LM3530UME-40/NOPB National Semiconductor, LM3530UME-40/NOPB Datasheet - Page 22

• Manufacturer Part Number: LM3530UME-40/NOPB
• Description: IC LED DRVR PROGRAM I2C 12USMD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3530UME-40/NOPB

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 500kHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 12-UFBGA
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: Adjustable
• Led Driver Application: LED Backlighting, Portable Electronics
• No. Of Outputs: 1
• Output Current: 29.5mA
• Output Voltage: 40V
• Input Voltage: 2.7V To 5.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Other names: LM3530UME-40TR

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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
(PWM Polarity bit = 0) for > 2ms 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 Con-
trol Register. When the PWM input is held low for > 2ms the
device will shut down. With the PWM Polarity bit = 1 the PWM
input is configured for active low operation. In this configura-
tion holding PWM low for > 2ms 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 > 2ms will put the device in shutdown.
Example: Simple Enable Disable with PWM Current Con-
trol)
As an example, assume that the HWEN input is toggled low
then high. This resets the LM3530 and sets all the registers
to their default value. When the PWM input is then pulled high
for > 2ms the LED current becomes:
where BRT is the % of I
Register.
If then the PWM input is fed with a 5kHz pulsed waveform at
40% duty cycle the LED current becomes:
BRT Data
(Hex)
0x1A
0x1B
0x1C
0x1D
0x1E
0x16
0x17
0x18
0x19
0x1F
13. In this mode, when the PWM input is held high
% Full-Scale
Current
(Linear)
17.32%
18.11%
18.90%
19.69%
20.47%
21.26%
22.05%
22.83%
23.62%
24.41%
LED_FS
as set in the Brightness Control
BRT Data
(Hex)
0x3C
0x3D
0x36
0x37
0x38
0x39
0x3A
0x3B
0x3E
0x3F
FIGURE 13. Simple Enable/Disable Timing
% of Full-
(Linear)
Current
Scale
42.52%
43.31%
44.09%
44.88%
45.67%
46.46%
47.24%
48.03%
48.82%
49.61%
22
BRT Data
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 < 2ms. 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 cur-
rent. 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/Dis-
able 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). Addi-
tionally, 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 I
Then, if the Brightness Control Register is loaded with 0x55
(9.6% of Full-Scale Current) the LED current becomes:
AMBIENT LIGHT CURRENT CONTROL
With bits [4:3] of the ALS Configuration Register both set to
1, the LM3530 is configured for Ambient Light Current Con-
trol. In this mode the ambient light sensing inputs (ALS1, and/
or ALS2) monitor the outputs of analog output ambient light
sensing photo diodes and adjust the LED current depending
on the ambient light. The ambient light sensing circuit has 4
(Hex)
0x5C
0x5D
0x5A
0x5B
0x5E
0x5F
0x56
0x57
0x58
0x59
% of Full-Scale
2
C-compatible bus.
Current
(Linear)
67.72%
68.50%
69.29%
70.08%
70.87%
71.65%
72.44%
73.23%
74.02%
74.80%
BRT Data
(Hex)
0x7C
0x7D
0x76
0x77
0x78
0x79
0x7A
0x7B
0x7E
0x7F
30086604
Scale Current
% of Full-
(Linear)
100.00%
92.91%
93.70%
94.49%
95.28%
96.06%
96.85%
97.64%
98.43%
99.21%