LM3697_15 Datasheet, PDF (9/43 Pages) Texas Instruments – High-Efficiency Three-String White LED Driver

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7 Detailed Description
LM3697
SNOSCS2C – NOVEMBER 2013 – REVISED OCTOBER 2015
7.1 Overview
The LM3697 provides the power for three high-voltage LED strings. The three high-voltage LED strings are
powered from an integrated boost converter. The device is configured over an I²C-compatible interface. The
LM3697 provides a Pulse Width Modulation (PWM) input for content adjustable brightness control.
7.1.1 PWM Input
The PWM input can be assigned to either of the high-voltage control banks. When assigned to a control bank,
the programmed current in the control bank becomes a function of the duty cycle (D_PWM) at the PWM input and
the control bank brightness setting. When PWM is disabled, D_PWM is equal to one.
7.1.2 HWEN Input
HWEN is the global hardware enable to the LM3697. HWEN must be pulled high to enable the device. HWEN is
a high-impedance input so it cannot be left floating. When HWEN is pulled low the LM3697 is placed in
shutdown, and all the registers are reset to their default state.
7.1.3 Thermal Shutdown
The LM3697 contains a thermal shutdown protection. In the event the die temperature reaches 140°C (typical),
the boost and current sink outputs shut down until the die temperature drops to typically 125°C (typical).
7.2 Functional Block Diagram
IN
SDA
SCL
I²C
Compatible Interface
HWEN
PWM
Hardware Enable,
Reference, and
Thermal Shutdown
Internal Low-Pass
Filter
Selectable
Overvoltage
Protection
(16V, 24V, 32V, 40V)
1-A Current Limit
Selectable
500-kHz/1-MHz
Switching
Frequency
LED String Open/
Short Detection
Backlight LED Control
1. 5-bit Full Scale
Current Select
2. 11-bit brightness
adjustment
3. Linear/Exponential
Dimming
4. LED Current
Ramping
SW
Boost
Converter
OVP
High-Voltage Current
Sinks
HVLED1
HVLED2
HVLED3
GND
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