LM3530UME-40/NOPB National Semiconductor, LM3530UME-40/NOPB Datasheet - Page 23

• 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

configurable Ambient Light Boundaries (ZB0 – ZB3) pro-
grammed through the four (8-bit) Zone Boundary Registers.
These zone boundaries define 5 ambient brightness zones
(Figure
ness setting which is programmable through the 5 Zone Tar-
get Registers (Z0T – Z4T). When the ALS1, and/or ALS2 input
(depending on the bit settings of the ALS Input Select bits)
detects that the ambient light has crossed to a new zone (as
defined by one of the Zone Boundary Registers) the LED cur-
rent becomes a function of the Brightness Code loaded in the
Zone Target Register which corresponds to the new ambient
light brightness zone.
On startup the 4 Zone Boundary Registers are pre-loaded
with 0x33 (51d), 0x66 (102d), 0x99 (153d), and 0xCC (204d).
Each ALS input has a 1V active input voltage range with a
4mV offset voltage which makes the default Zone Boundaries
set at:
Zone Boundary 0 = 1V × 51/255 + 4mV = 204mV
Zone Boundary 1 = 1V × 102/255 + 4mV = 404mV
Zone Boundary 2 = 1V × 153/255 + 4mV = 604mV
Zone Boundary 3 = 1V × 204/255 + 4mV = 804mV
These Zone Boundary Registers are all 8-bit (readable and
writable) registers. The first zone (Z0) is defined between 0
and 204mV, Z1’s default is defined between 204mV and
404mV, Z2’s default is defined between 404mV and 604mV,
Z3’s default is defined between 604mV and 804mV, and Z4’s
default is defined between 804mV and 1.004V. The default
settings for the 5 Zone Target Registers are 0x19, 0x33,
0x4C, 0x66, and 0x7F. This corresponds to LED brightness
settings of 0.336%, 1.43%, 5.781%, 24.844%, and 100% of
full-scale current respectively (assuming exponential back-
light mapping).
Example: Ambient Light Control Current
As an example, assume that the APDS-9005 is used as the
ambient light sensing photo diode with its output connected
to the ALS1 input. The ALS Resistor Select Register is loaded
with 0x04 which configures the ALS1 input for a 2.27kΩ in-
ternal pull-down resistor (see
a typical 400nA/LUX response. With a 2.27kΩ resistor the
sensor output would see a 0 to 908mV swing with a 0 to 1000
LUX change in ambient light. Next, the ALS Configuration
Register is programmed with 0x3C. From
figures the LM3530’s ambient light sensing interface for:
ALS1 as the active ALS input (bits [6:5] = 01)
Example: ALS Averaging
As an example, suppose the LM3530’s ALS Configuration
Register is loaded with 0x3B. This configures the device for:
ALS1 as the active ALS input (bits [6:5] = 01)
Enables Ambient Light Current Control (bit 4 = 1)
Enables the ALS circuitry (bit 3 = 1)
Sets the ALS Averaging Time to 256ms (bits [2:0] = 011)
Next, the ALS Resistor Select Register is loaded with 0x04.
This configures the ALS2 input as high impedance and con-
figures the ALS1 input with a 2.27kΩ internal pull-down re-
sistor. The Zone Boundary Registers and Zone Target
Registers are left with their default values. The Brightness
Ramp Rate Register is loaded with 0x2D. This sets up the
LED current ramp rate at 16.384ms/step. Finally, the General
4). Each zone corresponds to a programmable bright-
Table
9). The APDS-9005 has
Table
6, this con-
23
Ambient Light Current Control Enabled (bit 4 = 1)
ALS circuitry Enabled (bit 3 = 1)
Sets the ALS Averaging Time to 512ms (bits [2:0] = 100)
Next, the General Configuration Register is programmed with
0x19 which sets the Full-Scale Current to 26mA, selects Ex-
ponential Brightness Mapping, and enables the device via the
I
Now assume that the APDS-9005 ambient light sensor de-
tects a 100 LUX ambient light at its input. This forces the
ambient light sensors output (and the ALS1 input) to 87.5mV
corresponding to Zone 0. Since Zone 0 points to the bright-
ness code programmed in Zone Target Register 0 (loaded
with code 0x19), the LED current becomes:
Where the code in Zone Target Register 0 points to the % of
ILED_FS as given by
whether Exponential or Linear Mapping are selected.
Next, assume that the ambient light changes to 500 LUX (cor-
responding to an ALS1 voltage of 454mV). This moves the
ambient light into Zone 2 which corresponds to Zone Target
Register 2 (loaded with code 0x4C) the LED current then be-
comes:
AMBIENT LIGHT CURRENT CONTROL + PWM
The Ambient Light Current Control can also be a function of
the PWM input duty cycle. Assume the LM3530 is configured
as described in the above Ambient Light Current Control ex-
ample, but this time the Enable PWM bit set to ‘1’ (General
Configuration Register bit [5]).
Example: Ambient Light Current Control + PWM
In this example, the APDS-9005 detects that the ambient light
has changed to 1 kLUX. The voltage at ALS1 is now around
908mV and the ambient light falls within Zone 5. This causes
the LED brightness to be a function of Zone Target Register
5 (loaded with 0x7F). Now assume the PWM input is also
driven with a 50% duty cycle pulsed waveform. The LED cur-
rent now becomes:
Configuration Register is loaded with 0x15. This sets up the
device with:
Simple Enable OFF (bit 7 = 0)
PWM Polarity High (bit 6 = 0)
PWM Input Disabled (bit 5 = 0)
Full-Scale Current = 22.5mA (bits [4:2] = 101)
Brightness Mapping Mode as Exponential (bit 1 = 0)
Device Enabled via I
As the device starts up the APDS-9005 ambient light sensor
(connected to the ALS1 input) detects 500 LUX. This puts
approximately 437.5mV at ALS1 (see
the measured ambient light between Zone Boundary Regis-
ters 1 and 2, thus corresponding to Zone Target Register 2.
The default value for this register is 0x4C. The LED current is
programmed to:
2
C-compatible interface.
2
C (bit 0 = 1)
Table 2
30086626
or
Table
Figure
3, depending on
14). This places
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