LM3432/LM3432B 6-Channel Current Regulator for LED Backlight Application
May 22, 2008
LM3432/LM3432B
6-Channel Current Regulator for LED Backlight Application
General Description
The LM3432/LM3432B are 6-channel high voltage current
regulators which provide a simple solution for LED backlight
applications. These devices incorporate six individual current
regulator channels to give accurate driving current for each
LED string. The string-to-string tolerance is kept within ±2.0%.
Additionally, the Dynamic Headroom Control output can com-
municate with a LM3430 boost regulator to adjust the LED
supply voltage to the lowest level needed to keep the string
current in regulation, yielding optimal overall system efficien-
cy.
The 6-channel current sink can be adjusted from 15mA to
40mA by an external resistor. Their output drivers can with-
stand up to 80V. Digital PWM or analog voltage signal can be
used to control the duty cycle of all the channels. With a fast
current switching slew rate, t
r
= 60ns typical, accurate current
control and wide dimming ratio during PWM dimming are en-
sured.
The LM3432/LM3432B contain LED open/short circuit and
over-temperature fault signaling to the system micro-con-
troller (the LM3432B does not include open circuit fault sig-
naling). These devices are available in a low profile, thermally
enhanced 24 lead LLP package. The LM3432 is also avail-
able in the 28 lead eTSSOP.
Features
■
Dynamic Headroom Control (DHC) output to maximize
efficiency when used in conjunction with National
Semiconductor's LM3430 Boost Controller for LED
Backlighting
Current sinking adjustable up to 40mA in each string
Fast current switching slew rate, t
r
= 60ns typical
Wide dimming ratio, up to 4000:1 with f
DIM
= 500Hz
High LED driving voltage up to 80V
±2.0% current matching between strings
Accepts both Digital and Analog dimming control
LED open/short fault indication (For LM3432B, no open
fault indication)
Over-Temperature Indication
Internal Thermal Shutdown with Hysteresis
Low profile, thermally enhanced LLP-24 (5x4x0.8mm) and
eTSSOP-28 (9.7x6.4x1.1mm) packages (The LM3432B is
available in the LLP-24 only)
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Applications
■
LCD display backlight applications
■
General lighting solutions
© 2008 National Semiconductor Corporation
300064
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LM3432/LM3432B
Typical Application Circuit
30006401
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2
LM3432/LM3432B
Connection Diagrams
30006431
30006402
Top View
24 Lead Plastic LLP-24
NS Package Number SQA24B
Top View
28 Lead Plastic eTSSOP-28
NS Package Number MXA28A
Ordering Information
Part Number
For LM3432
LM3432SQ
LM3432SQX
LM3432SQE
LM3432MH
LM3432MHX
For LM3432B
LM3432BSQ
LM3432BSQX
LM3432BSQE
LLP-24
SQA24B
1000 Units on Tape and Reel
4500 Units on Tape and Reel
250 Units on Tape and Reel
eTSSOP-28
MXA28A
LLP-24
SQA24B
1000 Units on Tape and Reel
4500 Units on Tape and Reel
250 Units on Tape and Reel
Rail of 48 Units
2500 Units on Tape and Reel
Package Type
NS Package Drawing
Supplied As
3
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LM3432/LM3432B
Pin Descriptions
Pin Number
LLP-24
1
2
3
4
5
eTSSOP-28
5
6
7
8
9
VCC
IREF
AGND
CDHC
VDHC
Internal linear regulator output, needs 680nF minimum
for stability.
I
OUT
current setting pin. An external resistor is used to
program the string current.
Analog ground
An external capacitor to ground programs the Dynamic
Headroom Control (DHC) response time constant.
DHC voltage output. Connecting this output through a
gain setting resistor to the DHC pin of National
Semiconductor's LM3430 enables the DHC function.
Device Enable, active HIGH.
Dimming mode select pin. Short to ground for Digital
PWM dimming or connect to an external capacitor to
ground for analog dimming.
Digital PWM or Analog voltage input for IOUT duty cycle.
Open drain active LOW output for output fault.
Open drain active LOW over temperature warning
output.
Constant current sink outputs, adjustable 15mA to
40mA, voltage across this pin can be up to 80V max.
Power Ground.
Supply voltage input, from 6V to 40V.
No connection and should be left open.
Thermal connection pad, connect directly to GND.
