TI1 LM3648TTYFFR Synchronous boost led flash driver Datasheet

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LM3648, LM3648TT
SNVSA68B – OCTOBER 2014 – REVISED SEPTEMBER 2015
LM3648 Synchronous Boost LED Flash Driver with 1.5-A High-Side Current Source
1 Features
3 Description
•
•
The LM3648 is an LED flash driver that provides a
high level of adjustability within a small solution size.
The LM3648 utilizes a 2-MHz or 4-MHz fixedfrequency synchronous boost converter to provide
power to the 1.5-A constant current LED source. An
adaptive regulation method ensures the current
source remains in regulation and maximizes
efficiency.
1
•
•
•
•
•
•
•
•
•
•
•
1.5-A LED Current Source Programmability
Accurate and Programmable LED Current Range
from 1.954 mA to 1.5 A
Torch Currents up to 500 mA (LM3648TT)
Flash Timeout Values up to 1.6 Seconds
(LM3648TT)
Optimized Flash LED Current During Low Battery
Conditions (IVFM)
> 85% Efficiency in Torch Mode (at 100 mA) and
Flash Mode (at 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
– LM3648 (I2C Address = 0x63)
Features of the LM3648 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
64
programmable currents in Flash and 128 levels in
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.
Device Information(1)
PART NUMBER
LM3648
2 Applications
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 data sheet.
Camera Phone White LED Flash
Simplified Schematic
L1
1 PH
LM3648
VIN
2.5V t 5.5V
IN
C1
10 PF
HWEN
SW
OUT
C2
10 PF
SDA
SCL
PP/PC
STROBE
LED
TORCH/
TEMP
TX
D1
GND
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.
LM3648, LM3648TT
SNVSA68B – OCTOBER 2014 – REVISED SEPTEMBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
4
4
4
4
5
5
6
6
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ...............................................
Switching Characteristics ..........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 10
7.1 Overview ................................................................. 10
7.2 Functional Block Diagram ...................................... 11
7.3 Feature Description ................................................ 11
7.4 Device Functioning Modes...................................... 13
7.5 Programming........................................................... 16
7.6 Register Descriptions .............................................. 18
8
Applications and Implementation ...................... 22
8.1 Application Information............................................ 22
8.2 Typical Application ................................................. 22
9 Power Supply Recommendations...................... 27
10 Layout................................................................... 27
10.1 Layout Guidelines ................................................. 27
10.2 Layout Example ................................................... 28
11 Device and Documentation Support ................. 29
11.1
11.2
11.3
11.4
11.5
11.6
Device Support......................................................
Documentation Support ........................................
Trademarks ...........................................................
Community Resources..........................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
29
29
29
29
29
29
12 Mechanical, Packaging, and Orderable
Information ........................................................... 30
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (August 2015) to Revision B
Page
•
Added "or 0x04 for LM3648TT" to Device ID Register row, Register Descriptions table..................................................... 18
•
Changed "'011'" to "'000'" in Device Register Bits 5-3 description ....................................................................................... 21
Changes from Original (October 2014) to Revision A
Page
•
Added Torch Currents up to 500 mA (LM3648TT)................................................................................................................. 1
•
Added Flash Timeout Values up to 1.6 seconds (LM3648TT) .............................................................................................. 1
•
Changed Handling Ratings to ESD Ratings; moved storage temperature to Abs Max ......................................................... 4
•
Added ILED row for LM3648TT option .................................................................................................................................... 5
•
Added VHR row for LM3648TT option .................................................................................................................................... 5
•
Added several new graphs related to LM3648TT option performance ................................................................................. 5
•
Added to 1.6 s on LM3648TT in Flash Time-Out ................................................................................................................. 15
•
Added additional equation and LM3648TT values in LED Torch Brightness Register; added NOTE below LED Torch
Brightness Register description ........................................................................................................................................... 19
•
Added LM3648TT values for Timing Configuration Register; added NOTE below Timing Configuration Register
description ........................................................................................................................................................................... 20
•
Added "or '100'" for LM3648TT in Device ID Register Bits 2-0 description ......................................................................... 21
•
Added Application curves for LM3648TT performance ....................................................................................................... 24
2
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Product Folder Links: LM3648 LM3648TT
LM3648, LM3648TT
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SNVSA68B – OCTOBER 2014 – REVISED SEPTEMBER 2015
5 Pin Configuration and Functions
YFF Package
12-Pin DSBGA
Top View
A1
A2
Top View
A3
B1
B2
B3
C1
C2
C3
D1
D2
D3
Pin A1
Pin Functions
PIN
NUMBER
NAME
TYPE (1)
DESCRIPTION
A1
GND
G
Ground
A2
IN
P
Input voltage connection. Connect IN to the input supply and bypass to GND with a 10µF or larger ceramic capacitor.
A3
SDA
I/O
B1
SW
P
Drain connection for Internal NMOS and Synchronous PMOS Switches.
B2
STROBE
I
Active high hardware flash enable. Drive STROBE high to turn on Flash pulse. Internal
pulldown resistor of 300 kΩ between STROBE and GND.
