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LM2758
SNVS551E – APRIL 2008 – REVISED MAY 2016
LM2758 Switched Capacitor Flash LED Driver in DSBGA Package
1 Features
3 Description
•
•
•
•
The LM2758 device is an integrated low-noise, highcurrent switched capacitor DC-DC converter with a
regulated current sink. The device is capable of
driving loads up to 700 mA from a single-cell Li-Ion
battery. Maximum efficiency is achieved over the
input voltage range by actively selecting the proper
gain based on the LED forward voltage and current
requirements.
1
•
•
•
•
Up to 700-mA Output Current
90% Peak Efficiency
Indicator, Torch, and Flash Modes
Time-Out Circuitry Limits Flash Duration to 814
Milliseconds (Typical)
Adaptive 1× and 1.5× Gains for Maximum
Efficiency
True Shutdown
Internal Soft-Start Eliminates Inrush Current
Ultra-Small Solution Size
– No Inductor, Only 4 Capacitors and a Resistor
Required
– 2.022 mm × 1.527 mm × 0.6 mm Thin DSBGA
package
One external low-power resistor sets the desired
current for indicator, torch, and flash modes. To
protect the devices and the flash LED, internal timeout circuitry turns off the LM2758 in case of a faulty
prolonged flash mode. Internal soft-start circuitry
limits the amount of inrush current during start-up.
Device Information(1)
PART NUMBER
LM2758
2 Applications
•
•
PACKAGE
DSBGA (12)
BODY SIZE (MAX)
2.022 mm × 1.527 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Camera Flash in Mobile Phones
Flash for Digital Cameras
Typical Application Circuit
C1
C1-
C1+
2.7 V to 5.5 V
+
-
C2
C2+
VIN
C2CPOUT
CIN
COUT
LM2758
EN1
EN2
LEDISET
PGND SGND
RSET
Copyright © 2016, Texas Instruments Incorporated
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM2758
SNVS551E – APRIL 2008 – REVISED MAY 2016
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
4
4
4
4
5
6
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 7
7.1
7.2
7.3
7.4
Overview ................................................................... 7
Functional Block Diagram ......................................... 7
Feature Description................................................... 7
Device Functional Modes........................................ 10
8
Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Application ................................................. 11
9
Power Supply Recommendations...................... 14
9.1 Power Dissipation ................................................... 14
10 Layout................................................................... 15
10.1 Layout Guidelines ................................................. 15
10.2 Layout Example .................................................... 15
10.3 DSBGA Package Assembly and Use ................... 16
11 Device and Documentation Support ................. 17
11.1
11.2
11.3
11.4
11.5
11.6
Device Support......................................................
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
17
17
17
17
17
17
12 Mechanical, Packaging, and Orderable
Information ........................................................... 17
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision D (May 2013) to Revision E
Page
•
Added Device Information and Pin Configuration and Functions sections, ESD Ratings table, Feature Description,
Device Functional Modes, Application and Implementation, Power Supply Recommendations, Layout, Device and
Documentation Support, and Mechanical, Packaging, and Orderable Information sections ................................................. 1
•
Added Thermal Information table with revised RθJA value (from 56°C/W to 93.6°C/W) and additional thermal values. ....... 4
Changes from Revision C (May 2013) to Revision D
•
2
Page
Changed layout of National Semiconductor Data Sheet to TI format ................................................................................. 16
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SNVS551E – APRIL 2008 – REVISED MAY 2016
5 Pin Configuration and Functions
YZR Package
12-Pin DSBGA
Top View
LEDEN2
B3
B2
YZR Package
12-Pin DSBGA
Bottom View
PGND LED- EN2
D3
C3
ISET
A3
D3
PGND
A2
SGND
D2
C1
A1
EN1
D1
C2
B1
+
C1
C2
C2
+
C2
C2
C3
B3
+
-
SGND
A2
-
EN1
A1
C1
D2
C2
D1
C1
VIN
C1
VIN
ISET
A3
B2
CPOUT
B1
+
C1
Pin Functions
PIN
TYPE
DESCRIPTION
EN1
Input
The EN2 pins is used to select the modes (torch, indicator, flash), as well as to put the part into
shutdown mode.
