TNY284-290
Quick Design Checklist
As with any power supply design, all TinySwitch-4 designs
should be verified on the bench to make sure that component
specifications are not exceeded under worst case conditions.
The following minimum set of tests is strongly recommended:
1.
Maximum drain voltage – Verify that V
DS
does not exceed
675 V at highest input voltage and peak (overload) output
power. The 50 V margin to the 725 V BV
DSS
specification
gives margin for design variation.
2. Maximum drain current – At maximum ambient temperature,
maximum input voltage and peak output (overload) power,
verify drain current waveforms for any signs of transformer
saturation and excessive leading edge current spikes at
start-up. Repeat under steady-state conditions and verify
that the leading edge current spike event is below I
LIMIT(MIN)
at
the end of the t
LEB(MIN)
. Under all conditions, the maximum
drain current should be below the specified absolute
maximum ratings.
3. Thermal Check – At specified maximum output power,
minimum input voltage and maximum ambient temperature,
verify that the temperature specifications are not exceeded
for TinySwitch-4, transformer, output diode, and output
capacitors. Enough thermal margin should be allowed for
part-to-part variation of the R
DS(ON)
of TinySwitch-4 as
specified in the data sheet. Under low-line, maximum
power, a maximum TinySwitch-4 SOURCE pin temperature
of 110 °C is recommended to allow for these variations.
12
Rev. A 09/12
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