B3
SCL
I
Serial clock input for LM3648.
C1
OUT
P
Step-up DC-DC converter output. Connect a 10-µF ceramic capacitor between this
terminal and GND.
C2
HWEN
I
Active high enable pin. High = Standby, Low = Shutdown/Reset. Internal pulldown
resistor of 300 kΩ between HWEN and GND.
C3
TORCH/TEMP
I/P
Torch terminal input or threshold detector for NTC temperature sensing and current
scale back.
D1
LED
P
High-side current source output for flash LED. Connect pin D1 to D3 externally.
D2
TX
I
Configurable dual polarity power amplifier synchronization input. Internal pulldown
resistor of 300 kΩ between TX and GND.
D3
LED
P
High-side current source output for flash LED. Connect pin D1 to D3 externally.
(1)
Serial data input/output in the I2C Mode on LM3648.
A: Analog Pin, G: Ground Pin, P: Power Pin, I: Digital Input Pin
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
IN, SW, OUT, LED
−0.3
6
SDA, SCL, TX, TORCH/TEMP, HWEN, STROBE
−0.3
(VIN+ 0.3) w/ 6 V
max
Continuous power dissipation (3)
−65
Storage temperature, Tstg
(4)
150
°C
150
°C
See (4)
Maximum lead temperature (soldering)
(2)
(3)
V
Internally limited
Junction temperature (TJ-MAX)
(1)
UNIT
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 pin.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150°C (typical) and
disengages at TJ = 135°C (typical). Thermal shutdown is ensured by design.
For detailed soldering specifications and information, refer to Texas Instruments Application Note 1112: DSBGA Wafer Level Chip Scale
Package (SNVA009).
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2500
Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
±150
UNIT
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.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1) (2)
VIN
Junction temperature (TJ)
Ambient temperature (TA)
(1)
(2)
(3)
(3)
MIN
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).
6.4 Thermal Information
LM3648
THERMAL METRIC (1)
YFF (DSBGA)
UNIT
12 PINS
RθJA
Junction-to-ambient thermal resistance
90.2
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
0.5
°C/W
RθJB
Junction-to-board thermal resistance
40.0
°C/W
ΨJT
Junction-to-top characterization parameter
3.0
°C/W
ΨJB
Junction-to-board characterization parameter
39.2
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 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
VOUT = 4 V, torch code = 0x3F = 178.6 mA
torch
–10%
178.6
10%
mA
–10%
357.2
10%
mA
CURRENT SOURCE SPECIFICATIONS
ILED
VOUT = 4 V, flash code = 0x3F = 1.5 A
flash
Current source accuracy
ILED
Current source accuracy
(LM3648TT)
VOUT = 4 V, torch code = 0x3F = 357.2 mA
torch
VHR
LED current source regulation
voltage
ILED = 1.5 A
Flash
290
ILED = 178.6 mA
Torch
158
VHR
LED current source regulation
voltage (LM3648TT)
ILED = 357.2 mA
Torch and
Flash
270
VOVP
mV
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
VUVLO
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
0
0.4
V
1.2
VIN
V
A
V
HWEN, TORCH/TEMP, STROBE, TX VOLTAGE SPECIFICATIONS
VIL
Input logic low
VIH
Input logic high
2.5 V ≤ VIN ≤ 5.5 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
0
0.4
1.2
VIN
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.
6.6 Timing Requirements
MIN
NOM
MAX
UNIT
t1
SCL clock period
2.4
µs
t2
Data in set-up time to SCL high
100
ns
t3
Data out stable After SCL low
0
ns
t4
SDA low set-up time to SCL low (start)
100
ns
t5
SDA high hold time after SCL high (stop)
100
ns
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6.7 Switching Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
ƒSW
TEST CONDITIONS
2.5 V ≤ VIN ≤ 5.5 V
Switching frequency
MIN
TYP
MAX
UNIT
–6%
4
6%
MHz
t1
SCL
t5
t4
SDA_IN
t2
SDA_OUT
t3
Figure 1. I2C-Compatible Interface Specifications
6.8 Typical Characteristics
TA = 25°C, VIN = 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise noted.
1.6
0.4
TA = -40°C
TA = +25°C
TA = +85°C
1.4
TA = -40°C
TA = +25°C
TA = +85°C
0.36
0.32
1.2
0.28
ILED (A)
ILED (A)
1
0.8
0.6
0.24
0.2
0.16
0.12
0.4
0.08
0.2
0.04
0
0
0
16
32
LED Code (dec#)
48
0
64
48
64
80
LED Code (dec#)
96
112
128
D015
1.62
TA = -40C
TA = 25C
TA = 85C
0.5
0.45
1.58
0.4
1.56
0.35
1.54
0.3
0.25
1.52
1.5
0.2
1.48
0.15
1.46
0.1
1.44
0.05
1.42
0
0
8
16
24
TA = -40qC
TA = +25qC
TA = +85qC
1.6
ILED (A)
ILED (A)
32
Figure 3. LED Torch Current vs Brightness Code
Figure 2. LED Flash Current vs Brightness Code
0.55
32 40 48 56
LED Code (dec #)
64
72
80
88
3
ƒSW = 2 MHz
Brightness Code = 0x3F
Figure 4. LED Torch Current vs Brightness Code
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1.4
2.5
D031
LM3648TT
6
16
D001
3.5
4
VIN (V)
4.5
5
5.5
D021
Flash
Figure 5. LED Current vs Input Voltage
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Typical Characteristics (continued)
TA = 25°C, VIN = 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise noted.
