IRPLLED1A International Rectifier, IRPLLED1A Datasheet - Page 19

• Manufacturer Part Number: IRPLLED1A
• Description: Power Management IC Development Tools Hi-Vlt DC-DC Buck Cnvr HBLED Cur Cntrl
• Manufacturer: International Rectifier
• Type: DC/DC Converters, Regulators & Controllersr

Specifications of IRPLLED1A

• Product: Power Management Development Tools
• Tool Is For Evaluation Of: IRS25401PBF
• Output Voltage: 16 V to 24 V
• Output Current: 350 mA to 1.5 A
• Factory Pack Quantity: 1

20V, the HO “on” time will be 2.7µs (one-fourth of the period – see calculations below) according to standard buck
topology theory. This will set the minimum “off” time of the enable signal to 27µs.
If the IRS25401/11 is supplied from the output, a large enough capacitor on VCC is required to maintain sufficient
current while in a disabled state. For this evaluation board where the IC is supplied from the output a 10uF
capacitor is used to ensure continued operation during PWM off periods. The output may drop to 10V and still
sustain an adequate VCC supply. A “strobe light” effect in the LEDs may be observed if VCC drops too much or if
the dimming frequency is too low.
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100
90
80
70
60
50
40
30
20
10
Duty
HO
0
0
Fig. 23 Light Output vs Enable Pin Duty Cycle
on
Cycle
time
10
Fig. 24 IRS25401 Dimming Signals
Enable Duty Cycle Relationship to Light Output
=
20
20
=
RD-0608
%
V
V
out
30
in
*
Percentage of Light Output
1
∗
75
100
40
kHz
=
50
100
=
20
2
V
V
7 .
60
µ
*
s
100
70
=
80
20
%
90
100
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