A2
SGND
Ground
Analog and control ground for charge pump. Connect this pin directly to a low impedance
ground plane.
A3
ISET
Power
LED current programming resistor pin. A resistor connected between this pin, and GND is used
to set torch, flash and indicator currents.
B1
C1+
Power
Flying capacitor pin — connect a 1-µF ceramic capacitor from C1+ to C1−
B2
CPOUT
Output
Charge pump regulated output. A 2.2-µF ceramic capacitor is required from CPOUT to GND.
Connect flash LED anode to this pin.
B3
EN2
Input
The EN1 pin is used to select the modes (torch, indicator, flash), as well as to put the part into
Shutdown mode.
C1
VIN
Input
Supply voltage connection
NO.
NAME
A1
C2
C2+
Power
Flying capacitor pins — connect a 1-µF ceramic capacitor from C2+ to C2−.
C3
LED−
Output
Regulated current source output. Connect flash LED cathode to this pin.
D1
C2−
Power
Flying capacitor pin — connect a 1-µF ceramic capacitor from C2+ to C2−.
D2
C1−
Power
Flying capacitor pin — connect a 1-µF ceramic capacitor from C1+ to C1−
D3
PGND
Ground
Power ground for the charge pump and the current source. Connected the pin directly to a lowimpedance ground plane.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2) (3)
MIN
MAX
UNIT
VIN, CPOUT pins: voltage to GND
–0.3
6
V
EN1, EN2 pins: Voltage to GND
–0.3
(VIN + 0.3) w/ 6 V
maximum
V
150
°C
Continuous power dissipation
Junction temperature, TJ-MAX
See (4)
Maximum lead temperature (soldering)
Storage temperature, Tstg
(1)
(2)
(3)
(4)
–65°C
150
°C
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.
If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
All voltages are with respect to the potential to the GND pin.
For detailed soldering specifications and information, see AN-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)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±200
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)
MIN
MAX
Input voltage
2.7
5.5
V
Junction temperature, TJ
–40
125
°C
–40
85
°C
Ambient temperature, TA
(1)
(2)
(2)
UNIT
All voltages are with respect to the potential at the GND pin.
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 operation 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
LM2758
THERMAL METRIC (1)
YZR (DSBGA)
UNIT
12 PINS
RθJA
Junction-to-ambient thermal resistance
93.6
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
0.7
°C/W
RθJB
Junction-to-board thermal resistance
16.1
°C/W
ψJT
Junction-to-top characterization parameter
2.9
°C/W
ψJB
Junction-to-board characterization parameter
16.0
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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6.5 Electrical Characteristics
Unless otherwise specified, aspecifications apply to the Figure 8 with VIN = 3.6 V, VEN1 = VIN, VEN2 = 0 V,
C1 = C2 = 1 µF, CIN = COUT = 2.2 µF, RSET = 20 kΩ, TJ = 25°C. (1) (2) (3)
PARAMETER
ILED
LED current accuracy
TEST CONDITIONS
ILED = 500 mA, flash mode
ISET pin voltage
ID/ISET
LED current to set current
ratio
ILED-IND
Indicator current level
TYP
MAX
UNIT
550
mA
500
ILED = 500 mA, flash mode
–40°C ≤ TJ ≤ 125°C
VSET
MIN
450
1.3
Flash mode
V
7650
Torch mode
1639
1/32 ×
ILED-
Indicator mode
32-kHZ PWM mode
mA
TORCH
VGDX
VOUT
1× to 1.5× gain transition
