TB62757FUG Toshiba, TB62757FUG Datasheet - Page 6

• Manufacturer Part Number: TB62757FUG
• Manufacturer: Toshiba

Specifications of TB62757FUG

• Package: SOT23-6
• Supply Voltage: 2.8V to 5.5V
• # Leds Supported: 2 to 6 LEDs in series
• Sw Frequency: 1.1MHz
• Led Current Accuracy: ±5.23% (max)
• Protection Feature: Output overvoltage protection
• Other Features & Functions: -
• Rohs Compatible Product(s) (#): -

Brightness Control Method
Recommended Brightness Control Circuits are 4 types.
1) Input PWM signal to SHDN terminal
I
[Notice]
F
can be adjusted with PWM signal by inputting it to SHDN terminal.
<<Minimum ON-time of PWM signal input>>
<<PWM signal frequency>>
<<Constant number of external capacitor>>
<<PWM input signal>>
<<Current value in control with PWM: Ideal equation>>
<<Rush current in inputting>>
•
•
•
•
•
•
•
Set the minimum ON-time or OFF-time 33 μs or more in inputting the PWM signal.
Set the Duty ratio satisfying the condition above.
Ex) In case PWM Frequency is 1 kHz,
The recommended PWM signal frequency is from 100 Hz to 10 kHz. There is a possibility to arise
the audible frequency in mounting to the board because it is within the auditory area.
To reduce the fluctuation of input current and increase the accuracy of brightness, the values that
C
When the PWM signal is off, the time to drain C
so, the actual value is little different from the theoretical value.
Set the amplitude of PWM signal within the range of SHDN terminal specification.
In case dimming by inputting the PWM signal to the SHDN terminal, this IC turns on and off
repeatedly.
And the rush current, which provides the charge to C
the condenser.
I
F
1
1 ms (1 kHz) = 100%
(
= 4.7 (μF) or more, C
mA
1 kHz is 1 ms (PWM Width = 100%) and it takes 10 μs per 1%.
To set the pulse width 33 μs or more, necessary ON-or-OFF-time is calculated below.
33 μs ÷ 10 μs = 3.3% (Under the condition that 10 μs equals 1%.)
Finally, the Duty Ratio can be set in range of 3.3% to 96.7%.
)
=
325
[
mV
R
SENS
× ]
ON
2
[
Ω
= 0.1 (μF) or less are recommended.
Duty
]
[%]
Set On-time
Set Off-time
6
2
of charge depends on the constant number. And
2
, arises in turning on. Take care in selecting
33 μ s or more = 3.3%
Available Duty Ratio
(3.3% to 96.7%)
33 μ s or more = 3.3%
TB62757FUG
2010-06-306