999-032808
General Description
The MIC2230 is dual output, high-efficiency synchronous
step-down DC/DC converter. The MIC2230 is ideally
suited for portable systems which demand high power
conversion efficiencies and fast transient performance,
while offered in a very small package. The MIC2230 offers
an ultra-low quiescent current in light load mode assuring
minimum current draw from battery powered applications
in standby modes. The MIC2230 was designed to only
require miniature 2.2µH inductors and 10µF ceramic
capacitors.
The MIC2230 features a selectable mode that allows the
user to trade-off lowest noise performance for low power
efficiency. Trickle Mode
TM
operation provides ultra-high
efficiency at light loads, while PWM operation provides
very low ripple noise performance. To maximize battery life
in low-dropout conditions, MIC2230 can operate with a
maximum duty cycle of 100%.
The MIC2230 is available in a space-saving 3mm × 3mm
MLF
®
-12L package with a junction temperature 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
• High Efficiency: Over 96%
• Ultra-low quiescent current: Only 28µA
• Ultra-low shutdown current less than 1µA
• Fast transient performance
• 2.5MHz PWM operation
• High output current capability per channel: 800mA
• No Schottky Diodes Required
• Stable with 2.2µH inductor, 10µF ceramic capacitor
• Adjustable output voltage down to 0.8V
• Built-in soft-start circuitry
• Current limit protection
• Automatic switching into light load mode operation
• /FPWM pin allows low noise all-PWM mode operation
• Power good output with internal 5µA current source
allows sequencing with programmable delay time
• Small Thermally Enhanced 3mm × 3mm MLF
®
package
Applications
• Cellular phones
• PDAs
• Digital Cameras
• MP3 Players
• PC Cards
• Wireless and DSL Modems
___________________________________________________________________________________________________________
Typical Application
Micrel, Inc. MIC2230
March 2008
2 M9999-032808
Ordering Information
Part Number V
OUT1
V
OUT2
Junction
Temperature Range Package Lead Finish
MIC2230-AAYML Adj. Adj. –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-521YML 1.28V 1.65V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-G4YML 1.8V 1.2V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-GF9YML 1.8V 1.545V
–40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-GFHYML 1.8V 1.575V
–40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-GSYML 1.8V 3.3V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-GWYML 1.8V 1.6V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-J4YML 2.5V 1.2V
–40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-S4YML 3.3V 1.2V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
MIC2230-SSYML 3.3V 3.3V –40°C to +125°C 12-Pin 3mm x 3mm MLF
®
Pb-Free
Note:
Other voltages available. Contact Micrel Marketing for details.
Pin Configur ation
Adjustable
MIC2230-AAYML
12-Pin MLF
®
(ML)
(Top View)
Fixed
MIC2230-xxYML
12-Pin MLF
®
(ML)
(Top View)
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March 2008
3 M9999-032808
Pin Description
Pin Number
Adjustable Pin Number
Fixed
Pin Name Pin Name
1 – FB2
Feedback 2: For adjustable voltage options connect the
external resistor divider network to FB2 to set the output
voltage of regulator 2. Nominal value is 0.8V.
2 2 EN2
Enable 2 input. Logic low powers down regulator 2. Logic
high powers up regulator 2. MIC2230 features built-in soft-
start circuitry that reduces in-rush current and prevents the
output voltage from overshooting at start up.
3 3 AVIN
Analog Supply Voltage: Supply voltage for the analog control
circuitry. Requires bypass capacitor to GND.
4 4 SW2 Switch node for regulator 2, connected to external inductor.
5 5 AGND Analog (signal) ground.
6 6 PGND Power ground.
7 7 /FPWM
Forced PWM Mode Bar. Grounding this pin forces the device
to stay in constant frequency PWM mode only. Pulling this
pin high enables automatic Trickle Mode
TM
operation.
8 8 SW1 Switch node for regulator 1, connected to external inductor.
9 9 VIN
Supply Voltage: Supply voltage for the internal switches and
drivers.
