ame5142c AME, Inc., ame5142c Datasheet - Page 9

• Manufacturer Part Number: ame5142c
• Description: High Efficiency 6 White Led Driver With Open Led Protection
• Manufacturer: AME, Inc.

Thermal Considerations
Shutdown Pin Operation
directly to V
recommended). The EN pin must not be left unterminated.
Rev. B.01
AME5142C
power dissipation within the AME5142C switch. The switch power dissipation from ON-state conduction is calculated
by:
dissipation.
Calculating Load Current
The device is turned off by pulling the shutdown pin low. If this function is not going to be used, the pin should be tied
At higher duty cycles, the increased ON time of the FET means the maximum output current will be determined by
P
There will be some switching losses as well, so some derating needs to be applied when calculating IC power
The load current is related to the average inductor current by the relation:
I
Where “ D” is the duty cycle of the application. The switch current can be found by:
I
Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency:
I
Combining all terms, we can develop an expression which allows the maximum available load current to be calculated:
I
LOAD
SW
RIPPLE
LOAD
(SW)
= I
= I
= D x I
= ( 1-D ) x ( I
= D x (V
IND
IND
(AVG) + 1 /2 (I
(AVG) x (1 - D)
IN
. If the SHDN function will be needed, a pull-up resistor must be used to V
IND(AVE)2
AME
IN
-V
SW
x R
) / (f x L)
CL
DS
(max) -
RIPPLE
(ON)
)
D ( V
2fL
IN
-V
SW
)
)
High Efficiency 6 White LED Driver
With Open LED Protection
IN
(approximately 50k-100k
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