ALTAIR04-900TR Просмотр технического описания (PDF) - STMicroelectronics

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ALTAIR04-900TR

Off-line all-primary-sensing switching regulator

STMicroelectronics 

ALTAIR04-900

Pin connection

Table 1. Pin functions (continued)

Number Name

Function

Transformer demagnetization sensing for quasi-resonant operation. Input/output voltage

monitoring. A negative-going edge triggers the MOSFET turn-on. The current sourced by the

pin during on-time is monitored 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 50 µA, either a floating pin or a low input voltage is assumed, the device is stopped

6

ZCD/FB and restarted after Vcc has dropped below 5 V. Besides, the pin voltage is sampled-and-held

right at the end of the transformer 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 2.5 V. The maximum IZCD/FB sunk/sourced current doesn’t

exceed ±2 mA (AMR) in all Vin range conditions. No capacitor is allowed between the pin

and the auxiliary transformer.

Output of the internal transconductance error amplifier. The compensation network is placed

7

COMP 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.

13 to 16

DRAIN

Drain connection of the internal power section. The internal high voltage start-up generator

sinks current from these pins as well. Pins are connected to the internal metal frame to

facilitate heat dissipation.

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