10 10 PGOOD
Power Good Output. This output is pulled down unless the
regulator 1 output voltage is within +6.25% and -8.5% of
regulation. After the output voltage is in regulation, the output
starts to go high with an internal 5µA current source. A delay
time could be programmed by tying a capacitor to this pin.
11 11 EN1
Enable 1 input. Logic low powers down regulator 1. Logic
high powers up regulator 1. MIC2230 features built-in soft-
start circuitry that reduces in-rush current and prevents the
output voltage from overshooting at start up.
12 – FB1
Feedback 1: For adjustable voltage options connect to the
external resistor divider network to FB1 to set the output
voltage of regulator 1. Nominal value is 0.8V.
– 1 OUT2
Output Voltage 2. For fixed output voltage options connect
OUT2 to the output voltage of regulator 2.
– 12 OUT1
Output Voltage 1. For fixed output voltage options connect
OUT1 to the output voltage of regulator 1.
EP EP EP Back-side pad.
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March 2008
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Absolute Maximum Ratings(1)
Supply Voltage (V
IN
).......................................................+6V
Enable 1 Voltage ………………………………………... +6V
Enable 2 Voltage ……………………………………….. +6V
Logic Input Voltage (V
EN
, V
FPWM
)............................ 0V to V
IN
Storage Temperature (T
S
) ........................–65°C to +150°C
ESD .............................................................................. 2KV
Operating Ratings(2)
Supply Voltage (V
IN
) ........................................ 2.5V to 5.5V
Junction Temperature (T
J
) ........................ –40°C to +125°C
Package Thermal Resistance (θ
JA
) ..........................60°C/W
Electrical Characteristics(4)
T
A
= 25°C with V
IN
= V
EN1
= V
EN2
=3.6V, V
OUT1
, V
OUT2
, L= 2.2µH, C = 10µF, unless otherwise specified. Bold values indicate –40ºC ≤ T
J
≤ +125ºC.
Parameter Condition Min Typ Max Units
Supply Voltage and Current
Supply Voltage Range 2.5 5.5 V
UVLO (rising) 2.3 2.4 2.5 V
UVLO Hysteresis 100 mV
PWM Mode Supply
Current /FPWM = Low, I
OUT
= 200mA 560 950 µA
Trickle Mode
TM
Supply
Current /FPWM = High 28 50 µA
Shutdown Quiescent
Current V
EN
= 0V 0.1 1 µA
Output Voltage Accuracy
Feedback voltage, V
FB
Adjustable 0.780 0.8 0.820 V
Output voltage, V
OUT
Fixed Output Options
-2.5
+2.5 %
Feedback bias current 10 nA
Output Voltage Line
Regulation 2.5V ≤ V
IN
≤ 5.5V 0.1
0.5 %
Output Voltage Load
Regulation
V
IN
= 5V, I
OUT
= 10mA to 800mA, /FPWM = 0V
V
IN
= 3V; I
OUT
= 10mA to 800mA, /FPWM = 0V 0.5 %
Ripple in Trickle Mode
TM
V
IN
=3.6V; I
OUT
= 1mA; C
OUT
= 10µF, L = 2.2µH. 40 mV
Logic Inputs
On 0.8 1.2 V
EN Input Threshold
Off 0.3 0.7 V
EN Input Current 0.01 1 µA
On
0.6×V
IN
V /FPWM Input Threshold
Off
0.3×V
IN
V
/FPWM Input Current 0.01 1 µA
Micrel, Inc. MIC2230
March 2008
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Electrical Characteristics (cont.)(4)
Parameter Condition Min Typ Max Units
Protection
Current Limit Peak Switch Current, V
OUT
= 0V 0.9 1.2 1.8 A
Control
Maximum Duty Cycle V
FB
= 0.7V 100 %
Oscillator
PWM Mode Frequency 2.125 2.5 2.875 MHz
Power Good
Power Good Reset
Threshold
Upper Threshold
Lower Threshold
-14 6.25
-8.5
12
%
PGOOD Series
Resistance 1 1.4 kΩ
PGOOD Pull-Up Current Output within 8.5% of regulation 5 µA
Power Switch
Switch On-Resistance I
SW
= 150mA (PFET)
I
SW
= 150mA (NFET)
0.4
0.35
Ω
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.
