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LM3492, LM3492-Q1
SNVS656D – SEPTEMBER 2010 – REVISED OCTOBER 2016
LM3492/-Q1 Two-Channel Individual Dimmable LED Driver With Boost Converter and Fast
Current Regulator
1
1 Features
•
•
•
Boost Converter:
– LM3492-Q1 is an Automotive Grade Product
That is AEC Q100 Grade 1 Qualified
– Very Wide Input Voltage Ranged
From 4.5 V to 65 V
– Programmable Soft Start
– No Loop Compensation Required
– Stable With Ceramic and Other Low ESR
Capacitors With No Audible Noise
– Nearly Constant Switching Frequency
Programmable From 200 kHz to 1 MHz
Current Regulators:
– Programmable LED Current from 50 mA to
200 mA
– 1000:1 Contrast Ratio at a Dimming
Frequency of More Than 3 kHz, Minimum LED
Current Pulse Width is 300 ns
– Two Individual Dimmable LED Strings up to
65 V, Total 15 W (Typically 28 LEDs at
150 mA)
– Dynamic Headroom Control Maximizes
Efficiency
– Over-Power Protection
– ±3% Current Accuracy
Supervisory Functions:
– Precision Enable
– COMM I/O Pin for Diagnostic and Commands
– Thermal Shutdown Protection
– Thermally Enhanced 20-Pin HTSSOP package
2 Applications
•
•
Ultra-High Contrast Ratio 6.5”-10” LCD Display
Backlight up to 28 LEDs
Automotive or Marine GPS Displays
3 Description
The LM3492/-Q1 integrates a boost converter and a
two-channel current regulator to implement a high
efficient and cost effective LED driver for driving two
individually dimmable LED strings with a maximum
power of 15 W and an output voltage of up to 65 V.
The boost converter employs a proprietary ProjectedOn-Time control method to give a fast transient
response with no compensation required, and a
nearly constant switching frequency programmable
from 200 kHz to 1 MHz. The application circuit is
stable with ceramic capacitors and produces no
audible noise on dimming. The programmable peak
current limit and soft-start features reduce current
surges at start-up, and an integrated 190 mΩ, 3.9-A
N-Channel MOSFET switch minimizes the solution
size.
Device Information(1)
PART NUMBER
LM3492
LM3492-Q1
PACKAGE
HTSSOP (20)
BODY SIZE (NOM)
7.80 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
Copyright © 2016, Texas Instruments Incorporated
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.
LM3492, LM3492-Q1
SNVS656D – SEPTEMBER 2010 – REVISED OCTOBER 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Description (continued).........................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
5
7.1
7.2
7.3
7.4
7.5
7.6
5
5
5
5
6
8
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
8.1
8.2
8.3
8.4
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
11
12
12
18
8.5 Programming........................................................... 18
9
Application and Implementation ........................ 20
9.1 Application Information............................................ 20
9.2 Typical Application ................................................. 20
10 Power Supply Recommendations ..................... 23
11 Layout................................................................... 23
11.1 Layout Guidelines ................................................. 23
11.2 Layout Example .................................................... 23
12 Device and Documentation Support ................. 24
12.1
12.2
12.3
12.4
12.5
12.6
12.7
Documentation Support ........................................
Related Links ........................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
24
24
24
24
24
24
24
13 Mechanical, Packaging, and Orderable
Information ........................................................... 25
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (May 2013) to Revision D
Page
•
Added Added ESD Ratings table, Thermal Information table, Feature Description section, Device Functional Modes,
Application and Implementation section, Power Supply Recommendations section, Layout section, Device and
Documentation Support section, and Mechanical, Packaging, and Orderable Information section....................................... 1
•
Changed RθJA value from 32.7 to 36.5 in the Thermal Information table ............................................................................... 5
Changes from Revision B (May 2013) to Revision C
•
2
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 20
Submit Documentation Feedback
Copyright © 2010–2016, Texas Instruments Incorporated
Product Folder Links: LM3492 LM3492-Q1
LM3492, LM3492-Q1
www.ti.com
SNVS656D – SEPTEMBER 2010 – REVISED OCTOBER 2016
5 Description (continued)
The fast slew rate current regulator allows high frequency and narrow pulse width dimming signals to achieve a
very high contrast ratio of 1000:1 at a dimming frequency of more than 3 kHz. The LED current is programmable
from 50 mA to 200 mA by a single resistor.
