STLED524 datasheet(18/72 Pages) STMICROELECTRONICS

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Detailed description

STLED524

18/72

DocID026217 Rev 1

4.3

LED current setting

Although each current mirror can sink up to ~35 mA (that is more than test conditions), the

following conditions have to be met:

•

The sum of all current mirrors should not exceed 600 mA in bypass mode.

•

The sum of all current mirrors should not exceed 480 mA in boost mode.

•

If sum of all current mirrors exceeds test conditions, it may exceed the related

specifications. The device is not guaranteed to sink current greater than test

conditions.

Maximum current of all current mirrors can be adjusted by RSET resistor value according to

the following formula:

Equation 1

where: VSET = 1.25 V typically.

Current of each dot can be adjusted in its register, so each LED may have an independent

setting of current.

Current can be adjusted in 255 steps; 1 step represents approximately 0.392% of ILEDMAX.

Current settings are carried out by Dn_xx registers, where n is the pattern number and xx

are the coordinates of a dot in the matrix.

Table 9. Blanking time register

Blanking time

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Add = 15h

BLK[2:0]

Default

---

Table 10. Impact of blanking time on the maximum PWM duty cycle

Blanking time

Blanking time [TCLK]TRTCR [TCLK]TRTCF [TCLK] Max. PWM duty cycle

000

255/255

001

254/255

010

253/255

011

252/255

100

251/255

101

250/255

110

249/255

111

248/255

LEDMAX

SET

--------------

400

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