ILED (mA) | 25 x 0.85

[44 ± {(N+1)/2.91}]

LM3537

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SNVS634B – JUNE 2011 – REVISED MAY 2013

Current Control Registers

A0 GROUP A BRIGHTNESS

This is the LED driver current control register for Group A. The register is effective when the ALS isn't used. The

resolution is 7 bits, so in linear dimming mode the step size from zero up to full brightness is fixed (25.0mA/127)

= 197 µA. Exponential dimming scheme provides a more fine-grained level of control over low level LED

currents. Group A exponential dimming curve current can be approximated by the following equation (where N =

the decimal value stored in the Group A Brightness register):

(1)

Current vs. code is shown below.

Figure 10. LED current (typ.) vs. register code, exponential dimming curve

B0 GROUP B BRIGHTNESS

Bits [2:0] set the GroupB Brightness Levels, as shown in below:

Table 6. Group B Brightness Levels

dxb[2]

dxb[1]

dxb[0]

GroupB LED Current (typ.)

1

1

1

25.0 mA

1

1

0

17.5 mA

1

0

1

15.0 mA

1

0

0

12.5 mA

0

1

0

10.0 mA

0

1

0

7.5 mA

0

0

1

5.0 mA

0

0

0

2.5 mA

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