1.62
TA = -40qC
TA = +25qC
TA = +85qC
1.6
1.58
1.54
ILED (A)
ILED (A)
1.56
1.52
1.5
1.48
1.46
1.44
1.42
1.4
2.5
3
3.5
ƒSW = 4 MHz
Brightness Code = 0x3F
4
VIN (V)
4.5
5
5.5
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
3
3.5
D022
Flash
ƒSW = 2 MHz
Brightness Code = 0x2B
Figure 6. LED Current vs Input Voltage
4
VIN (V)
4.5
5
5.5
D023
Flash
Figure 7. LED Current vs Input Voltage
0.4
0.39
TA = -40qC
TA = +25qC
TA = +85qC
0.55
TA = -40qC
TA = -+25qC
TA = +85qC
0.54
0.53
0.38
TA = -40C
TA = 25C
TA = 85C
0.52
ILED (A)
ILED (A)
0.37
0.36
0.35
0.51
0.5
0.49
0.48
0.34
0.47
0.33
0.32
2.5
0.46
3
3.5
ƒSW = 2 MHz
Brightness Code = 0x7F
4
VIN (V)
4.5
5
0.45
2.5
5.5
Torch
3.5
4
VIN (V)
4.5
5
Figure 8. LED Current vs Input Voltage
5.5
D032
LM3648TT
ƒSW = 2 MHz
Brightness Code = 0x59
Torch
Figure 9. LED Current vs Input Voltage
0.4
0.39
3
D025
0.55
TA = -40qC
TA = -+25qC
TA = +85qC
0.54
0.53
0.38
TA = -40C
TA = 25C
TA = 85C
0.52
ILED (A)
ILED (A)
0.37
0.36
0.35
0.51
0.5
0.49
0.48
0.34
0.47
0.33
0.32
2.5
0.46
3
ƒSW = 4 MHz
Brightness Code = 0x7F
3.5
4
VIN (V)
4.5
5
5.5
0.45
2.5
3
D026
Torch
3.5
4
VIN (V)
LM3648TT
ƒSW = 4 MHz
Brightness Code = 0x59
Figure 10. LED Current vs Input Voltage
4.5
5
5.5
D033
Torch
Figure 11. LED Current vs Input Voltage
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Typical Characteristics (continued)
TA = 25°C, VIN = 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise noted.
3
1.2
TA = -40qC
TA = +25qC
TA = +85qC
1
2
ISB (PA)
0.8
ISD (PA)
TA = -40qC
TA = +25qC
TA = +85qC
2.5
0.6
1.5
0.4
1
0.2
0.5
0
2.5
3
3.5
HWEN = 0 V
4
VIN (V)
4.5
5
0
2.5
5.5
I2C = 0 V
4.5
5
5.5
D009
I2C = VIN
7
TA = -40qC
TA = +25qC
TA = +85qC
6
5
5
4
4
3
3
2
2
1
1
0
2.5
3
TA = -40qC
TA = +25qC
TA = +85qC
6
ISB (PA)
ISB (PA)
4
VIN (V)
Figure 13. Standby Current vs Input Voltage
7
3.5
HWEN = 1.8 V
4
VIN (V)
4.5
5
0
2.5
5.5
I2C = 0 V
2.9
ƒSW = 2 MHz
Brightness Code = 0x3F
3.1
3.3
3.5
VIN (V)
Flash
3.7
3.9
4.1
4.3
4.5
5
5.5
D010
I2C = 1.8 V
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
TA = -40qC
TA = +25qC
TA = +85qC
2.7
2.9
D011
VLED = 4.5 V
ICL = 1.9 A
Figure 16. Inductor Current Limit vs Input Voltage
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4
VIN (V)
Figure 15. Standby Current vs Input Voltage
TA = -40qC
TA = +25qC
TA = +85qC
2.7
3.5
HWEN = 1.8 V
ICL (A)
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
3
D008
Figure 14. Standby Current vs Input Voltage
ICL (A)
3.5
HWEN = VIN
Figure 12. Shutdown Current vs Input Voltage
8
3
D007
ƒSW = 4 MHz
Brightness Code = 0x3F
3.1
3.3
3.5
VIN (V)
Flash
3.7
3.9
4.1
4.3
D012
VLED = 4.5 V
ICL = 1.9 A
Figure 17. Inductor Current Limit vs Input Voltage
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Typical Characteristics (continued)
3
3
2.8
2.8
2.6
2.6
2.4
2.4
ICL (A)
ICL (A)
TA = 25°C, VIN = 3.6 V, HWEN = VIN, CIN = COUT = 2 × 10 µF and L = 1 µH, unless otherwise noted.
