Operations
VIPer22A-E, VIPer22ADIP-E, VIPer22AS-E
4.2
Wide range of VDD voltage
The V pin voltage range extends from 9 V to 38 V. This feature offers a great flexibility in
DD
design to achieve various behaviors. In Figure 4 on page 7 a forward configuration has been
chosen to supply the device with two benefits:
●
As soon as the device starts switching, it immediately receives some energy from the
auxiliary winding. C5 can be therefore reduced and a small ceramic chip (100 nF) is
sufficient to insure the filtering function. The total start up time from the switch on of
input voltage to output voltage presence is dramatically decreased.
●
The output current characteristic can be maintained even with very low or zero output
voltage. Since the TSM101 is also supplied in forward mode, it keeps the current
regulation up whatever the output voltage is.The V pin voltage may vary as much as
DD
the input voltage, that is to say with a ratio of about 4 for a wide range application.
4.3
Feedback pin principle of operation
A feedback pin controls the operation of the device. Unlike conventional PWM control
circuits which use a voltage input (the inverted input of an operational amplifier), the FB pin
is sensitive to current. Figure 5. presents the internal current mode structure.
Figure 5.
Internal current control structure
8/21
Doc ID 12050 Rev 2
STMICROELECTRONICS [ ST ]
