LM3646_16 Datasheet, PDF (1/40 Pages) Texas Instruments – 1.5-A Synchronous Boost Converter

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LM3646
SNVS962A – DECEMBER 2013 – REVISED NOVEMBER 2014
LM3646 1.5-A Synchronous Boost Converter With Dual High-Side Current Sources
and I²C-Compatible Interface
1 Features
•1 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 1.5 A in 11.7-mA Steps
• Accurate and Programmable Torch LED Current
from 2.5 mA to 187 mA in 1.5-mA Steps
• Dual 1.5-A 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
2 Applications
Camera Phone LED Flash and Torch
3 Description
The LM3646 utilizes a 4-MHz fixed-frequency
synchronous boost converter to provide power to dual
1.5-A constant current LED sources. The high-side
current sources allow for grounded cathode LED
operation providing flash current up to 1.5 A total. An
adaptive headroom regulation scheme ensures the
LED currents remain in regulation and maximizes
efficiency. The combination of dual LED driving
capability, high LED current, small solution size and
high level of adjustability make the LM3646 perfect
for camera phone LED flash and torch applications.
The LM3646 is controlled through 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, overvoltage
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.
Device Information⁽¹⁾
PART NUMBER PACKAGE BODY SIZE (NOM)
LM3646
DSBGA (20) 2.015 mm x 1.615 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
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
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
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.