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IS31BL3229 Datasheet(PDF) 8 Page - Integrated Silicon Solution, Inc |
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IS31BL3229 Datasheet(HTML) 8 Page - Integrated Silicon Solution, Inc |
8 / 11 page IS31BL3229 Integrated Silicon Solution, Inc. – www.issi.com 8 Rev.A, 09/17/2012 APPLICATION INFORMATION GENERAL DESCRIPTION The IS31BL3229 with a smart charge-pump circuit is a parallel white-LED driver with eight matched 20mA current outputs. CHARGE PUMP The built-in charge pump converter switches on automatically to ensure constant current output when the voltage of channel 1 (VD1) is below the threshold voltage VTH (180mV). The charge pump converter only needs three external components: supply decoupling capacitor, output bypass capacitor and flying capacitor. Choose low ESR capacitors to ensure the best operating performance and place the capacitors as close as possible to the IS31BL3229. OUTPUT CURRENT SETTING The maximum current (IMAX) of each LED can be set by the extra resister RSET follow the Equation (1) below. 1600 / 25 . 1 SET MAX R I (1) For example, in Figure 1, RSET = 100kΩ, So, mA k I MAX 20 1600 100 / 25 . 1 The recommended minimum RSET is 82kΩ, then the maximum IMAX is 24mA. The recommended maximum RSET is 110kΩ, then the minimum IMAX is 18mA. FUNCTIONAL DESCRIPTION The LED intensity can be modulated by pulse count or PWM signal. EN DIMMING MODE The current level magnitude is controlled by Pulse Count Control (PCC wire) serial interface. The interface records rising edges of the EN pin and decodes them into 32 different states. The 32 current level settings available are indicated in Table 1. The PWM pin should be pulled to high if modulated by EN pin only. PWM SIGNAL DIMMING MODE The PWM pin of the IS31BL3229 can accept a PWM signal to implement LED dimming by changing the PWM duty cycle. Recommended PWM frequency is in the range of 100Hz ~ 50kHz. Table 1 Current Level Setting (Typical) VCC = 3.6V, RSET = 100kΩ, PWM pin is high. Pulse ILED (mA/Ch) Pulse ILED (mA/Ch) Pulse ILED (mA/Ch) 1 20.0 12 13.125 23 6.25 2 19.375 13 12.5 24 5.625 3 18.75 14 11.875 25 5 4 18.125 15 11.25 26 4.375 5 17.5 16 10.625 27 3.75 6 16.875 17 10 28 3.125 7 16.25 18 9.375 29 2.5 8 15.625 19 8.75 30 1.875 9 15 20 8.125 31 1.25 10 14.375 21 7.5 ≥32 0.625 11 13.75 22 6.875 FADE IN AND FADE OUT MODE By floating the OPT pin the fade in and fade out mode enable. When the EN pin is pulled high to enable the IC, LED fade in. When the EN pin is pulled low at last tOFF to shutdown the IC, LED fade out. Pulling OPT pin low to disable this mode (Figure 6). Figure 6 FIFO Function TIMING CONTROL The EN pin should be configured as the Figure 7. tLAT is the latch time. High level should be at last tLAT to active the pulse signal. tOFF is the shutdown time. EN pin is pulled low at last tOFF the IC will be shutdown. Figure 7 EN pin timing |
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