2.2
2
2.2
2
1.8
1.8
TA = -40qC
TA = +25qC
TA = +85qC
1.6
1.4
2.5
2.75
3
3.25
ƒSW = 2 MHz
Brightness Code = 0x3F
3.5
3.75 4
VIN (V)
4.25
4.5
4.75
1.4
2.5
5
2.75
3
3.25
3.5
D013
Flash
VLED = 4.5 V
ICL = 2.8 A
ƒSW = 4 MHz
Brightness Code = 0x3F
Figure 18. Inductor Current Limit vs Input Voltage
3.75 4
VIN (V)
4.25
4.5
4.75
5
D014
Flash
VLED = 4.5 V
ICL = 2.8 A
Figure 19. Inductor Current Limit vs Input Voltage
2.125
4.25
TA = +25qC
TA = +85qC
TA = -40qC
2.1
2.075
4.15
2.05
4.1
2.025
4.05
2
1.975
4
3.95
1.95
3.9
1.925
3.85
1.9
3.8
1.875
2.5
3.75
2.5
2.75
3
3.25
3.5
3.75 4
VIN (V)
4.25
4.5
4.75
TA = +25qC
TA = +85qC
TA = -40qC
4.2
fSW (MHz)
fSW (MHz)
TA = -40qC
TA = +25qC
TA = +85qC
1.6
5
2.75
D017
Figure 20. 2-MHz Switching Frequency vs Input Voltage
3
3.25
3.5
3.75 4
VIN (V)
4.25
4.5
4.75
5
D017
D018
Figure 21. 4-MHz Switching Frequency vs Input Voltage
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7 Detailed Description
7.1 Overview
The LM3648 is a high-power white LED flash driver capable of delivering up to 1.5 A to the LED. The device
incorporates a 2-MHz or 4-MHz constant frequency-synchronous current-mode PWM boost converter and a highside current source to regulate the LED current over the 2.5-V to 5.5-V input voltage range.
The LM3648 PWM DC/DC boost converter switches and boosts the output to maintain at least VHR across the
current source. This minimum headroom voltage ensures that the current source remains 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 × RPMOS) and the
voltage across the LED is dropped across the current source.
The LM3648 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 (typical) pulldown resistors to GND.
Additional features of the LM3648 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.
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7.2 Functional Block Diagram
SW
Over Voltage
Comparator
VREF
86 m:
Input Voltage
Flash Monitor
UVLO
VOVP
OUT
ILED
PWM
Control
+
-
+
-
TORCH/
TEMP
2/4 MHz
Oscillator
+
-
IN
65 m:
INTC
Thermal
Shutdown
+150oC
+
-
LED
Error
Amplifier
+
-
+
-
OUT-VHR
Current Sense/
Current Limit
NTC VTRIP
Slope
Compensation
SDA
Control
Logic/
Registers
2
SCL
Soft-Start
I C
Interface
ENABLE
STROBE
TX
GND
7.3 Feature Description
7.3.1 Flash Mode
In Flash Mode, the LED current source (LED) provides 64 target current levels from 21.8 mA to 1500 mA. 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 current source can be
regulated to provide 21.8 mA to 1.5 A.
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.
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Feature Description (continued)
7.3.2 Torch Mode
In Torch mode, the LED current source (LED) provide 128 target current levels from 1.954 mA to 358 mA or
3.908 mA to 502.308 mA on LM3648TT. The Torch current is adjusted via the LED Torch Brightness Register.
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 source (LED) 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.
7.3.3 IR Mode
In IR Mode, the target LED current is equal to the value stored in the LED Flash Brightness Registers. When IR
mode is enabled (setting M1, M0 to '01'), the boost converter turns on and sets the output equal to the input
(pass-mode). At this point, toggling the STROBE pin enables and disables the LED current source (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 source does not ramp the LED output to the target. The current transitions immediately
from off to on and then on to off.
BOOST
VOUT
PASS
OFF
STROBE
M1,M0 = Z00[
STROBE EN = Z1[
M1,M0 = Z01[
STROBE EN = Z1[
ILED
Figure 22. IR Mode with Boost
VOUT
STROBE
M1,M0 = Z00[
EN = Z1[
M1,M0 = Z01[
STROBE EN = Z1[
ILED
Figure 23. IR Mode Pass Only
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Feature Description (continued)
VOUT
STROBE
TIME-OUT
Reached
VOUT goes
low, LED turn
off
TIME-OUT
Start
TIME-OUT
RESET
TIME-OUT
Start
TIME-OUT
RESET
TIME-OUT
Start
M1,M0 = Z01[
STROBE EN = Z1[
ILED
Figure 24. IR Mode Timeout
7.4 Device Functioning Modes
7.4.1 Start-Up (Enabling The Device)
Turnon of the LM3648 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.
