LM3501TL-16/NOPB [TI]
适用于白光 LED 应用的同步升压直流/直流转换器 | YZR | 8 | -40 to 85;
| 型号： | LM3501TL-16/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 适用于白光 LED 应用的同步升压直流/直流转换器 | YZR | 8 | -40 to 85 驱动 接口集成电路 转换器 |
| 文件： | 总27页 (文件大小：1406K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LM3501
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SNVS230C –DECEMBER 2003–REVISED MAY 2013
LM3501 Synchronous Step-up DC/DC Converter for White LED Applications
Check for Samples: LM3501
1
FEATURES
APPLICATIONS
2
•
Synchronous Rectification, High Efficiency
and no External Schottky Diode required
•
•
•
•
•
LCD Bias Supplies
White LED Back-Lighting
Handheld Devices
Digital Cameras
•
•
Uses Small Surface Mount Components
Can Drive 2-5 White LEDs in Series (May
Function with More Low VF LEDs)
Portable Applications
•
•
2.7V to 7V Input Range
True Shutdown Isolation, no LED Leakage
Current
DESCRIPTION
The LM3501 is a fixed-frequency step-up DC/DC
converter that is ideal for driving white LEDs for
display backlighting and other lighting functions. With
fully integrated synchronous switching (no external
schottky diode required) and a low feedback voltage
(515 mV), power efficiency of the LM3501 circuit has
been optimized for lighting applications in wireless
phones and other portable products (single cell Li-Ion
or 3-cell NiMH battery supplies). The LM3501
operates with a fixed 1 MHz switching frequency.
When used with ceramic input and output capacitors,
the LM3501 provides a small, low-noise, low-cost
solution.
•
•
•
DC Voltage LED Current Control
Input Undervoltage Lockout
Internal Output Over-Voltage Protection (OVP)
Circuitry, with no External Zener Diode
Required LM3501-16: 15.5V OVP; LM3501-21:
20.5V OVP.
•
Requires Only a Small 16V (LM3501-16) or 25V
(LM3501-21) Ceramic Capacitor at the Input
and Output
•
•
•
Thermal Shutdown
0.1µA shutdown Current
Small 8-Bump Thin DSBGA Package
Typical Application Circuit
L
VIN
2.7V - 5.5V
22 mH
Voltage
Control
B1
VIN
C2
VSW
A3
A2
COUT
CIN
CNTRL
LM3501-16
C1
1mF
Ceramic
VOUT
1mF
Ceramic
>1.1V
<0.3V
B3
SHDN
FB
AGND GND
C3
A1
R2
24W
Figure 1. Typical 3 LED Application
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 © 2003–2013, Texas Instruments Incorporated
LM3501
SNVS230C –DECEMBER 2003–REVISED MAY 2013
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DESCRIPTION (CONTINUED)
Two LM3501 options are available with different output voltage capabilities. The LM3501-21 has a maximum
output voltage of 21V and is typically suited for driving 4 or 5 white LEDs in series. The LM3501-16 has a
maximum output voltage of 16V and is typically suited for driving 3 or 4 white LEDs in series (maximum number
of series LEDs dependent on LED forward voltage). If the primary white LED network should be disconnected,
the LM3501 uses internal protection circuitry on the output to prevent a destructive overvoltage event.
A single external resistor is used to set the maximum LED current in LED-drive applications. The LED current
can easily be adjusted by varying the analog control voltage on the control pin or by using a pulse width
modulated (PWM) signal on the shutdown pin. In shutdown, the LM3501 completely disconnects the input from
output, creating total isolation and preventing any leakage currents from trickling into the LEDs.
Connection Diagram
A2
A1
A3
B3
C3
B1
C1
C2
Figure 2. 8-Bump DSBGA
Top View
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SNVS230C –DECEMBER 2003–REVISED MAY 2013
PIN DESCRIPTIONS
Pin
A1
B1
C1
C2
C3
B3
A3
A2
Name
AGND
VIN
Function
Analog ground.
Analog and Power supply input.
PMOS source connection for synchronous rectification.
VOUT
VSW
Switch pin. Drain connections of both NMOS and PMOS power devices.
Power Ground.
GND
FB
Output voltage feedback connection.
Analog LED current control.
CNTRL
SHDN
Shutdown control pin.
AGND (pin A1): Analog ground pin
The analog ground pin should tie directly to the GND pin.
VIN (pin B1):Analog and Power supply pin
Bypass this pin with a capacitor, as close to the device as possible, connected between the
VIN and GND pins.
VOUT (pin C1):Source connection of internal PMOS power device
Connect the output capacitor between the VOUT and GND pins as close as possible to the
device.
VSW (pin C2):Drain connection of internal NMOS and PMOS switch devices
Keep the inductor connection close to this pin to minimize EMI radiation.
