MSK163 View Datasheet(PDF) - M.S. Kennedy
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MSK163 Datasheet PDF : 5 Pages
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APPLICATION NOTES
CURRENT LIMIT
Current limit resistor value can be calculated as follows:
Rcl=3/Ilim
It is recommended that the user set up the value of current limit
as close as possible to the maximum expected output current
to protect the amplifier. The minumum value of current limit
resistance is 33 ohms. The maximum practical value is 500
ohms. Current limit will vary with case temperature. Refer to
the typical performance graphs as a guide. Since load current
passes through the current limit resistor, a loss in output volt-
age swing will occur. The following formula approximates out-
put voltage swing reduction:
Vr= Io * Rcl
When the device is in current limit, there will be spurious oscil-
lations present on the negative half cycle. The frequency of
the oscillation is application dependent and can not be pre-
dicted. Oscillation will cease when the device comes out of
current limit.
INPUT PROTECTION
Input protection curcuitry within the MSK 162/163 will clip
differential input voltages greater than 16 volts. The inputs are
also protected against common mode voltages up to the supply
rails as well as static discharge. There are 300 ohm current
limiting resistors in series with each input. These resistors may
become damaged in the event the input overload is capable of
driving currents above 1mA. If severe overload conditions are
expected, external input current limiting resistors are recom-
mended.
SAFE OPERATING AREA (SOA)
The MOSFET output stage of this power operational ampli-
fier has two distinct limitations:
1. The current handling capability of the die metallization.
2. The temperature of the output MOSFET's.
NOTE: The output stage is protected against transient flyback.
However, for protection against sustained, high energy flyback,
external fast-recovery reverse biased diodes should be used.
OUTPUT SNUBBER NETWORK
A 100 ohm resistor and a 330pF capacitor connected in se-
ries from the output of the amplifier to ground is recommended
for applications where load capacitance is less than 330pF.
For larger values of load capacitance, the output snubber net-
work may be omitted. If loop stability becomes a problem due
to excessively high load capacitance, a 100 ohm resistor may
be added between the output of the amplifier and the load. A
small tradeoff with bandwidth must be made in this configura-
tion. The graph below illustrates the effect of capacitive load.
Note that the compensation capacitor must have a voltage rat-
ing greater than the total rail to rail power supply voltage.
STABILITY
The MSK 162/163 are internally compensated for closed loop
gains of 10 V/V or greater. The majority of applications the
MSK 162/163 are used in involve gains greater than 10 V/V
because the output is capable of swinging up to +/- 141V and
the maximum differential input voltage is only +/- 16V. A
large gain is necessary to make full use of the output voltage
swing capability of the amplifier when input voltages are small.
If closed loop gains of less than 10 V/V are required, refer to
the MSK 158/159 data sheets. The MSK 158/159 operational
amplifiers are identical to the MSK 162/163 except pins two
and six are compensation pins. The user can tailor op-amp
performance with the external connection of a series resistor-
capacitor snubber network. An effective method of checking
amplifier stability is to apply the worst case capacitive load to
the output of the amplifier and drive a small signal square wave
across it. If overshoot is less than 25%, the system will gen-
erally be stable.
3
Rev. C 6/02
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