LM2754SQ/NOPB [TI]
具有超时保护功能的 800mA 开关电容器 LED 闪光灯驱动器 | RTW | 24 | -40 to 85;
| 型号： | LM2754SQ/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 具有超时保护功能的 800mA 开关电容器 LED 闪光灯驱动器 | RTW | 24 | -40 to 85 开关 驱动 闪光灯 接口集成电路 电容器 驱动器 |
| 文件： | 总20页 (文件大小：2393K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LM2754
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SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
LM2754 800mA Switched Capacitor Flash LED Driver with Time-Out Protection
Check for Samples: LM2754
1
FEATURES
APPLICATIONS
2
•
Up to 800mA Output Current
•
•
•
Camera Flash in Mobile Phones
Flash for Digital Cameras
•
Wide Operating Input Voltage Range: 2.8V to
5.5V
Supplies for DSP’s, Microprocessors, Memory,
MP3 Players, Pagers, Other Portable Devices
•
•
Drives 1, 2, 3 or 4 LEDs in Parallel
Ability to Disable One Current Sink Via the
SEL Pin to Accommodate 3-LED Flash
Modules
DESCRIPTION
The LM2754 is an integrated low noise, high current
switched capacitor DC/DC converter with four
regulated current sinks. The device is optimized for
driving 1 to 4 high power white LEDs in parallel with a
maximum current of 800mA. Maximum efficiency is
achieved over the input voltage range by actively
selecting the proper gain based on the LED forward
voltage and current requirements.
•
•
•
Time-Out Circuitry Limits Flash Duration to 1
Second
TX Input Ensures Synchronization with RF
Power Amplifier Pulse
Adaptive 1x, 1.5x and 2x Gains for Maximum
Efficiency
Two external low power resistors set the desired
current for Torch and Flash modes. The TX pin
allows the device to be forced into Torch mode during
a Flash pulse, allowing for synchronization between
the RF power amplifier pulse and Flash/Torch modes.
To protect the device and Flash LEDs, internal Time-
Out circuitry turns off the LM2754 in case of a faulty
prolonged Flash mode. Internal soft-start circuitry
limits the amount of inrush current during start-up.
•
•
•
•
•
•
•
•
1MHz Constant Frequency Operation
Output Current Limit
True Shutdown Output Disconnect
<1µA Shutdown Current
Internal Soft-Start Limits Inrush Current
No Inductor Required
Total Solution Size without LED <28mm2
Low Profile 24-Pin WQFN Package (4mm x
4mm x 0.8mm)
The LM2754 is available in a small 24-pin thermally
enhanced WQFN package.
Typical Application Circuit
I
F
= 800 mA max
V
= 3.0V - 5.5V
IN
V
IN
V
OUT
C +
1
C
OUT
2.2 µF
4.7 µF
C
IN
D
1
D
2
D
3
D
4
2.2 µF
2.2 µF
C
1
C -
1
D
1
D
2
D
3
D
4
C +
2
LM2754
C
2
EN
T/F
TX
C -
2
I
I
SET1
SET2
SEL
GND
R
R
SET1
SET2
TDK: 2.2 µF œ C1608X5R1C225
4.7 µF œ C2012X5R1C475
1
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.
2
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.
Copyright © 2006–2013, Texas Instruments Incorporated
LM2754
SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
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Connection Diagram
24-pin No-Pullback Leadless Leadframe Package (WQFN-24)
4mm x 4mm x 0.8mm
See Package Number RTW0024A
7
8
9
10 11 12
24 23 22 21 20 19
1
2
3
4
5
6
18
17
16
15
14
13
6
5
4
3
2
1
13
14
15
16
17
18
DAP
DAP
24 23 22 21 20 19
Bottom View
7
8
9
10 11 12
Top View
PIN DESCRIPTIONS
Pin
Name
Description
23,24
VINSW
Input Voltage Connection for Switch Array. Pins 23 and 24 are connected internally on the die.
