A5974ADTR STMicroelectronics, A5974ADTR Datasheet - Page 31

• 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
8.4
Figure 17. Measurement of the thermal impedance of the demonstration board
As can be seen, for example, for load pulses with a duration of 1 second, the actual thermal
impedance is lower than 20 °C/W. This means that, for short pulses, the device can deliver a
higher output current value.
Short-circuit protection
In overcurrent protection mode, when the peak current reaches the current limit, the device
reduces the T
frequency to approximately one third of its nominal value even when synchronized to an
external signal (see
strongly reduced and, in most applications, this is enough to limit the current to I
event, in case of heavy short-circuit at the output (V
application conditions (V
peak could reach values higher than I
current ripple during the ON and OFF phases:
●
Equation 29
●
Equation 30
where V
In short-circuit conditions V
is very small, as equal to the voltage drop across parasitic components (typically the DCR of
On phase
Off phase
D
is the voltage drop across the diode, DCR
ON
down to its minimum value (approximately 250 nsec) and the switching
Section 5.4: Current
Δ
CC
I
L TON
Δ
OUT
value and parasitic effect of external components), the current
I
L TOFF
Doc ID 018762 Rev 1
=
is negligible, so during T
V
------------------------------------------------------------------------------------- - T
IN
=
–
–
------------------------------------------------------------- - T
LIM
(
V
V
out
D
. This can be understood considering the inductor
protection). In these conditions, the duty cycle is
+
–
V
(
DCR
out
L
L
+
L
DCR
+
L
O
R
is the series resistance of the inductor.
= 0 V) and depending on the
DS(on)
L
I ⋅
OFF
)
(
) I ⋅
the voltage across the inductor
OFF
(
)
ON
Application information
)
LIM
. In any
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