EVALA5970D STMicroelectronics, EVALA5970D Datasheet - Page 20

• Manufacturer Part Number: EVALA5970D
• Description: Power Management Modules & Development Tools EVAL BOARD A5970D Auto Grade
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of EVALA5970D

• Input Voltage: 4.4 V to 36 V
• Output Voltage: 1.235 V to 35 V
• Board Size: 23 mm x 20 mm
• Product: Power Management Modules
• Supply Current: 1 A
• Dimensions: 23 mm x 20 mm
• For Use With/related Products: AN1330
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application information
5.3
20/31
Thermal considerations
The dissipated power of the device is tied to three different sources:
●
Equation 21
Where D is the duty cycle of the application. Note that the duty cycle is theoretically given by
the ratio between V
compensate for the losses of the overall application. For this reason, the switching losses
related to the R
●
Equation 22
where T
current flowing into it during the turn ON and turn OFF phases. T
switching time.
●
Equation 23
Where I
●
R
@ 150 °C. We can consider a value of 0.4 Ω.
T
losses are:
Equation 24
The junction temperature of the device will be:
Equation 25
where T
ambient.
SW
DSON
switching losses due to the not negligible R
Switching losses due to turning ON and OFF. These are derived using the following
equation:
Quiescent current losses.
Example:
–
–
–
is approximately 120 ns. I
has a typical value of 0.25 Ω @ 25 °C and increases up to a maximum value of 0.5 Ω
Q
A
ON
V
V
I
is the ambient temperature and Rth
is the quiescent current.
OUT
IN
OUT
P
and T
SW
P
= 5 V
TOT
= 1 A
DSON
= 3.3 V
0.4 1
=
OFF
⋅
V
OUT
=
IN
increase compared to an ideal case.
2
are the overlap times of the voltage across the power switch and the
R DSON
⋅
•
and V
0.7
I
OUT
+
5 1 120 10
IN
Q
⋅
•
⋅
P
(
, but in practice it is substantially higher than this value to
(
---------------------------------------- -
ON
I OUT
has a typical value of 2.5 mA @ V
T
⋅
T
ON
J
=
=
)
+
⋅
2
R
2
P
T
T
⋅
DS on
Q
A
OFF
D
–
+
=
9
+
(
Rth
⋅
V
V
)
250 10
J-A
IN I OUT T SW F SW
IN
)
•
J A
•
DSON
F
–
⋅
is the thermal resistance junction-to-
•
(
⋅
SW
I
I
OUT
Q
•
3
P
. These are equal to:
=
TOT
+
)
⋅
V
5 2.5 10
2
IN
⋅
•
D
•
I
⋅
⋅
OUT
SW
–
3
IN
•
+
≅
is the equivalent
T
= 12 V. The overall
V IN I Q =
0.44W
SW
⋅
•
F
SW
AN1330