A5974ADTR STMicroelectronics, A5974ADTR Datasheet - Page 39

• 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
Figure 28. 350 mA LED boost current source
The device is powered from the output voltage so the maximum voltage drop across the
LEDs and resistor sense is 36 V.
The output voltage is given by:
Equation 42
where the ideal duty cycle D for the boost converter is:
Equation 43
As for positive and inverting buck-boost (see
real duty cycle must be used to calculate the switch current level.
The peak current flowing in the embedded switch is:
Equation 44
while its average current is equal to:
Equation 45
This is due to the fact that the current flowing through the internal power switch is delivered
to the output only during the OFF phase.
The switch peak current must be lower than the minimum current limit of the overcurrent
protection (see
DC current of the device.
Table 4
for details) while the average current must be lower than the rated
I
SW
=
Doc ID 018762 Rev 1
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1 D
LOAD
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D
V
I
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I
RIPPLE
SW
OUT
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2
V
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=
OUT
Section 8.6
=
V
I
-------------- -
1 D
LOAD
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------------ -
1 D
=
V
–
–
–
IN
I
-------------- -
V
1 D
LOAD
IN
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+
and
---------- -
2 L
V
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IN
Section
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---------
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SW
D
Application information
8.7) the measured
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