voltage threshold on VLED–
Output voltage
IOUT = 500 mA
300
1× mode, IOUT = 0 mA
VIN
1.5× mode, IOUT = 0 mA (4)
4.8
1.5× mode, IOUT = 0 mA
–40°C ≤ TJ ≤ 125°C (4)
1× mode output impedance
1.5× mode output
impedance
FSW
IOUT = 200 mA, VIN = 3.3 V
–40°C ≤ TJ ≤ 125°C
Switching frequency
IOUT = 500 mA, VIN = 3.3 V
0.33
0.53
(5)
1.5
0.8
Quiescent current
1.5
Shutdown current
TOUT
Timeout duration
0.8
IOUT = 0 mA 1.5× mode
4
640
1.2
Pins: EN1, EN2, –40°C ≤ TJ ≤ 125°C
Pins: EN1, EN2, –40°C ≤ TJ ≤ 125°C
(3)
(4)
(5)
(6)
(7)
814
See (7)
Input logic low
µA
1
–40°C ≤ TJ ≤ 125°C, see (7)
Input logic high
(1)
(2)
0.01
Device disabled, –40°C ≤ TJ ≤ 125°C (6)
VIL
mA
5
Device disabled (6)
VIH
MHz
0.7
IOUT = 0 mA 1x mode
IOUT = 0 mA 1.5× mode, –40°C ≤ TJ ≤ 125°C
ISD
Ω
2.0
1.25
–40°C ≤ TJ ≤ 125°C
IOUT = 0 mA 1× mode, –40°C ≤ TJ ≤ 125°C
IQ
V
5.3
IOUT = 200 mA, VIN = 3.3 V (5)
ROUT
mV
msec
1000
V
0.4
V
All voltages are with respect to the potential at the GND pin.
Minimum (MIN) and maximum (MAX) limits are specified by design, test, or statistical analysis. Typical (TYP) numbers are not ensured,
but do represent the most likely norm. Unless otherwise specified, conditions for TTYP specifications are: VIN = 3.6 V and TA = 25°C.
CIN, COUT, C1, C2: Low-ESR surface-mount ceramic capacitors (MLCCs) used in setting electrical characteristics.
Output voltage is internally limited not to exceed maximum specified value.
These table entries are specified by design. These parameters are not ensured by production testing. The temperature limits for test are
(–40°C ≤ TA ≤ +85°C).
The temperature limits for ISD (shutdown current) test are -40°C ≤ TA ≤ +85°C, as in shutdown mode ambient temperature is equal to
junction temperature.
The timeout specifications are calculated values based on the switching frequency spread.
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6.6 Typical Characteristics
Unless otherwise specified: TA = 25°C, VIN = 3.6 V, CIN = COUT = 2.2 µF, C1 = C2 = 1 µF. Capacitors are low-ESR multi-layer
ceramic capacitors (MLCCs). Luxeon PWF1 Flash LED.
110
1.15
500 mA
1.13
FREQUENCY (MHz)
EFFICIENCY (%)
90
70
50
700 mA
100 mA
30
1.11
1.09
1.07
10
2.7
3.2
3.7
4.2
4.7
1.05
2.7
5.2
3.2
3.7
4.2
VIN (V)
4.7
5.2
VIN (V)
Figure 1. Efficiency vs VIN
Figure 2. Oscillator Frequency vs VIN
5.000
0.04
1.5x
4.000
ISHUTDOWN (µA)
IQUIESCENT (mA)
0.03
3.000
2.000
1x
0.02
EN1 = EN2 = 0V
0.01
1.000
0.000
2.7
3.1
3.5
3.9
4.3
4.7
5.1
0.00
2.7
5.5
3.1
3.5
3.9
4.3
4.7
5.1
5.5
VIN (V)
VIN (V)
Figure 3. Quiescent Current vs VIN
Figure 4. Shutdown Current vs VIN
800
1k
700
900
800
700 mA
700
500
ILED (mA)
ILED (mA)
600
400
500 mA
300
100 mA
Flash
600
500
400
300
Torch
200
200
100
0
0.0
100
0.5
1.0
0
10
1.5
VLED- (V)
20
25
30
35
R SET (k:)
Figure 5. ILED vs VLED–
6
15
Figure 6. LED Current vs RSET
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7 Detailed Description
7.1 Overview
The LM2758 is an adaptive 1× and 1.5× CMOS charge pump, optimized for driving flash LEDs in camera phones
and other portable applications. It provides a constant current of 500 mA (typical) for flash mode and 107 mA
(typical) for torch mode with RSET = 20 kΩ. These current can change (see Setting LED Currents).