Micrel, Inc. MIC2230
March 2008
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Typical Characteristics
Micrel, Inc. MIC2230
March 2008
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Typical Characteristics (continued)
Micrel, Inc. MIC2230
March 2008
8 M9999-032808
Functional Characteristics
VIN = 3.6V, VOUT = 1.8V, L = 2.2µH, /FPWM = 0 VIN = 3.6V, VOUT = 1.8V, L = 2.2µH, /FPWM = 3.6V
Micrel, Inc. MIC2230
March 2008
9 M9999-032808
Functional Characteristics (continued)
Micrel, Inc. MIC2230
March 2008
10 M9999-032808
Functional Block Diagram
Functional Description
VIN
VIN provides power to the MOSFETs for the switch
mode regulator section, along with the current limiting
sensing. Due to the high switching speeds, a 10µF
capacitor is recommended close to VIN and the power
ground (PGND) pin for bypassing. Please refer to layout
recommendations.
AVIN
Analog V
IN
(AVIN) provides power to the analog supply
circuitry. AVIN and VIN must be tied together. Careful
layout should be considered to ensure high frequency
switching noise caused by VIN is reduced before
reaching AVIN. A 1µF capacitor as close to AVIN as
possible is recommended. See layout recommendations
for detail.
EN1
Enable 1 controls the on and off state of regulator 1. A
high logic on Enable 1 (EN1) activates regulator 1 while
a low logic deactivates regulator 1. MIC2230 features
built-in soft-start circuitry that reduces in-rush current
and prevents the output voltage from overshooting at
start up.
EN2
Enable 2 controls the on and off state of regulator 2. A
high logic on Enable 2 (EN2) activates regulator 2 while
a low logic deactivates regulator 2. MIC2230 features
built-in soft-start circuitry that reduces in-rush current
and prevents the output voltage from overshooting at
start up.
/FPWM
The Forced PWM Mode selects the mode of operation
for this device. Grounding this pin forces the device to
stay in constant frequency PWM mode only. Pulling this
pin high enables automatic selection of Trickle or PWM
mode operation, depending on the load. While /FPWM is
high and the load is below 100mA, the device will go into
Trickle Mode™. If the load is above 100mA, PWM mode
will automatically be selected. Do not leave this pin
floating.
PGOOD
The Power Good Output is pulled down unless the
regulator 1 output voltage is within +6.25% or -8.5% of
regulation. After the output voltage is in regulation, the
output starts to go high with an internal 5µA current
source. A delay time could be programmed by tying a
Micrel, Inc. MIC2230
March 2008
11 M9999-032808
capacitor to this pin. Using the circuit in Figure 1, if the
NFET is off and the input voltage is at 5 volts, a 390pF
external capacitor at the PGOOD pin will cause the
PGOOD pin voltage to rise from low to high in around
390µs.
Figure 1. Power Good Circuit
FB1/FB2
The feedback pin (FB) provides the control path to
control the output. For adjustable versions, a resistor
divider connecting the feedback to the output is used to
adjust the desired output voltage. The output voltage is
calculated as follows:
V
OUT
=V
REF
×R1
R2 +1
⎛
⎝
⎜
⎞
⎠
⎟
where V
REF
is equal to 0.8V.
A feedforward capacitor is recommended for most
designs using the adjustable output voltage option. To
reduce battery current draw, a 100kΩ feedback resistor
is recommended for use from the output to the FB pin
(R1). Also, a feedforward capacitor should be connected
between the output and feedback (across R1). The large
resistor value and the parasitic capacitance of the FB pin
can cause a high frequency pole that can reduce the
overall system phase margin. By placing a feedforward
capacitor, these effects can be significantly reduced.
Typically, a 22pF small ceramic capacitor is
recommended.
