A5974ADTR STMicroelectronics, A5974ADTR Datasheet - Page 27

• Manufacturer Part Number: A5974ADTR
• Description: IC REG SW STEP-DOWN 2A 8SOIC
• Manufacturer: STMicroelectronics
• Series: -r
• Type: Step-Down (Buck), PWMr

Specifications of A5974ADTR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.235 V ~ 35 V
• Current - Output: 2A
• Frequency - Switching: 500kHz
• Voltage - Input: 4 V ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-11423-2

A5974AD
8.3
8.3.1
Figure 13. Layout example
Thermal considerations
Thermal resistance R
R
calculated as the parallel of many paths of heat conduction from the junction to the ambient.
For this device, the path through the exposed pad is the one conducting the largest amount
of heat. The static R
The junction temperature of device is:
Equation 22
The dissipated power of the device is tied to three different sources:
●
Equation 23
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 in the overall application. For this reason, the switching losses
related to the R
●
Equation 24
THJ-A
Conduction losses due to the not insignificant R
Switching losses due to turning on and off. These are derived using the following
equation:
is the equivalent static thermal resistance junction-to-ambient of the device; it can be
P
DS(on)
SW
OUT
THJ-A
=
increases compared to an ideal case.
V
and V
IN
measured on the application is about 40 °C/W.
⋅
I
THJ-A
OUT
Doc ID 018762 Rev 1
IN
P
, but in practice it is substantially higher than this value to
⋅
ON
(
----------------------------------- - F
T
T
J
ON
=
=
+
R
2
T
T
DS on
A
OFF
+
(
R
)
thJA
)
⋅
⋅
(
I
SW
OUT
⋅
P
=
TOT
)
DS(on)
2
V
⋅
IN
D
⋅
I
, which are equal to:
OUT
⋅
T
SW
Application information
⋅
F
SW
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