GND (pin C3):Power ground pin
Tie directly to ground plane.
FB (pin B3):Output voltage feedback connection
Set the primary White LED network current with a resistor from the FB pin to GND. Keep the
current setting resistor close to the device and connected between the FB and GND pins.
CNTRL (pin A3): Analog control of LED current
A voltage above 125 mV will begin to regulate the LED current. Decreasing the voltage
below 75 mV will turn off the LEDs.
SHDN (pin A2):Shutdown control pin
Disable the device with a voltage less than 0.3V and enable the device with a voltage
greater than 1.1V. The white LED current can be controlled using a PWM signal at this pin.
There is an internal pull down on the SHDN pin, the device is in a normally off state.
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.
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(1)(2)
Absolute Maximum Ratings
VIN
−0.3V to 7.5V
−0.3V to 16V
VOUT (LM3501-16)(3)
VOUT (LM3501-21)(3)
−0.3V to 21V
(3)
VSW
−0.3V to VOUT+0.3V
−0.3V to 7.5V
−0.3V to VIN+0.3V
−0.3V to 7.5V
150°C
FB Voltage
SHDN Voltage
CNTRL
Maximum Junction Temperature
Lead Temperature
(Soldering 10 sec.)
300°C
215°C
220°C
Vapor Phase
(60 sec.)
Infrared
(15 sec.)
(4)
ESD Ratings
Human Body Model
Machine Model
2kV
200V
(1) Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the
device is intended to be functional, but device parameter specifications may not be specified. For specifications and test conditions, see
the Electrical Characteristics.
(2) Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(3) This condition applies if VIN < VOUT. If VIN > VOUT, a voltage greater than VIN + 0.3V should not be applied to the VOUT or VSW pins.
(4) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF
capacitor discharged directly into each pin.
Operating Conditions
Junction Temperature
(1)
−40°C to +125°C
Supply Voltage
CNTRL Max.
2.7V to 7V
2.7V
(1) The maximum allowable power dissipation is a function of the maximum operating junction temperature, TJ(MAX), the junction-to-ambient
thermal resistance, θJA, and the ambient temperature, TA. See the Thermal Properties section for the thermal resistance. The maximum
allowable power dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum
allowable power dissipation will cause excessive die temperature.
Thermal Properties
Junction to Ambient Thermal Resistance (θJA
(1)
)
75°C/W
(1) Junction-to-ambient thermal resistance (θJA) is highly application and board-layout dependent. The 75ºC/W figure provided was
measured on a 4-layer test board conforming to JEDEC standards. In applications where high maximum power dissipation exists,
special care must be paid to thermal dissipation issues when designing the board layout.
4
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SNVS230C –DECEMBER 2003–REVISED MAY 2013
Electrical Characteristics
Specifications in standard type face are for TA = 25°C and those in boldface type apply over the Operating Temperature
Range of TA = −10°C to +85°C. Unless otherwise specified VIN = 2.7V and specifications apply to both LM3501-16 and
LM3501-21.
Min
Typ
Max
Symbol
Parameter
Conditions
Units
(1)
(2)
(1)
IQ
Quiescent Current, Device Not
Switching
FB > 0.54V
FB = 0V
0.95
1.2
mA
µA
V
Quiescent Current, Device
Switching
2
2.5
2
Shutdown
SHDN = 0V
0.1
VFB
Feedback Voltage
CNTRL = 2.7V,
VIN = 2.7V to 7V
0.485
0.14
0.515
0.545
CNTRL = 1V,
VIN = 2.7V to 7V
0.19
0.1
0.24
0.5
ΔVFB
Feedback Voltage Line Regulation
VIN = 2.7V to 7V
%/V
ICL
Switch Current Limit
(LM3501-16)
VIN = 2.7V,
Duty Cycle = 80%
275
255
420
450
400
480
VIN = 3.0V,
Duty Cycle = 70%
400
640
530
770
800
mA
Switch Current Limit
(LM3501-21)
VIN = 2.7V,
Duty Cycle = 70%
VIN = 3.0V,
Duty Cycle = 63%
670
45
(3)
IB
FB Pin Bias Current
Input Voltage Range
NMOS Switch RDSON
PMOS Switch RDSON
FB = 0.5V
200
7.0
nA
V
VIN
2.7
80
RDSON
VIN = 2.7V, ISW = 300 mA
VOUT = 6V, ISW = 300 mA
FB = 0V
0.43
2.3
Ω
1.3
87
DLimit
Duty Cycle Limit
(LM3501-16)
%
Duty Cycle Limit
(LM3501-21)
FB = 0V
85
94
FSW
ISD
Switching Frequency
0.85
1.0
1.8
1
1.15
4
MHz
µA
(4)
SHDN Pin Current
SHDN = 5.5V
SHDN = 2.7V
SHDN = GND
VCNTRL = 2.7V
VCNTRL = 1V
VSW = 15V
2.5
0.1
10
4
(4)
ICNTRL
CNTRL Pin Current
20
15
µA
µA
IL
Switch Leakage Current
(LM3501-16)
0.01
0.01
0.5
2.0
Switch Leakage Current
(LM3501-21)
VSW = 20V
UVP
OVP
Input Undervoltage Lockout
ON Threshold
OFF Threshold
ON Threshold
OFF Threshold
ON Threshold
OFF Threshold
2.4
2.3
15
14
20
19
2.5
2.4
2.6
2.5
16
15
21
20
V
V
V
Output Overvoltage Protection
(LM3501-16)
15.5
14.6
20.5
19.5
Output Overvoltage Protection
(LM3501-21)
(1) All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are
production tested, specified through statistical analysis or specified by design. All limits at temperature extremes are specified via
correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level
(AOQL).