7.4.2 Pass Mode
The LM3648 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 ×
RPMOS. In Pass Mode the inductor current is not limited by the peak current limit.
7.4.3 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 LM3648 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.
7.4.4 Input Voltage Flash Monitor (IVFM)
The LM3648 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 LM3648 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 LM3648 to start ramping the flash current back up towards the target.
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Device Functioning Modes (continued)
IVFM ENABLE
LEVEL STROBE
VIN PROFILE for Stop and Hold Mode
IVFM-D
Set Target Flash Current
VIN PROFILE for Down Mode
Dotted line shows O/P Current
Profile with IVFM Disabled
T-Filter = 4Ps
O/P Current
Profile in Stop
and Hold Mode
SET RAMP FROM
THE RAMP
REGISTER USED
Hysteresis
IVFM-D
VIN PROFILE for Up/ Down Mode
T-Filter = 4Ps
O/P Current Profile
in Down Mode
Hysteresis
IVFM-D
O/P Current Profile
in Up and Down
Mode
Figure 25. IVFM Modes
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Device Functioning Modes (continued)
7.4.5 Fault/Protections
7.4.5.1 Fault Operation
If the LM3648 enters a fault condition, the device sets the appropriate flag in the Flags1 and Flags2 Registers
(0x0A and 0x0B), and places the device into standby by clearing the Mode Bits ([1],[0]) in the Enable Register.
The LM3648 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
LM3648 re-enters the fault state and enters standby again.
7.4.5.2 Flash Time-Out
The Flash Time-Out period sets the amount of time that the Flash Current is being sourced from the current
source (LED). The LM3648 has 16 timeout levels ranging from 10 ms to 400 ms or 40 ms (see Timing
Configuration Register (0x08) for more detail).
7.4.5.3 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 LM3648 raises the output voltage in order to keep the LED current at its target value. When
VOUT reaches 5 V (typical), the overvoltage comparator trips and turns off the internal NFET. When VOUT falls
below the “VOVP Off Threshold”, the LM3648 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.
7.4.5.4 Current Limit
The LM3648 features two selectable inductor current limits that are programmable through the I2C-compatible
interface. When the inductor current limit is reached, the LM3648 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.
Because 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 LM3648 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.
7.4.5.5 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 LM3648 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 26. Temp Detection Diagram
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Device Functioning Modes (continued)
7.4.5.6 Undervoltage Lockout (UVLO)
The LM3648 has an internal comparator that monitors the voltage at IN and forces the LM3648 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 LM3648 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.
7.4.5.7 Thermal Shutdown (TSD)
When the LM3648 die temperature reaches 150°C, the thermal shutdown detection circuit trips, forcing the
LM3648 into standby and writing a '1' to the corresponding bit of the Flags1 Register (0x0A) (Thermal Shutdown
bit). The LM3648 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 LM3648 resets the Fault flag and re-enters standby.
7.4.5.8 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 the 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 LED 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 LM3648, setting HWEN to '0', setting the SW
RESET bit to a '1', or by reading back the Flags1 Register (0x0A on LM3648). The mode bits are cleared upon
an LED and/or VOUT short fault.
7.5 Programming
7.5.1 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
7.5.2 I2C-Compatible Interface
7.5.2.1 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 27. 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.
7.5.2.2 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 28. Start and Stop Conditions
7.5.2.3 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 LM3648 pulls down
the SDA line during the 9th clock pulse, signifying an acknowledge. The LM3648 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 LM3648 7-bit address is 0x63. 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 29. 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 LM3648
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7.5.2.4 I2C-Compatible Chip Address
The device address for the LM3648 is 1100011 (0x63). 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 30. I2C-Compatible Chip Address
7.6 Register Descriptions
REGISTER NAME
POWER ON/RESET VALUE
INTERNAL HEX ADDRESS
LM3648
Enable Register
0x01
0x80
IVFM Register
0x02
0x01
LED Flash Brightness Register
0x03
0xBF
LED Torch Brightness Register
0x05
0xBF
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 or 0x04 for LM3648TT
Last Flash Register
0x0D
0x00
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7.6.1 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
Bit 4
Strobe Enable
0 = Disabled
(Default )
1 = Enabled
TORCH/TEMP
Pin Enable
0 = Disabled
(Default )
1 = Enabled
Bit 3
Bit 2
Bit 1
Mode Bits: M1, M0
'00' = Standby (Default)
'01' = IR Drive
'10' = Torch
'11' = Flash
Bit 0
LED Enable
00 = OFF (Default )
11 = ON
01 and 10 are not valid settings
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.
7.6.2 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
Bit 1
IVFM
Hysteresis
0 = 0 mV
(Default)
1 = 50 mV
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 LM3648 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.
7.6.3 LED Flash Brightness Register (0x03)
Bit 7
Bit 6
MUST BE SET TO '10' FOR
PROPER OPERATION
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 2
Bit 1
Bit 0
LED Flash Brightness Level
IFLASH (mA) ≈ (Brightness Code × 23.45 mA) + 21.8 mA
000000 = 21.8 mA
.......................
