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LM3643, LM3643A
SNVS967A – AUGUST 2014 – REVISED NOVEMBER 2014
LM3643 Synchronous Boost Dual LED Flash Driver with 1.5-A High-Side Current Sources
1 Features
3 Description
•
The LM3643 is a dual LED flash driver that provides
a high level of adjustability within a small solution
size. The LM3643 utilizes a 2-MHz or 4-MHz fixedfrequency synchronous boost converter to provide
power to the dual 1.5-A constant current LED
sources. The total LED current the LM3643 boost can
deliver is 1.5 A (ILED1 + ILED2 ). The dual 128 level
current sources provide the flexibility to adjust the
current ratios between LED1 and LED2 with each
driver capable of delivering a maximum of 1.5 A (ex:
ILED1 = 1.5 A and ILED2 = 0FF, ILED1 = 0FF and ILED2 =
1.5 A, or a current configuration with a current less
than 1.5 A , ILED1 = 950 mA and ILED2 = 250 mA). An
adaptive regulation method ensures the current
sources remain in regulation and maximizes
efficiency.
1
•
•
•
•
•
•
•
•
•
•
•
1.5 A Total Allowed LED Current During Operation
(ILED1 + ILED2 = 1.5 A)
Dual Independent LED Current Source
Programmability
Accurate and Programmable LED Current Range
from 1.4 mA to 1.5 A
Optimized Flash LED Current During Low Battery
Conditions (IVFM)
> 85% Efficiency in Torch Mode (@ 100 mA) and
Flash Mode (@1 A to 1.5 A)
Grounded Cathode LED Operation for Improved
Thermal Management
Small Solution Size: < 16 mm2
Hardware Strobe Enable (STROBE)
Synchronization Input for RF Power Amplifier
Pulse Events (TX)
Hardware Torch Enable (TORCH/TEMP)
Remote NTC Monitoring (TORCH/TEMP)
400-kHz I2C-Compatible Interface
– LM3643 (I2C Address = 0x63)
– LM3643A (I2C Address = 0x67)
Features of the LM3643 are controlled via an I2Ccompatible interface. These features include:
hardware flash and hardware torch pins (STROBE
and TORCH/TEMP), a TX interrupt, and an NTC
thermistor monitor. The device offers independently
programmable currents in each output leg to drive the
LEDs in a Flash or Movie Mode (Torch) condition.
The 2-MHz or 4-MHz switching frequency options,
overvoltage protection (OVP), and adjustable current
limit allow for the use of tiny, low-profile inductors and
(10-µF) ceramic capacitors. The device operates over
a –40°C to 85°C ambient temperature range.
2 Applications
Camera Phone White LED Flash
Device Information(1)
PART NUMBER
LM3643
PACKAGE
DSBGA (12)
BODY SIZE (MAX)
1.69 mm x 1.31 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Simplified Schematic
1 PH
IN
2.5V to 5.5V
SW
OUT
10 PF
10 PF
LM3643
LED1
TORCH/TEMP
STROBE
HWEN
TX
LED2
SDA
SCL
GND
Flash
LED
Flash
LED
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.
LM3643, LM3643A
SNVS967A – AUGUST 2014 – REVISED NOVEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
9
Features ..................................................................
Applications ...........................................................
Description .............................................................
Simplified Schematic.............................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
1
2
2
3
4
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
4
4
4
4
5
5
5
6
Absolute Maximum Ratings ......................................
Handling Ratings ......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ...............................................
Switching Characteristics ..........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 10
9.1 Overview ................................................................. 10
9.2 Functional Block Diagram ...................................... 11
9.3
9.4
9.5
9.6
Feature Description ................................................
Device Functioning Modes......................................
Programming...........................................................
Register Descriptions ..............................................
12
13
17
19
10 Applications and Implementation...................... 23
10.1 Application Information.......................................... 23
10.2 Typical Application ............................................... 23
11 Power Supply Recommendations ..................... 29
12 Layout................................................................... 29
12.1 Layout Guidelines ................................................. 29
12.2 Layout Example ................................................... 30
13 Device and Documentation Support ................. 31
13.1
13.2
13.3
13.4
13.5
Device Support......................................................
Related Documentation.........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
31
31
31
31
31
14 Mechanical, Packaging, and Orderable
Information ........................................................... 31
5 Revision History
Changes from Original (August 2014) to Revision A
Page
•
Added Information about LM3643A ....................................................................................................................................... 1
•
Changed 0x00 to 0x02 - typo ............................................................................................................................................... 19
•
Changed '011' to '000' - typo ................................................................................................................................................ 22
6 Device Comparison Table
2
ORDERING PART NUMBER
I2C ADDRESS
LM3643YFFR
0x63
LM3643AYFFR
0x67
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SNVS967A – AUGUST 2014 – REVISED NOVEMBER 2014
7 Pin Configuration and Functions
DSBGA
12 Pins
Top View
A1
A2
Top View
A3
B1
B2
B3
C1
C2
C3
D1
D2
D3
Pin A1
Pin Functions
PIN
DESCRIPTION
NUMBER
NAME
A1
GND
A2
IN
A3
SDA
Serial data input/output in the I2C Mode on LM3643.
B1
SW
Drain Connection for Internal NMOS and Synchronous PMOS Switches.
B2
STROBE
B3
SCL
Serial clock input for LM3643.
C1
OUT
Step-up DC/DC Converter Output. Connect a 10-µF ceramic capacitor between this terminal and GND.
C2
HWEN
C3
TORCH/TEMP
D1
LED2
D2
TX
D3
LED1
Ground
Input voltage connection. Connect IN to the input supply and bypass to GND with a 10-µF or larger
ceramic capacitor.
Active high hardware flash enable. Drive STROBE high to turn on Flash pulse. Internal pulldown
resistor of 300 kΩ between STROBE and GND.
Active high enable pin. High = Standby, Low = Shutdown/Reset. Internal pulldown resistor of 300 kΩ
between HWEN and GND.
Torch terminal input or threshold detector for NTC temperature sensing and current scale back.
High-side current source output for flash LED.
Configurable dual polarity power amplifier synchronization input. Internal pulldown resistor of 300 kΩ
between TX and GND.
High-side current source output for flash LED.
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8 Specifications
8.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
IN, SW, OUT, LED1, LED2
−0.3
6
SDA, SCL, TX, TORCH/TEMP, HWEN, STROBE
−0.3 to the lesser of
(VIN+0.3) w/ 6 V max
Continuous power dissipation (3)
150
Maximum lead temperature (soldering)
(2)
(3)
(4)
V
Internally limited
Junction temperature (TJ-MAX)
(1)
UNIT
Note
°C
(4)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the potential at the GND terminal.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150°C (typ.) and
disengages at TJ = 135°C (typ.). Thermal shutdown is ensured by design.
For detailed soldering specifications and information, please refer to TI Application Note DSBGA Wafer Level Chip Scale Package
(SNVA009).
8.2 Handling Ratings
Tstg
V(ESD)
(1)
(2)
MIN
MAX
UNIT
−65
150
°C
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (1)
−2500
2500
Charged device model (CDM), per JEDEC specification
JESD22-C101, all pins (2)
−1500
1500
Storage temperature range
Electrostatic discharge
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
8.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
VIN
Junction temperature (TJ)
Ambient temperature (TA)
(1)
(2)
(3)
(3)
MAX
2.5
5.5
−40
125
−40
85
UNIT
V
°C
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the potential at the GND terminal.
In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may
have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP =
125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the
part/package in the application (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA × PD-MAX).
