BD81A24MUV-M Datasheet, PDF (24/40 Pages) Rohm – 4ch White LED Driver with Buck-Boost

BD81A24MUV-M/EFV-M
Datasheet
Open Detection OVP Pin Voltage
( ) = 1.9
If ROVP1=20kΩ, please set by ROVP2 > 286.3kΩ from (1)
Sample 2: VF=3.2V±0.3V LED is used in 3series
( )[ ] = 1.1 (
) + (3.2 + 0.3 ) × 3 = 11.6
Open Detection OVP Pin Voltage
( ) = 1.9
If ROVP1=20kΩ, please set by ROVP2 > 102.21kΩ from (1).
10. Setting of Soft Start time
The soft start circuit minimizes the coil current at the input and overshoot at the output voltage during the start-up condition.
A capacitance in the range of 0.047 to 0.47µF is recommended. A capacitance of less than 0.047µF may cause overshoot at
the output voltage. However, a capacitance greater than 0.47µF may cause massive reverse current through the parasitic
elements when power supply is OFF and may damage the IC.
Soft start time TSS (Typ) is below.
[ ] = [ ] × 3.3[ ] ∕ 5[ ]
CSS: The capacitance at SS terminal
11. Check the Start up time
If the PWM duty at start up is small, the start up time is longer. If you want to setup the Startup Time shorter, small CPC value
is available, but it needs phase margin check. Below data is PWM duty vs Startup Time of representative two conditions.
Condition 1 (Boost, below figure left side)
Vcc = 12V, Vout = 30V (assumed LED 8 series), RRT = 27kΩ (Fosc = 300kHz), CPC=0.01μF, RPC=5.1kΩ, CSS = 0.1μF,
ROVP1 = 20kΩ, ROVP2 = 360kΩ
PWM duty vs Startup Time
(Boost)
1000
PWM duty vs Startup Time
(Boost, Zoom up)
1000
900
900
800
800
700
700
600
600
500
500
400
400
300
300
200
200
100
100
0
0
20
40
60
80
100
PWM duty [%]
0
0
0.2
0.4
0.6
0.8
1
PWM duty [%]
Figure 27. PWM Duty vs Startup Time (Boost)
Condition 2 (Buck Boost, below figure right side)
Vcc = 12V, Vout = 20V (assumed LED 5 series), RRT = 27kΩ (Fosc = 300kHz), CPC=0.01μF, RPC=5.1kΩ, CSS = 0.1μF,
ROVP1 = 30kΩ, ROVP2 = 360kΩ
1000
900
800
700
600
500
400
300
200
100
0
0
PWM duty vs Startup Time
(BuckBoost)
20
40
60
80
100
PWM duty [%]
PWM duty vs Startup Time
(BuckBoost, Zoom up)
1000
900
800
700
600
500
400
300
200
100
0
0
0.2
0.4
0.6
0.8
1
PWM duty [%]
Figure 28. PWM Duty vs Startup Time (Buck Boost)
Above data is only reference data. Actual Startup Time depends on layout pattern, parts value and part characteristics,
Please verify your design by the actual measurements.
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TSZ02201-0T3T0C600070-1-2
2016.10.19 Rev.003