LM3530TME-40SLASHNOPB datasheet(21/50 Pages) TI1

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LM3530

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SNVS606L – JUNE 2009 – REVISED DECEMBER 2014

Table 3. ILED vs. Brightness Register Data (Linear Mapping) (continued)

BRT DATA

% FULL-

BRT DATA

% OF FULL-

BRT DATA

% OF

BRT DATA (HEX)

% OF FULL-SCALE

(HEX)

SCALE

(HEX)

SCALE

(HEX)

FULL-

CURRENT (LINEAR)

CURREN

CURRENT

SCALE

(LINEAR)

CURRE

(LINEAR)

(LINEA

0x13

15.63%

0x33

40.63%

0x53

65.63%

0x73

90.63%

0x14

16.41%

0x34

41.41%

0x54

66.41%

0x74

91.41%

0x15

17.19%

0x35

42.19%

0x55

67.19%

0x75

92.19%

0x16

17.97%

0x36

42.97%

0x56

67.97%

0x76

92.97%

0x17

18.76%

0x37

43.75%

0x57

68.75%

0x77

93.75%

0x18

19.54%

0x38

44.53%

0x58

69.53%

0x78

94.53%

0x19

20.32%

0x39

45.32%

0x59

70.39%

0x79

95.31%

0x1A

21.10%

0x3A

46.10%

0x5A

71.10%

0x7A

96.09%

0x1B

21.88%

0x3B

46.88%

0x5B

71.88%

0x7B

96.88%

0x1C

22.66%

0x3C

47.66%

0x5C

72.66%

0x7C

97.66%

0x1D

23.44%

0x3D

48.44%

0x5D

73.44%

0x7D

98.44%

0x1E

24.22%

0x3E

49.22%

0x5E

74.22%

0x7E

99.22%

0x1F

25.00%

0x3F

50.00%

0x5F

75.00%

0x7F

100.00%

NOTE

When determining the LED current from (Table 2 and Table 3 ) there is a typical offset of

113 µA with a ±300-µA variation that must be added to the calculated value for codes

0x0A and below. For example, in linear mode with IFULL_SCALE = 19 mA and brightness

code 0x09 chosen, the nominal current setting is 0.0782 × 19 mA = 1.4858 mA. Adding in

the 113-µA typical offset gives 1.4858 mA + 0.113 mA = 1.5988 mA. With the typical

±300-µA range, the high and low currents can be ILOW = 1.2988 mA, IHIGH = 1.8988 mA.

For exponential mode with codes 0x0A and below, this offset and variation error gets

divided down by 10 (11.3 µA offset with ±30-µA typical range).

8.3.13 Simple Enable Disable With PWM Current Control

With bits [7 and 5] of the General Configuration Register set to ‘1’ the PWM input is enabled as a simple

enable/disable. The simple enable/disable feature operates as described in Figure 36. In this mode, when the

PWM input is held high (PWM Polarity bit = 0) for > 2 ms the LM3530 will turn on the LED current at the

programmed Full-Scale Current × % of Full-Scale Current as set by the code in the Brightness Control Register.

When the PWM input is held low for > 2 ms the device will shut down. With the PWM Polarity bit = 1 the PWM

input is configured for active low operation. In this configuration holding PWM low for > 2 ms will turn on the

device at the programmed Full-Scale Current × % of Full-Scale Current as set by the code in the Brightness

Control Register. Likewise, holding PWM high for > 2 ms will put the device in shutdown.

Driving the PWM input with a pulsed waveform at a variable duty cycle is also possible in simple enable/Disable

mode, so long as the low pulse width is < 2 ms. When a PWM signal is used in this mode the input duty cycle

information is internally filtered, and an analog voltage is used to control the LED current. This type of PWM

control (PWM to Analog current control) prevents large voltage excursions across the output capacitor that can

result in audible noise. Simple Enable/Disable mode can be useful since the default bit setting for the General

Configuration Register is 0xCC (Simple Enable bit = 1, PWM Enable = 1, and Full-Scale Current = 19mA).

Additionally, the default Brightness Register setting is 0x7F (100% of Full-Scale current). This gives the LM3530

the ability to turn on after power up (or after reset) without having to do any writes to the I2C-compatible bus.

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