EUP7961
Power Dissipation
EUP7961 can deliver a continuous current of 2A over the
full operating temperature range. A heatsink may be
required depending on the maximum power dissipation
and maximum ambient temperature of the application.
Under all possible conditions, the junction temperature
must be within the range specified under operating
conditions. The total power dissipation of the device is
given by:
P
=
V
−
V
I
+
V
I
D
IN
IN GND
OUT OUT
(
)
( )
Where I
GND
is the operating ground current of the device
(specified under Electrical Characteristics).
The maximum allowable temperature rise (T
Rmax
)
depends on the maximum ambient temperature (T
Amax
)
of the application, and the maximum allowable junction
temperature (T
Jmax
):
T
Rmax
= T
Jmax
-T
Amax
The maximum allowable value for junction to ambient
Thermal Resistance,
θ
JA
, can be calculated using the
formula:
PCB Layout
Good PC layout practices must be used or instability can
be induced because of ground loops and voltages drops.
The input and output capacitors must be directly
connected to the input, output, and ground pins of the
regulator using traces which do not have other currents
flowing in them.
The best way to do this is to lay out C
IN
and C
OUT
near
the device with short traces to the V
IN
, V
OUT
, and ground
pins. The regulator ground pin should be connected to
the external circuit ground so that the regulator and its
capacitors have a “single point ground”.
It should be noted that stability problems have been seen
in applications where “vias” to an internal ground plane
were used at the ground points of the IC and the input
and output capacitors. This was caused by varying
ground potentials at these nodes resulting from current
flowing through the ground plane. Using a single point
ground technique for the regulator and it’s capacitors
fixed the problem.
Since high current flows through the traces going into
V
IN
and coming from V
OUT
, Kelvin connect the capacitor
leads to these pins so there is no voltage drop in series
with the input and output capacitors.
θ
JA
=T
Rmax
/P
D
DS7961 Ver 1.2 Dec. 2006
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
