TI1 LM2759SDX/NOPB Lm2759 1a switched capacitor flash led driver with i2c compatible interface Datasheet

LM2759
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LM2759 1A Switched Capacitor Flash LED Driver with I2C Compatible Interface
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FEATURES
APPLICATIONS
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Up to 1A Output Current
Solution Area < 22 mm2
No Inductor Required
90% Peak Efficiency
Adaptive 1x, 1.5x and 2x Gains for Maximum
Efficiency
Load Disconnect in Shutdown
Accurate Input Current Control During Gain
Transitions
Flash Time-Out
TX Input Pin Ensures Synchronization with RF
Power Amplifier Pulse
Torch, Flash, and Indicator Modes
External Flash Enable via Strobe Input Pin
Strobe Input Disable via I2C
Programmable Flash Pulse Duration, and
Torch and Flash Currents via I2C-Compatible
Interface
1MHz Constant Frequency Operation
Low Profile 12–Pin WSON (3mm x 3mm x
0.8mm)
Camera Flash in Cellular Phones
DESCRIPTION
LM2759 is an integrated low-noise, high-current
switched capacitor DC/DC converter with a regulated
current source. The device requires only four small
ceramic capacitors making the total solution area less
than 22 mm2 and the height less than 1 mm. The
LM2759 is capable of driving loads up to 1A 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.
The LED current can be programmed up to 1A via an
I2C-compatible interface, along with eight selectable
Flash Time-Out durations. One high-current Flash
LED can be driven either in a high-power Flash mode
or a low-power Torch mode. The Strobe pin allows
the flash to be toggled via a Flash enable signal from
a camera module. The TX input pin limits the Flash
LED current to the Torch current level during a RF
PA pulse, to reduce high loads on the battery.
Internal soft-start circuitry limits the amount of inrush
current during start-up.
LM2759 is offered in a small 12-pin thermally
enhanced WSON package.
Typical Application Circuit
ILED = Up to 1A
VIN = 3.0V - 5.5V
VIN
CIN
2.2 µF
C1
VOUT
C 1+
4.7 µF
COUT
D1
2.2 µF
C 1C 2+
ISINK
LM2759
C2
2.2 µF
C 2SDA
SCL
Strobe
TX
GND
TDK: 2.2 µF ± C1608X5R1C225
4.7 µF ± C2012X5R1C475
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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LM2759
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Connection Diagram
1
12
12
1
2
11
11
2
3
10
10
3
4
9
9
4
5
8
8
5
6
7
7
6
Die-Attach Pad: GND
Die-Attach Pad: GND
Top View
Bottom View
Figure 1. 12-Pin WSON Package
3mm x 3mm x 0.8mm
Package Number DQB0012A
PIN DESCRIPTIONS
Pin
Name
10
VIN
3
VOUT
12
C1−
11
C1+
2
C2+
Description
Input voltage connection.
Charge pump regulated output.
Flying capacitor connections.
1
C2−
4
GND
Ground connection.
6
ISINK
Regulated current sink input.
8
SDA
Serial data I/O pin.
7
Strobe
5
TX
9
SCL
Manual flash enable pin. Flash will remain on for the duration that the Strobe pin is held high or
when the Flash Timeout occurs, whichever comes first.
Transmission pulse Flash interrupt pin. High = RF PA pulse active, LED current reduced to Torch
level, Low = RF PA pulse off, LED at full programmed current level.
Serial clock pin.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
2
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Absolute Maximum Ratings (1) (2) (3)
VIN pin: Voltage to GND
-0.3V to 6.0V
Strobe, TX, SDA, SCL, ISINK pins: Voltage to GND
-0.3V to (VIN + 0.3V)
w/ 6.0V max
Continuous Power Dissipation (4)
Internally Limited
Junction Temperature (TJ-MAX)
150°C
Storage Temperature Range
-65°C to 150°C
(5)
Maximum Lead Temp. (Soldering)
ESD Rating
(1)
(2)
(3)
(4)
(5)
(6)
Human Body Model
(6)
2.5KV
Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits
and associated test conditions, see the Electrical Characteristics tables.
All voltages are with respect to the potential to the GND pin.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150°C (typ.) and
disengages at TJ = 120°C (typ.).
For detailed soldering specifications and information, please refer to Texas Instruments Application Note AN-1187 (SNOA401).