Name
Description
6
7
10
11
EN
MODE
8
9
10
12,13,15,17,19,20
22
24
11,14,16,18,21,23
EP
12
13
14
15, 17, 19, 21, 23, 25
27, 28
1
2, 3, 4, 16, 18, 20, 22,
24, 26
EP
DIM
FAULTb
OTMb
IOUT1-6
PGND
VIN
NC
EP
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4
LM3432/LM3432B
Absolute Maximum Ratings
(Notes 1, 6)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VIN Voltage
IREF Voltage
IOUT1 through IOUT6 Voltage
VCC Voltage
EN Voltage
FAULTb, OTMb Voltage
MODE Voltage
PWM Voltage
VDHC Voltage
CDHC Voltage
-0.3V to 42V
-0.3V to 7V
-0.3V to 82V
-0.3V to 7V
-0.3V to 7V
-0.3V to 7V
-0.3V to 7V
-0.3V to 7V
-0.3V to 7V
-0.3V to 7V
ESD Susceptibility (Note 2)
Human Body Model
Lead Temperature
Vapor Phase (60 sec.)
Infra-red (15 sec.)
Maximum Junction Temp.
2.0kV
215°C
220°C
150°C
(Note 1)
6 to 40V
0 to 80V
-40°C to +125°C
-65°C to +150°C
33.2°C/W
29°C/W
Operating Ranges
Supply Voltage, VIN
IOUT1 through IOUT6 Voltage
Operating Junction Temp.
Storage Temperature
Thermal Resistance,
θ
JA
(Note 3)
LLP-24
eTSSOP-28
Limits in standard type are for T
J
= 25°C only; limits in
boldface type
apply over the
junction temperature (T
J
) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical
correlation. V
IN
= 18V, R
IREF
= 54.7 kΩ, V
EN
= 5V, V
MODE
= 0V, V
DIM
= 5V and V
OUT1-6
= 1.2V unless otherwise indicated (Note
4). Parameter limits apply to both the LM3432 and LM3432B unless otherwise indicated.
Symbol
I
SHDN
I
Q
V
EN
V
EN_HYST
I
EN
Parameter
Shutdown Input Supply Current
Quiescent Current from VIN
Enable Threshold Voltage
Enable Threshold Hysteresis
Enable pin Pull-up Current
EN = 0V
EN = 2V
VCC Regulator
V
CCreg
V
CCreg_1
V
CCreg_2
I
VCC_SC
V
CCUVLO
VCC Regulated Output
VCC Regulated Output at Max. VIN
VCC Regulated Output at Min. VIN
VCC Short-Circuit Current
VCC UVLO Upper Threshold
V
IN
= 40V
V
IN
= 6V, I
VCC
= 2mA
V
IN
= 6V, VCC = 0V
VCC rising
3.9
4.7
4.7
5
5
4.8
9
4.15
0.375
MODE = 2V
C
MODE
= 5.6nF
C
MODE
= 5.6nF
MODE = GND
MODE = GND
I
VDHC
= 2mA
V
DHC
= 1.2V
R
IREF
= 54.7k, C
DHC
= 100nF
R
IREF
= 27.5k, C
DHC
= 100nF
2
5
2.5
9
0.625
1.25
1.7
1
34
3.1
1.0
4.4
5.25
5.25
V
V
V
mA
V
V
µA
V
V
V
V
V
mA
V
V
V
EN
rising
1.48
Conditions
EN = 0V, DIM = 0V
Min
Typ
40
2.25
1.75
0.4
0.5
5
Max
90
2.65
2
Units
µA
mA
V
V
µA
Input Characteristics
Electrical Characteristics
V
CCUVLO_HYST
VCC UVLO Hysteresis
Analog PWM control
I
MODE
V
MODE_PK
V
MODE_VA
V
PWM_HIGH
V
PWM_LOW
V
DHC_MAX
I
VDHC_MAX
MODE pin Output Current
MODE pin Peak Voltage
MODE pin Valley Voltage
PWM Voltage HIGH
PWM Voltage LOW
VDHC pin Max. Output Voltage
VDHC pin Max. Output Current
Digital PWM control
Dynamic Headroom Control Output
V
DHC_REG_20
VDHC Regulation at 20mA
V
DHC_REG_40
VDHC Regulation at 40mA
5
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