SW1/SW2
The switch (SW) pin connects directly to the inductor
and provides the switching current necessary to operate
in PWM mode. Due to the high speed switching on this
pin, the switch node should be routed away from
sensitive nodes.
PGND
Power ground (PGND) is the ground path for the high
current PWM mode. The current loop for the power
ground should be as small as possible and separate
from the Analog ground (AGND) loop. Refer to the layout
considerations for more details.
AGND
Signal 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 considerations for more
details.
Micrel, Inc. MIC2230
March 2008
12 M9999-032808
Applications Information
Input Capacitor
A minimum 2.2µF ceramic is recommended on the VIN
pin 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 high
frequency noise.
Output Capacitor
The MIC2230 was designed specifically for use with a
10µF or greater ceramic output capacitor. 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.
Inductor Selection
Inductor selection will be determined by the following
(not necessarily in the order of importance);
• Inductance
• Rated current value
• Size requirements
• DC resistance (DCR)
The MIC2230 was designed for use with a 2.2µH
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 to 20% 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 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.
Compensation
The MIC2230 is an internally compensated, current
mode buck regulator. Current mode is achieved by
sampling the peak current and using the output of the
error amplifier to pulse width modulate the switch node
and maintain output voltage regulation.
The MIC2230 is designed to be stable with a 2.2µH
inductor with a 10µF ceramic (X5R) output capacitor.
Feedback
The MIC2230 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
0.8V reference voltage and adjusts the output voltage to
maintain regulation. Calculating the resistor divider
network for the desired output is as follows;
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
=
1
V
V
R1
R2
REF
OUT
Where V
REF
is 0.8V and V
OUT
is the desired output
voltage.
A 100kΩ from the output to the feedback is
recommended for R1. Larger resistor values require an
additional capacitor (feed-forward) from the output to the
feedback. The large high-side resistor value and the
parasitic capacitance on the feedback pin (~10pF) can
cause an additional pole in the control loop. The
additional pole can create a phase loss at high
frequencies. This phase loss degrades transient
response by reducing phase margin. Adding feed-
forward capacitance negates the parasitic capacitive
effects of the feedback pin. A minimum 100pF capacitor
is recommended for feed forward capacitance.
Large feedback resistor values increase impedance,
making the feedback node more susceptible to noise
pick-up. A feed forward capacitor would also reduce
noise pick-up by providing a low impedance path to the
output.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied.
100
IV
IV
_%Efficiency
ININ
OUTOUT
×
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
×
×
=
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.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I
2
R. Power is dissipated in the
high-side switch during the on cycle. Power loss is equal
to the high side MOSFET R
DSON
multiplied by the Switch
Micrel, Inc. MIC2230
March 2008 13
M9999-032808
Current
2
. 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
is another DC loss. The current required driving the
gates on and off at a constant 2.5MHz frequency and the
switching transitions make up the switching losses.
The figure above shows an efficiency curve. From no
load to 100mA, efficiency losses are dominated by
quiescent current losses, gate drive and transition
losses. By forcing the MIC2230 into Trickle Mode™
(/FPWM=High), the buck regulator significantly reduces
the required switching current by entering into a PFM
(Pulse Frequency Modulation) mode. This significantly
increases efficiency at low output currents.
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, 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;
DCRIoutL_Pd
2
×=
From that, the loss in efficiency due to inductor
resistance can be calculated as follows;
100
L_PdIV
IV
1_LossEfficiency
OUTOUT
OUTOUT
×
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+×
×
−=
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.
Trickle Mode™ Operation
Trickle Mode™ operation is achieved by clamping the
minimum peak current to approximately 150mA. This
forces a PFM mode by comparing the output voltage to
the internal reference. If the voltage is less than 0.8V,
the MIC2230 turns on the high side until the peak
inductor current reaches approximately 150mA. A
separate comparator then monitors the output voltage. If
the feedback voltage is greater than 0.8V, the high side
switch is then used as a 10µA current source, never
turning off completely. This creates a highly efficient light
load mode by increasing the time it takes for the output
capacitor to discharge, delaying the amount of switching
required and increasing light load efficiency. When the
load current is greater than approximately 100mA, the
MIC2230 automatically switches to PWM mode.