(2) Typical numbers are at 25°C and represent the most likely norm.
(3) Feedback current flows out of the pin.
(4) Current flows into the pin.
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Electrical Characteristics (continued)
Specifications in standard type face are for TA = 25°C and those in boldface type apply over the Operating Temperature
Range of TA = −10°C to +85°C. Unless otherwise specified VIN = 2.7V and specifications apply to both LM3501-16 and
LM3501-21.
Min
Typ
Max
Symbol
IVout
Parameter
Conditions
Units
(1)
(2)
(1)
VOUT Bias Current
(LM3501-16)
VOUT = 15V, SHDN = 1.5V
260
300
400
460
3
µA
VOUT Bias Current
(LM3501-21)
VOUT = 20V, SHDN = 1.5V
VOUT = 15V, VSW = 0V
VOUT = 20V, VSW = 0V
IVL
PMOS Switch Leakage Current
(LM3501-16)
0.01
0.01
µA
PMOS Switch Leakage Current
(LM3501-21)
3
CNTRL
Threshold
LED power off
LED power on
75
mV
V
125
0.65
0.65
SHDN
Threshold
SHDN low
0.3
SHDN High
1.1
Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature
Range (TJ = −40°C to +125°C). Unless otherwise specified VIN =2.7V and specifications apply to both LM3501-16 and
LM3501-21.
Min
Typ
Max
Symbol
Parameter
Conditions
Units
(1)
(2)
(1)
IQ
Quiescent Current, Device Not
Switching
FB > 0.54V
FB = 0V
0.95
2
1.2
2.5
mA
Quiescent Current, Device
Switching
Shutdown
SHDN = 0V
0.1
0.515
0.19
0.1
2
µA
V
VFB
Feedback Voltage
CNTRL = 2.7V, VIN = 2.7V to 7V
CNTRL = 1V, VIN = 2.7V to 7V
VIN = 2.7V to 7V
0.485
0.14
0.545
0.24
0.5
ΔVFB
Feedback Voltage Line Regulation
%/V
ICL
Switch Current Limit
(LM3501-16)
VIN = 3.0V,
Duty Cycle = 70%
400
mA
Switch Current Limit
(LM3501-21)
VIN = 3.0V,
Duty Cycle = 63%
670
45
(3)
IB
FB Pin Bias Current
Input Voltage Range
NMOS Switch RDSON
PMOS Switch RDSON
FB = 0.5V
200
7.0
nA
V
VIN
2.7
RDSON
VIN = 2.7V, ISW = 300 mA
VOUT = 6V, ISW = 300 mA
FB = 0V
0.43
2.3
Ω
1.3
87
DLimit
Duty Cycle Limit
(LM3501-16)
%
Duty Cycle Limit
(LM3501-21)
FB = 0V
94
FSW
ISD
Switching Frequency
0.8
1.0
1.8
1
1.2
4
MHz
µA
(4)
SHDN Pin Current
SHDN = 5.5V
SHDN = 2.7V
SHDN = GND
2.5
0.1
(1) All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are
production tested, specified through statistical analysis or specified by design. All limits at temperature extremes are specified via
correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level
(AOQL).
(2) Typical numbers are at 25°C and represent the most likely norm.
(3) Feedback current flows out of the pin.
(4) Current flows into the pin.
6
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Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature
Range (TJ = −40°C to +125°C). Unless otherwise specified VIN =2.7V and specifications apply to both LM3501-16 and
LM3501-21.