Connect VIN and VINSW pins together.
22
VIN
Input Voltage Connection. Connect VIN and VINSW pins together.
Output Voltage. Connect to LED Anodes.
8
12, 13, 14, 15
1, 2, 7, 5
3
VOUT
D1, D2, D3, D4*
C1+, C1-, C2+, C2-
GNDSW
Regulated Current Sink Inputs. (* See SEL PIN description)
Flying Capacitor Connections.
Switch Array Ground Connection. Connect GND and GNDSW pins together.
Ground Connection. Connect GND and GNDSW pins together.
9, 16, 17
21
GND
EN
Enable Control Pin. Logic High = Normal Operation in Torch Mode.
Logic Low = Device Shut-Down. (See Note)
20
T/F
Torch/Flash Control Pin. Logic High = Flash Mode. Logic Low = Torch Mode. Device must be
enabled for Torch or Flash to operate. (See Note)
10, 11
ISET1, ISET2
Current Set Resistor Connections. Connect 1% resistors to ground to set the desired current
through the LEDs. LED current is approximated by the equation: 800 x (1.25V ÷ R). This
equation corresponds to the current through one current sink. Total LED current is equal to the
sum of currents through all current sinks connected to the LED. The equation used for Torch
(ISET1) and Flash (ISET2) resistors are the same.
19
TX
RF PA synchronization control pin. Logic High = Force Torch Mode. Logic Low = Normal
Operation. (See APPLICATION INFORMATION Applications Information section for the full
operational description)
18
SEL
D4 Control Pin. Logic Low = Normal 4-LED Operation. Logic High = Disable D4 LED Input.
Connect D4 to VOUT when not used. (See Note)
4, 6
No Connect
Do not connect to any node.
Note: EN, T/F, TX, and SEL pins each have a 500kΩ resistor connected internally to GND
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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SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
(1) (2)(3)
Absolute Maximum Ratings
VIN, VOUT pins
-0.3V to 6.0V
EN, T/F, TX, SEL pins
-0.3V to (VIN + 0.3V)
w/ 6.0V max
Continuous Power Dissipation
(4)
Internally Limited
150°C
Junction Temperature (TJ-MAX-ABS
Storage Temperature Range
Lead Temp. (Soldering, 5 sec.)
)
-65°C to 150°C
260°C
(5)
ESD Rating
Human Body Model
2kV
(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is specified. Operating Ratings do not imply performance limits. For performance limits and associated test
conditions, see the Electrical Characteristics .
(2) All voltages are with respect to the potential at the GND pin.
(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office / Distributors for
availability and specifications.
(4) 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.).
(5) The Human-body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin.
(1) (2)
Operating Ratings
Input Voltage (VIN
)
2.8V to 5.5V
Junction Temperature Range (TJ)
-40°C to +125°C
Ambient Temperature Range (TA)
(3)
-40°C to +85 °C
(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is specified. Operating Ratings do not imply performance limits. For performance limits and associated test
conditions, see the Electrical Characteristics .
(2) All voltages are with respect to the potential at the GND pin.
(3) 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,
(1)
WQFN-24 Package (θJA
)
42°C/W
(1) 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 102mm x 76mm x 1.6mm. The 2 imbedded
copper layers cover roughly the same area as the board. Thickness of copper layers are 70µm/35µm/35µm/70µm(2oz/1oz/1oz/2oz).
Thermal vias are placed between the die attach pad in the 1st copper layer and the 2nd copper layer. Ambient temperature in simulation
is 22°C, still air. Power dissipation is 1W. The value of θJA of the LM2754 in WQFN-24 could fall in a range as wide as 35ºC/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 Gain, 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 sections of this
datasheet.
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Electrical Characteristics(1) (2)
Limits in standard typeface are for TJ = 25°C, and limits in boldface type apply over the full operating junction temperature
range (-40°C to +125 °C). Unless otherwise noted, specifications apply to the LM2754 Typical Application Circuit (pg.1) with
(3)
V(IN, INSW) = 3.6V, VEN = 1.8V, VT/F = 0V, VTX = 0V, VSEL = 0V, CIN = C1 = C2 = 2.2µF, COUT = 4.7µF.
