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GM19371

BOOST WHITE LED DRIVER WITH OVP

Gamma Microelectronics Inc. 

GM19371

BOOST WHITE LED DRIVER

WITH OVP

4. Using a Logic Signal

For applications that need to adjust the LED current in

discrete steps, a logic signal can be used as shown in

figure 8. RSET sets the minimum LED current (when the

NMOS is off). RINC sets how much the LED current

increases when the NMOS is turned on. The selection

of RSET and RINC follows the formula and Table in “LED

Current Control” section.

Logic Signal

GM19371

RINC

Figure 8

RSET

6.3Ω

Board Layout Consideration

As with all switching regulators, careful attention must be paid to the PCB board layout and component

placement. To maximize efficiency, the rising and falling times of the switch are made as short as possible.

To prevent electromagnetic interference (EMI) problems, proper layout of the high frequency switching path

is essential. The voltage signal of the SW pin has sharp rising and falling edges. Minimize the length and

area of all traces connected to the SW pin and always use a ground plane under the switching regulator to

minimize inter-plane coupling. In addition, the ground connection for the feedback resistor RSET should be

tied directly to the GND pin and not shared with any other component, ensuring a clean, noise-free

connection.

8

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