Min
Typ
Max
Symbol
ICNTRL
Parameter
Conditions
Units
(1)
(2)
(1)
(4)
CNTRL Pin Current
VCNTRL = 2.7V
10
4
20
15
µA
VCNTRL = 1V
VSW = 15V
IL
Switch Leakage Current
(LM3501-16)
0.01
0.5
µA
V
Switch Leakage Current
(LM3501-21)
VSW = 20V
0.01
2.0
UVP
OVP
Input Undervoltage Lockout
ON Threshold
2.4
2.3
15
14
20
19
2.5
2.4
2.6
2.5
16
15
21
20
OFF Threshold
ON Threshold
Output Overvoltage Protection
(LM3501-16)
15.5
14.6
20.5
19.5
OFF Threshold
ON Threshold
V
Output Overvoltage Protection
(LM3501-21)
OFF Threshold
VOUT = 15V, SHDN = 1.5V
IVout
VOUT Leakage Current
(LM3501-16)
260
300
400
460
3
µA
µA
VOUT Leakage Current
(LM3501-21)
VOUT = 20V, SHDN = 1.5V
VOUT = 15V, VSW = 0V
VOUT = 20V, VSW = 0V
IVL
PMOS Switch Leakage Current
(LM3501-16)
0.01
0.01
PMOS Switch Leakage Current
(LM3501-21)
3
CNTRL
Threshold
LED power off
LED power on
75
mV
V
125
0.65
0.65
SHDN
Threshold
SHDN low
0.3
SHDN High
1.1
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Typical Performance Characteristics
Switching Quiescent Current
Non-Switching Quiescent Current
vs.
VIN
vs.
VIN
Figure 3.
Figure 4.
2 LED Efficiency
vs.
3 LED Efficiency
vs.
Load Current
Load Current
L = Coilcraft DT1608C-223,
Efficiency = 100*(PIN/(2VLED*ILED))
L = Coilcraft DT1608C-223,
Efficiency = 100*(PIN/(3VLED*ILED))
Figure 5.
Figure 6.
4 LED Efficiency
vs.
Output Power
Load Current
vs.
VIN
L = Coilcraft DT1608C-223,
Efficiency = 100*(PIN/(4VLED*ILED))
(LM3501-16, L = Coilcraft DT1608C-223)
Figure 7.
Figure 8.
8
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Typical Performance Characteristics (continued)
Output Power
vs.
FB Pin Current
vs.
Temperature
Temperature
(LM3501-16, L = Coilcraft DT1608C-223)
Figure 9.
Figure 10.
SHDN Pin Current
vs.
SHDN Pin Voltage
CNTRL Pin Current
vs.
CNTRL Pin Voltage
Figure 11.
Figure 12.
Switch Current Limit
FB Voltage
vs.
CNTRL Voltage
vs.
VIN
(LM3501-16)
Figure 13.
Figure 14.
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Typical Performance Characteristics (continued)
Switch Current Limit
vs.
Switch Current Limit
vs.
Temperature
Temperature
(LM3501-16, VOUT = 8V)
(LM3501-16, VOUT = 12V)
Figure 15.
Figure 16.
Switch Current Limit
Switch Current Limit
vs.
vs.
VIN
Temperature
(LM3501-21)
(LM3501-21, VOUT = 8V)
1100
1000
900
800
700
600
500
400
300
200
1300
1200
1100
1000
900
V
= 8V
OUT
= 5.5V
= 4.2V
V
IN
V
IN
800
700
V
OUT
= 18V
600
= 3.0V
V
IN
500
-40
-15
10
35
60
85
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
TEMPERATURE (ºC)
INPUT VOLTAGE (V)
Figure 17.
Figure 18.
Switch Current Limit
vs.
Switch Current Limit
vs.
Temperature
Temperature
(LM3501-21, VOUT = 12V)
(LM3501-21, VOUT = 18V)
850
800
750
700
650
600
550
500
450
440
420
400
380
360
340
320
300
280
260
240
= 5.5V
V
IN
V
= 5.5V
IN
V
= 3.0V
IN
= 4.2V
V
IN
V
= 4.2V
IN
= 3.0V
35
V
IN
-40
-15
10
60
85
-40
-15
10
35
60
85
TEMPERATURE °C
TEMPERATURE (ºC)
Figure 19.
Figure 20.
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Typical Performance Characteristics (continued)
VOUT DC Bias
vs.
VOUT Voltage
(LM3501-16)
Oscillator Frequency
vs.
VIN
Figure 21.
Figure 22.
FB Voltage
vs.
Temperature
FB Voltage
vs.
Temperature
Figure 23.
Figure 24.
NMOS RDSON
FB Voltage
vs.
VIN
vs.
VIN
(ISW = 300 mA)
Figure 25.
Figure 26.
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Typical Performance Characteristics (continued)
PMOS RDSON
vs.
