LM3697_15 Datasheet, PDF (32/43 Pages) Texas Instruments – High-Efficiency Three-String White LED Driver

LM3697
SNOSCS2C – NOVEMBER 2013 – REVISED OCTOBER 2015
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Table 26 illustrates the minimum number of register writes required for a two-parallel, six-series LED
configuration with PWM Enabled. This example uses the default settings for ramp times (2048 µsec), mapping
mode (exponential) and full-scale current (20.2 mA). In this mode of operation the host controller must update
both the brightness LSB and MSB registers whenever a brightness change is required.
Table 26. Control Bank A, 11-Bit Control, Two-String, Six Series LED Configuration Example
REGISTER NAME
HVLED Current Sink Output
Configuration
HVLED Current Sink Feedback
Enables
Boost Control
PWM Configuration
Control Bank Enables
Control A Brightness LSB
Control A Brightness MSB
ADDRESS
0x10
0x19
0x1A
0x1C
0x24
0x20
0x21
DATA
0x04
DESCRIPTION
HVLED1 & 2 assigned to Control Bank A
0x03
0x02
0x0D
0x01
User Value
User Value
Enable feedback on HVLED1 & 2, disable feedback on HVLED3
OVP = 24 V, ƒ_sw = 500 kHz
PWM Zero Detect = Enabled, PWM Polarity = Active HIgh, Control
B PWM = Disabled, Control A PWM = Enabled
Enable Control Bank A
Control A Brightness LSB updated as required
(NOTE: The Brightness LSB change does not take effect until the
Brightness MSB register is written.)
Control A Brightness MSB updated as required
(NOTE: Anytime the Brightness LSB is changed the Brightness
MSB must be written for the Brightness LSB change to take effect.)
9 Power Supply Recommendations
The LM3697 is designed to operate from an input supply range of 2.7 V to 5.5 V. This input supply must be well
regulated and provide the peak current required by the LED configuration and inductor selected.
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