The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. (MIL-STD-883 3015.7)
Operating Ratings (1) (2)
Input Voltage Range
2.7V to 5.5V
LED Voltage Range
2.0V to 4.0V
Junction Temperature Range (TJ)
-30°C to +125°C
Ambient Temperature Range (TA) (3)
(1)
(2)
(3)
-30°C to +85°C
Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits
and associated test conditions, see the Electrical Characteristics tables.
All voltages are with respect to the potential to 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 =
125ºC), 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 (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP - (θJA × PD-MAX).
Thermal Information
Junction-to-Ambient Thermal Resistance, (θJA),
(1)
(1)
36.7°C/W
Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set
forth in the JEDEC standard JESD51-7. The test board is a 4–layer FR-4 board measuring 102 mm x 76 mm x 1.6 mm with a 2x1 array
of thermal vias. The ground plane on the board is 50 mm x 50 mm. Thickness of copper layers are 53µm/35µm/35µm/53µm
(1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C, still air. Power dissipation is 1W.The value of θJA of this product in the
WSON package could fall in a range as wide as 30ºC/W to 150ºC/W (if not wider), depending on PWB material, layout, and
environmental conditions. In applications where high maximum power dissipation exists (high VIN, high IOUT), special care must be paid
to thermal dissipation issues. For more information on these topics, please refer to Application Note AN-1187 (SNOA401): and the
Power Efficiency and Power Dissipation section of this datasheet.
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Electrical Characteristics (1) (2)
Limits in standard typeface are for TJ = 25°C. Limits in boldface type apply over the full operating junction temperature range
(-30°C ≤ TJ ≤ +125 °C). Unless otherwise noted, specifications apply to the LM2759 Typical Application Circuit (pg.1) with VIN
= 3.6V, VTX = 0V, VSTROBE = 0V, CIN = C1 = C2 = 2.2 µF, COUT = 4.7 µF. (3)
Symbol
Parameter
Conditions
ILED
LED Current Sink Accuracy
Flash Mode
ADDR xB0 = 0x02
IFLASH
Max Flash Output Current
Flash Mode
ADDR xB0 = 0x0F
VGDX
Gain Transition Voltage
Threshold on ISINK
VOUT
Output Voltage
ROUT
Min
Typ
Max
Units
198
−10%
220
242
+10%
mA
1
A
ILED = 500mA
(VISINK falling)
350
mV
1x Mode, IOUT = 0 mA (VIN >VOUT) (4)
4.7
4.9
1.5x Mode, IOUT = 0 mA
4.7
4.9
2x Mode, IOUT = 0 mA
5.1
5.4
x1 Mode Output Impedance IOUT = 200mA, VIN = 3.3V
0.33
1.5x Mode Output
Impedance
1.9
IOUT = 500mA, VIN = 3.3V
x2 Mode Output Impedance
Switching Frequency
2.7V ≤ VIN ≤ 5.5V
0.7
VIH
Input Logic High
Pins: TX, Strobe
1.26
VIL
Input Logic Low
Pins: TX, Strobe
IQ
Quiescent Current
Shutdown Current
Ω
2.25
FSW
ISD
V
1
1.3
MHz
V
0.7
V
IOUT = 0 mA, 1x Mode
0.6
0.9
IOUT = 0 mA, 1.5x Mode
3.4
4.0
IOUT = 0 mA, 2x Mode
5.9
7.0
Device Disabled
2.7V ≤ VIN ≤ 5.5V
5.8
9.7
µA
0.72
V
300
mV
mA
I2C Compatible Interface Voltage Specifications (SCL, SDA)
VIL
Input Logic Low “0”
2.7V ≤ VIN ≤ 5.5V
VIH
Input Logic High “1'
2.7V ≤ VIN ≤ 5.5V
VOL
Output Logic Low “0”
ILOAD = 3 mA
1.25
V
I2C Compatible Interface Timing Voltage Specifications (SCL, SDA) (5)
t1
SCL (Clock Period)
2.5
µs
t2
Data in Setup Time to SCL
High
100
ns
t3
Data Out Stable After SCL
Low
0
ns
t4
SDA Low Setup Time to
SCL Low (Start)
100
ns
t5
SDA High Hold Time After
SCL High (Stop)
100
ns
(1)
(2)
(3)
(4)
(5)
4
All voltages are with respect to the potential to the GND pin.
Min and 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 Typ specifications are: VIN = 3.6V and TA = 25°C.
CIN, COUT, C1, C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics.
For input voltage below the regulation target during the gain of 1x, the output voltage will typically be equal to the input voltage.
SCL and SDA should be glitch-free in order for proper brightness control to be realized.