Temperature
Typical VIN Ripple
3 LEDs, RLED = 22Ω, VIN = 3.0V, CNTRL = 2.7V
1) SW, 10 V/div, DC
3) IL, 100 mA/div, DC
4) VIN, 100 mV/div, AC
T = 250 ns/div
Figure 27.
Figure 28.
Start-Up (LM3501-16)
SHDN Pin Duty Cycle Control Waveforms
3 LEDs, RLED = 22Ω, VIN = 3.0V, CNTRL = 2.7V
1) SHDN, 1 V/div, DC
LM3501-16, 3 LEDs, RLED = 22Ω, VIN = 3.0V, SHDN frequency = 200
Hz
1) SHDN, 1 V/div, DC
2) IL, 100 mA/div, DC
3) ILED, 20 mA/div, DC
4) VOUT, 10 V/div, DC
2) IL, 100 mA/div, DC
3) ILED, 20 mA/div, DC
T = 100 µs/div
T = 1 ms/div
Figure 29.
Figure 30.
Typical VOUT Ripple, OVP Functioning (LM3501-16)
Typical VOUT Ripple, OVP Functioning (LM3501-21)
T
1
VOUT open circuit and equals approximately 15V DC, VIN = 3.0V
3) VOUT, 200 mV/div, AC
T = 1 ms/div
VOUT open circuit and equals approximately 20V DC, VIN = 3.0V
1) VOUT, 200 mV/div, AC
T = 400 µs/div
Figure 31.
Figure 32.
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Operation
L
VIN
VSW
B1 VIN
C2
UVP
COMP
VOUT
-
OVP
COMP
+
-
C1
UVP
REF
THERMAL
SHUTDOWN
+
LIGHT LOAD
COMP
OVP
REF
+
-
REF
CIN
FB
COUT
Reset Reset Reset
Reset
-
DriveP
B3
-
EAMP
+
LOGIC
PWM
COMP
+
Reset
DriveN
SET Reset Reset
Body Diode
Control
FB
Current
Sense
+
R
osc
LED
CNTRL
A3
-
Duty Limit
Comp
SHUTDOWN
COMP
+
-
Dlimit
A1
A2
C3
SHDN
GND
AGND
Figure 33. LM3501 Block Diagram
The LM3501 utilizes a synchronous Current Mode PWM control scheme to regulate the feedback voltage over
almost all load conditions. The DC/DC controller acts as a controlled current source ideal for white LED
applications. The LM3501 is internally compensated thus eliminating the requirement for any external
compensation components providing a compact overall solution. The operation can best be understood referring
to the block diagram in Figure 33. At the start of each cycle, the oscillator sets the driver logic and turns on the
NMOS power device conducting current through the inductor and turns off the PMOS power device isolating the
output from the VSW pin. The LED current is supplied by the output capacitor when the NMOS power device is
active. During this cycle, the output voltage of the EAMP controls the current through the inductor. This voltage
will increase for larger loads and decrease for smaller loads limiting the peak current in the inductor minimizing
EMI radiation. The EAMP voltage is compared with a voltage ramp and the sensed switch voltage. Once this
voltage reaches the EAMP output voltage, the PWM COMP will then reset the logic turning off the NMOS power
device and turning on the PMOS power device. The inductor current then flows through the PMOS power device
to the white LED load and output capacitor. The inductor current recharges the output capacitor and supplies the
current for the white LED branches. The oscillator then sets the driver logic again repeating the process. The
Duty Limit Comp is always operational preventing the NMOS power switch from being on more than one cycle
and conducting large amounts of current.
The LM3501 has dedicated protection circuitry active during normal operation to protect the IC and the external
components. The Thermal Shutdown circuitry turns off both the NMOS and PMOS power devices when the die
temperature reaches excessive levels. The LM3501 has a UVP Comp that disables both the NMOS and PMOS
power devices when battery voltages are too low preventing an on state of the power devices which could
conduct large amounts of current. The OVP Comp prevents the output voltage from increasing beyond 15.5V
(LM3501-16) and 20.5V (LM3501-21) when the primary white LED network is removed or if there is an LED
failure, allowing the use of small (16V for LM3501-16 and 25V for LM3501-21) ceramic capacitors at the output.
This comparator has hysteresis that will regulate the output voltage between 15.5V and 14.6V typically for the
LM3501-16, and between 20.5V and 19.5V for the LM3501-21. The LM3501 features a shutdown mode that
reduces the supply current to 0.1 uA and isolates the input and output of the converter. The CNTRL pin can be
used to change the white LED current. A CNTRL voltage above 125 mV will enable power to the LEDs and a
voltage lower than 75 mV will turn off the power to the LEDs.
