T E C H N I C A L I N F O R M A T I O N
pin to be pulled up through a large valued resistor (1MΩ recommended) to VDD. To disable SLEEP
mode, the sleep pin should be grounded.
Fault Pin
The FAULT pin is a 5V logic output that indicates various fault conditions within the device. These
conditions include: low supply voltage, low charge pump voltage, low 5V regulator voltage, over
current at any output, and junction temperature greater than approximately 155°C. The FAULT
output is capable of directly driving an LED through a series 200Ω. The FAULT output is capable of
directly driving an LED through a series 200Ω resistor. If the FAULT pin is connected directly to the
MUTE input an automatic reset will occur in the event of an over-current condition.
Heat Sink Requirements
In some applications it may be necessary to fasten the TA2020-020 to a heat sink. The determining
factor is that the 150°C maximum junction temperature, TJ(max) cannot be exceeded, as specified
by the following equation:
TJ(MAX ) − TA
PDISS
=
JA
θ
where…
DISS = maximum power dissipation
JMAX = maximum junction temperature of TA2020-020
P
T
TA = operating ambient temperature
θJC = junction-to-case thermal resistance of TA2020-020
Example:
What size heat sink is required to operate the TA2020-020 at 20W per channel continuously in a
70ºC ambient temperature?
PDISS is determined by:
POUT
POUT
POUT
Efficiency = η =
=
P
P
−
IN
DISS
POUT
η
20
0.8
PDISS (per channel) =
P
20 5W
=
−
=
−
OUT
Thus, PDISS for two channels = 10W
TJ(MAX ) − TA
150 −70
θJA
=
=
= 8°C/W
10
PDISS
10 of 13
TA2020-020, Rev. 4.0, 09.00
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
