ALTAIR05T-800 STMicroelectronics, ALTAIR05T-800 Datasheet - Page 11

• Manufacturer Part Number: ALTAIR05T-800
• Description: IC PRIMARY SWITCHING REG 16NSOIC
• Manufacturer: STMicroelectronics

Specifications of ALTAIR05T-800

• Output Isolation: Isolated
• Voltage - Input: 11.5 ~ 23 V
• Voltage - Output: 800V
• Power (watts): 900mW
• Operating Temperature: -25°C ~ 125°C
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ALTAIR05T-800
5
Application information
The device is an off-line all-primary sensing switching regulator, based on quasi-resonant
flyback topology.
Depending on converter’s load condition, the device is able to work in different modes (see
Figure
1.
2.
3.
Figure 9.
QR mode at heavy load. Quasi-resonant operation lies in synchronizing MOSFET's
turn-on to the transformer’s demagnetization by detecting the resulting negative-going
edge of the voltage across any winding of the transformer. Then the system works
close to the boundary between discontinuous (DCM) and continuous conduction
(CCM) of the transformer. As a result, the switching frequency is different for different
line/load conditions (see the hyperbolic-like portion of the curves in
turn-on losses, low EMI emission and safe behavior in short circuit are the main
benefits of this kind of operation.
Valley-skipping mode at medium/ light load. Depending on voltage on COMP pin, the
device defines the maximum operating frequency of the converter. As the load is
reduced MOSFET’s turn-on does not occur any more on the first valley but on the
second one, the third one and so on. In this way the switching frequency is no longer
increased (piecewise linear portion in
Burst-mode with no or very light load. When the load is extremely light or disconnected,
the converter enters a controlled on/off operation with constant peak current.
Decreasing the load result in frequency reduction, which can go down even to few
hundred hertz, thus minimizing all frequency-related losses and making it easier to
comply with energy saving regulations or recommendations. Being the peak current
very low, no issue of audible noise arises.
9):
f
f
f
sw
sw
sw
Multi-mode operation of ALTAIR05T-800
0
0
0
f
f
f
osc
osc
osc
Burst-mode
Burst-mode
Burst-mode
Valley-skipping
Valley-skipping
Valley-skipping
mode
mode
mode
Doc ID 17957 Rev 1
Quasi-resonant mode
Quasi-resonant mode
Quasi-resonant mode
Figure
P
P
P
in
in
in
9).
Input voltage
Input voltage
Input voltage
Application information
Figure
Pinmax
Pinmax
Pinmax
9). Minimum
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