MIC912YM5 MICREL [Micrel Semiconductor], MIC912YM5 Datasheet - Page 11

• Manufacturer Part Number: MIC912YM5
• Description: 200MHz Low-Power SOT23-5 Op Amp
• Manufacturer: MICREL [Micrel Semiconductor]

Application Information
The
operational amplifier featuring very low supply current
and excellent stability. This device is unity gain stable
with RL ≤ 200Ω and capable of driving high capacitance
loads.
Stability Considerations
The MIC912 is unity gain stable and it is capable of
driving unlimited capacitance loads, but some design
considerations are required to ensure stability. The
output needs to be loaded with 200Ω resistance or
less and/or have sufficient load capacitance to
achieve stability (refer to the “Load Capacitance vs.
Phase Margin” graph).
For applications requiring a little less speed, Micrel offers
the MIC910, a more heavily compensated version of the
MIC912 which provides extremely stable operation for all
load resistance and capacitance.
Driving High Capacitance
The MIC912 is stable when driving high capacitance
(see “Typical Characteristics: Gain Bandwidth and
Phase Margin vs. Load Capacitance”) making it ideal for
driving long coaxial cables or other high-capacitance
loads.
Phase margin remains constant as load capacitance is
increased. Most high-speed op amps are only able to
drive limited capacitance.
Feedback Resistor Selection
Conventional op amp gain configurations and resistor
selection apply, the MIC912 is NOT a current feedback
device. Resistor values in the range of 1k to 10k are
recommended.
Micrel, Inc.
October 2007
MIC912
Note: increasing load capacitance does reduce
the speed of the device (see “Typical Character-
istics: Gain Bandwidth and Phase Margin vs.
Load”). In applications where the load capaci-
tance reduces the speed of the op amp to an
unacceptable level, the effect of the load capaci-
tance can be reduced by adding a small resistor
(<100Ω) in series with the output.
is
a
high-speed,
voltage-feedback
11
Layout Considerations
All high speed devices require careful PCB layout. The
following guidelines should be observed: Capacitance,
particularly on the two inputs pins will degrade
performance; avoid large copper traces to the inputs.
Keep the output signal away from the inputs and use a
ground plane.
It is important to ensure adequate supply bypassing
capacitors are located close to the device.
Power Supply Bypassing
Regular supply bypassing techniques are recom-
mended. A 10µF capacitor in parallel with a 0.1µF
capacitor on both the positive and negative supplies are
ideal. For best performance all bypassing capacitors
should be located as close to the op amp as possible
and all capacitors should be low ESL (equivalent series
inductance),
Surface-mount ceramic capacitors are ideal.
Thermal Considerations
The SOT23-5 package, like all small packages, has a
high thermal resistance. It is important to ensure the IC
does not exceed the maximum operating junction (die)
temperature of 85°C. The part can be operated up to the
absolute maximum temperature rating of 125°C, but
between 85°C and 125°C performance will degrade, in
particular CMRR will reduce.
A MIC912 with no load, dissipates power equal to the
quiescent supply current * supply voltage.
When a load is added, the additional power is dissipated
in the output stage of the op amp. The power dissipated
in the device is a function of supply voltage, output
voltage and output current.
Ensure the total power dissipated in the device is no
greater than the thermal capacity of the package. The
SOT23-5 package has a thermal resistance of 260°C/W.
Max.
Total Power Dissipation = P
Allowable
P
P
D(no load)
D(output stage)
ESR
= (V
Power
= (V
V+
(equivalent
– V
V+
Dissipatio
– V
V–
)I
S
V–
D(no load)
)I
OUT
n
series
=
T
+ P
J(max)
M9999-100507
D(output stage)
260W
resistance).
−
T
MIC912
A(max)