STLDC08PUR STMicroelectronics, STLDC08PUR Datasheet - Page 17

• Manufacturer Part Number: STLDC08PUR
• Description: IC CTLR STEP-UP FOR LED 10-DFN
• Manufacturer: STMicroelectronics

Specifications of STLDC08PUR

• Internal Driver: No
• Type - Primary: General Purpose
• Mounting Type: *
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Voltage - Supply: 0.8 V ~ 3.6 V
• Package / Case: *
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Voltage - Output: -
• Lead Free Status / Rohs Status: Details
• Other names: 497-11140-2

STLDC08
Figure 18. Timing diagram
As a first approximation we choose the inductor ripple current, I
% of the output current. Higher ripple current allows for smaller inductors, but it also
increases the output capacitance for a given LED current ripple requirement. Conversely,
lower ripple current can be obtained increasing the value of the inductance, and this enables
a reduction of the output capacitor value. This trade-off can be altered once standard
inductance and capacitance values are chosen.
I
The minimum value of inductance which guarantees the fixed inductor ripple current can be
determined using the following equation:
Equation 4
where V
T
The following equation shows the average inductor current as a function of the output
current and duty cycle.
Equation 5
An inductor that can carry the maximum input DC current which occurs at the minimum
input voltage should be chosen. The peak-to-peak ripple current is set by the inductance
and a good starting point is to choose a ripple current of at least 40 % of its maximum value
of the:
L
OFF
is determined by the input and output voltage, the value of the inductance, and T
is the constant OFF time.
I
I
I
I
L
L
OUT
OUT
d
I
I
PEAK
PEAK
T
T
is the forward drop of the Schottky diode, I
ON
ON
T
T
OFF
OFF
Doc ID 18476 Rev 1
L
>
(V
I
I
OUT
IN
IN
I
( L
=
=
+
AVG
(
I
I
1
1
OUT
OUT
V
Δ
−
−
d
I
L
)
D
D
-
)
=
V
INMIN
I
1
LED
−
D
L
)
is the fixed inductor ripple current, and
×
T
OFF
AM07848v1
AM07848v1
L
, equal to approximately 40
Application information
I
I
RIPPLE
RIPPLE
t
t
OFF
.
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