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Block Diagram
COUT
4.7 µF
D
FLASH
LED
MODULE
VOUT
Gain
Control
VIN
CIN
VREF
2.2 µF
C1+
2.2 µF
Thermal
Shutdown
FLASH
Timeout
VOUT
REG
GND
Current
Control
C1C2+
2.2 µF
C2-
STROBE
1x,1.5x,
2x
Charge
Pump
TX
2
I C Control
Logic
Power
on Reset
LM2759
SCL
SDA
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Typical Performance Characteristics
Unless otherwise specified: TA = 25°C, VIN = 3.6V, CIN = C1 = C2 = 2.2µF, COUT = 4.7µF. Capacitors are low-ESR multi-layer
ceramic capacitors (MLCC's). Luxeon PWF3 Flash LED.
6
Efficiency
vs
VIN
Input Current
vs
VIN
Figure 2.
Figure 3.
Quiescent Current
vs
VIN, Gain = 1X
Quiescent Current
vs
VIN, Gain = 2X
Figure 4.
Figure 5.
ILED
vs
VISINK
Shutdown Current
vs
VIN
Figure 6.
Figure 7.
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Typical Performance Characteristics (continued)
Unless otherwise specified: TA = 25°C, VIN = 3.6V, CIN = C1 = C2 = 2.2µF, COUT = 4.7µF. Capacitors are low-ESR multi-layer
ceramic capacitors (MLCC's). Luxeon PWF3 Flash LED.
Oscillator Frequency
vs
VIN
Torch Code Levels
Figure 8.
Figure 9.
Flash Code Levels
Shutdown to Torch Mode, 100mA
CH1: SDA; Scale: 2V/Div, DC Coupled
CH2: VOUT; Scale: 2V/Div, DC Coupled
CH3: IIN; Scale: 100mA/Div, DC Coupled
CH4: ILED; Scale: 100mA/Div, DC Coupled
Time scale: 400µs/Div
Figure 11.
Figure 10.
Shutdown to Flash Mode, 1A
Torch to Flash Mode, 100mA to 1A
CH1: SDA; Scale: 2V/Div, DC Coupled
CH2: VOUT; Scale: 2V/Div, DC Coupled
CH3: IIN; Scale: 1A/Div, DC Coupled
CH4: ILED; Scale: 1A/Div, DC Coupled
Time scale: 1ms/Div
Figure 12.
CH1: SDA; Scale: 2V/Div, DC Coupled
CH2: VOUT; Scale: 2V/Div, DC Coupled
CH3: IIN; Scale: 1A/Div, DC Coupled
CH4: ILED; Scale: 1A/Div, DC Coupled
Time scale: 1ms/Div
Figure 13.
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Typical Performance Characteristics (continued)
Unless otherwise specified: TA = 25°C, VIN = 3.6V, CIN = C1 = C2 = 2.2µF, COUT = 4.7µF. Capacitors are low-ESR multi-layer
ceramic capacitors (MLCC's). Luxeon PWF3 Flash LED.
Flash Timeout, Timeout Code (x03) = 325ms
Torch Level (x0F) = 180mA, Flash Level (x05) = 410mA
CH1(bottom): IIN; Scale: 200mA/Div, DC Coupled
CH2(middle): SDA; Scale: 2V/Div, DC Coupled
CH3(top): VOUT; Scale: 2V/Div, DC Coupled
Time scale: 100ms/Div
Figure 14.
8
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APPLICATION INFORMATION
CIRCUIT DESCRIPTION
The LM2759 is an adaptive CMOS charge pump with gains of 1x, 1.5x, and 2x, optimized for driving Flash LEDs
in camera phones and other portable applications. It provides a constant current of up to 1A (typ.) for Flash mode
and 180 mA (typ.) for Torch mode.
The LM2759 has selectable modes including Flash, Torch, Indicator and Shutdown. Flash mode for the LM2759
can also be enabled via the Strobe input pin. The LED is driven from VOUT and connected to the current sink.
The LED drive current and operating modes are programmed via an I2C compatible interface. The LM2759
adaptively selects the next highest gain mode when needed to maintain the programmed LED current level.
To prevent a high battery load condition during a simultaneous RF PA transmission and Flash event, LM2759
has a Flash interrupt pin (TX) to reduce the LED current to the programmed Torch current level for the duration
of the RF PA transmission pulse.