8.4 Thermal Information
LM3643
THERMAL METRIC (1)
DSBGA
UNIT
12 PINS
RθJA
(1)
4
Junction-to-ambient thermal resistance
67.8
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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8.5 Electrical Characteristics
Typical limits tested at TA = 25°C. Minimum and maximum limits apply over the full operating ambient temperature range
(−40°C ≤ TA ≤ 85°C). Unless otherwise specified, VIN = 3.6 V, HWEN = VIN. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
–7%
1.5
7%
A
–10%
89.3
10%
mA
CURRENT SOURCE SPECIFICATIONS
ILED1/2
Current source accuracy
LED1 and LED2 current source
regulation voltage
VHR
VOVP
VOUT = 4 V, flash code = 0x7F = 1.5 A
flash
VOUT = 4 V, torch code = 0x3F = 89.3 mA
torch
ILED1/2 = 729 mA
Flash
290
ILED1/2 = 179 mA
Torch
158
mV
ON threshold
4.86
5
5.1
OFF threshold
4.75
4.88
4.99
V
STEP-UP DC/DC CONVERTER SPECIFICATIONS
RPMOS
PMOS switch on-resistance
86
RNMOS
NMOS switch on-resistance
65
ICL
Switch current limit
UVLO
Undervoltage lockout threshold
VTRIP
NTC comparator trip threshold
INTC
NTC current
VIVFM
Input voltage flash monitor trip
threshold
Reg 0x02, bits[5:3] = '000'
IQ
Quiescent supply current
ISD
ISB
mΩ
Reg 0x07, bit[0] = 0
–12%
1.9
12%
Reg 0x07, bit[0] = 1
–12%
2.8
12%
Falling VIN
–2%
2.5
2%
Reg 0x09, bits[3:1] = '100'
–5%
0.6
5%
V
–6%
50
6%
µA
–3%
2.9
3%
V
Device not switching pass mode
0.3
0.75
mA
Shutdown supply current
Device disabled, HWEN = 0 V
2.5 V ≤ VIN ≤ 5.5 V
0.1
4
µA
Standby supply current
Device disabled, HWEN = 1.8 V
2.5 V ≤ VIN ≤ 5.5 V
2.5
10
µA
A
V
HWEN, TORCH/TEMP, STROBE, TX VOLTAGE SPECIFICATIONS
VIL
Input logic low
VIH
Input logic high
2.5 V ≤ VIN ≤ 5.5 V
0
0.4
1.2
VIN
0
0.4
1.2
VIN
V
I2C-COMPATIBLE INTERFACE SPECIFICATIONS (SCL, SDA)
VIL
Input logic low
VIH
Input logic high
VOL
Output logic low
(1)
(2)
2.5 V ≤ VIN ≤ 4.2 V
ILOAD = 3 mA
V
400
mV
Minimum (Min) and Maximum (Max) limits are specified by design, test, or statistical analysis. Typical (typ.) numbers are not verified, but
do represent the most likely norm. Unless otherwise specified, conditions for typical specifications are: VIN = 3.6 V and TA = 25°C.
All voltages are with respect to the potential at the GND pin.
8.6 Timing Requirements
MIN
t1
SCL clock period
2.4
t2
Data in set-up time to SCL high
100
t3
Data out stable After SCL low
t4
SDA low set-up time to SCL Low (start)
100
t5
SDA high hold time after SCL high (stop)
100
NOM
MAX
UNIT
µs
0
ns
8.7 Switching Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
ƒSW
Switching frequency
TEST CONDITIONS
2.5 V ≤ VIN ≤ 5.5 V
MIN
TYP
MAX
UNIT
–6%
4
6%
MHz
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t1
SCL
t5
t4
SDA_IN
t2
SDA_OUT
t3
Figure 1. I2C-Compatible Interface Specifications
8.8 Typical Characteristics
Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise
noted .
1.6
1.6
TA = -40°C
TA = +25°C
TA = +85°C
TA = -40°C
TA = +25°C
TA = +85°C
1.4
1.2
1.2
1
1
ILED2 (A)
ILED1 (A)
1.4
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
0
16
32
48
64
80
LED1 Code (dec#)
96
112
128
0
Figure 2. LED1 Flash Current vs Brightness Code
48
64
80
LED2 Code (dec#)
96
112
128
D002
0.2
TA = -40°C
TA = +25°C
TA = +85°C
0.16
TA = -40°C
TA = +25°C
TA = +85°C
0.18
0.16
0.14
0.14
0.12
0.12
ILED2 (A)
ILED1 (A)
32
Figure 3. LED2 Flash Current vs Brightness Code
0.2
0.18
0.1
0.08
0.1
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
0
0
16
32
48
64
80
LED1 Code (dec#)
96
112
128
0
16
D015
Figure 4. LED1 Torch Current vs Brightness Code
6
16
D001
32
48
64
80
LED2 Code (dec#)
96
112
128
D016
Figure 5. LED2 Torch Current vs Brightness Code
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Typical Characteristics (continued)
Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise
noted .
0.8
1.6
BRC = 0
BRC = 7
BRC = 15
BRC = 23
BRC = 31
BRC = 39
BRC = 47
BRC = 55
BRC = 63
ILED1 (A)
0.6
0.5
0.4
BRC = 71
BRC = 79
BRC = 87
BRC = 95
BRC = 103
BRC = 111
BRC = 119
BRC = 127
1.5
1.4
1.3
ILED1 (A)
0.7
0.3
1.2
1.1
1
0.2
0.9
0.1
0.8
0
2.5
3
3.5
4
VIN (V)
4.5
5
0.7
2.5
5.5
Figure 6. LED1 Current vs Input Voltage
4
VIN (V)
4.5
5
5.5
D004
1.6
BRC = 0
BRC = 7
BRC = 15
BRC = 23
BRC = 31
BRC = 39
BRC = 47
BRC = 55
BRC = 63
0.6
0.5
0.4
BRC = 71
BRC = 79
BRC = 87
BRC = 95
BRC = 103
BRC = 111
BRC = 119
BRC = 127
1.5
1.4
1.3
ILED2 (A)
0.7
ILED2 (A)
3.5
Figure 7. LED1 Current vs Input Voltage
0.8
0.3
1.2
1.1
1
0.2
0.9
0.1
0.8
0
2.5
3
3.5
4
VIN (V)
4.5
5
0.7
2.5
5.5
1.6
3.5
4
VIN (V)
4.5
5
5.5
D006
Figure 9. LED2 Current vs Input Voltage
1.62
TA = -40qC
TA = +25qC
TA = +85qC
1.58
TA = -40qC
TA = +25qC
TA = +85qC
1.6
1.58
1.56
1.56
1.54
1.54
ILED (A)
1.52
1.5
1.48
1.52
1.5
1.48
1.46
1.46
1.44
1.44
1.42
1.42
1.4
2.5
3
D005
Figure 8. LED2 Current vs Input Voltage
ILED (A)
3
D003
3
ILED = 1.5 A
3.5
4
VIN (V)
4.5
5
5.5
1.4
2.5
3
D021
ƒSW = 2 MHz
Flash
Figure 10. LED1/2 Current vs Input Voltage
ILED = 1.5 A
3.5
4
VIN (V)
4.5
5
ƒSW = 4 MHz
5.5
D022
Flash
Figure 11. LED1/2 Current vs Input Voltage
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Typical Characteristics (continued)
1.07
1.06
1.05
1.04
1.03
1.02
1.01
1
0.99
0.98
0.97
0.96
0.95
0.94
0.93
2.5
0.78
TA = -40qC
TA = +25qC
TA = +85qC
0.77
0.76
0.75
ILED (A)
ILED (A)
Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise
noted .
