SA303 Datasheet, PDF (13/14 Pages) Cirrus Logic – 3 Phase Switching Amplifier

Product Innova tionFrom
Figure 10. Timing Diagrams
TOP INPUT
BOTTOM INPUT
SA303
DISABLE
OUTPUT
DELAY TIMING
td(fall)
td(rise)
td(dis)
td(dis)
td(dis)
td(dis)
3. POWER DISSIPATION
The thermally enhanced package of the SA303 al-
lows several options for managing the power dissi-
pated in the three output stages. Power dissipation
in traditional PWM applications is a combination
of output power dissipation and switching losses.
Output power dissipation depends on the quadrant
of operation and whether external flyback diodes
are used to carry the reverse or commutating cur-
rents. Switching losses are dependent on the fre-
quency of the PWM cycle as described in the typi-
cal performance graphs.
Figure 11. OUTPUT RESPONSE
80%
OUTPUT
20%
The size and orientation of the heatsink must be
selected to manage the average power dissipation
t(rise)
t(fall)
of the SA303. Applications vary widely and various
thermal techniques are available to match the re-
quired performance. The patent pending mounting
TOP INPUT
technique shown in Figure 12, with the SA303 in-
verted and suspended through a cutout in the PCB _{BOTTOM INPUT}
is adequate for power dissipation up to 17W with
the HS33, a 1.5 inch long aluminum extrusion with
four fins. In free air, mounting the PCB perpendicular to the ground, such that the heated air flows upward along the
channels of the fins can provide a total Θ_JA of less than 14 ºC/W (9W max average P_D). Mounting the PCB parallel to
the ground impedes the flow of heated air and provides a Θ_JA of 16.66 ºC/W (7.5W max average P_D). In applications
in which higher power dissipation is expected or lower junction or case temperatures are required, a larger heatsink
or circulated air can significantly improve the performance.
4. ORDERING AND PRODUCT STATUS INFORMATION
MODEL
TEMPERATURE PACKAGE
SA303-IHZ -25 to 85ºC
64 pin Power QFP (HQ package drawing)
PRODUCTION STATUS
Samples Available 1Q09
SA303U
13