Datasheet

Datasheet

24/36

BD81A24MUV-M/EFV-M

TSZ02201-0T3T0C600070-1-2

© 2016 ROHM Co., Ltd. All rights reserved.

2016.10.19 Rev.003

www.rohm.com

TSZ22111・15・001

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

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

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.

0

100

200

300

400

500

600

700

800

900

1000

0

2040

6080

100

PWM duty [%]

PWM duty vs Startup Time

(Boost)

0

100

200

300

400

500

600

700

800

900

1000

0

0.2

0.4

0.6

0.8

1

PWM duty [%]

PWM duty vs Startup Time

(Boost, Zoom up)

0

100

200

300

400

500

600

700

800

900

1000

0

204060

80

100

PWM duty [%]

PWM duty vs Startup Time

(BuckBoost)

0

100

200

300

400

500

600

700

800

900

1000

00.2

0.4

0.6

0.81

PWM duty [%]

PWM duty vs Startup Time

(BuckBoost, Zoom up)