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APPLICATION INFORMATION
ADJUSTING LED CURRENT
The maximum White LED current is set using the following equation:
ILED
=
VFB(MAX)/RLED
(1)
The LED current can be controlled using an external DC voltage. The recommended operating range for the
voltage on the CNTRL pin is 0V to 2.7V. When CNTRL is 2.7V, FB = 0.515V (typ.) The FB voltage will continue
to increase if CNTRL is brought above 2.7V (not recommended). The CNTRL to FB voltage relationship is:
0.191*CNTRL
FB =
(2)
The LED current can be controlled using a PWM signal on the SHDN pin with frequencies in the range of 100 Hz
(greater than visible frequency spectrum) to 1 kHz. For controlling LED currents down to the µA levels, it is best
to use a PWM signal frequency between 200-500 Hz. The LM3501 LED current can be controlled with PWM
signal frequencies above 1 kHz but the controllable current decreases with higher frequency. The maximum LED
current would be achieved using the equation above with 100% duty cycle, ie. the SHDN pin always high.
Applying a voltage greater than 125 mV to the CNTRL pin will begin regulating current to the LEDs. A voltage
below 75 mV will prevent application or regulation of the LED current.
LED-DRIVE CAPABILITY
The maximum number of LEDs that can be driven by the LM3501 is limited by the output voltage capability of the
LM3501. When using the LM3501 in the typical application configuration, with LEDs stacked in series between
the VOUT and FB pins, the maximum number of LEDs that can be placed in series (NMAX) is dependent on the
maximum LED forward voltage (VF-MAX), the voltage of the LM3501 feedback pin (VFB-MAX = 0.545V), and the
minimum output overvoltage protection level of the chosen LM3501 option (LM3501-16: OVPMIN = 15V; LM3501-
21: OVPMIN = 20V). For the circuit to function properly, the following inequality must be met:
(NMAX x VF-MAX) + 0.545V ≤ OVPMIN
(3)
When inserting a value for maximum LED VF, LED forward voltage variation over the operating temperature
range should be considered. The table below provides maximum LED voltage numbers for the LM3501-16 and
LM3501-21 in the typical application circuit configuration (with 3, 4, 5, 6, or 7 LEDs placed in series between the
VOUT and FB pins).
Maximum LED VF
# of LEDs
(in series)
LM3501-16
4.82V
3.61V
2.89V
X
LM3501-21
6.49V
3
4
5
6
7
4.86V
3.89V
3.24V
X
2.78V
For the LM3501 to operate properly, the output voltage must be kept above the input voltage during operation.
For most applications, this requires a minimum of 2 LEDs (total of 6V or more) between the FB and VOUT pins.
OUTPUT OVERVOLTAGE PROTECTION
The LM3501 contains dedicated circuitry for monitoring the output voltage. In the event that the primary LED
network is disconnected from the LM3501-16, the output voltage will increase and be limited to 15.5V (typ.).
There is a 900 mV hysteresis associated with this circuitry which will cause the output to fluctuate between 15.5V
and 14.6V (typ.) if the primary network is disconnected. In the event that the network is reconnected regulation
will begin at the appropriate output voltage. The 15.5V limit allows the use of 16V 1 µF ceramic output capacitors
creating an overall small solution for white LED applications.
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In the event that the primary LED network is disconnected from the LM3501-21, the output voltage will increase
and be limited to 20.5V (typ.). There is a 1V hysteresis associated with this circuitry which will cause the output
to fluctuate between 20.5V and 19.5V (typ.) if the primary network is disconnected. In the event that the network
is reconnected regulation will begin at the appropriate output voltage. The 20.5V limit allows the use of 25V 1 µF
ceramic output capacitors.
RELIABILITY AND THERMAL SHUTDOWN
The maximum continuous pin current for the 8 pin thin DSBGA package is 535 mA. When driving the device near
its power output limits the VSW pin can see a higher DC current than 535 mA (see INDUCTOR SELECTION
section for average switch current). To preserve the long term reliability of the device the average switch current
should not exceed 535 mA.
The LM3501 has an internal thermal shutdown function to protect the die from excessive temperatures. The
thermal shutdown trip point is typically 150°C. There is a hysteresis of typically 35°C so the die temperature must
decrease to approximately 115°C before the LM3501 will return to normal operation.
INDUCTOR SELECTION
The inductor used with the LM3501 must have a saturation current greater than the cycle by cycle peak inductor
current (see Table 1 below). Choosing inductors with low DCR decreases power losses and increases efficiency.