CHARGE PUMP AND GAIN TRANSITIONS
The input to the 1x, 1.5x, 2x charge pump is connected to the VIN pin, and the loosely regulated output of the
charge pump is connected to the VOUT pin. In 1x mode, as long as the input voltage is less than 4.7V (typ.), the
output voltage is approximately equal to the input voltage. When the input voltage is over 4.7V (typ.) the output
voltage is regulated to 4.7V (typ.). In 1.5x mode, the output voltage is regulated to 4.7V (typ.) over entire input
voltage range. For the gain of 2x, the output voltage is regulated to 5.1V (typ.). When under load, the voltage at
VOUT can be less than the target regulation voltage while the charge pump is still in closed loop operation. This is
due to the load regulation topology of the LM2759.
The charge pump’s gain is selected according to the headroom voltage across the current sink of LM2759. When
the headroom voltage VGDX (at the LED cathode) drops below 350 mV (typ.) the charge pump gain transitions to
the next available higher gain mode. Once the charge pump transitions to a higher gain, it will remain at that gain
for as long as the device remains enabled. Shutting down and then re-enabling the device resets the gain mode
to the minimum gain required to maintain the load.
SOFT START
The LM2759 contains internal soft-start circuitry to limit inrush currents when the part is enabled. Soft start is
implemented internally with a controlled turn-on of the internal voltage reference.
CURRENT LIMIT PROTECTION
The LM2759 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 1.4A typically.
LOGIC CONTROL PINS
LM2759 has two asynchronous logic pins, Strobe and TX. These logic inputs function according to the table
below:
TX
STROBE
FUNCTION
0
0
Current I2C programmed state (Off, Torch,
Flash, Indicator)
1
0
Current I2C programmed state (Off, Torch,
Flash, Indicator). If Flash is enabled via I2C
and TX is logic High, the LED current will be
at the programmed Torch level.
0
1
Flash Mode (Total LED "ON" Duration limited
by Flash Timeout)
1
1
Torch Mode (Total LED "ON" Duration limited
by Flash Timeout)
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I2C COMPATIBLE INTERFACE
START AND STOP CONDITIONS
START and STOP conditions classify the beginning and the end of the I2C session. A START condition is
defined as 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 to be 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 15. Start and Stop Conditions
DATA VALIDITY
The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words, state of
the data line can only be changed when SCL is LOW.
SCL
SDA
data
change
allowed
data
valid
data
change
allowed
data
valid
data
change
allowed
Figure 16. Data Validity Diagram
A pull-up resistor between the controller's VIO line and SDA must be greater than [(VIO-VOL) / 3.5mA] to meet
the VOL requirement on SDA. Using a larger pull-up resistor results in lower switching current with slower edges,
while using a smaller pull-up results in higher switching currents with faster edges.
TRANSFERING 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 LM2759 pulls down
the SDA line during the 9th clock pulse, signifying an acknowledge. The LM2759 generates an acknowledge
after each byte is received.
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 LM2759 address is 53h. 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 will be written. The
third byte contains data to write to the selected register.
10
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ack from slave
ack from slave
start
msb Chip Address lsb
w
ack
msb Register Add lsb
ack
start
Id = 53h
w
ack
addr = 10h
ack
ack from slave
msb
DATA
lsb
ack
stop
GDWD K¶03 (Flash)
ack
stop
SCL
SDA
w = write (SDA = "0")
r = read (SDA = "1")
ack = acknowledge (SDA pulled down by either master or slave)
id = chip address, 53h for LM2759
Figure 17. Write Cycle
I2C COMPATIBLE CHIP ADDRESS
The chip address for LM2759 is 1010011, or 53h.
MSB
LSB
ADR6
ADR5
ADR4
ADR3
ADR2
ADR1
ADR0
R/W
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
0
1
10
1
0
0
1
1
1
0
2
I C SLAVE address (chip address)
INTERNAL REGISTERS
General Purpose
Register Address: 0x10
MSB
1
bit7
1
bit6
1
bit5
1
bit6
1
bit5
1
bit6
1
bit5
G1
bit1
1
bit4
A3
bit3
1
bit4
B3
bit3
1
bit6
1
bit5
1
bit4
1
bit3
G0
bit0
LSB
A2
bit2
A1
bit1
A0
bit0
LSB
B2
bit2
B1
bit1
Flash Timeout Duration
Register Address: 0xC0
MSB
1
bit7
G2
bit2
Flash Current
Register Address: 0xB0
MSB
1
bit7
G4
bit3
Torch Current
Register Address: 0xA0
MSB
1
bit7
1
bit4
LSB
B0
bit0
LSB
C2
bit2
C1
bit1
C0
bit0
Internal Hex Address
Power On Value
(lowest 4 bits)
General Purpose Register
10h
0000
Flash Current Register
B0h
1010
Torch Current Register
A0h
0111
Register
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Register
Flash Timeout Duration Register
Internal Hex Address
Power On Value
(lowest 4 bits)
C0h
1011
GENERAL PURPOSE REGISTER AND STROBE INHIBIT FUNCTION
The general purpose register (x10) is used set the mode of operation for the LM2759. The selectable operating
modes using the lower 4 bits in the general purpose register are listed in the table below.