There are four modes of operation for LM2758: the flash mode, torch mode, indicator mode, and shutdown mode
(see Table 1). Torch and flash modes sink a constant DC current while indicator mode operates in pulsating DC
at 1/32 positive duty cycle with same current magnitude as torch mode. The LED is driven from CPOUT and
connected to the current sink. LED drive current mode is programmed by connecting a resistor, RSET, to the
current set pin, ISET. The LM2758 device also controls CPOUT with variable gain (1× or 1.5×) and adjustable
impedance (ROUT) to provide an output voltage that would account for LED forward voltage drop and headroom
for the current sink to drive desired current through LED.
7.2 Functional Block Diagram
LED
COUT = 2.2 µF
LED-
CPOUT
VIN
Gain Control
GND
CIN
= 2.2 µF
Ind.
Current
Control
C1+
Torch
Flash
Flash, Torch
Mode
Control
EN1
EN2
1 µF
C1-
1x, 1.5x
Charge Pump
VREF
C2+
1 µF
OSC
C2-
ISET
RSET
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7.3 Feature Description
7.3.1 Charge Pump and Gain Transitions
The input to the 1×/1.5× charge pump is connected to the VIN pin, and the loosely regulated output of the charge
pump is connected to the CPOUT pin. In 1× mode, as long as the input voltage is less than 4.7 V, the output
voltage is approximately equal to the input voltage. When input voltage is over 4.7 V the output voltage is
regulated to 4.7 V. In 1.5× mode, the output voltage is always less than or equal to 4.7 V over entire input
voltage range.
The gain of the charge pump is selected depending on the headroom voltage across the current sink of LM2758.
When headroom voltage VLED– (at the LED pin) drops below 300 mV (typical) the charge-pump gain transition
happens from 1× to 1.5× to maintain current regulation across the LED. Once the charge pump transition to a
higher gain, it remains at that gain for as long as the device remains enabled. Shutting down and then reenabling the device resets the gain mode to the minimum gain required to maintain the load.
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Feature Description (continued)
7.3.2 Soft Start
The LM2758 contains internal soft-start circuitry to limit inrush currents when the part is enabled. Soft start is
implemented internally with a controlled turnon of the internal voltage reference.
7.3.3 Current Limit Protection
The LM2758 charge pump contains current limit protection circuitry that protects the device during VOUT fault
conditions where excessive current is drawn. Output current is limited to 1.2 A typically.
7.3.4 Flash Time-out Feature
Flash time-out protection circuitry disables the current sinks when the signal on EN1 and EN2 is held high for
more than 814 msec (typical). This prevents the device from self-heating due to the high power dissipation during
flash conditions. During the time-out condition, voltage is still present on CPOUT but the current sinks are shut off,
resulting in no current through the flash LED. When the device goes into a time-out condition, placing a logic low
signal on EN1 and EN2 resets the timeout; a subsequent logic high signal on EN1 or EN2 returns the device to
normal operation.
7.3.5 Setting LED Currents
The current through the LED can be set by connecting an appropriately sized resistor RSET between the ISET pin
of the LM2758 and GND.
The LED current in torch mode is approximately 1639 times greater than the current of ISET, while the LED
current in flash mode is approximately 7650 times of the same ISET current. The feedback loop of an internal
amplifier sets the voltage of the ISET pin to 1.3 V (typical). The statements above are simplified in Equation 1:
ILED = GAINFLASH/TORCH × (1.3 / RSET)
(1)
The maximum recommended current through LED is 500 mA in torch mode / 700 mA in flash mode.
NOTE
If the ISET for torch mode setting at 500 mA, the flash mode would be over 700 mA
(maximum). See Figure 6. Using the device in conditions where the junction temperature
might rise above the rated maximum requires that the operating ranges and/or conditions
be de-rated. The printed circuit board also must be carefully laid out to account for high
thermal dissipation in the part.
