MC33072AP ,HIGH BANDWIDTH SINGLE SUPPLY OPERATIONAL AMPLIFIERSELECTRICAL CHARACTERISTICS (V = +15 V, V = –15 V, R = connected to ground, unless otherwise noted. ..
MC33072AP ,HIGH BANDWIDTH SINGLE SUPPLY OPERATIONAL AMPLIFIERS
MC33072D ,Single Supply 3V to 44V, Dual Operational AmplifierMAXIMUM RATINGSRating Symbol Value UnitSupply Voltage (from V to V ) V +44 VEE CC SInput Differenti ..
MC33072DG , Single Supply 3.0 V to 44 V Operational Amplifiers
MC33072DR2 ,Single Supply 3V to 44V, Dual Operational Amplifier
MC33072DR2 ,Single Supply 3V to 44V, Dual Operational Amplifier
MC74HC154DW ,1-of-16 Decoder/Demultiplexer
MC74HC154N ,1-of-16 Decoder/DemultiplexerMAXIMUM RATINGS*ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ..
MC74HC157 ,Quad 2-Input Data Selectors/MultiplexersMaximum Ratings are those values beyond which damage to the device may occur.ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ..
MC74HC157A ,Data Selector/Multiplexer 2-Input QLOGIC DIAGRAM112A0A = Assembly Location5A1NIBBLE WL = Wafer Lot11A INPUTS 4 YY = YearA2Y014 WW = Wo ..
MC74HC157AD ,Data Selector/Multiplexer 2-Input QELECTRICAL CHARACTERISTICS (C = 50 pF, Input t = t = 6.0 ns)L r fÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ..
MC74HC157ADR2 ,Data Selector/Multiplexer 2-Input QMAXIMUM RATINGS*ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ SymbolÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ParameterÎÎÎÎÎ ValueÎÎÎ UnitThis d ..
MC33072ADR2-MC33072AP-MC33072DR2-MC33341-MC33364D2R2-TL431IDR2
Single Supply 3V to 44V, Dual Operational Amplifier
AND8024/D
Off-Line Critical
Conduction Switching
Power Supply with Voltage
and Current Limiting
Prepared by: Larry Hayes, Jim Spangler
ON Semiconductor
Phoenix, AZ 85008
ABSTRACTThe need for a small, economical solution for switching
power supplies and for battery chargers has increased.
These applications generally require both voltage limiting
and current limiting. These must be very efficient and
produce a low amount of EMI radiated noise. The MC33364
is a critical conduction control IC that can be configured in
a resonant turn–off mode to reduce the amount of EMI
generated during turn–off of the power MOSFET. The
MC33341 is a secondary side controller that contains the
band gap reference to provide a very tight tolerance voltage
reference. The MC33341 also allows for current limiting
thus providing an almost square loop of voltage and current
needed for lithium–ion battery charging. Combining these
two devices produces a much more cost–effective solution
than other approaches offer.
THE CLASSIC APPROACHIn prior years, a very cost efficient and economical design
approach was demanded for battery chargers and power
supplies. The unit had to be current limited on the secondary
side and provide the proper voltage output. The supply often
did not support universal input. One circuit approach to
meet this need is shown in Figure 1. This is a classical
blocking oscillator. This circuit has its roots back to the old
vacuum tube days, and was updated by Bob Haver in 1984
and presented at various switching power supply seminars
[1], [2]. This is a variable frequency unit that operates in
what is known today as the critical conduction mode.
The unit starts by having the gate of the TMOS� or power
MOSFET turned on by the series resistors R1 and R2. The
current through the primary of the coupled inductor
transformer ramps up linearly. The auxiliary winding on the
transformer is phased to provide positive (in phase) gate
voltage. The TMOS device is “turned off” when
primary current produces approximately 0.7 volts across the
source resistor (Rsource), the bipolar junction transistor
(BJT) becomes forward biased and “turns on”.
When the BJT is “turned on”, the charge on the gate is
removed and the TMOS power FET is “turned off”. The
auxiliary voltage is reversed as the voltage on the primary is
reversed in order to release its stored energy to the
secondary. As long as there is energy flowing to the
secondary, the auxiliary voltage is negative and the gate
voltage is negative. The small signal diode (1N914) in series
with the collector of the BJT keeps the device from operating
in a reverse mode. In lieu of 1N914, a 1N4148 or 1N4150
may be used.
With the TMOS power FET in the “off” mode, the coupled
energy stored in the air gap of the inductor is released to the
secondary. The secondary energy flows to the load by way
of Schottky diode D2. When the coupled energy is depleted,
the voltage across the both the primary, secondary and
auxiliary windings decreases to zero.
The transformer is not a perfect device, so there is a small
amount of energy remaining in the primary. This is the
energy in the leakage inductance of the primary. This causes
the voltage across the transformer to start to ring with the
COSS capacitance of the FET. This “turn–off” ring has the
effect of reducing the drain–source voltage of the FET, and
causes the auxiliary winding to develop a positive voltage.
This positive voltage, along with two resistors R1 and R2
places a positive voltage on the gate of the TMOS power
FET; this restarts the energy storage cycle.