0.74
0.73
0.72
0.71
0.7
0.69
3
3.5
ILED = 1 A
4
VIN (V)
4.5
5
0.68
2.5
5.5
ƒSW = 2 MHz
Flash
4.5
5
5.5
D024
ƒSW = 2 MHz
Flash
0.2
TA = -40qC
TA = -+25qC
TA = +85qC
0.19
ILED (A)
0.19
ILED (A)
4
VIN (V)
Figure 13. LED1 and LED2 Current vs Input Voltage
TA = -40qC
TA = -+25qC
TA = +85qC
0.18
0.17
0.18
0.17
3
3.5
ILED = 179 mA
4
VIN (V)
4.5
5
0.16
2.5
5.5
3
3.5
D025
ƒSW = 2 MHz
Torch
ILED = 179 mA
Figure 14. LED Current vs Input Voltage
4
VIN (V)
4.5
5
5.5
D026
ƒSW = 4 MHz
Torch
Figure 15. LED Current vs Input Voltage
1.2
0.2
LED1, TA = -40qC
LED2, TA = -40qC
LED1, TA = +25qC
LED2, TA = +25qC
LED1, TA = +85qC
LED2, TA = +85qC
1
TA = -40qC
TA = +25qC
TA = +85qC
0.8
ISD (PA)
ILED (A)
3.5
ILED = 730 mA
0.2
0.19
3
D023
Figure 12. LED1/2 Current vs Input Voltage
0.16
2.5
LED1, TA = -40qC
LED2, TA = -40qC
LED1, TA = +25qC
LED2, TA = +25qC
LED1, TA = +85qC
LED2, TA = +85qC
0.18
0.6
0.4
0.17
0.2
0.16
2.5
3
ILED = 179 mA
3.5
4
VIN (V)
4.5
ƒSW = 2 MHz
5
5.5
3
D027
Torch
Figure 16. LED1 and LED2 Current vs Input Voltage
8
0
2.5
HWEN = 0 V
3.5
4
VIN (V)
4.5
5
5.5
D007
I2C = 0 V
Figure 17. Shutdown Current vs Input Voltage
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Typical Characteristics (continued)
Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise
noted .
3
7
TA = -40qC
TA = +25qC
TA = +85qC
2.5
5
ISB (PA)
2
ISB (PA)
TA = -40qC
TA = +25qC
TA = +85qC
6
1.5
1
4
3
2
0.5
1
0
2.5
3
3.5
HWEN = VIN
4
VIN (V)
4.5
5
0
2.5
5.5
I2C = VIN
TA = -40qC
TA = +25qC
TA = +85qC
4
ICL (A)
ISB (PA)
5
3
2
1
3
3.5
HWEN = 1.8 V
4
VIN (V)
4.5
5
5.5
2.2
2.16
2.12
2.08
2.04
2
1.96
1.92
1.88
1.84
1.8
1.76
1.72
1.68
1.64
1.6
2.5
I2C = 1.8 V
5
5.5
D008
TA = -40qC
TA = +25qC
TA = +85qC
2.7
2.9
3.1
ILED = 1.5 A
ICL = 1.9 A
3.3
3.5
VIN (V)
3.7
3.9
4.1
4.3
D011
ƒSW = 2 MHz
VLED = 4.5 V
Figure 21. Inductor Current Limit vs Input Voltage
3
2.8
2.6
2.4
ICL (A)
ICL (A)
4.5
I2C = 0 V
D010
Figure 20. Standby Current vs Input Voltage
2.2
2.16
2.12
2.08
2.04
2
1.96
1.92
1.88
1.84
1.8
1.76
1.72
1.68
1.64
1.6
2.5
4
VIN (V)
Figure 19. Standby Current vs Input Voltage
7
0
2.5
3.5
HWEN = 1.8 V
Figure 18. Standby Current vs Input Voltage
6
3
D009
2.2
2
1.8
TA = -40qC
TA = +25qC
TA = +85qC
2.7
2.9
ILED = 1.5 A
ICL = 1.9 A
TA = -40qC
TA = +25qC
TA = +85qC
1.6
3.1
3.3
3.5
VIN (V)
3.7
ƒSW = 4 MHz
3.9
4.1
4.3
1.4
2.5
2.75
3
D012
VLED = 4.5 V
Figure 22. Inductor Current Limit vs Input Voltage
ILED = 1.5 A
ICL = 2.8 A
3.25
3.5
3.75 4
VIN (V)
ƒSW = 2 MHz
4.25
4.5
4.75
5
D013
VLED = 4.5 V
Figure 23. Inductor Current Limit vs Input Voltage
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Typical Characteristics (continued)
Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise
noted .
3
2.125
2.8
2.1
TA = +25qC
TA = +85qC
TA = -40qC
2.075
2.6
2.05
fSW (MHz)
ICL (A)
2.4
2.2
2
2.025
2
1.975
1.95
1.8
1.925
TA = -40qC
TA = +25qC
TA = +85qC
1.6
1.4
2.5
2.75
3
ILED = 1.5 A
ICL = 2.8 A
3.25
1.9
3.5
3.75 4
VIN (V)
4.25
4.5
4.75
1.875
2.5
5
2.75
3
3.25
3.5
D014
ƒSW = 4 MHz
3.75 4
VIN (V)
4.25
4.5
4.75
5
D017
VLED = 4.5 V
Figure 24. Inductor Current Limit vs Input Voltage
Figure 25. 2-MHz Switching Frequency vs Input Voltage
4.25
TA = +25qC
TA = +85qC
TA = -40qC
4.2
4.15
fSW (MHz)
4.1
4.05
4
3.95
3.9
3.85
3.8
3.75
2.5
2.75
3
3.25
3.5
3.75 4
VIN (V)
4.25
4.5
4.75
5
D017
D018
Figure 26. 4-MHz Switching Frequency vs Input Voltage
9 Detailed Description
9.1 Overview
The LM3643 is a high-power white LED flash driver capable of delivering up to 1.5 A in either of the two parallel
LEDs. The total allowed LED current during operation of the LM3643 (ILED1+ILED2) is 1.5 A. The device
incorporates a 2-MHz or 4-MHz constant frequency-synchronous current-mode PWM boost converter and dual
high-side current sources to regulate the LED current over the 2.5-V to 5.5-V input voltage range.
The LM3643 PWM DC/DC boost converter switches and boosts the output to maintain at least VHR across each
of the current sources (LED1/2). This minimum headroom voltage ensures that both current sources remain in
regulation. If the input voltage is above the LED voltage + current source headroom voltage the device does not
switch, but turns the PFET on continuously (Pass mode). In Pass mode the difference between (VIN − ILED x
RPMOS) and the voltage across the LED is dropped across the current source.
10
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Overview (continued)
The LM3643 has three logic inputs including a hardware Flash Enable (STROBE), a hardware Torch Enable
(TORCH/TEMP, TORCH = default), and a Flash Interrupt input (TX) designed to interrupt the flash pulse during
high battery-current conditions. These logic inputs have internal 300-kΩ (typ.) pulldown resistors to GND.
Additional features of the LM3643 include an internal comparator for LED thermal sensing via an external NTC
thermistor and an input voltage monitor that can reduce the Flash current during low VIN conditions. It also has a
Hardware Enable (HWEN) pin that can be used to reset the state of the device and the registers by pulling the
HWEN pin to ground.
Control is done via an I2C-compatible interface. This includes adjustment of the Flash and Torch current levels,
changing the Flash Timeout Duration, and changing the switch current limit. Additionally, there are flag and
status bits that indicate flash current time-out, LED overtemperature condition, LED failure (open/short), device
thermal shutdown, TX interrupt, and VIN undervoltage conditions.
9.2 Functional Block Diagram
SW
Over Voltage
Comparator
IN
2/4 MHz
Oscillator
+
-
VREF
86 m:
Input Voltage
Flash Monitor
UVLO
ILED1
OUT
ILED2
PWM
Control
+
-
+
-
TORCH/
TEMP
VOVP
65 m:
INTC
Thermal
Shutdown
+150oC
+
-
LED1
Error
Amplifier
FB
SELECT
LED2
+
-
+
-
OUT-VHR
Current Sense/
Current Limit
NTC VTRIP
Slope
Compensation
SDA
Control
Logic/
Registers
2
SCL
Soft-Start
I C
Interface
HWEN
STROBE
TX
GND
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9.3 Feature Description
9.3.1 Flash Mode
In Flash Mode, the LED current sources (LED1/2) provide 128 target current levels from 10.9 mA to 1500 mA.