The Strobe Input Pin can be disabled via I2C to ignore external signals into this pin when desired. This function is
implemented through bit 3 of the General Purpose Register (See table below). In the default state, input signals
on the Strobe Input are enabled. (Bit3 = “0”, inputs into the Strobe Pin are not inhibited).
Table 1. General Purpose Register (Reg x10)
Bit3
Bit2
Bit1
Bit0
Mode
X
X
X
0
Shutdown
X
0
0
1
Torch
X
X
1
1
Flash
X
1
0
1
Indicator (Lowest Torch Level)
1
X
X
X
Inhibit Inputs into the Strobe Pin
SETTING LED CURRENT
The current through the LED is set by programming the appropriate register with the desired current level code
for Flash and Torch. The time that Flash mode is active is dependent on the lesser of the duration that it is set to
"ON" (via I2C or the Strobe pin), or the duration of the Flash Timeout. Use the tables below to select the desired
current level.
Using the part 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.
Table 2. Flash Current Table (Reg xB0)
12
CODE (Hex)
FLASH CURRENT (mA)
00
80
01
150
02
220
03
280
04
350
05
410
06
470
07
530
08
590
09
650
0A
710
0B
770
0C
830
0D
890
0E
950
0F
1010
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Table 3. Torch Current Table (Reg xA0)
CODE (Hex)
TORCH CURRENT (mA)
00
15
01
30
02
40
03
50
04
65
05
80
06
90
07
100
08
110
09
120
0A
130
0B
140
0C
150
0D
160
0E
170
0F
180
FLASH TIME-OUT FEATURE
Time-out Protection Circuitry disables the current sink when either the Strobe pin is held at logic high or the
Flash mode is enabled via the I2C compatible interface longer than the programmed timeout duration. This
prevents the device from self-heating due to the high power dissipation during Flash conditions. During the timeout condition, voltage will still be present on VOUT but the current sink will be shut off, resulting in no current
through the Flash LED. When the device goes into a time-out condition, disabling and then re-enabling the
device will reset the time-out. Use the table below to set the desired Flash timeout duration.
Table 4. Flash Timeout Duration (Reg xC0)
CODE (Hex)
TIME (ms)
00
60
01
125
02
250
03
375
04
500
05
625
06
750
07
1100
CAPACITOR SELECTION
The LM2759 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 typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are not
recommended for use with the LM2759 due to their high ESR, as compared to ceramic capacitors. For most
applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with the
LM2759. These 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 LM2759. Capacitors with these
temperature characteristics typically have wide capacitance tolerance (+80%, -20%) and vary significantly over
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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 LM2759. The voltage rating of the output capacitor should be 6.3V or more. For example, a
6.3V 0603 4.7 μF output capacitor (TDK C1608X5R0J475) is acceptable for use with the LM2759, as long as the
capacitance on the output does not fall below a minimum of 3μF in the intended application. All other capacitors
should have a voltage rating at or above the maximum input voltage of the application and should have a
minimum capacitance of 1 μF.
Table 5. Suggested Capacitors and Suppliers
MFG Part No.
Type
MFG
Voltage Rating
Case Size
Inch (mm)
4.7 µF for COUT
C1608X5R0J475
Ceramic X5R
TDK
6.3V
0603 (1608)
JMK107BJ475
Ceramic X5R
Taiyo-Yuden
6.3V
0603 (1608)
C1608X5R0J225
Ceramic X5R
TDK
6.3V
0603 (1608)
JMK107BJ225
Ceramic X5R
Taiyo-Yuden
6.3V
0603 (1608)
2.2 µF for C1, C2, CIN
POWER EFFICIENCY
Efficiency of LED drivers is commonly taken to be the ratio of power consumed by the LED (PLED) to the power
drawn at the input of the part (PIN). With a 1x, 1.5x, 2x charge pump, the input current is equal to the charge
pump gain times the output current (total LED current). The efficiency of the LM2759 can be predicted as follows:
PLED = VLED × ILED
PIN = VIN × IIN
PIN = VIN × (Gain × ILED + IQ)
E = (PLED ÷ PIN)
(1)
(2)
(3)
(4)
For a simple approximation, the current consumed by internal circuitry (IQ) can be neglected, and the resulting
efficiency will become:
E = VLED ÷ (VIN × Gain)
(5)
Neglecting IQ will result 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 (100mA - 1A). 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 x IIN) be evaluated rather than power
efficiency.
