Datasheet

Datasheet

25/36

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

12. EN restart check

EN restart when Vout voltage is remain, it possible to detect SCP. Please set the condition according to applications.

When use the Buck Boost or Buck application.

Please connect Vout and VDISC terminal and set EN=Low time refer to the below equation.

[ ] =

×

[ ]×

[ ]

×

[ ]

<

[ ]

Regarding Tdisc details, please refer P.8.

When use the Boost application.

Please adjust CSS and Cpc value according to below. If Cpc value is changed, phase margin will changed, and if CSS value

is changed, start up time is changed. Please verifying by actual measurements.

1[ ] =(

0.4+2.7× −

[ ]

0.4 + 2.7 ×

×

1

[

] ×

[

] × 138

+ 1.56) ×

[

]/(0.46 ×

[%])

2[ ] =

[

] × 0.61 + 29791/

[

]

Please adjust CSS and Cpc value with

1[ ] < 2[ ]

n: LED series number

VCC [V]: Power supply

Fosc [kHz]: DCDC Frequency

RRT [kΩ]: RT resistance

Cpc [μF]: COMP capacitor

Duty [%]: PWM Duty

CSS [μF]: SS capacitor

Ex.) n=7, Vcc=7V, Fosc=300kHz, RRT=27kΩ, Cpc=0.01μF, CSS=0.1μF, PWM Duty = 1%

1[ ] =(

0.4 + 2.7 × 7 − 7

0.4+2.7× 7

×

1

300 × 27 × 138

+ 1.56) × 0.01/(0.46 × 1) =46.3

2[ ] = 0.1 × 0.61 +

29791

300

= 99.4

1[ ] < 2[ ] This condition is OK.

13. Verification of the operation by taking measurements

The overall characteristics may change based on load current, input voltage, output voltage, inductance, load capacitance,

switching frequency, and PCB layout. We strongly recommend verifying your design by the actual measurements.