SC5010H View Datasheet(PDF) - Semtech Corporation

Part Name

Description

MFG CO.

SC5010H

High Efficiency 8-Channel LED Driver with I2C Interface and Phase-Shifted PWM Dimming

Semtech Corporation 

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SC5010H

Applications Information (continued)

range. The PWMI input is usually generated by the system

graphics processor. This mode allows the user to set the

PWM output dimming frequency independent of the

PWMI input.

If the PWMI signal has jitter, then SC5010H provides an

option to filter it out. Hysteresis is also provided by select-

ing the WND[1:0] bits in the DCR register (address 0x01).

WND[1:0] bits set the window comparator such that if a

change in the duty cycle is detected which is smaller than

the set window, then it is ignored.

And the dimming duty cycle with FAST_FREQ = 1 can be

calculated as:

LED Dimming Duty Cycle = {D[9:1]decimal + 1}/29

In both cases mentioned above, duty cycle is fixed to be 0

when D[9:0] is set as 0x00.

As for the PWM dimming frequency, it is controlled the

same way as used in “Indirect Control” introduced in the

previous page.

Mode 3 — I2C Control

In this mode (refer to Figure 1 on page 18), both the output

LED dimming duty cycle and the dimming frequency are

set via the internal registers. PWMI pin should be con-

nected to ground in this mode. In this mode, the LED

dimming duty cycle is set via the duty cycle registers

(address 0x03, 0x04); and the dimming frequency is set via

the FREQ register (address 0x05) and the FAST_FREQ bit.

With FAST_FREQ = 0, the LED duty cycle can achieve 10-bit

resolution, D[9:0], which is combined by two portions: (1)

MSB portion - register address 0x03 [1:0] and (2) LSB portion

- register address 0x04 [7:0] as shown below.

And the dimming duty cycle with FAST_FREQ = 0 can be

calculated as:

LED Dimming Duty Cycle = {D[9:0]decimal + 1}/210

With FAST_FREQ = 1, the LED duty cycle can achieve 9-bit

resolution, D[9:1], which is combined by two portions: (1)

MSB portion - register address 0x03 [1:0] and (2) LSB portion

- register address 0x04 [7:1] as shown below.

Phase-Shifted PWM Dimming

The SC5010H provides an option for the phase shifted LED

PWM dimming. This option is available in both PWMI indi-

rect control and I2C control. Phase-shift option is set by the

PH_SHIFT bit in the Device Control Register (register address

0x01). This option delays the turn-on of the LED strings

based on the number of the strings in operation (the

number of the strings in operation is determined during

the start-up). The delay time can be calculated by the fol-

lowing equation:

TIphase

1

fPWM ,

N

N number of strings in operation

fPWM LED PWM dimming frequency

Phase-shift mode is disabled during soft-start, this allows

the output to ramp up to the correct voltage in a con-

trolled fashion.

Phase-shifting reduces the peak input current, decreases

EMI and improves the dimming linearity. The figures in the

Typical Characteristic Section shows the reduction in the

input current with phase shift feature enabled compared

to the non-phase shifted mode of operation.

Backlight Fade-in and Fade-out Options

The SC5010H features an option for fade-in and fade-out

brightness control, which allows smooth transition from

one brightness level to another.

Registers associated with this fading functions are shown

in this section.

1. Fade Option (register address 0x09) — sets fade

19

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