The total allowed LED current during operation is 1.5A (ILED1 + ILED2 = 1.5 A). Once the Flash sequence is
activated the current source (LED) ramps up to the programmed Flash current by stepping through all current
steps until the programmed current is reached. The headroom in the two current sources can be regulated to
provide 10.9 mA to 1.5 A on each of the two output legs. There is an option in the register settings to keep the
two currents in the output leg the same.
When the device is enabled in Flash Mode through the Enable Register, all mode bits in the Enable Register are
cleared after a flash time-out event.
9.3.2 Torch Mode
In Torch mode, the LED current sources (LED1/2) provide 128 target current levels from 0.977 mA to 179 mA.
The Torch currents are adjusted via the LED1 and LED2 LED Torch Brightness Registers. Torch mode is
activated by the Enable Register (setting M1, M0 to '10'), or by pulling the TORCH/TEMP pin HIGH when the pin
is enabled (Enable Register) and set to Torch Mode. Once the TORCH sequence is activated the active current
sources (LED1/2) ramps up to the programmed Torch current by stepping through all current steps until the
programmed current is reached. The rate at which the current ramps is determined by the value chosen in the
Timing Register.
Torch Mode is not affected by Flash Timeout or by a TX Interrupt event.
9.3.3 IR Mode
In IR Mode, the target LED current is equal to the value stored in the LED1/2 Flash Brightness Registers. When
IR mode is enabled (setting M1, M0 to '01'), the boost converter turns on and set the output equal to the input
(pass-mode). At this point, toggling the STROBE pin enables and disables the LED1/2 current sources (if
enabled). The strobe pin can only be set to be Level sensitive, meaning all timing of the IR pulse is externally
controlled. In IR Mode, the current sources do not ramp the LED outputs to the target. The current transitions
immediately from off to on and then on to off.
BOOST
VOUT
PASS
OFF
STROBE
ILED1
M1,M0 = Z00[
LED1,LED2 = Z11[
STROBE EN = Z1[
M1,M0 = Z01[
LED1,LED2 = Z10[
STROBE EN = Z1[
M1,M0 = Z01[
LED1,LED2 = Z11[
STROBE EN = Z1[
ILED2
Figure 27. IR Mode with Boost
12
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Feature Description (continued)
VOUT
STROBE
ILED1
M1,M0 = Z00[
LED1,LED2 = Z11[
STROBE EN = Z1[
M1,M0 = Z01[
LED1,LED2 = Z11[
STROBE EN = Z1[
M1,M0 = Z01[
LED1,LED2 = Z10[
STROBE EN = Z1[
ILED2
Figure 28. IR Mode Pass Only
VOUT
STROBE
ILED1
ILED2
TIME-OUT
Reached
VOUT goes
low, LED1 and
2 turn off
TIME-OUT
Start
TIME-OUT
RESET
TIME-OUT
Start
TIME-OUT
RESET
TIME-OUT
Start
M1,M0 = Z01[
LED1,LED2 = Z11[
STROBE EN = Z1[
Time-Out
Value
Figure 29. IR Mode Timeout
9.4 Device Functioning Modes
9.4.1 Start-Up (Enabling The Device)
Turn on of the LM3643 Torch and Flash modes can be done through the Enable Register. On start-up, when
VOUT is less than VIN the internal synchronous PFET turns on as a current source and delivers 200 mA (typ.) to
the output capacitor. During this time the current source (LED) is off. When the voltage across the output
capacitor reaches 2.2 V (typ.) the current source turns on. At turnon the current source steps through each
FLASH or TORCH level until the target LED current is reached. This gives the device a controlled turnon and
limits inrush current from the VIN supply.
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Device Functioning Modes (continued)
9.4.2 Pass Mode
The LM3643 starts up in Pass Mode and stays there until Boost Mode is needed to maintain regulation. If the
voltage difference between VOUT and VLED falls below VHR, the device switches to Boost Mode. In Pass Mode the
boost converter does not switch, and the synchronous PFET turns fully on bringing VOUT up to VIN − ILED x
RPMOS. In Pass Mode the inductor current is not limited by the peak current limit.
9.4.3 Power Amplifier Synchronization (TX)
The TX pin is a Power Amplifier Synchronization input. This is designed to reduce the flash LED current and thus
limit the battery current during high battery current conditions such as PA transmit events. When the LM3643 is
engaged in a Flash event, and the TX pin is pulled high, the LED current is forced into Torch Mode at the
programmed Torch current setting. If the TX pin is then pulled low before the Flash pulse terminates, the LED
current returns to the previous Flash current level. At the end of the Flash time-out, whether the TX pin is high or
low, the LED current turns off.
9.4.4 Input Voltage Flash Monitor (IVFM)
The LM3643 has the ability to adjust the flash current based upon the voltage level present at the IN pin utilizing
the Input Voltage Flash Monitor (IVFM). The adjustable threshold IVFM-D ranges from 2.9 V to 3.6 V in 100-mV
steps, with three different usage modes (Stop and Hold, Adjust Down Only, Adjust Up and Down). The Flags2
Register has the IVFM flag bit set when the input voltage crosses the IVFM-D value. Additionally, the IVFM-D
threshold sets the input voltage boundary that forces the LM3643 to either stop ramping the flash current during
start-up (Stop and Hold Mode) or to start decreasing the LED current during the flash (Down Adjust Only and Up
and Down Adjust). In Adjust Up and Down mode, the IVFM-D value plus the hysteresis voltage threshold set the
input voltage boundary that forces the LM3643 to start ramping the flash current back up towards the target.
14
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Device Functioning Modes (continued)
IVFM ENABLE
LEVEL STROBE
VIN PROFILE for Stop and Hold Mode
IVFM-D
Output Current
Profile in Stop
and Hold Mode
VIN PROFILE for Down Mode
T-Filter = 4Ps
Set Target Flash Current
Dotted line shows Output
Current Profile with IVFM
Disabled
SET RAMP FROM
THE RAMP
REGISTER USED
Hysteresis = 0 V or 50 mV
Hysteresis
IVFM-D
VIN PROFILE for Up/ Down Mode
T-Filter = 4Ps
Output Current
Profile in Down
Mode
Hysteresis
IVFM-D
Output Current
Profile in Up and
Down Mode
Figure 30. IVFM Modes
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Device Functioning Modes (continued)
9.4.5 Fault/Protections
9.4.5.1 Fault Operation
If the LM3643 enters a fault condition, the device sets the appropriate flag in the Flags1 and Flags2 Registers
(0x0A and 0x0B), and place the device into standby by clearing the Mode Bits ([1],[0]) in the Enable Register.
The LM3643 remains in standby until an I2C read of the Flags1 and Flags2 Registers are completed. Upon
clearing the flags/faults, the device can be restarted (Flash, Torch, IR, etc.). If the fault is still present, the
LM3643 re-enters the fault state and enters standby again.
9.4.5.2 Flash Time-Out
The Flash Time-Out period sets the amount of time that the Flash Current is being sourced from the current
sources (LED1/2). The LM3643 has 16 timeout levels ranging from 10 ms to 400 ms (see Timing Configuration
Register (0x08) for more detail).
9.4.5.3 Overvoltage Protection (OVP)
The output voltage is limited to typically 5 V (see VOVP spec in the Electrical Characteristics). In situations such
as an open LED, the LM3643 raises the output voltage in order to try and keep the LED current at its target
value. When VOUT reaches 5 V (typ.) the overvoltage comparator trips and turns off the internal NFET. When
VOUT falls below the “VOVP Off Threshold”, the LM3643 begins switching again. The mode bits are cleared, and
the OVP flag is set, when an OVP condition is present for three rising OVP edges. This prevents momentary
OVP events from forcing the device to shut down.
