SGM3725

38V Step-Up LED Driver

APPLICATION INFORMATION

Current Setting at CTRL Pin

Current control can be as simple as a bi-level signal at

LED OFF state. However, more sophisticated control

techniques can be achieved by pulsing the CTRL pin.

An example for programming the output current is

shown in Figure 4.

There are two ways to adjust the channels’ ON/OFF

state or current level. The first way is by simply adding

the number of pulses according to Table 2. For example,

example, the user can add 12 more pulses when

the current level can be accomplished by two ways,

allowing for more flexible programming.

Since the data in Table 1 automatically circles around

after 32 pulses, adding 32-8 = 24 pulses changes from

6/32 (DATA 27) to 14/32 (DATA 19). The second way is

to reset the IC by pulling CTRL pin low for 3ms

(guaranteed shutdown), and then inputting the desired

number of pulses.

Example: going from 6/32 (DATA 27) to 14/32 (DATA

19)

Option 1: send in 24 pulses (19+32-27 = 24);

Option 2: pull low for 3ms and then send in 19 pulses.

Layout Considerations

PCB layout is very important for high frequency

switching regulators in order to keep the loop stable

and minimize noise. The input capacitor should be very

close to the IC to get the best decoupling. The path of

the inductor and output capacitor should be kept as

short as possible to minimize noise and ringing. Please

see the SGM3725 evaluation document for detailed

PCB layout guidelines.

CTRL

I_LED

OFF

OFF

100%

31/32 30/32

4/32 3/32

2/32

1/32

Figure 4. Output Current Programming via CTRL Pin

10

SG Micro Corp

www.sg-micro.com