The minimum inductor value required for the LM3501-16 can be calculated using the following equation:
(
VIN RDSON
0.29
D
-1
L >
D'
(4)
The minimum inductor value required for the LM3501-21 can be calculated using the following equation:
(
VIN RDSON
0.58
D
-1
L >
D'
(5)
For both equations above, L is in µH, VIN is the input supply of the chip in Volts, RDSON is the ON resistance of
the NMOS power switch found in Typical Performance Characteristics in ohms and D is the duty cycle of the
switching regulator. The above equation is only valid for D greater than or equal to 0.5. For applications where
the minimum duty cycle is less than 0.5, a 22 µH inductor is the typical recommendation for use with most
applications. Bench-level verification of circuit performance is required in these special cases, however. The duty
cycle, D, is given by the following equation:
VIN
D' =
=1-D
VOUT
(6)
where VOUT is the voltage at pin C1.
Table 1. Typical Peak Inductor Current (mA)(1)
LED Current
VIN
(V)
# LEDs
(in series)
15
mA
20
mA
30
40
50
60
mA
134
190
244
319
116
168
212
288
mA
mA
mA
2.7
3.3
2
3
4
5
2
3
4
5
82
100
138
174
232
90
160
244
322
413
136
210
270
365
204
294
X
234
352
X
118
142
191
76
X
X
172
250
320
446
198
290
X
110
132
183
126
158
216
X
(1) CIN = COUT = 1 μF, L = 22 μH, 160 mΩ DCR max. Coilcraft DT1608C-2232 and 3 LED applications: LM3501-16 or LM3501-21; LED VF
= 3.77V at 20mA; TA = 25°C4 LED applications: LM3501-16 or LM3501-21; LED VF = 3.41V at 20mA; TA = 25°C5 LED applications:
LM3501-21 only; LED VF = 3.28V at 20mA; TA = 25°C
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Table 1. Typical Peak Inductor Current (mA)(1) (continued)
LED Current
VIN
(V)
# LEDs
(in series)
15
mA
20
mA
30
40
50
60
mA
mA
mA
mA
4.2
2
3
4
5
64
76
96
116
180
232
324
142
210
272
388
162
246
318
456
102
122
179
116
146
206
148
186
263
The typical cycle-by-cycle peak inductor current can be calculated from the following equation:
ö I
+
VIND
OUT
IPK
hD' 2LFSW
(7)
where IOUT is the total load current, FSW is the switching frequency, L is the inductance and η is the converter
efficiency of the total driven load. A good typical number to use for η is 0.8. The value of η can vary with load and
duty cycle. The average inductor current, which is also the average VSW pin current, is given by the following
equation:
IL(AVE) ö I
OUT
hD'
(8)
The maximum output current capability of the LM3501 can be estimated with the following equation:
VIND
-
ICL
IOUT
ö hD'
2LFSW
(9)
where ICL is the current limit. Some recommended inductors include but are not limited to:
Coilcraft DT1608C series
Coilcraft DO1608C series
TDK VLP4612 series
TDK VLP5610 series
TDK VLF4012A series
CAPACITOR SELECTION
Choose low ESR ceramic capacitors for the output to minimize output voltage ripple. Multilayer X7R or X5R type
ceramic capacitors are the best choice. For most applications, a 1 µF ceramic output capacitor is sufficient.
Local bypassing for the input is needed on the LM3501. Multilayer X7R or X5R ceramic capacitors with low ESR
are a good choice for this as well. A 1 µF ceramic capacitor is sufficient for most applications. However, for some
applications at least a 4.7 µF ceramic capacitor may be required for proper startup of the LM3501. Using
capacitors with low ESR decreases input voltage ripple. For additional bypassing, a 100 nF ceramic capacitor
can be used to shunt high frequency ripple on the input. Some recommended capacitors include but are not
limited to:
TDK C2012X7R1C105K
Taiyo-Yuden EMK212BJ105 G
LAYOUT CONSIDERATIONS
The input bypass capacitor CIN, as shown in Figure 33, must be placed close to the device and connect between
the VIN and GND pins. This will reduce copper trace resistance which effects the input voltage ripple of the IC.
For additional input voltage filtering, a 100 nF bypass capacitor can be placed in parallel with CIN to shunt any
high frequency noise to ground. The output capacitor, COUT, should also be placed close to the LM3501 and
connected directly between the VOUT and GND pins. Any copper trace connections for the COUT capacitor can
increase the series resistance, which directly effects output voltage ripple and efficiency. The current setting
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resistor, RLED, should be kept close to the FB pin to minimize copper trace connections that can inject noise into
the system. The ground connection for the current setting resistor should connect directly to the GND pin. The
AGND pin should connect directly to the GND pin. Not connecting the AGND pin directly, as close to the chip as
possible, may affect the performance of the LM3501 and limit its current driving capability. Trace connections
made to the inductor should be minimized to reduce power dissipation, EMI radiation and increase overall
efficiency. It is good practice to keep the VSW routing away from sensitive pins such as the FB pin. Failure to do
so may inject noise into the FB pin and affect the regulation of the device. See Figure 34 and Figure 35 for an
example of a good layout as used for the LM3501 evaluation board.