9.4.5.4 Current Limit
The LM3643 features two selectable inductor current limits that are programmable through the I2C-compatible
interface. When the inductor current limit is reached, the LM3643 terminates the charging phase of the switching
cycle. Switching resumes at the start of the next switching period. If the overcurrent condition persists, the device
operates continuously in current limit.
Since the current limit is sensed in the NMOS switch, there is no mechanism to limit the current when the device
operates in Pass Mode (current does not flow through the NMOS in pass mode). In Boost mode or Pass mode if
VOUT falls below 2.3 V, the device stops switching, and the PFET operates as a current source limiting the
current to 200 mA. This prevents damage to the LM3643 and excessive current draw from the battery during
output short-circuit conditions. The mode bits are not cleared upon a Current Limit event, but a flag is set.
9.4.5.5 NTC Thermistor Input (Torch/Temp)
The TORCH/TEMP pin, when set to TEMP mode, serves as a threshold detector and bias source for negative
temperature coefficient (NTC) thermistors. When the voltage at TEMP goes below the programmed threshold,
the LM3643 is placed into standby mode. The NTC threshold voltage is adjustable from 200 mV to 900 mV in
100-mV steps. The NTC bias current is set to 50 µA. The NTC detection circuitry can be enabled or disabled via
the Enable Register. If enabled, the NTC block turns on and off during the start and stop of a Flash/Torch event.
Additionally, the NTC input looks for an open NTC connection and a shorted NTC connection. If the NTC input
falls below 100 mV, the NTC short flag is set, and the device is disabled. If the NTC input rises above 2.3 V, the
NTC Open flag is set, and the device is disabled. These fault detections can be individually disabled/enabled via
the NTC Open Fault Enable bit and the NTC Short Fault Enable bit.
VIN
NTC Control Block
INTC
TEMP
VTRIP
NTC
+
Control
Logic
Figure 31. Temp Detection Diagram
16
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Device Functioning Modes (continued)
9.4.5.6 Undervoltage Lockout (UVLO)
The LM3643 has an internal comparator that monitors the voltage at IN and forces the LM3643 into standby if
the input voltage drops to 2.5 V. If the UVLO monitor threshold is tripped, the UVLO flag bit is set in the Flags1
Register (0x0A). If the input voltage rises above 2.5 V, the LM3643 is not available for operation until there is an
I2C read of the Flags1 Register (0x0A). Upon a read, the Flags1 register is cleared, and normal operation can
resume if the input voltage is greater than 2.5 V.
9.4.5.7 Thermal Shutdown (TSD)
When the LM3643 die temperature reaches 150°C, the thermal shutdown detection circuit trips, forcing the
LM3643 into standby and writing a '1' to the corresponding bit of the Flags1 Register (0x0A) (Thermal Shutdown
bit). The LM3643 is only allowed to restart after the Flags1 Register (0x0A) is read, clearing the fault flag. Upon
restart, if the die temperature is still above 150°C, the LM3643 resets the Fault flag and re-enters standby.
9.4.5.8 LED and/or VOUT Short Fault
The LED Fault flags read back a '1' if the device is active in Flash or Torch mode and either active LED output
experiences a short condition. The Output Short Fault flag reads back a '1' if the device is active in Flash or
Torch mode and the boost output experiences a short condition. An LED short condition is determined if the
voltage at LED1 or LED2 goes below 500 mV (typ.) while the device is in Torch or Flash mode. There is a
deglitch time of 256 μs before the LED Short flag is valid and a deglitch time of 2.048 ms before the VOUT Short
flag is valid. The LED Short Faults can be reset to '0' by removing power to the LM3643, setting HWEN to '0',
setting the SW RESET bit to a '1', or by reading back the Flags1 Register (0x0A on LM3643). The mode bits are
cleared upon an LED and/or VOUT short fault.
9.5 Programming
9.5.1 Control Truth Table
MODE1
MODE0
STROBE EN
TORCH EN
STROBE PIN
TORCH PIN
ACTION
0
0
0
0
X
X
Standby
0
0
0
1
X
pos edge
Ext Torch
0
0
1
0
pos edge
X
Ext Flash
0
0
1
1
0
pos edge
Standalone Torch
0
0
1
1
pos edge
0
Standalone Flash
0
0
1
1
pos edge
pos edge
Standalone Flash
1
0
X
X
X
X
Int Torch
1
1
X
X
X
X
Int Flash
0
1
0
X
X
X
IRLED Standby
0
1
1
X
0
X
IRLED Standby
0
1
1
X
pos edge
X
IRLED enabled
9.5.2 I2C-Compatible Interface
9.5.2.1 Data Validity
The data on SDA must be stable during the HIGH period of the clock signal (SCL). In other words, the state of
the data line can only be changed when SCL is LOW.
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SCL
SDA
data
change
allowed
data
valid
data
valid
data
change
allowed
data
change
allowed
Figure 32. Data Validity Data
A pullup resistor between the controller's VIO line and SDA must be greater than [(VIO-VOL) / 3mA] to meet the
VOL requirement on SDA. Using a larger pullup resistor results in lower switching current with slower edges, while
using a smaller pullup results in higher switching currents with faster edges.
9.5.2.2 Start and Stop Conditions
START and STOP conditions classify the beginning and the end of the I2C session. A START condition is
defined as the SDA signal transitioning from HIGH to LOW while SCL line is HIGH. A STOP condition is defined
as the SDA transitioning from LOW to HIGH while SCL is HIGH. The I2C master always generates START and
STOP conditions. The I2C bus is considered busy after a START condition and free after a STOP condition.
During data transmission, the I2C master can generate repeated START conditions. First START and repeated
START conditions are equivalent, function-wise.
SDA
SCL
S
P
Start Condition
Stop Condition
Figure 33. Start and Stop Conditions
9.5.2.3 Transferring Data
Every byte put on the SDA line must be eight bits long, with the most significant bit (MSB) transferred first. Each
byte of data has to be followed by an acknowledge bit. The acknowledge related clock pulse is generated by the
master. The master releases the SDA line (HIGH) during the acknowledge clock pulse. The LM3643 pulls down
the SDA line during the 9th clock pulse, signifying an acknowledge. The LM3643 generates an acknowledge
after each byte is received. There is no acknowledge created after data is read from the device.
After the START condition, the I2C master sends a chip address. This address is seven bits long followed by an
eighth bit which is a data direction bit (R/W). The LM3643 7-bit address is 0x63. The device address for the
LM3643A is 0x67. For the eighth bit, a '0' indicates a WRITE and a '1' indicates a READ. The second byte
selects the register to which the data is written. The third byte contains data to write to the selected register.
ack from slave
ack from slave
start
msb Chip Address lsb
w
ack
msb Register Add lsb
ack
start
Id = 63h
w
ack
addr = 0Ah
ack
ack from slave
msb
DATA
lsb
ack
stop
ack
stop
SCL
SDA
Data = 03h
Figure 34. Write Cycle W = Write (SDA = "0") R = Read (SDA = "1") Ack = Acknowledge
(SDA Pulled Down by Either Master or Slave) ID = Chip Address, 63h for LM3643
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9.5.2.4 I2C-Compatible Chip Address
The device address for the LM3643 is 1100011 (0x63). The device address for the LM3643A is 1100111
(0x67).After the START condition, the I2C-compatible master sends the 7-bit address followed by an eighth read
or write bit (R/W). R/W = 0 indicates a WRITE and R/W = 1 indicates a READ. The second byte following the
device address selects the register address to which the data is written. The third byte contains the data for the
selected register.