Symbol
VSETx
IDx/ISETx
Parameter
ISETx Pin Voltage
Conditions
Min
−3.5%
−7%
Typ
1.244
795
820
550
150
4.7
Max
+3.5%
+7%
Units
V
RSETx = 20kΩ
LED Current to Set Current
IDx = 50mA to 100mA
IDx = 200mA
mA/mA
(4)
Ratio
−11.5%
+11.5%
VHR
Current Sink Headroom
IDx = 200mA
mV
V
(5)
Voltage
IDx = 50mA
VOUT
Output Voltage
1x Mode, IDx = 0mA
1.5x Mode, IDx = 0mA
2x Mode, IDx = 0mA
1x Mode
4.7
5.1
ROUT
Output Impedance
Quiescent Supply Current
0.25
1.3
Ω
1.5x Mode
2x Mode
1.5
IQ
1x Mode, IDx = 0mA
1.5x Mode, IDx = 0mA
2x Mode, IDx = 0mA
VEN = 0V
0.7
mA
3.4
6.3
8
1
ISD
fSW
VIH
VIL
IIH
Shutdown Supply Current
Switching Frequency
Logic Input High
0.1
µA
MHz
V
0.7
1.2
1
1.3
Input Pins: EN, T/F, TX, SEL
Input Pins: EN, T/F, TX, SEL
V(EN, T/F, TX, SEL) = 1.8V
Logic Input Low
0.4
(6)
Logic Input High Current
4
µA
µA
(6)
IIL
Logic Input Low Current
V(EN, T/F, TX, SEL) = 0V
0.5
(1) All voltages are with respect to the potential at the GND pin.
(2) Min and Max limits are specified by design, test, or statistical analysis. Typical numbers represent the most likely norm.
(3) CIN, COUT, C1, C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics
(4) IDx/ISETx Ratio was tested with the Charge Pump in a gain of 1x.
(5) Headroom Voltage (VHR) is the voltage across the current sinks (VDx) at which the current falls to 95% of the nominal programmed
current. VHR is measured from VDx to GND. If the headroom voltage requirement is not met, LED current regulation will be
compromised.
(6) There is a 500kΩ resistor connected internally between each logic pin (EN, T/F, TX, SEL) and GND.
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SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
BLOCK DIAGRAM
4.7 µF
C
OUT
4 - LED
FLASH
D
D
D
D
4
1
2
3
MODULE
V
OUT
D
4
Gain
Control
V
IN
OFF
SEL
2.2 µF
C
IN
C +
1
V
OUT
GND
Current
Control
2.2 µF
FLASH
Timeout
REG
C -
1
T/F
TX
EN
1x,1.5x,
2x
Charge
Pump
C +
2
V
REF
2.2 µF
Torch
Flash
C -
2
OSC
I
I
SET2
SET1
LM2754
R
R
FLASH
TORCH
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TYPICAL PERFORMANCE CHARACTERISTICS
Unless otherwise specified: TA = 25°C, VDx = 1V, V(IN, INSW) = 3.6V, VEN = VIN, VT/F = VTX = VSEL = 0V, CIN = C1 = C2 = 2.2µF,
COUT = 4.7µF. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's).
Dx Current vs. RSET
Dx Current vs. Headroom Voltage
Figure 1.
Figure 2.
Quiescent Current vs. Input Voltage
Shutdown Current vs. Input Voltage
Figure 3.
Figure 4.
Efficiency vs. Input Voltage
Oscillator Frequency vs. Input Voltage
Figure 5.
Figure 6.
6
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified: TA = 25°C, VDx = 1V, V(IN, INSW) = 3.6V, VEN = VIN, VT/F = VTX = VSEL = 0V, CIN = C1 = C2 = 2.2µF,
COUT = 4.7µF. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's).