011111 = 748.75 mA (Default)
.......................
111111 = 1.5 A
7.6.4 LED Torch Brightness Register (0x05)
Bit 7
MUST BE SET
TO '1' FOR
PROPER
OPERATION
Bit 6
Bit 5
Bit 4
Bit 3
LED Torch Brightness Levels
ITORCH (mA) ≈ (Brightness Code × 2.8 mA) + 1.954 mA or ITORCH (mA) ≈ (Brightness Code × 5.6 mA) + 3.908 mA
0000000 = 1.954 mA or 3.908 mA for LM3648TT
.......................
0111111 = 178.35 mA (Default) or 356.71 mA for LM3648TT
.......................
1011001 = 251.15 mA or 502.31 mA for LM3648TT
.......................
1111111 = 357.6 mA
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NOTE
Maximum Torch Brightness Code allowed for the LM3648TT is 0x59 (1011001), which
results in 502.31 mA current setting. Higher settings may result in over-heating and
potentially damaging the device.
7.6.5 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
Boost Mode
0 = Normal
(Default)
1 = Pass Mode
Only
Bit 1
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)
7.6.6 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
Flash Time-Out Duration
0000 = 10 ms or 40 ms (LM3648TT)
0001 = 20 ms or 80 ms (LM3648TT)
0010 = 30 ms or 120 ms (LM3648TT)
0011 = 40 ms or 160 ms (LM3648TT)
0100 = 50 ms or 200 ms (LM3648TT)
0101 = 60 ms or 240 ms (LM3648TT)
0110 = 70 ms or 280 ms (LM3648TT)
0111 = 80 ms or 320 ms (LM3648TT)
1000 = 90 ms or 360 ms (LM3648TT)
1001 = 100 ms or 400 ms (LM3648TT)
1010 = 150 ms (Default) or 600 ms (LM3648TT)
1011 = 200 ms or 800 ms (LM3648TT)
1100 = 250 ms or 1000 ms (LM3648TT)
1101 = 300 ms or 1200 ms (LM3648TT)
1110 = 350 ms or 1400 ms (LM3648TT)
1111 = 400 ms or 1600 ms (LM3648TT)
NOTE
On the LM3648TT, special care must be taken with regards to thermal management when
using time-out values greater than 400 ms. Depending on the PCB layout, input voltage,
and output current, it is possible to have the internal thermal shutdown circuit trip prior to
reaching the desired flash time-out value.
7.6.7 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
Bit 1
Bit 0
TORCH/TEMP
Function
Select
0 = TORCH
(Default)
1 = TEMP
NOTE
The Torch Polarity bit is static once the LM3648 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.
20
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7.6.8 Flags1 Register (0x0A)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
TX Flag
VOUT Short
Fault
VLED Short
Fault
VLED 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
7.6.9 Flags2 Register (0x0B)
Bit 7
RFU
Bit 6
RFU
7.6.10 Device ID Register (0x0C)
Bit 7
Bit 6
Bit 5
RFU
RFU
Device ID
'000'
Silicon Revision Bits
'010' or '100' for LM3648TT
7.6.11 Last Flash Register (0x0D)
Bit 7
RFU
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
The value stored is always the last current value the IVFM detection block set. ILED = IFLASH-TARGET × ((Code + 1) / 128)
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8 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.
8.1 Application Information
The LM3648 can drive a flash LED at currents up to 1.5 A. The 2-MHz or 4-MHz DC-DC boost regulator allows
for the use of small value discrete external components.
8.2 Typical Application
L1
1 PH
LM3648
VIN
2.5V t 5.5V
IN
C1
10 PF
SW
HWEN
OUT
C2
10 PF
SDA
SCL
LED
PP/PC
STROBE
TORCH/
TEMP
TX
GND
Figure 31. LM3648 Typical Application
8.2.1 Design Requirements
Example requirements based on default register values:
Table 1. Design Parameters
22
DESIGN PARAMETER
EXAMPLE VALUE
Input Voltage Range
2.5 V to 5.5 V
Brightness Control
I2C Register
LED Configuration
1 Flash LED
Boost Switching Frequency
2 MHz (4 MHz selectable)
Flash Brightness
1.5-A Max Current
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8.2.2 Detailed Design Procedure
8.2.2.1 Output Capacitor Selection
The LM3648 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 or 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 2 lists different manufacturers for various output capacitors and
their case sizes suitable for use with the LM3648.
8.2.2.2 Input Capacitor Selection
Choosing the correct size and type of input capacitor helps minimize the voltage ripple caused by the switching
of the LM3648 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 LM3648 input (IN) pin. This reduces the series
resistance and inductance that can inject noise into the device due to the input switching currents. Table 2 lists
various input capacitors recommended for use with the LM3648.