MSB
1
Bit 7
LSB
1
Bit 6
0
Bit 5
0
Bit 4
0
Bit 3
1
Bit 2
1
Bit 1
R/W
Bit 0
2
I C Slave Address (chip address)
Figure 35. I2C-Compatible Chip Address
9.6 Register Descriptions
REGISTER NAME
POWER ON/RESET VALUE
INTERNAL HEX ADDRESS
LM3643
Enable Register
0x01
IVFM Register
0x02
0x80
0x01
LED1 Flash Brightness Register
0x03
0xBF
LED2 Flash Brightness Register
0x04
0x3F
LED1 Torch Brightness Register
0x05
0xBF
LED2 Torch Brightness Register
0x06
0x3F
Boost Configuration Register
0x07
0x09
Timing Configuration Register
0x08
0x1A
TEMP Register
0x09
0x08
Flags1 Register
0x0A
0x00
Flags2 Register
0x0B
0x00
Device ID Register
0x0C
0x02
Last Flash Register
0x0D
0x00
9.6.1 Enable Register (0x01)
Bit 7
Bit 6
TX Pin Enable
0 = Disabled
1 = Enabled
(Default )
Strobe Type
0 = Level
Triggered
(Default)
1 = Edge
Triggered
Bit 5
Strobe Enable
0 = Disabled
(Default )
1 = Enabled
Bit 4
TORCH/TEMP
Pin Enable
0 = Disabled
(Default )
1 = Enabled
Bit 3
Mode Bits: M1, M0
'00' = Standby (Default)
'01' = IR Drive
'10' = Torch
'11' = Flash
Bit 2
Bit 1
LED2 Enable
0 = OFF
(Default )
1 = ON
Bit 0
LED1 Enable
0 = OFF
(Default)
1 = ON
NOTE
Edge Strobe Mode is not valid in IR MODE. Switching between Level and Edge Strobe
Types while the device is enabled is not recommended.
In Edge or Level Strobe Mode, it is recommended that the trigger pulse width be set
greater than 1 ms to ensure proper turn-on of the device.
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9.6.2 IVFM Register (0x02)
Bit 7
Bit 6
UVLO
Circuitry
(Default)
0 = Disabled
(Default)
1 = Enabled
RFU
Bit 5
Bit 4
Bit 3
IVFM Levels
000 = 2.9 V (Default)
001 = 3 V
010 = 3.1 V
011 = 3.2 V
100 = 3.3 V
101 = 3.4 V
110 = 3.5 V
111 = 3.6 V
Bit 2
IVFM
Hysteresis
0 = 0 mV
(Default)
1 = 50 mV
Bit 1
Bit 0
IVFM Selection
00 = Disabled
01 = Stop and Hold Mode (Default)
10 = Down Mode
11 = Up and Down Mode
NOTE
IVFM Mode Bits are static once the LM3643 is enabled in Torch, Flash or IR modes. If the
IVFM mode needs to be updated, disable the device and then change the mode bits to the
desired state.
9.6.3 LED1 Flash Brightness Register (0x03)
Bit 7
LED2 Flash
Current
Override
0 = LED2
Flash Current
is not set to
LED1 Flash
Current
1 = LED2
Flash Current
is set to LED1
Flash Current
(Default)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 2
Bit 1
Bit 0
Bit 2
Bit 1
Bit 0
LED1 Flash Brightness Level
IFLASH1/2 (mA) ≈ (Brightness Code × 11.725 mA) + 10.9 mA
0000000 = 10.9 mA
.......................
0111111 = 729 mA (Default)
.......................
1111111 = 1.5 A
9.6.4 LED2 Flash Brightness Register (0x04)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
LED2 Flash Brightness Levels
IFLASH1/2 (mA) ≈ (Brightness Code × 11.725 mA) + 10.9 mA
0000000 = 10.9 mA
.......................
0111111 = 729 mA (Default)
.......................
1111111 = 1.5 A
RFU
9.6.5 LED1 Torch Brightness Register (0x05)
Bit 7
LED2 Torch
Current
Override
0 = LED2
Torch Current
is not set to
LED1 Torch
Current
1 = LED2
Torch Current
is set to LED1
Torch Current
(Default)
20
Bit 6
Bit 5
Bit 4
Bit 3
LED1 Torch Brightness Levels
ITORCH1/2 (mA) ≈ (Brightness Code × 1.4 mA) + 0.977 mA
0000000 = 0.977 mA
.......................
0111111 = 89.3 mA (Default)
.......................
1111111 = 179 mA
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9.6.6 LED2 Torch Brightness Register (0x06)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LED2 Torch Brightness Levels
ITORCH1/2 (mA) ≈ (Brightness Code × 1.4 mA) + 0.977 mA
0000000 = 0.977 mA
.......................
0111111 = 89.3 mA (Default)
.......................
1111111 = 179 mA
RFU
9.6.7 Boost Configuration Register (0x07)
Bit 7
Bit 6
Software
Reset Bit
0 = Not Reset
(Default)
1 = Reset
Bit 5
RFU
RFU
Bit 4
RFU
Bit 3
LED Pin Short
Fault Detect
0 = Disabled
1 = Enabled
(Default)
Bit 2
Bit 1
Boost Mode
0 = Normal
(Default)
1 = Pass Mode
Only
Boost
Frequency
Select
0 = 2 MHz
(Default)
1 = 4 MHz
Bit 0
Boost Current
Limit Setting
0 = 1.9 A
1 = 2.8 A
(Default)
9.6.8 Timing Configuration Register (0x08)
Bit 7
RFU
Bit 6
Bit 5
Bit 4
Torch Current Ramp Time
000 = No Ramp
001 = 1 ms (Default)
010 = 32 ms
011 = 64 ms
100 = 128 ms
101 = 256 ms
110 = 512 ms
111 = 1024 ms
Bit 3
Bit 2
Bit 1
Bit 0
Bit 1
Bit 0
Flash Time-Out Duration
0000 = 10 ms
0001 = 20 ms
0010 = 30 ms
0011 = 40 ms
0100 = 50 ms
0101 = 60 ms
0110 = 70 ms
0111 = 80 ms
1000 = 90 ms
1001 = 100 ms
1010 = 150 ms (Default)
1011 = 200 ms
1100 = 250 ms
1101 = 300 ms
1110 = 350 ms
1111 = 400 ms
9.6.9 TEMP Register (0x09)
Bit 7
Bit 6
RFU
TORCH
Polarity
0 = Active
High (Default)
(Pulldown
Resistor
Enabled)
1 = Active Low
(Pulldown
Resistor
Disabled)
Bit 5
NTC Open
Fault Enable
0 = Disabled
(Default)
1 =Enable
Bit 4
NTC Short
Fault Enable
0 = Disabled
(Default)
1 =Enable
Bit 3
Bit 2
TEMP Detect Voltage Threshold
000 = 0.2 V
001 = 0.3 V
010 = 0.4 V
011 = 0.5 V
100 = 0.6 V (Default)
101 = 0.7 V
110 = 0.8 V
111 = 0.9 V
TORCH/TEMP
Function
Select
0 = TORCH
(Default)
1 = TEMP
NOTE
The Torch Polarity bit is static once the LM3643 is enabled in Torch, Flash or IR modes. If
the Torch Polarity bit needs to be updated, disable the device and then change the Torch
Polarity bit to the desired state.
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9.6.10 Flags1 Register (0x0A)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
TX Flag
VOUT Short
Fault
VLED1 Short
Fault
VLED2 Short
Fault
Current Limit
Flag
Thermal
Shutdown
(TSD) Fault
UVLO Fault
Flash Time-Out
Flag
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RFU
NTC Short
Fault
NTC Open Fault
IVFM Trip
Flag
OVP Fault
TEMP Trip
Fault
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 1
Bit 0
9.6.11 Flags2 Register (0x0B)
Bit 7
RFU
Bit 6
RFU
9.6.12 Device ID Register (0x0C)
Bit 7
Bit 6
Bit 5
RFU
RFU
Device ID
'000'
Silicon Revision Bit
'010'
9.6.13 Last Flash Register (0x0D)
Bit 7
RFU
22
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
The value stored is always the last current value the IVFM detection block set. ILED = IFLASH-TARGET × ((Code + 1) / 128)
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10 Applications and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
The LM3643 can drive two flash LEDs at currents up to 1.5 A per LED. The total LED current the LM3643 boost
can deliver is 1.5 A (ILED1 + ILED2 ). The 2-MHz/4-MHz DC/DC boost regulator allows for the use of small value
discrete external components.