Flash Mode with TX Pulse
Torch to Flash Mode
VIN = 3.6V, Load = 700mA (Flash), LED = PWF1
CH1 (TOP): VTX; Scale: 1V/Div, DC Coupled
CH2 (BOTTOM): ILED; Scale: 200mA/Div
Time scale: 1ms/Div
VIN = 3.6V, Load = 200mA/800mA (Torch/Flash), LED = PWF1;
CH1 (TOP): VIN; Scale: 1V/Div, DC Coupled
CH2 (MIDDLE): VOUT; Scale: 1V/Div, DC Coupled
CH3 (BOTTOM): IIN; Scale: 200mA/Div
Time scale: 100ms/Div
Figure 7.
Figure 8.
Flash to Torch Mode
Falling Edge
Torch to Flash Mode Rising Edge
VIN = 3.6V, Load = 200mA/800mA (Torch/Flash), LED = PWF1
CH1 (TOP): VIN; Scale: 1V/Div, DC Coupled
CH2 (MIDDLE): VOUT; Scale: 1V/Div, DC Coupled
CH3 (BOTTOM): IIN; Scale: 200mA/Div
VIN = 3.6V, Load = 800mA/200mA (Flash/Torch), LED = PWF1
CH1 (TOP): VIN; Scale: 1V/Div, DC Coupled
CH2 (MIDDLE): VOUT; Scale: 1V/Div, DC Coupled
CH3 (BOTTOM): IIN; Scale: 200mA/Div
Time scale: 400µs/Div
Time scale: 100µs/Div
Figure 9.
Figure 10.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified: TA = 25°C, VDx = 1V, V(IN, INSW) = 3.6V, VEN = VIN, VT/F = VTX = VSEL = 0V, CIN = C1 = C2 = 2.2µF,
COUT = 4.7µF. Capacitors are low-ESR multi-layer ceramic capacitors (MLCC's).
Battery Ripple, Gain = 1.5x
Battery Ripple, Gain = 2x
VIN = Li-Ion Battery at 3.7V, Load = 400mA, LED = PWF1;
CH1 (MID-TOP): VOUT; Scale: 20mV/Div, AC Coupled;
CH2 (MID-BOTTOM): VIN; Scale: 50mV/Div, AC Coupled;
CH3 (TOP): VIN; Scale: 1V/Div, DC Coupled;
VIN = Li-Ion Battery at 3.7V, Load = 400mA; LED = PWF1;
CH1 (MID-TOP): VOUT; Scale: 20mV/Div, AC Coupled;
CH2 (MID-BOTTOM): VIN; Scale: 50mV/Div, AC Coupled;
CH3 (TOP): VIN; Scale: 1V/Div, DC Coupled;
CH4 (BOTTOM): IIN; Scale: 500mA/Div;
CH4 (BOTTOM): IIN; Scale: 500mA/Div; Time scale: 1µs/Div
Time scale: 1µs/Div
Figure 11.
Figure 12.
Startup and Shutdown Response
Torch Mode (400mA)
VIN = 3.6V, Load = 400mA, LED = PWF1;
CH1 (TOP): VOUT; Scale: 1V/Div, DC Coupled;
CH4 (MIDDLE): IIN; Scale: 200mA/Div
CH3 (BOTTOM): IOUT; Scale: 200mA/Div ;
Time scale: 100ms/Div
Figure 13.
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APPLICATION INFORMATION
CIRCUIT DESCRIPTION
The LM2754 is an adaptive 1x/1.5x/2x CMOS charge pump, optimized for driving Flash LEDs in camera phone
and other portable applications. It provides four constant current inputs, each capable of sinking up to 200mA for
Flash mode, and 100mA for Torch mode.