Table 2. 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
8.2.2.3 Inductor Selection
The LM3648 is designed to use a 0.47-µH or 1-µH inductor. Table 3 lists various inductors and their
manufacturers that work well with the LM3648. 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 must be greater than the maximum
operating peak current of the LM3648. 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 LM3648 are greater than IPEAK in Equation 3:
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IPEAK =
www.ti.com
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 3. 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
8.2.3 Application Curves
100
100
95
95
90
90
85
85
80
80
KLED (%)
KLED (%)
Ambient temperature is 25°C, input voltage is 3.6 V, 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
60
55
3.5
ƒSW = 2 MHz
Brightness Code = 0x3F
4
VIN (V)
4.5
5
50
2.5
5.5
Flash
4
VIN (V)
4.5
5
5.5
D020
Flash
Figure 33. 4-MHz LED Efficiency vs Input Voltage
100
TA = -40qC
TA = +25qC
TA = +85qC
96
92
92
88
88
84
84
80
76
80
76
72
72
68
68
64
64
3
ƒSW = 2 MHz
Brightness Code = 0x3F
3.5
4
VIN (V)
Flash
4.5
5
5.5
60
2.5
3
D028
VLED = 3.55 V
Figure 34. LED Efficiency vs Input Voltage
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TA = -40qC
TA = +25qC
TA = +85qC
96
KLED (%)
KLED (%)
3.5
ƒSW = 4 MHz
Brightness Code = 0x3F
100
24
3
D019
Figure 32. 2-MHz LED Efficiency vs Input Voltage
60
2.5
VLED = 3.0V
VLED = 3.2V
VLED = 3.5V
VLED = 3.8V
VLED = 4.1V
VLED = 4.4V
65
ƒSW = 4 MHz
Brightness Code = 0x3F
3.5
4
VIN (V)
Flash
4.5
5
5.5
D029
VLED = 3.55 V
Figure 35. LED Efficiency vs Input Voltage
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Ambient temperature is 25°C, input voltage is 3.6 V, 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
90
88
85
84
80
KLED (%)
KLED (%)
92
80
76
75
70
72
65
68
60
64
55
60
2.5
50
2.5
3
3.5
ƒSW = 2 MHz
Brightness Code = 0x2B
4
VIN (V)
4.5
5
5.5
Flash
VLED = 3.32 V
4
VIN (V)
4.5
5
5.5
D033
Torch
VLED = 2.83 V
Figure 37. LED Efficiency vs Input Voltage
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
ƒSW = 4 MHz
Brightness Code = 0x3F
4
VIN (V)
4.5
5
TA = -40qC
TA = +25qC
TA = +85qC
95
KLED (%)
KLED (%)
3.5
ƒSW = 2 MHz
Brightness Code = 0x3F
100
5.5
3
3.5
D034
Torch
VLED = 2.83 V
ƒSW = 2 MHz
Brightness Code = 0x7F
Figure 38. LED Efficiency vs Input Voltage
4
VIN (V)
4.5
5
5.5
D035
Torch
Figure 39. 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
3
ƒSW = 4 MHz
Brightness Code = 0x7F
3.5
4
VIN (V)
4.5
5
TA = -40C
TA = 25C
TA = 85C
95
KLED (%)
KLED (%)
3
D030
Figure 36. LED Efficiency vs Input Voltage
50
2.5
TA = -40qC
TA = +25qC
TA = +85qC
95
5.5
50
2.5
3
D036
Torch
VLED = 2.83 V
Figure 40. LED Efficiency vs Input Voltage
3.5
4
VIN (V)
LM3648TT
ƒSW = 2 MHz
Brightness Code = 0x59
4.5
5
5.5
D034
Torch
VLED = 3.03 V
Figure 41. LED Efficiency vs Input Voltage
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Ambient temperature is 25°C, input voltage is 3.6 V, HWEN = VIN, CIN = 2 × 10 µF, COUT = 2 × 10 µF and L = 1 µH, unless
otherwise noted.
100
TA = -40C
TA = 25C
TA = 85C
95
90
VOUT (2 V/DIV)
KLED (%)
85
ILED (500 mA/DIV)
80
75
IIN (500 mA/DIV)
70
65
60
55
50
2.5
3
3.5
4
VIN (V)
4.5
5
Time (400 Ps / DIV)
5.5
D035
LM3648TT
ƒSW = 4 MHz
Brightness Code = 0x59
Torch
VLED = 3.03 V
ƒSW = 2 MHz
Brightness Code = 0x7F
Figure 42. LED Efficiency vs Input Voltage
VLED = 3.18 V
Figure 43. Start-Up
Tx Signal
VOUT (2 V/DIV)
VOUT (2 V/DIV)
ILED (500 mA/DIV)
ILED (500 mA/DIV)
IIN (500 mA/DIV)
IIN (1 A/DIV)
Time (400 Ps / DIV)
ƒSW = 2 MHz
Brightness Code = 0x7F
Time (2 ms / DIV)
VLED = 3.18 V
ƒSW = 2 MHz
Brightness Code = 0x7F
Figure 44. Ramp Down
VLED = 3.18 V
Figure 45. TX Interrupt
VOUT (50 mV/DIV)
VOUT (50 mV/DIV)
ILED (20 mA/DIV)
ILED (20 mA/DIV)
IL (100 mA/DIV)
IL (100 mA/DIV)
Time (400 ns / DIV)
ƒSW = 2 MHz
Brightness Code = 0x7F
Time (400 ns / DIV)
VLED = 3.18 V
ƒSW = 4 MHz
Brightness Code = 0x7F
Figure 46. Ripple at 2 MHz
26
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VLED = 3.18 V
Figure 47. Ripple at 4 MHz
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9 Power Supply Recommendations
The LM3648 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 LM3648 additional bulk capacitance may be required in addition to the ceramic bypass capacitors.
