Datasheet

Datasheet

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BD9271KUT

TSZ02201-0F1F0C100260-1-2

27.Feb.2015 Rev.004

www.rohm.com

TSZ22111・15・001

Application of BD9271KUT

1. About the Feedback Between External LED Power Supply for DCDC Converter and COMP Pin

By connecting the COMP1,2 which are the error amplifier outputs of BD9271KUT to the feedback pins of DCDC converter (inv

input), the state which the cathode voltages of LED bars are lower than the EAMP standard voltage (typ.0.6V) which is set by

writing the registers is transmitted to DCDC side, and the DCDC voltage can be raised.

The error amplifier outputs of D1～D8, D9～D16 pins correspond the COMP1 pin and COMP2 pin respectively.

Due to the COMP1,2 pins of BD9271KUT are OPEN collector pins, basically the adjustment can be only allowed on the

direction in which the DCDC output is raised. We suggest set the initial setting of the power supply of DCDC converter 10%

lower than voltage at which the LEDs work normally.

In order to achieve a feedback which has good stability and efficiency to the LED power supply, we suggest insert the CR

which practices the lead compensation to DCDC converter and the COMP output of BD9271KUT. The current-mode type DCDC

converter is used more widely because it is easy to set the response speed and so on.

If it is hard to guarantee the stability of DCDC output, it may cause the heat of the external NMOS-FET. In this case, we

suggest raise the initial value of the DCDC output, and increase the DCDC output capacity.

Figure 26. COMP Pin feedback