Each LED is driven from VOUT and connected to one of the four current sinks. LED drive current for Torch mode
is programmed by connecting a resistor, RSET1, to the current set pin, ISET1. LED drive current for Flash mode is
set by connecting a resistor, RSET2, to the current set pin, ISET2. Torch mode is enabled by the EN pin, and the
transition from Torch to Flash mode is controlled by the T/F pin. This device also has an option to disable the D4
current sink via the SEL pin, for Flash LED modules with only 3 LEDs.
To prevent high battery load during a simultaneous RF PA transmission pulse and Flash condition, this device
has a Flash interrupt pin (TX) to reduce the LED current to the Torch mode level for the duration of the RF PA
transmission pulse.
CHARGE PUMP
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. The device's loosely-regulated charge pump has both open loop and
closed loop modes of operation. Under no-load conditions, open loop operation occurs when VOUT is equal to the
product of the input voltage and the charge pump gain, and is less than the nominal output regulation voltage.
Over the recommended input voltage range of 3.0V to 5.5V, unloaded open loop operation will only occur in 1x
and 1.5x gains. When the LM2754 is in closed loop operation with no-load, the voltage at VOUT is loosely
regulated to 4.7V (typ.) for the 1x and 1.5x gains, and 5.1V (typ.) for the 2x gain. 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 LM2754.
The charge pump gain transitions are actively selected to maintain regulation based on LED forward voltage and
load requirements. The charge pump only transitions to higher gains, from 1x to 1.5x and 1.5x to 2x. Each
transition from one gain to the next takes 125ms (typ.) for Torch mode and 2ms (typ.) for Flash 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 LM2754 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 LM2754 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 1.2A (typ.).
LOGIC CONTROL PINS
There are 4 logic control pins for the LM2754. All pins are active-High logic (High = Function ON). There is an
internal pull-down resistor (500kΩ typ.) connected between each logic pin and GND. The operating modes for
the part function according to Table 1:
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Table 1. LM2754 Logic Control Pins
EN
0
T/F
X
0
TX
X
X
X
0
SEL
Mode
X
0
1
0
1
0
Part in Shutdown
1
Part Enabled, Current set by RSET1, D1-4 Active
Part Enabled, Current set by RSET1, D1-3 Active, D4 Disabled
Part Enabled, Current set by RSET2, D1-4 Active
Part Enabled, Current set by RSET2, D1-3 Active, D4 Disabled
1
0
1
1
1
1
0
1
1
1
Part Enabled, Current set by RSET1, TX signal from RF PA, D1-4 Active
Part Enabled, Current set by RSET1, TX signal from RF PA, D1-3 Active, D4
Disabled
1
1
1
1
EN PIN (TORCH)
The EN pin is the master enable pin for the part. When the voltage on this pin is Low (<0.4V), the part is in
shutdown mode. In this mode, all internal circuitry is OFF, VOUT is disconnected from the VIN, and the part
consumes very little supply current (<1µA typ.). When the voltage on the EN pin is High (>1.2V), the part will
activate the charge pump and regulate the output voltage to its nominal value. When the output voltage reaches
its regulation level, the current sinks will turn on and sink the current programmed by RSET1 (assuming the logic
on T/F is Low). Enabling the device is also referred to as Torch Mode. For correct start-up sequencing, power
must be applied to VIN before a High logic signal is applied to the EN pin.
T/F PIN (FLASH) AND FLASH TIMEOUT
A logic Low (<0.4V) signal on the T/F pin disables the Flash mode, defaulting the current through the LEDs to the
Torch level programmed by RSET1. Applying a logic High (>1.2V) signal to T/F places the device in Flash mode,
with the LED current set by RSET2
.
Flash Timeout Protection Circuitry disables the current sinks when the signal on T/F is held high for more than 1
second (typ). 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 sinks will be shut off,
resulting in no current through the Flash LEDs. When the device goes into a timeout condition, placing a logic
Low signal on EN will reset the timeout and a subsequent logic High signal on EN will return the device to normal
operation. Flash timeout is not active during TX mode.