8
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Feature Description (continued)
7.3.6 Analog Brightness Control
C1
1 µF
C2
1 µF
C1-
C1+
VIN
CPOUT
COUT
2.2 µF
CIN
2.2 µF
+
-
C2-
C2+
LM2758
EN1
EN2
LEDISET
PGND SGND
VA
RA
RSET
Copyright © 2016, Texas Instruments Incorporated
Figure 7. Analog Brightness Control
The current through the LED can be varied dynamically by changing the ISET current. Figure 7 shows the circuit.
The current though the LED can be calculated with Equation 2:
ILED = GainTORCH/FLASH
1.3V
RSET
VA
1.3V
RA
(2)
7.3.7 Thermal Protection
Internal thermal protection circuitry disables the LM2758 when the junction temperature exceeds 150°C (typical).
This feature protects the device from being damaged by high die temperatures that might otherwise result from
excessive power dissipation. The device recovers and operates normally when the junction temperature falls
below 140°C (typical). It is important that the board layout provide good thermal conduction to keep the junction
temperature within the specified operating ratings.
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7.4 Device Functional Modes
7.4.1 Modes
There are four modes of operation for LM2758: the flash mode, torch mode, indicator mode and shutdown mode
(see Table 1). Torch and flash modes sink a constant DC current while indicator mode operates in pulsating DC
at 1/32 positive duty cycle with same current magnitude as torch mode.
7.4.2 Logic Control Pins
The LM2758 has two logic pins, EN1 and EN2. There is a 500-kΩ (typical) pulldown resistor connected from EN1
to GND and from EN2 to GND. The operating modes of the part function according to Table 1:
Table 1. EN1 and EN2 Truth Table
10
EN1
EN2
MODE
0
0
Shutdown
1
0
Indicator
0
1
Torch
1
1
Flash
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8 Application 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 LM2758 can drive one flash LED at currents up to 700 mA. The multi-gain charge-pump boost regulator
allows for the use of small value discrete external components.
8.2 Typical Application
C1
C1-
C1+
2.7 V to 5.5 V
+
-
C2
C2-
C2+
VIN
CPOUT
CIN
COUT
LM2758
EN1
EN2
LEDISET
PGND SGND
RSET
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Figure 8. LM2758 Typical Application
8.2.1 Design Requirements
For typical switched-capacitor LED-driver applications, use the parameters listed in Table 2.
Table 2. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Minimum input voltage
2.7 V
Maximum output current
700 mA
8.2.2 Detailed Design Procedure
8.2.2.1 Capacitor Selection
The LM2758 device requires 4 external capacitors for proper operation. Surface-mount multi-layer ceramic
capacitors are recommended. These capacitors are small, inexpensive and have very low equivalent series
resistance (ESR < 20 mΩ typical). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic
capacitors are not recommended for use with the LM2758 due to their high ESR compared to ceramic
capacitors. For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred
for use with the LM2758. Ceramic capacitors have tight capacitance tolerance (as good as ±10%) and hold their
value over temperature (X7R: ±15% over –55°C to +125°C; X5R: ±15% over –55°C to +85°C). Capacitors with
Y5V or Z5U temperature characteristic are generally not recommended for use with the LM2758. Capacitors with
these temperature characteristics typically have wide capacitance tolerance (+80%, –20%) and vary significantly
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over temperature (Y5V: 22%, –82% over –30°C to +85°C range; Z5U: 22%, –56% over 10°C to 85°C range).
Under some conditions, a nominal 1 μF Y5V or Z5U capacitor could have a capacitance of only 0.1 μF. Such
detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum capacitance
requirements of the LM2758. The voltage rating of the output capacitor must be 6.3 V or more. For example, a
6.3-V, 0603, 2.2-μF output capacitor (TDK C1608X5R0J225) is acceptable for use with the LM2758, as long as
the capacitance on the output does not fall below a minimum of 1 μF in the intended application. All other
capacitors must have a voltage rating at or above the maximum input voltage of the application and a minimum
capacitance of 1 μF.