10 Layout
10.1 Layout Guidelines
The high switching frequency and large switching currents of the LM3648 make the choice of layout important.
The following steps are to 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 LM3648) and as close to the device as possible. The input
capacitor conducts the driver currents during the low-side MOSFET turnon and turnoff 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 the LM3648) and as close as possible to the OUT and GND pins.
The returns for both CIN and COUT must 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 must 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 must 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 cathode directly to the GND pin of the LM3648. If possible, route the LED return
with a dedicated path so as to keep the high amplitude LED current out of the GND plane. For a Flash LED
that is routed relatively far away from the LM3648, 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
path.
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10.2 Layout Example
IN
VIAs to GND
Plane
10 PF
GND
IN
SDA
SDA
SW
STROBE
SCL
SCL
OUT
HWEN
TORCH/
TEMP
LED
TX
LED
1 P+
10 PF
SW
OUT
TORCH/
TEMP
TX
LED
LED
Figure 48. LM3648 Layout Example
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11 Device and Documentation Support
11.1 Device Support
11.1.1 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.
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation, see the following:
Texas Instruments Application Note 1112: DSBGA Wafer Level Chip Scale Package (SNVA009).
11.2.2 Related Links
Table 4 lists quick access links. Categories include technical documents, support and community resources,
tools and software, and quick access to sample or buy.
Table 4. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM3648
Click here
Click here
Click here
Click here
Click here
LM3648TT
Click here
Click here
Click here
Click here
Click here
11.3 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.5 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.
11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
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12 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
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29-Sep-2015
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM3648TTYFFR
ACTIVE
DSBGA
YFF
12
3000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 85
3648TT
LM3648YFFR
ACTIVE
DSBGA
YFF
12
3000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 85
3648
(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)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
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29-Sep-2015
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
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30-Sep-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
LM3648TTYFFR
DSBGA
YFF
12
3000
180.0
8.4
LM3648YFFR
DSBGA
YFF
12
3000
180.0
8.4
Pack Materials-Page 1
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1.38
1.76
0.77
4.0
8.0
Q1
1.38
1.76
0.77
4.0
8.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
30-Sep-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM3648TTYFFR
DSBGA
YFF
12
3000
182.0
182.0
20.0
LM3648YFFR
DSBGA
YFF
12
3000
182.0
182.0
20.0
Pack Materials-Page 2
PACKAGE OUTLINE
YFF0012
DSBGA - 0.625 mm max height
SCALE 8.000
DIE SIZE BALL GRID ARRAY
B
A
E
BALL A1
CORNER
D
0.625 MAX
C
SEATING PLANE
BALL TYP
0.30
0.12
0.05 C
0.8 TYP
0.4 TYP
D
SYMM
C
1.2
TYP
B
D: Max = 1.69 mm, Min = 1.63 mm
E: Max = 1.31 mm, Min = 1.25 mm
A
12X
0.015
0.3
0.2
C A
1
2
3
0.4 TYP
SYMM
B
4222191/A 07/2015
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
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EXAMPLE BOARD LAYOUT
YFF0012
DSBGA - 0.625 mm max height
DIE SIZE BALL GRID ARRAY
(0.4) TYP
12X ( 0.23)
1
2
3
A
(0.4) TYP
B
SYMM
C
D
SYMM
LAND PATTERN EXAMPLE
SCALE:30X
0.05 MAX
( 0.23)
METAL
METAL UNDER
SOLDER MASK
0.05 MIN
( 0.23)
SOLDER MASK
OPENING
SOLDER MASK
OPENING
NON-SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
NOT TO SCALE
4222191/A 07/2015
NOTES: (continued)
3. Final dimensions may vary due to manufacturing tolerance considerations and also routing constraints. For more information,
see Texas Instruments literature number SNVA009 (www.ti.com/lit/snva009).
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EXAMPLE STENCIL DESIGN
YFF0012
DSBGA - 0.625 mm max height
DIE SIZE BALL GRID ARRAY
(0.4) TYP
12X ( 0.25)
(R0.05) TYP
1
2
3
A
(0.4) TYP
B
SYMM
METAL
TYP
C
D
SYMM
SOLDER PASTE EXAMPLE
BASED ON 0.1 mm THICK STENCIL
SCALE:30X
4222191/A 07/2015
NOTES: (continued)
4. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release.
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