TB62731FU Ver la hoja de datos (PDF) - Marktech Optoelectronics
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TB62731FU Datasheet PDF : 9 Pages
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TOSHIBA
TB62731FU
[Important Notice]
In a Typical Application Circuit, the total Vf of LED lamps must be kept larger than VCC. As the external
inductor, Schottky diode, LED lamps and R_sens are connected in a series, if the total Vf is below VCC,
very high currents are likely to surge into the LED lamps.
[Setting LED Driving Current]
TB62731FU is a constant output current DC/DC converter. R_sens sets the average LED driving current.
(See LED driving current, Total Vf vs. Feedback resistor in this section). Also maximum supply power is
limited by the following equation:
Io(K) x Total Vf(max) =< 320mW
Where Io(K) is the average LED current. Therefore, 20mA driving current can be supplied for LEDs with
the total Vf(max) of 16V and this current is given by R_sens of 1.8ohm. Note that Io(K) x Total Vf(max)
over 320mW makes output voltage smaller than Total Vf(max) and turns the LED lamps off.
40
35
30
25
20
15
10
5
0
0.5
LED driving current, total Vf
vs. Feedback resistor
24
20
16
12
8
1 1.5 2 2.5 3
R_sens (ohm)
[Output Capacitor Selection]
The LED current ripple level deeply depends on the output buffering capacitor value. Larger values help
to reduce output ripple and noise. TB62731FU, however, monitors the average voltage at R_sens,
therefore low ripple driving current, like a DC current, is not necessarily needed. The capacitor value is
not critical as viewed from LED current controlability. The output capacitance value will be decided by
peak level of LED current and noise.
Available from:
Marktech Optoelectronics
120 Broadway • Menands, NY 12203
800.984.5337 FAX: 518.432.7454
Website: www.marktechopto.com
Email: info@marktechopto.com
The information contained herein is subject to change without notice.
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