TX PIN
The TX pin on the LM2754 disables the Flash operation during a RF PA transmission pulse, and sets the LED
current to the Torch level programmed by RSET1 for the duration of that pulse. At the end of each transmission
interrupt pulse signal on the TX pin, the LED current level returns to the Flash current level set by RSET2. The TX
pin responds to the typical logic High (>1.2V) and logic Low (<0.4V) signal levels. Flash Timeout is not active
during the TX mode operation.
SEL PIN
Connecting the SEL pin to a logic Low (<0.4V) signal places the device in normal operation, with all 4 current
sinks active. To accommodate Flash LED modules with only 3 LEDs, place a logic High (>1.2V) signal on the
SEL pin to disable the current sink D4. If only 3 current sinks are used, the 200mA per current sink
recommendation still applies, and the maximum Flash current will be 600mA. Connect D4 to VOUT when the logic
in the SEL pin is High. Optional use of the SEL pin is to reduce the LED current used for Torch or Flash by 25%
for high battery load conditions.
SETTING LED CURRENTS
The current through the LEDs connected to D1-4 can be set simply by connecting an appropriately sized resistor
(RSETx) between the ISET1 pin of the LM2754 and GND for Torch mode and the ISET2 pin and GND for Flash
Mode. The LED currents are proportional to the current that flows out of the ISETx pin and are a factor of
approximately 800 times greater than the ISETx current. The feedback loop of an internal amplifier sets the voltage
of the ISET pin to 1.25V (typ.). The statements above are simplified in the equations below:
IDx = 800 ×(VSET / RSET
)
(1)
(2)
RSET = 800 × (1.25V / IDx
)
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The maximum recommended current through each current sink is 100mA during Torch mode and 200mA during
Flash mode. Maximum recommended total Flash current with all 4 current sinks used is 800mA (max 200mA per
current sink). 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.
PARALLEL DX OUTPUTS FOR INCREASED CURRENT DRIVE
Outputs D1-4 may be connected together to drive a one or two LEDs at higher currents. In applications using a
single LED, all four parallel current sinks of equal value drive the single LED. For this type of configuration, the
LED current should be programmed so that the current through each of the outputs is 25% of the total desired
LED current. For example, if 200mA is the desired drive current for the single LED, RSET should be selected such
that the current through each of the current sink inputs is 50mA. Similarly, if two LEDs are to be driven by pairing
up the D1-4 inputs (i.e D1-2, D3-4), RSET should be selected such that the current through each current sink input is
50% of the desired LED current.
Connecting the outputs in parallel does not affect internal operation of the LM2754 and has no impact on the
Electrical Characteristics and limits previously presented. The available diode output current, maximum diode
voltage, and all other specifications provided in the Electrical Characteristics table apply to this parallel output
configuration, just as they do to the standard 4-LED application circuit.
Maximum recommended LED current for any configuration is 200mA per current sink, and 800mA total. For
situations where only 3 current sinks will be used for the application, see the SEL PIN operation section.
CAPACITOR SELECTION
The LM2754 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
<20mΩ typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are not
recommended for use with the LM2754 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 LM2754. 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 LM2754.
Capacitors with these temperature characteristics typically have wide capacitance tolerance (+80%, -20%) and
vary significantly 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 1µF Y5V or Z5U capacitor could have a capacitance of only
0.1µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum
capacitance requirements of the LM2754.
The voltage rating of the output capacitor should be 10V or more. For example, a 10V 0603 4.7µF output
capacitor (TDK C1608X5R1A475) is acceptable for use with the LM2754, 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 1µF.
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 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 LM2754 can be predicted as follows:
PLED = N × VLED × ILED
PIN = VIN × IIN
(3)
(4)
(5)
(6)
PIN = VIN × (Gain × N × ILED + IQ)
E = (PLED ÷ PIN)
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)
Copyright © 2006–2013, Texas Instruments Incorporated
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LM2754
SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
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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 (100-800mA). 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 LM2754 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 LEDs, TA
is the ambient temperature, and θJA is the junction-to-ambient thermal resistance for the WQFN-24 package. VIN
is the input voltage to the LM2754, VLED is the nominal LED forward voltage, and ILED is the programmed LED
current.
