LM3646 Datasheet, PDF (1/31 Pages) Texas Instruments – 1.5A Synchronous Boost Converter with Dual High-Side Current Sources and I2CCompatible Interface

LM3646
www.ti.com
SNVS962 – DECEMBER 2013
1.5A Synchronous Boost Converter with Dual High-Side Current Sources and I²C-
Compatible Interface
Check for Samples: LM3646
FEATURES
1
•2 High-Side Current Sources allowing for
Grounded LED Cathode for Improved Thermal
Management
• > 85% Efficiency in Torch and Flash Modes
• Small Solution Size < 20 mm²
• Accurate and Programmable Flash LED
Current from 24 mA to 1.5A in 11.7 mA steps
• Accurate and Programmable Torch LED
Current from 2.5 mA to 187 mA in 1.5 mA
steps
• Dual 1.5A High-Side Current Sources for Dual
LED Drive
• Hardware Flash and Torch Enables
• Hardware Enable Pin
• Soft-Start Operation for Battery Protection
• LED Thermal Sensing and Current Scale-Back
• Synchronization Input for RF Power Amplifier
Pulse Events
• VIN Flash Monitor Optimization
• 1 MHz I²C-Compatible Interface
• I²C-Programmable NTC Trip Point
• 0.4 mm pitch, 20-Bump DSBGA
APPLICATIONS
• Camera Phone LED Flash/Torch
DESCRIPTION
The LM3646 is a 4 MHz fixed-frequency, Current
Mode synchronous boost converter. The device is
designed to operate as a dual 1.5A constant current
driver for high current LEDs. The high-side current
sources allow for grounded cathode LED operation
providing Flash current up to 1.5A total. An adaptive
headroom regulation scheme ensures the LED
currents remain in regulation and maximizes
efficiency.
The LM3646 is controlled via an I²C-compatible
interface. The main features of the LM3646 include: a
hardware flash enable (STROBE) input for direct
triggering of the Flash pulse, a hardware Torch
enable (TORCH) for Movie Mode or Flashlight
functions, a TX input which forces the flash pulse into
a low-current Torch Mode allowing for
synchronization to RF power amplifier events or other
high-current conditions, an integrated comparator
designed to monitor an NTC thermistor and provide
an interrupt to the LED current, and a programmable
input voltage monitor which monitors the battery
voltage and can reduce the flash current during low
battery conditions. A hardware enable (ENABLE)
input provides a hardware shutdown during system
software failures.
The 4 MHz switching frequency, over-voltage
protection, and adjustable current limit allow for the
use of tiny, low-profile inductors and (10 μF) ceramic
capacitors. The device is available in a small 20-
bump DSBGA package and operates over the −40°C
to +85°C temperature range.
SYSTEM PERFORMANCE
2800
2600
2400
I_LED = 1.5A, V_LED = 3.7V
TA = +25ºC
TA = -40ºC
TA = +85ºC
2200
2000
1800
1600
1400
1200
2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5
V_IN (V)
C032
TYPICAL APPLICATION CIRCUIT
1 2H
2.7V to 5.5V
10 2F
IN
SW _OUT
LM3646
ENABLE
STROBE
LED1
LED2
TORCH
TX
TEMP
SDA
SCL
GND
10 2F
1
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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2013, Texas Instruments Incorporated