To maximize the efficiency, Dynamic Headroom Control (DHC) automatically adjusts the output voltage to a
minimum. DHC also facilitates a single BOM for different number of LED in a string, which is required for
backlight panels of different size, thereby reducing overall development time and cost. The LM3492/-Q1 comes
with a versatile COMM pin which serves as a bidirectional I/O pin interfacing with an external MCU for the
following functions: power-good, overtemperature, IOUT overvoltage and undervoltage indications, switching
frequency tuning, and channel 1 disabling. Other supervisory functions of the LM3492/-Q1 include precise
enable, VCC undervoltage lockout, current regulator over-power protection, and thermal shutdown protection.
The LM3492/-Q1 is available in the thermally enhanced 20-pin HTSSOP package.
Copyright © 2010–2016, Texas Instruments Incorporated
Product Folder Links: LM3492 LM3492-Q1
Submit Documentation Feedback
3
LM3492, LM3492-Q1
SNVS656D – SEPTEMBER 2010 – REVISED OCTOBER 2016
www.ti.com
6 Pin Configuration and Functions
PWP PowerPAD™ Package
20-Pin HTSSOP
Top View
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
APPLICATION INFORMATION
1
EN
I
Enable
Internally pullup. Connect to a voltage higher than 1.63 V to provide precision enable
for the device.
2
VIN
I
Input Supply Voltage
Supply pin to the device. Input range is 4.5 V to 65 V.
SW
I
Switch Node
Internally connected to the drain of the integrated MOSFET.
5
VOUT
I
Output Voltage Sense
Sense the output voltage for nearly constant switching frequency control.
6
RT
I
Frequency Control
An external resistor from the VOUT pin to this pin sets the switching frequency.
7
FB
I
Output Voltage
Feedback
The output voltage is connected to this pin through a feedback resistor divider for
output voltage regulation. The voltage of this pin is from 1.05 V to 2.5 V.
8
GND
G
Analog Ground
Signal ground
3
4
9
IOUT2
I
Current Regulator Input Input of the current regulator of channel 2. The regulated current is programmable
of Channel 2
(refer to the IREF pin).
10
IOUT1
I
Current Regulator Input Input of the current regulator of channel 1. The regulated current is programmable
of Channel 1
(refer to the IREF pin).
11
CDHC
I
Dynamic Headroom
Control
An external capacitor connected to this pin sets the DHC sensitivity. At start-up, a
120-µA internal current source charges an external capacitor to provide a soft-start
function.
12
IREF
I
Current Setting of the
Current Regulator
An external resistor connected from this pin to ground programs the regulated current
of the current regulator of channels 1 and 2.
13
COMM
I/O
Bidirectional Logic
Communication
This pin is open drain for various indications (power-good, overtemperature, IOUT
overvoltage and undervoltage) and command sending (switching frequency tuning
and channel 1 disabling).
14
LGND
G
Ground of the Current
Regulator
Current regulator ground. Must be connected to the GND pin for normal operation.
The LGND and GND pins are not internally connected.
15
DIM1/CLK
I/O
Dimming Control of
Channel 1
Control the ON/OFF of the current regulator of channel 1. This pin is internally pulled
low by a 5-µA current. This pin also serves as a clock signal for latching input/output
data of the COMM pin.
16
DIM2
I
Dimming Control of
Channel 2
Control the ON/OFF of the current regulator of channel 2. This pin is internally pulled
low by a 5-µA current.
PGND
G
Power Ground
Integrated MOSFET ground. Must be connected to the GND pin for normal operation.
The PGND and GND pins are not internally connected.
19
VCC
O
LDO Regulator Output
Nominally regulated to 5.5 V. Connect a capacitor of larger than 0.47 µF between the
VCC and GND pins.
20
ILIM
I
Peak Current Limit
Adjust
Connect an external resistor from the ILIM pin to the VCC pin reduces peak current
limit. Connect the ILIM pin to the ground to obtain the maximum current limit.
DAP
DAP
—
Exposed Pad
Thermal connection pad. Connect to a ground plane.
17
18
4
Submit Documentation Feedback
Copyright © 2010–2016, Texas Instruments Incorporated
Product Folder Links: LM3492 LM3492-Q1
LM3492, LM3492-Q1
www.ti.com
SNVS656D – SEPTEMBER 2010 – REVISED OCTOBER 2016
7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
Input voltage
MIN
MAX
VIN, RT, VOUT to GND
−0.3
67
SW to GND
−0.3
UNIT
67
V
−2 (