10.2 Typical Application
L1
1 PH
LM3643
VIN
2.5V t 5.5V
IN
C1
10 PF
SW
HWEN
OUT
10 PF
SDA
SCL
PP/PC
STROBE
C2
LED1
LED2
TORCH/
TEMP
TX
D1
D2
GND
Figure 36. LM3643 Typical Application
10.2.1 Design Requirements
Example requirements based on default register values:
DESIGN PARAMETER
EXAMPLE VALUE
Input Voltage Range
2.5 V to 5.5 V
Brightness Control
I2C Register
LED Configuration
2 Parallel Flash LEDs
Boost Switching Frequency
2 MHz (4 MHz selectable)
Flash Brightness
750 mA per LED
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10.2.2 Detailed Design Procedure
10.2.2.1 Output Capacitor Selection
The LM3643 is designed to operate with a 10-µF ceramic output capacitor. When the boost converter is running,
the output capacitor supplies the load current during the boost converter on-time. When the NMOS switch turns
off, the inductor energy is discharged through the internal PMOS switch, supplying power to the load and
restoring charge to the output capacitor. This causes a sag in the output voltage during the on-time and a rise in
the output voltage during the off-time. The output capacitor is therefore chosen to limit the output ripple to an
acceptable level depending on load current and input/output voltage differentials and also to ensure the converter
remains stable.
Larger capacitors such as a 22-µF or capacitors in parallel can be used if lower output voltage ripple is desired.
To estimate the output voltage ripple considering the ripple due to capacitor discharge (ΔVQ) and the ripple due
to the capacitors ESR (ΔVESR) use the following equations:
For continuous conduction mode, the output voltage ripple due to the capacitor discharge is:
ILED x (VOUT - VIN)
'VQ =
fSW x VOUT x COUT
(1)
The output voltage ripple due to the output capacitors ESR is found by:
I LED x VOUT
+ 'I L·
'VESR = R ESR x §
VIN
¹
©
where
'IL =
VIN x (VOUT - VIN )
2 x f SW x L x VOUT
(2)
In ceramic capacitors the ESR is very low so the assumption is that 80% of the output voltage ripple is due to
capacitor discharge and 20% from ESR. Table 1 lists different manufacturers for various output capacitors and
their case sizes suitable for use with the LM3643.
10.2.2.2 Input Capacitor Selection
Choosing the correct size and type of input capacitor helps minimize the voltage ripple caused by the switching
of the LM3643 boost converter and reduce noise on the boost converter's input pin that can feed through and
disrupt internal analog signals. In the typical application circuit a 10-µF ceramic input capacitor works well. It is
important to place the input capacitor as close as possible to the LM3643 input (IN) pin. This reduces the series
resistance and inductance that can inject noise into the device due to the input switching currents. Table 1 lists
various input capacitors recommended for use with the LM3643.
Table 1. Recommended Input/Output Capacitors (X5R/X7R Dielectric)
MANUFACTURER
TDK Corporation
TDK Corporation
PART NUMBER
VALUE
CASE SIZE
VOLTAGE RATING
C1608JB0J106M
10 µF
0603 (1.6 mm × 0.8 mm × 0.8 mm)
6.3 V
C2012JB1A106M
10 µF
0805 (2.0 mm × 1.25 mm × 1.25 mm)
10 V
Murata
GRM188R60J106M
10 µF
0603 (1.6 mm x 0.8 mm x 0.8 mm)
6.3 V
Murata
GRM21BR61A106KE19
10 µF
0805 (2.0 mm × 1.25 mm × 1.25 mm)
10 V
10.2.2.3 Inductor Selection
The LM3643 is designed to use a 0.47-µH or 1-µH inductor. Table 2 lists various inductors and their
manufacturers that work well with the LM3643. When the device is boosting (VOUT > VIN) the inductor is typically
the largest area of efficiency loss in the circuit. Therefore, choosing an inductor with the lowest possible series
resistance is important. Additionally, the saturation rating of the inductor should be greater than the maximum
operating peak current of the LM3643. This prevents excess efficiency loss that can occur with inductors that
operate in saturation. For proper inductor operation and circuit performance, ensure that the inductor saturation
and the peak current limit setting of the LM3643 are greater than IPEAK in the following calculation:
24
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IPEAK =
I LOAD VOUT
V x (VOUT - VIN)
x
+ 'IL where 'IL = IN
K
VIN
2 x f SW x L x VOUT
where
•
ƒSW = 2 or 4 MHz
(3)
Efficiency details can be found in the Application Curves .
Table 2. Recommended Inductors
MANUFACTURER
L
PART NUMBER
DIMENSIONS (L×W×H)
ISAT
RDC
TOKO
0.47 µH
DFE201610P-R470M
2.0 mm x 1.6 mm x 1.0 mm
4.1 A
32 mΩ
TOKO
1 µH
DFE201610P-1R0M
2.0 mm x 1.6 mm x 1.0 mm
3.7 A
58 mΩ
10.2.3 Application Curves
100
100
95
95
90
90
85
85
80
80
KLED (%)
KLED (%)
Ambient temperature is 25°C, input voltage is 3.6V, HWEN = VIN, CIN = 2 × 10 µF, COUT = 2 × 10 µF and L = 1 µH, unless
otherwise noted.
75
70
VLED = 3.0V
VLED = 3.2V
VLED = 3.5V
VLED = 3.8V
VLED = 4.1V
VLED = 4.4V
65
60
55
50
2.5
3
75
70
VLED = 3.0V
VLED = 3.2V
VLED = 3.5V
VLED = 3.8V
VLED = 4.1V
VLED = 4.4V
65
60
55
3.5
ILED = 1.5 A
4
VIN (V)
4.5
5
50
2.5
5.5
ƒSW = 2 MHz
Flash
3.5
ILED = 1.5 A
Figure 37. 2-MHz LED Efficiency vs Input Voltage
4
VIN (V)
4.5
5
5.5
D020
ƒSW = 2 MHz
Flash
Figure 38. 4-MHz LED Efficiency vs Input Voltage
100
100
TA = -40qC
TA = +25qC
TA = +85qC
96
92
92
88
88
84
84
80
76
80
76
72
72
68
68
64
64
60
2.5
60
2.5
3
ILED = 1.5A
VLED = 3.55 V
3.5
4
VIN (V)
4.5
5
TA = -40qC
TA = +25qC
TA = +85qC
96
KLED (%)
KLED (%)
3
D019
5.5
3
D028
ƒSW = 2 MHz
Flash
Figure 39. LED Efficiency vs Input Voltage
ILED = 1.5A
VLED = 3.55 V
3.5
4
VIN (V)
4.5
5
5.5
ƒSW = 4 MHz
D029
Flash
Figure 40. LED Efficiency vs Input Voltage
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Ambient temperature is 25°C, input voltage is 3.6V, HWEN = VIN, CIN = 2 × 10 µF, COUT = 2 × 10 µF and L = 1 µH, unless
otherwise noted.