FPWM Operation
In forced PWM Mode (/FPWM=LOW) the MIC2230 is
forced to provides constant switching at 2.5MHz with
synchronous internal MOSFETs throughout the load
current. In FPWM Mode, the output ripple can be as low
as 7mV.
Micrel, Inc. MIC2230
March 2008 14
M9999-032808
MIC2230 Adjustable Opti on (1.8V, 1.8V)
Bill of Materials
Item Part Number Manufacturer Description Qty
C1 C1608X5R0J106K TDK 10µF Ceramic Capacitor, 6.3V, X5R, Size 0603 1
C2 C1005X5R0J105K TDK 1µF Ceramic Capacitor, 6.3V, X5R, Size 0402 1
C3 C0603Y391KXXA Vishay 390pF Ceramic Capacitor, 25V, X7R, Size 0603 1
C4, C7 0603ZD106MAT AVX 10µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2
C5, C6 VJ0603A220KXXAT Vishay 22pF Ceramic Capacitor, 25V, NPO, Size 0603 2
CDRH2D11/HPNP-2R2NC Sumida 2.2µH, 1.1A I
SAT
., 120mΩ, (1.2mm × 3.2mm × 3.2mm)
LQH43CN2R2M03 Murata 2.2µH, 900mA I
SAT
., 110mΩ, (2.6mm × 3.2mm × 4.5mm)
L1, L2
EPL2014-222MLB Coilcraft 2.2µH, 1.3A I
SAT
., 120mΩ, (1.4mm x 1.8mm x 2.0mm)
2
R2, R4 CRCW06034423FT1 Vishay 442kΩ, 1%, Size 0603 2
R1, R3 CRCW06035493FT1 Vishay 549kΩ, 1%, Size 0603 2
U1 MIC2230-AAYML Micrel 2.5MHz Dual Phase PWM Buck Regulator 1
1. TDK: www.tdk.com
2. Murata: www.murata.com
3. Sumida: www.sumida.com
4. Vishay-Dale: www.vishay.com
5. AVX: www.avx.com
6. Micrel, Inc: www.micrel.com
Micrel, Inc. MIC2230
March 2008 15
M9999-032808
MIC2230 Fixed Option (1.8V, 1.575V)
Bill of Materials
Item Part Number Manufacturer Description Qty
C1 C1608X5R0J106K TDK 10µF Ceramic Capacitor, 6.3V, X5R, Size 0603 1
C2 C1005X5R0J105K TDK 1µF Ceramic Capacitor, 6.3V, X5R, Size 0402 1
C3 C0603Y391KXXA Vishay 390pF Ceramic Capacitor, 25V, X7R, Size 0603 1
C4, C5 0603ZD106MAT AVX 10µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2
CDRH2D11/HPNP-2R2NC Sumida 2.2µH, 1.1A I
SAT
., 120mΩ, (1.2mm × 3.2mm × 3.2mm)
LQH43CN2R2M03 Murata 2.2µH, 900mA I
SAT
., 110mΩ, (2.6mm × 3.2mm × 4.5mm)
L1, L2
EPL2014-222MLB Coilcraft 2.2µH, 1.3A I
SAT
., 120mΩ, (1.4mm x 1.8mm x 2.0mm)
2
U1 MIC2230-GFHYML Micrel 2.5MHz Dual Phase PWM Buck Regulator 1
1. TDK: www.tdk.com
2. Murata: www.murata.com
3. Sumida: www.sumida.com
4. Vishay-Dale: www.vishay.com
5. AVX: www.avx.com
6. Micrel, Inc: www.micrel.com
Micrel, Inc. MIC2230
March 2008 16
M9999-032808
Layout Recommendations
Top Layer
Bottom Layer
Micrel, Inc. MIC2230
March 2008 17
M9999-032808
Package Information
12-Pin 3mm × 3mm 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.
© 2007 Micrel, Incorporated.
