MSK183(2001) 查看數據表（PDF） - M.S. Kennedy
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MSK183 Datasheet PDF : 6 Pages
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APPLICATION NOTES
POWER SUPPLIES:
For the MSK 182/183 maximum total supply voltage is speci-
fied as 60V. However, dual and unbalanced power supply op-
eration is permissible as long as total supply voltage does not
exceed 60V.
POWER SUPPLY BYPASSING:
Power supply terminals must be effectively decoupled with a
high and low frequency bypass circuit to avoid power supply
induced oscillation. An effective decoupling scheme consists
of a 0.1µF ceramic capacitor in parallel with a 10µF tantalum
capacitor for each power supply pin to ground. In addition, it is
recommended that a 0.01µF capacitor be placed between ±Vcc
as close to the MSK 182 as possible.
CURRENT LIMIT:
The MSK 182 and MSK 183 offer accurate, user-selectable
current limit. Unlike typical designs that use a power resistor in
series with the output to sense load, the MSK 182 and MSK
183 sense the load indirectly and therefore do not require a
resistor to handle the full output current. Current limit is se-
lected by controlling the input to the ILIM pin.
The easiest method is to use a resistor or potentiometer con-
nected between-Vcc and the ILIM pin. Use the following equa-
tion to select proper resistor value:
Rcc=
71,250
ILIM
-13.75KΩ
A low level control signal (0-330µA) can also be used to con-
trol the current level digitally. If the pin is left open, the current
is programmed to OA, while connecting ILIM directly to -Vcc
sets the output current to it's maximum, typically 5A.
SAFE OPERATING AREA:
The safe operating area curve is a graphical representation of
the power handling capability of the amplifier under various
conditions. Power dissipation of the device is equal to the prod-
uct of the voltage across the output transistor times the output
current. As can be seen in the curve, safe operating current
decreases with an increase in temperature as well as an in-
crease in the voltage across the output transistor. Therefore,
for maximum amplifier performance it is important to keep case
temperature as low as possible and to keep ±Vcc as close to
the output rail as achievable.
THERMAL PROTECTION:
The MSK 182 and MSK 183 are equipped with thermal pro-
tection circuitry that protects each amplifier from damage caused
by excessive junction temperature. The output is disabled when
the junction temperature reaches approximately 160°C. After
the junction temperature cools to approximately 140°C, the
output is again enabled. The thermal protection may cycle on
and off depending on the output load and signal conditions;
this may have an undesirable effect on the load.
It should be noted that even though this internal protection
circuitry does protect against overload conditions, it does not
take the place of proper heat sinking. For reliable operation,
junction temperature should be limited to 150°C, maximum.
ENABLE/STATUS PIN:
This pin actually has a dual function. First, when the pin is
forced low, the output stage is disabled. Second, it can be
monitored to determine if the device is in thermal shutdown.
These functions can be used on the same device with either
single or dual supplies. For normal operation, the E/S pin must
be left open or pulled at least 2.4 volts above the negative rail.
In noisy applications, a small value capacitor between the E/S
pin and -Vcc may be required.
To disable the output, the user must pull the E/S pin low, no
greater than 0.8V above -Vcc. To once again enable the de-
vice, the E/S pin must be brought at least 2.4 volts above -Vcc
or be disconnected. It should be noted that when the E/S pin is
high, the internal thermal shutdown is still active.
If the E/S pin is used to monitor thermal shutdown, during
normal operation the voltage on the E/S pin is typically 3.5V
above -Vcc. Once shutdown has occurred this voltage will drop
to approximately 350mV above -Vcc.
COMPENSATION:
For normal operation output compensation is not typically
required. However, if the MSK 182 or MSK 183 is intended to
be driven into current limit the user may find that an R/C net-
work is required. A snubber network from the output to ground
for each amplifier will provide stability. If driving large capaci-
tive or inductive loads, a snubber network will also enhance
stability. Typically 3Ω to 10Ω in series with 0.01µF is accept-
able.
TYPICAL CONNECTION DIAGRAM
3
PRELIMINARY Rev. C 8/01
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