Table 3. Suggested Capacitors And Suppliers
MANUFACTURER
PART NUMBER
TYPE
MANUFACTURER
VOLTAGE RATING
CASE SIZE
INCH (mm)
2.2 µF for CIN and COUT
C1608X5R0J225
Ceramic X5R
TDK
6.3 V
0603 (1608)
JMK107BJ225
Ceramic X5R
Taiyo-Yuden
6.3 V
0603 (1608)
1 µF for C1 and C2
C1608X5R0J105
Ceramic X5R
TDK
6.3 V
0603 (1608)
JMK107BJ105M
Ceramic X5R
Taiyo-Yuden
6.3 V
0603 (1608)
8.2.2.2 Power Efficiency
Efficiency of LED drivers is commonly taken to be the ratio of power consumed by the LEDs (PLED) to the power
drawn at the input of the part (PIN). With a 1×/1.5× charge pump, the input current is equal to the charge pump
gain times the output current (total LED current). The efficiency of the LM2758 can be predicted as follows:
PLED = VLED × ILED
PIN = VIN × IIN
PIN = VIN × (Gain × ILED + IQ)
E = (PLED ÷ PIN)
(3)
(4)
(5)
(6)
For a simple approximation, the current consumed by internal circuitry (IQ) can be neglected, and the resulting
efficiency will become:
E = VLED ÷ (VIN × Gain)
(7)
Neglecting IQ results in a slightly higher efficiency prediction, but this impact will be negligible due to the value of
IQ being very low compared to the typical torch and flash current levels (100 mA to 500 mA). It is also worth
noting that efficiency as defined here is in part dependent on LED voltage. Variation in LED voltage does not
affect power consumed by the circuit and typically does not relate to the brightness of the LED. For an advanced
analysis, it is recommended that power consumed by the circuit (VIN × IIN) be evaluated rather than power
efficiency.
12
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8.2.3 Application Curves
110
500 mA
2V/DIV
90
EFFICIENCY (%)
GAIN = 1.5x
VOUT
70
50
2V/DIV
200 mA/DIV
700 mA
EN1,
EN2
100 mA
200 mA/DIV
30
10
2.7
3.2
3.7
4.2
4.7
IIN
ILED
5.2
400 µs/DIV
VIN (V)
VIN = 3.6 V
ILED = 500 mA
Figure 10. Shutdown to Flash Mode
Figure 9. Efficiency vs VIN
2V/DIV
VOUT
GAIN = 1.5x
2V/DIV
VOUT
2V/DIV
EN1
2V/DIV
EN2
100 mA/DIV
IIN
100 mA/DIV
ILED
100 mA/DIV
IIN
100 mA/DIV
1 ms/DIV
ILED
100 µs/DIV
VIN = 3.6 V
EN1 = 0 V
ILED = 108 mA
Gain = 1×
VIN = 3.6 V
EN2 = 0 V
Figure 11. Shutdown to Torch Mode
ILED (torch) = 108 mA
Figure 12. Shutdown to Indicator Mode
2V/DIV
2V/DIV
EN1
2V/DIV
VOUT
VOUT
200 mA/DIV
100 mA/DIV
ILED
IIN
200 mA/DIV
ILED
20 mA/DIV
IIN
200 ms/DIV
10 µS/DIV
EN1 = VIN = 3.6 V
EN2 = 0 V
ILED (torch) = 108 mA
Gain = 1×
EN2 = VIN = 3.6 V
Figure 13. Indicator Mode
ILED (flash) = 500 mA
Gain = 1.5×
Figure 14. Torch to Flash Mode Transition
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2V/DIV
EN2
2V/DIV
VOUT
200 mA/DIV
IIN
200 mA/DIV
ILED
200 ms/DIV
EN1 = VIN = 3.6 V
ILED (flash) = 500 mA
Gain = 1.5×
Figure 15. Indicator to Flash Mode Transition
9 Power Supply Recommendations
The LM2758 is designed to operate from an input voltage supply range from 2.7 V to 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
device, additional bulk capacitance may be required in addition to the ceramic bypass capacitors.
