MC33166D2TR4(2002) Просмотр технического описания (PDF) - ON Semiconductor
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MC33166D2TR4 Datasheet PDF : 20 Pages
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MC34166, MC33166
Switch Output
The output transistor is designed to switch a maximum
of 40 V, with a minimum peak collector current of 3.3 A.
When configured for step–down or voltage–inverting
applications, as in Figures 19 and 23, the inductor will
forward bias the output rectifier when the switch turns off.
Rectifiers with a high forward voltage drop or long turn–on
delay time should not be used. If the emitter is allowed to
go sufficiently negative, collector current will flow,
causing additional device heating and reduced conversion
efficiency. Figure 9 shows that by clamping the emitter to
0.5 V, the collector current will be in the range of 100 µA
over temperature. A 1N5822 or equivalent Schottky barrier
rectifier is recommended to fulfill these requirements.
Undervoltage Lockout
An Undervoltage Lockout comparator has been
incorporated to guarantee that the integrated circuit is fully
functional before the output stage is enabled. The internal
5.05 V reference is monitored by the comparator which
enables the output stage when VCC exceeds 5.9 V. To
prevent erratic output switching as the threshold is crossed,
0.9 V of hysteresis is provided.
Thermal Protection
Internal Thermal Shutdown circuitry is provided to protect
the integrated circuit in the event that the maximum junction
temperature is exceeded. When activated, typically at 170°C,
the latch is forced into a ‘reset’ state, disabling the output
switch. This feature is provided to prevent catastrophic
failures from accidental device overheating. It is not
intended to be used as a substitute for proper heatsinking.
The MC34166 is contained in a 5–lead TO–220 type package.
The tab of the package is common with the center pin (Pin 3)
and is normally connected to ground.
DESIGN CONSIDERATIONS
Do not attempt to construct a converter on wire–wrap
or plug–in prototype boards. Special care should be taken
to separate ground paths from signal currents and ground
paths from load currents. All high current loops should be
kept as short as possible using heavy copper runs to
minimize ringing and radiated EMI. For best operation, a
tight component layout is recommended. Capacitors CIN,
CO, and all feedback components should be placed as close
to the IC as physically possible. It is also imperative that the
Schottky diode connected to the Switch Output be located as
close to the IC as possible.
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