STMicroelectronics Double output SMPS for power line application using ALTAIR04-900 primary controller EVLALTAIR900-M1 EVLALTAIR900-M1 Fiche De Données

Doc ID 18211 Rev 2

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6

ZCD/FB

Transformer’s demagnetization sensing for quasi-resonant operation. Input/output voltage 
monitor. A negative-going edge triggers MOSFET’s turn-on. The current sourced by the pin 
during ON-time is monitored to get an image of the input voltage to the converter, in order to 
compensate the internal delay of the current sensing circuit and achieve a CC regulation 
independent of the mains voltage. If this current does not exceed 50µA, either a floating pin 
or an abnormally low input voltage is assumed, the device is stopped and restarted after Vcc 
has dropped below 5V. Still, the pin voltage is sampled-and-held right at the end of 
transformer’s demagnetization to get an accurate image of the output voltage to be fed to the 
inverting input of the internal, transconductance-type, error amplifier, whose non-inverting 
input is referenced to 2.5V. Please note that the maximum I

ZCD/FB

 sunk/sourced current has 

to not exceed ±2 mA (AMR) in all the Vin range conditions. No capacitor is allowed between 
the pin and the auxiliary transformer.

7

COMP

Output of the internal transconductance error amplifier. The compensation network is placed 
between this pin and GND to achieve stability and good dynamic performance of the voltage 
control loop. 

8-11

N.A

Not available. These pins must be left not connected

12

N.C

Not internally connected. Provision for clearance on the PCB to meet safety requirements.

13 to 16

DRAIN

Drain connection of the internal power section. The internal high-voltage start-up generator 
sinks current from this pin as well. Pins connected to the internal metal frame to facilitate 
heat dissipation.