9.1 Power Dissipation
The power dissipation (PDISSIPATION) and junction temperature (TJ) can be approximated with the equations
below. PIN is the power generated by the 1×/1.5× charge pump, PLED is the power consumed by the LEDs, TA is
the ambient temperature, and RθJA is the junction-to-ambient thermal resistance for the 12-pin DSBGA package.
VIN is the input voltage to the LM2758, VLED is the nominal LED forward voltage, and ILED is the programmed
LED current.
PDISSIPATION = PIN – PLED
= (Gain × VIN × ILED) − (VLED × ILED)
TJ = TA + (PDISSIPATION × RJθA)
(8)
(9)
(10)
The junction temperature rating takes precedence over the ambient temperature rating. The LM2758 may be
operated outside the ambient temperature rating, so long as the junction temperature of the device does not
exceed the maximum operating rating of 125°C. The maximum ambient temperature rating must be derated in
applications where high power dissipation and/or poor thermal resistance causes the junction temperature to
exceed 125°C.
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10 Layout
10.1 Layout Guidelines
PC board layout is an important part of DC-DC converter design. Poor board layout can disrupt the performance
of a DC-DC converter and surrounding circuitry by contributing to EMI, ground bounce, and resistive voltage loss
in the traces. These can send erroneous signals to the DC-DC converter device, resulting in poor regulation or
instability. Poor layout can also result in re-flow problems leading to poor solder joints between the DSBGA
package and board pads. Poor solder joints can result in erratic or degraded performance.
10.2 Layout Example
GND
EN1
SGND
ISET
C1+
CPOUT
EN2
VIN
C2+
CPOUT
LED-
C2-
C1-
VIN
PGND
GND
GND
Figure 16. LM2758 Layout Example
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10.3 DSBGA Package Assembly and Use
Use of the DSBGA package requires specialized board layout, precision mounting and careful re-flow techniques
as detailed in AN-1112 DSBGA Wafer Level Chip Scale Package (SNVA009). Refer to the section Surface
Mount Assembly Considerations" For best results in assembly, use alignment ordinals on the PC board to
facilitate placement of the device. The pad style used with the DSBGA package must be the NSMD (non-solder
mask defined) typical. This means that the solder-mask opening is larger than the pad size. This prevents a lip
that otherwise forms if the solder mask and pad overlap, from holding the device off the surface of the board and
interfering with mounting. See SNVA009 for specific instructions how to do this. The 12-pin package used for
LM2758 has 300 micron solder balls and requires 10.82 mils pads for mounting on the circuit board. The trace to
each pad should enter the pad with a 90° entry angle to prevent debris from being caught in deep corners.
Initially, the trace to each pad should be 7 mil. wide, for a section approximately 7 mil. long or longer, as a
thermal relief. Then each trace should neck up or down to its optimal width. The important criteria is symmetry.
This ensures the solder bumps on the LM2758 re-flow evenly and that the device solders level to the board. In
particular, special attention must be paid to the pads for bumps C1 and D3, because VIN and GND are typically
connected to large copper planes, thus inadequate thermal relief can result in late or inadequate re-flow of these
bumps.
The DSBGA package is optimized for the smallest possible size in applications with red or infrared opaque
cases. Because the DSBGA package lacks the plastic encapsulation characteristic of larger devices, it is
vulnerable to light. Backside metallization and/or epoxy coating, along with front side shading by the printed
circuit board, reduce this sensitivity. However, the package has exposed die edges. In particular, DSBGA
devices are sensitive to light, in the red and infrared range, shining on the exposed die edges of the package.
16
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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 additional information, see the following:
AN-1112 DSBGA Wafer Level Chip Scale Package (SNVA009)
11.3 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.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
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.
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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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)
LM2758TL/NOPB
ACTIVE
DSBGA
YZR
12
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
2758
LM2758TLX/NOPB
ACTIVE
DSBGA
YZR
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
2758
(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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