100
100
TA = -40qC
TA = +25qC
TA = +85qC
96
92
88
88
84
84
KLED (%)
KLED (%)
92
80
76
80
76
72
72
68
68
64
64
60
2.5
60
2.5
3
3.5
ILED = 1 A
VLED = 3.32 V
4
VIN (V)
4.5
5
5.5
ƒSW = 2 MHz
Flash
4
VIN (V)
4.5
5
5.5
D031
ƒSW = 2 MHz
Flash
Figure 42. LED Efficiency vs Input Voltage
100
TA = -40qC
TA = +25qC
TA = +85qC
96
92
90
88
85
84
80
80
76
75
70
72
65
68
60
64
55
60
2.5
50
2.5
3
3.5
ILED1 and LED2 = 729 mA
VLED = 3.18 V
4
VIN (V)
4.5
5
TA = -40qC
TA = +25qC
TA = +85qC
95
KLED (%)
KLED (%)
3.5
ILED = 729 mA
VLED = 3.18 V
100
5.5
3
3.5
D032
Flash
ƒSW = 2 MHz
ILED = 179 mA
VLED = 2.83 V
Figure 43. LED Efficiency vs Input Voltage
4
VIN (V)
4.5
5
5.5
D033
Torch
ƒSW = 2 MHz
Figure 44. LED Efficiency vs Input Voltage
100
100
TA = -40qC
TA = +25qC
TA = +85qC
95
90
90
85
85
80
80
75
70
75
70
65
65
60
60
55
55
50
2.5
50
2.5
3
3.5
ILED = 179 mA
VLED = 2.83 V
4
VIN (V)
4.5
5
TA = -40qC
TA = +25qC
TA = +85qC
95
KLED (%)
KLED (%)
3
D030
Figure 41. LED Efficiency vs Input Voltage
5.5
3
3.5
D034
ƒSW = 4 MHz
Torch
Figure 45. LED Efficiency vs Input Voltage
26
TA = -40qC
TA = +25qC
TA = +85qC
96
ILED1 and LED2 = 179 mA
VLED = 2.83 V
4
VIN (V)
4.5
5
5.5
D035
ƒSW = 2 MHz
Torch
Figure 46. LED Efficiency vs Input Voltage
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Ambient temperature is 25°C, input voltage is 3.6V, HWEN = VIN, CIN = 2 × 10 µF, COUT = 2 × 10 µF and L = 1 µH, unless
otherwise noted.
100
TA = -40qC
TA = +25qC
TA = +85qC
95
90
VOUT (2 V/DIV)
ILED1 (500 mA/DIV)
KLED (%)
85
80
ILED2 (500 mA/DIV)
75
70
IIN (1 A/DIV)
65
60
55
50
2.5
3
3.5
ILED1 and LED2 = 179 mA
VLED = 2.83 V
4
VIN (V)
4.5
5
Time (400 Ps / DIV)
5.5
D036
ƒSW = 4 MHz
Torch
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Figure 47. LED Efficiency vs Input Voltage
ƒSW = 2 MHz
Figure 48. Start-Up
Tx Signal
VOUT (2 V/DIV)
VOUT (2 V/DIV)
ILED1 (500 mA/DIV)
ILED1 (500 mA/DIV)
ILED2 (500 mA/DIV)
ILED2 (500 mA/DIV)
IIN (1 A/DIV)
IIN (1 A/DIV)
Time (400 Ps / DIV)
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Time (2 ms / DIV)
ƒSW = 2 MHz
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Figure 49. Ramp Down
ƒSW = 2 MHz
Figure 50. TX Interrupt
VOUT (50 mV/DIV)
VOUT (50 mV/DIV)
ILED1 (20 mA/DIV)
ILED1 (20 mA/DIV)
ILED2 (20 mA/DIV)
ILED2 (20 mA/DIV)
IL (100 mA/DIV)
IL (100 mA/DIV)
Time (400 ns / DIV)
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Time (400 ns / DIV)
ƒSW = 2 MHz
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Figure 51. Ripple @ 2 MHz
ƒSW = 4 MHz
Figure 52. Ripple @ 4 MHz
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Ambient temperature is 25°C, input voltage is 3.6V, HWEN = VIN, CIN = 2 × 10 µF, COUT = 2 × 10 µF and L = 1 µH, unless
otherwise noted.
VIN (50 mV/DIV) w/ Offset = 3.2V
VIN (50 mV/DIV) w/ Offset = 3.2V
ILED1 (200 mA/DIV)
ILED1 (200 mA/DIV)
ILED2 (200 mA/DIV)
ILED2 (200 mA/DIV)
IIN (500 mA/DIV)
IIN (500 mA/DIV)
Time (400 Ps / DIV)
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Time (400 Ps / DIV)
ƒSW = 2 MHz
VIVFM = 3.2 V
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
Figure 53. IVFM - Ramp and Hold
ƒSW = 2 MHz
VIVFM = 3.2 V
Figure 54. IVFM - Down Adjust Only
VIN (50 mV/DIV) w/ Offset = 3.2V
ILED1 (200 mA/DIV)
ILED2 (200 mA/DIV)
IIN (500 mA/DIV)
Time (400 Ps / DIV)
ILED1 = ILED2 = 730 mA
VLED = 3.18 V
ƒSW = 2 MHz
VIVFM = 3.2 V
Figure 55. IVFM - Up and Down Adjust
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11 Power Supply Recommendations
The LM3643 is designed to operate from an input voltage supply range between 2.5 V and 5.5 V. This input
supply must be well regulated and capable to supply the required input current. If the input supply is located far
from the LM3643 additional bulk capacitance may be required in addition to the ceramic bypass capacitors.
12 Layout
12.1 Layout Guidelines
The high switching frequency and large switching currents of the LM3643 make the choice of layout important.
The following steps should be used as a reference to ensure the device is stable and maintains proper LED
current regulation across its intended operating voltage and current range.
1. Place CIN on the top layer (same layer as the LM3643) and as close to the device as possible. The input
capacitor conducts the driver currents during the low-side MOSFET turn-on and turn-off and can detect
current spikes over 1 A in amplitude. Connecting the input capacitor through short, wide traces to both the IN
and GND pins reduces the inductive voltage spikes that occur during switching which can corrupt the VIN
line.
2. Place COUT on the top layer (same layer as theLM3643) and as close as possible to the OUT and GND pin.
The returns for both CIN and COUT should come together at one point, as close to the GND pin as possible.
Connecting COUT through short, wide traces reduce the series inductance on the OUT and GND pins that can
corrupt the VOUT and GND lines and cause excessive noise in the device and surrounding circuitry.
3. Connect the inductor on the top layer close to the SW pin. There should be a low-impedance connection
from the inductor to SW due to the large DC inductor current, and at the same time the area occupied by the
SW node should be small so as to reduce the capacitive coupling of the high dV/dT present at SW that can
couple into nearby traces.
4. Avoid routing logic traces near the SW node so as to avoid any capacitively coupled voltages from SW onto
any high-impedance logic lines such as TORCH/TEMP, STROBE, HWEN, SDA, and SCL. A good approach
is to insert an inner layer GND plane underneath the SW node and between any nearby routed traces. This
creates a shield from the electric field generated at SW.
5. Terminate the Flash LED cathodes directly to the GND pin of the LM3643. If possible, route the LED returns
with a dedicated path so as to keep the high amplitude LED currents out of the GND plane. For Flash LEDs
that are routed relatively far away from the LM3643, a good approach is to sandwich the forward and return
current paths over the top of each other on two layers. This helps reduce the inductance of the LED current
paths.
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12.2 Layout Example
IN
VIAs to GND
Plane
10 PF
GND
IN
SDA
SDA
SW
STROBE
SCL
SCL
OUT
HWEN
TORCH/
TEMP
LED2
TX
LED1
TX
LED1
1 P+
10 PF
SW
OUT
LED2
TORCH/
TEMP
Figure 56. Layout Example
30
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13 Device and Documentation Support
13.1 Device Support
13.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
13.2 Related Documentation
13.2.1 Related Links
Table 3 below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 3. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM3643
Click here
Click here
Click here
Click here
Click here
LM3643A
Click here
Click here
Click here
Click here
Click here
13.3 Trademarks
13.4 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
13.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
14 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM3643AYFFR
ACTIVE
DSBGA
YFF
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
ZAAI
LM3643YFFR
ACTIVE
DSBGA
YFF
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
3643
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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