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M1014A View Datasheet(PDF) - STMicroelectronics

Part Name
Description
Manufacturer
M1014A Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
TSM1014
Principles of Operation and Application Tips
Therefore, for most adapter and battery charger applications, a quarter-watt, or half-watt resistor to make
the current sensing function is sufficient.
The current sinking outputs of the two trans-conductance operational amplifiers are common (to the
output of the IC). This makes an ORing function which ensures that whenever the current or the voltage
reaches too high values, the optocoupler is activated.
The relation between the controlled current and the controlled output voltage can be described with a
square characteristic as shown in the following V/I output-power graph.
Figure 3: Output Voltage versus Output Current
Vout
Voltage regulation
TSM1014 Vcc : independent power supply
Secondary current regulation
Iout
0
TSM1014 Vcc : On power output
Primary current regulation
5.3 Compensation
The voltage-control trans-conductance operational amplifier can be fully compensated. Both its output
and negative input are directly accessible for external compensation components.
An example of a suitable voltage-control compensation network is shown in Figure 2 on page 4. It
consists of a capacitor Cvc1=2.2nF and a resistor Rcv1=22Kin series.
The current-control trans-conductance operational amplifier can be fully compensated. Both of its output
and negative input are directly accessible for external compensation components.
An example of a suitable current-control compensation network is also shown in Figure 2 on page 4. It
consists of a capacitor Cic1=2.2nF and a resistor Ric1=22Kin series.
5.4 Start-up and short circuit conditions
Under start-up or short-circuit conditions the TSM1014 is not provided with a high enough supply voltage.
This is due to the fact that the chip has its power supply line in common with the power supply line of the
system.
Therefore, the current limitation can only be ensured by the primary PWM module, which should be
chosen accordingly.
If the primary current limitation is considered not to be precise enough for the application, then a sufficient
supply for the TSM1014 has to be ensured under all conditions. For this, it would be necessary to add
some circuitry to supply the chip with a separate power line. This can be achieved in a number of ways,
including putting an additional winding on the transformer.
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