PDISSIPATION = PIN - PLED
(8)
(9)
= [Gain × VIN × (4 x ILED)] − (VLED × 4 x ILED
)
TJ = TA + (PDISSIPATION × θJA)
(10)
The junction temperature rating takes precedence over the ambient temperature rating. The LM2754 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.
PCB Layout Considerations
The WQFN is a leadframe based Chip Scale Package (CSP) with very good thermal properties. This package
has an exposed DAP (die attach pad) at the center of the package measuring 2.6mm x 2.6mm. The main
advantage of this exposed DAP is to offer lower thermal resistance when it is soldered to the thermal land on the
PCB. For PCB layout, a 1:1 ratio between the package and the PCB thermal land is recommended. To further
enhance thermal conductivity, the PCB thermal land may include vias to a ground plane. For more detailed
instructions on mounting WQFN packages, please refer to Application Note AN-1187 (SNOA401).
12
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Product Folder Links: LM2754
LM2754
www.ti.com
SNVS463A –SEPTEMBER 2006–REVISED MAY 2013
REVISION HISTORY
Changes from Original (May 2013) to Revision A
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 12
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status Package Type Package Pins Package
Eco Plan
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
Samples
Drawing
Qty
(1)
(2)
(3)
(4/5)
(6)
LM2754SQ/NOPB
ACTIVE
WQFN
RTW
24
1000 RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LM2754
(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 <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(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 finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material 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.
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
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Sep-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
LM2754SQ/NOPB
WQFN
RTW
24
1000
178.0
12.4
4.3
4.3
1.3
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Sep-2015
*All dimensions are nominal
Device
Package Type Package Drawing Pins
WQFN RTW 24
SPQ
Length (mm) Width (mm) Height (mm)
210.0 185.0 35.0
LM2754SQ/NOPB
1000
Pack Materials-Page 2
PACKAGE OUTLINE
RTW0024A
WQFN - 0.8 mm max height
S
C
A
L
E
3
.
0
0
0
PLASTIC QUAD FLATPACK - NO LEAD
4.1
3.9
B
A
PIN 1 INDEX AREA
4.1
3.9
C
0.8 MAX
SEATING PLANE
0.08 C
0.05
0.00
2X 2.5
(0.1) TYP
EXPOSED
THERMAL PAD
7
12
20X 0.5
6
13
2X
25
2.5
2.6 0.1
1
18
0.3
24X
0.2
24
19
PIN 1 ID
(OPTIONAL)
0.1
C A B
C
0.05
0.5
0.3
24X
4222815/A 03/2016
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.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
www.ti.com
EXAMPLE BOARD LAYOUT
RTW0024A
WQFN - 0.8 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
(
2.6)
SYMM
24
19
24X (0.6)
1
18
24X (0.25)
(1.05)
SYMM
25
(3.8)
20X (0.5)
(R0.05)
TYP
6
13
(
0.2) TYP
VIA
7
12
(1.05)
(3.8)
LAND PATTERN EXAMPLE
SCALE:15X
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
SOLDER MASK
OPENING
METAL
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
NON SOLDER MASK
DEFINED
SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK DETAILS
4222815/A 03/2016
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
number SLUA271 (www.ti.com/lit/slua271).
www.ti.com
EXAMPLE STENCIL DESIGN
RTW0024A
WQFN - 0.8 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
4X ( 1.15)
(0.675) TYP
19
(R0.05) TYP
24
24X (0.6)
1
18
24X (0.25)
(0.675)
TYP
SYMM
20X (0.5)
25
(3.8)
6
13
METAL
TYP
7
12
SYMM
(3.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD 25:
78% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE
SCALE:20X
4222815/A 03/2016
NOTES: (continued)
5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
www.ti.com
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