DM133

點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC.

16-Bit Constant Current LED Drivers

-9-

Version

：A.024

Detailed Description

1)Constant Current Output Value Setting

The output current is determined by resistor value multiplying a ratio. The resistor

connected between REXT pin and GND decides the base current output. The resistor

should be located as close to REXT terminal as possible to avoid the noise influence.

The graph below shows the approximate relation between resistor value and output

current value.

In the monochrome or full color LED display cases, for obtaining the uniformity or for

the white balance between modules or ICs, the DM133 offers a more convenient way to

let control system to reach the goal by fine tuning the output current. To further adjust

the current level, the system shall set the DATASEL pin to low and then shift in 6 bits

data code through SERIAL_IN pin. The MSB should be shifted-in first. Take the input

code = (MSB)100101(LSB) for example. The new current is then equal to the base

current multiplied by

)

1

2

2

2

2

2

2

(

)

2

2

2

(

0

1

2

3

4

5

0

2

5

+

+

+

+

+

+

+

+

. The 6 bits data won’t be

changed until the next new data is latched. For some cases, the data only need to be

shifted once after power-on. Note that code: 011111 exists in chip when power on so

that the output current is nearly half amount of the base current.

2)Serial_In Data and Latch

As the DATASEL pin is set high, the SERIAL_IN data will be clocked into the 16 bits

shift register synchronized on the rising edge of CLOCK. And the data ‘1’ represents the

corresponding current output ‘ON’, while the data ‘0’ stands for ‘OFF’. The data will be

transferred into the latch as the LATCH pin goes high. And the data will be latched when

LATCH goes low.

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

02

46

8

10

12

14

16

Rext (Kohm)

Conditions:

Vout=1.5V, Vrext=1.2V.

1 channel turned on.

Iout is approximate to Vrext/Rrext*49.5 (5V)

Vrext/Rrext*46.6 (3.3V)

VDD=3.3V

VDD=5.0V