THERMAL PROTECTION
Internal thermal protection circuitry disables the LM2759 when the junction temperature exceeds 150°C (typ.).
This feature protects the device from being damaged by high die temperatures that might otherwise result from
excessive power dissipation. The device will recover and operate normally when the junction temperature falls
below 120°C (typ.). It is important that the board layout provide good thermal conduction to keep the junction
temperature within the specified operating ratings.
POWER DISSIPATION
The power dissipation (PDISSIPATION) and junction temperature (TJ) can be approximated with the equations
below. PIN is the power generated by the 1x, 1.5x, 2x charge pump, PLED is the power consumed by the LED, TA
is the ambient temperature, and θJA is the junction-to-ambient thermal resistance for the 12 pin WSON package.
VIN is the input voltage to the LM2759, 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 × θJA)
14
(6)
(7)
(8)
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SNVS577D – JUNE 2008 – REVISED MAY 2013
The junction temperature rating takes precedence over the ambient temperature rating. The LM2759 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 105°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 105°C.
MAXIMUM OUTPUT CURRENT
The maximum LED current that can be used for a particular application depends on the rated forward voltage of
the LED used, the input voltage range of the application, and the Gain mode of the LM2759’s charge pump. The
following equation can be used to approximate the relationship between the maximum LED current, the LED
forward voltage, the minimum input voltage, and the charge pump gain:
(VIN_MIN x Gain) > (VF + VHR) + (ILED x ROUT_GAIN)
(9)
VHR or the voltage required across the current sink to remain in regulation can be approximated by (ILED x KHR),
where KHR is 0.8 mV/mA (typ). ROUT_GAIN is the output impedance of the charge pump according to its gain
mode. When using the equation above, keep in mind that the (VF + VHR) portion of the equation can not be
greater than the nominal output regulation voltage for a particular gain. In other words, when making calculations
for an application where the term (VF + VHR) is higher than a particular gain’s regulation voltage, the next higher
gain level must be used for the calculation.
Example: VF = 4V @ 1A, Charge Pump in the Gain of 2x with a ROUT of 2.25Ω (typ.)
VIN_MIN > [(4V + 0.8V) + (1A x 2.25Ω) ] ÷ 2
VIN_MIN > 3.53V (typ.)
The maximum power dissipation in the LM2759 must also be taken into account when selecting the conditions
for an application, such that the junction temperature of the device never exceeds its rated maximum. The input
voltage range, operating temperature range, and/or current level of the application may have to be adjusted to
keep the LM2759 within normal operating ratings.
BOARD LAYOUT CONSIDERATIONS
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 IC, resulting in poor regulation or
instability. Poor layout can also result in re-flow problems leading to poor solder joints between the WSON
package and board pads. Poor solder joints can result in erratic or degraded performance.
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REVISION HISTORY
Changes from Revision C (May 2013) to Revision D
•
16
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 15
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PACKAGE OPTION ADDENDUM
www.ti.com
3-May-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
(4)
LM2759SD/NOPB
ACTIVE
WSON
DQB
12
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-30 to 85
L2759
LM2759SDX/NOPB
ACTIVE
WSON
DQB
12
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-30 to 85
L2759
(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)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side 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 Top-Side Marking for that device.
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.
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 1
Samples
PACKAGE MATERIALS INFORMATION
www.ti.com
10-Jul-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
LM2759SD/NOPB
WSON
DQB
12
1000
178.0
12.4
3.3
3.3
1.0
8.0
12.0
Q1
LM2759SDX/NOPB
WSON
DQB
12
4500
330.0
12.4
3.3
3.3
1.0
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
10-Jul-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM2759SD/NOPB
WSON
DQB
12
1000
213.0
191.0
55.0
LM2759SDX/NOPB
WSON
DQB
12
4500
367.0
367.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
DQB0012A
SDF12A (Rev B)
www.ti.com
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