Figure 34. Evaluation Board Layout (2X Magnification)
Top Layer
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Figure 35. Evaluation Board Layout (2X Magnification)
Bottom Layer (as viewed from the top)
L
VIN
2.7V - 5.5V
22 mH
Voltage
Control
B1
VIN
C2
VSW
A3
A2
COUT
CIN
CNTRL
LM3501-16
C1
B3
1mF
Ceramic
VOUT
1mF
Ceramic
>1.1V
<0.3V
SHDN
FB
AGND GND
C3
A1
R2
24W
Figure 36. 2 White LED Application
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L
V
IN
22 mH
2.7V - 5.5V
Voltage
Control
B1
C2
V
V
SW
IN
A3
A2
COUT
C1
B3
V
OUT
C
CNTRL
LM3501-16
IN
1 mF
Ceramic
1 mF
Ceramic
>1.1V
<0.3V
SHDN
AGND GND
C3
FB
Control with DC
voltage, NMOS
FET switch, or tie
directly to ground.
R2
A1
R1
24W
Figure 37. Multiple 2 LED String Application
L
V
IN
22 mH
2.7V - 5.5V
Voltage
Control
B1
V
C2
V
SW
IN
A3
A2
C1
B3
C
OUT
C
CNTRL
LM3501-16
IN
V
OUT
1 mF
Ceramic
1 mF
Ceramic
>1.1V
<0.3V
SHDN
AGND GND
C3
FB
A1
R1
24W
R2
24W
Figure 38. Multiple 3 LED String Application
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L
V
IN
22 mH
2.7V - 5.5V
Voltage
Control
B1
V
C2
V
IN
SW
A3
A2
C1
B3
C
OUT
CNTRL
C
V
IN
OUT
1 mF
Ceramic
1 mF
LM3501-21
Ceramic
>1.1V
<0.3V
SHDN
FB
AGND GND
C3
A1
R2
24W
Figure 39. LM3501-21 5 LED Application
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REVISION HISTORY
Changes from Revision B (May 2013) to Revision C
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 20
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PACKAGE OPTION ADDENDUM
www.ti.com
2-May-2013
PACKAGING INFORMATION
Orderable Device
LM3501TL-16/NOPB
LM3501TL-21/NOPB
LM3501TLX-16/NOPB
LM3501TLX-21/NOPB
Status Package Type Package Pins Package
Eco Plan Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
-40 to 85
Top-Side Markings
Samples
Drawing
Qty
(1)
(2)
(3)
(4)
ACTIVE
DSBGA
DSBGA
DSBGA
DSBGA
YZR
8
8
8
8
250
Green (RoHS
& no Sb/Br)
SNAGCU
SNAGCU
SNAGCU
SNAGCU
Level-1-260C-UNLIM
Level-1-260C-UNLIM
Level-1-260C-UNLIM
Level-1-260C-UNLIM
S
19
ACTIVE
ACTIVE
ACTIVE
YZR
YZR
YZR
250
3000
3000
Green (RoHS
& no Sb/Br)
-40 to 85
S
30
Green (RoHS
& no Sb/Br)
-40 to 85
S
19
Green (RoHS
& no Sb/Br)
-40 to 85
S
30
(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
PACKAGE OPTION ADDENDUM
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Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
25-Jun-2013
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)
LM3501TL-16/NOPB
LM3501TL-21/NOPB
LM3501TLX-16/NOPB
LM3501TLX-21/NOPB
DSBGA
DSBGA
DSBGA
DSBGA
YZR
YZR
YZR
YZR
8
8
8
8
250
250
178.0
178.0
178.0
178.0
8.4
8.4
8.4
8.4
2.08
2.08
2.08
2.08
2.08
2.08
2.08
2.08
0.76
0.76
0.76
0.76
4.0
4.0
4.0
4.0
8.0
8.0
8.0
8.0
Q1
Q1
Q1
Q1
3000
3000
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
25-Jun-2013
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
LM3501TL-16/NOPB
LM3501TL-21/NOPB
LM3501TLX-16/NOPB
LM3501TLX-21/NOPB
DSBGA
DSBGA
DSBGA
DSBGA
YZR
YZR
YZR
YZR
8
8
8
8
250
250
210.0
210.0
210.0
210.0
185.0
185.0
185.0
185.0
35.0
35.0
35.0
35.0
3000
3000
Pack Materials-Page 2
MECHANICAL DATA
YZR0008xxx
D
0.600±0.075
E
TLA08XXX (Rev C)
D: Max = 1.972 mm, Min =1.911 mm
E: Max = 1.972 mm, Min =1.911 mm
4215045/A
12/12
A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
NOTES:
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LM3501TLX-21/NOPB
Synchronous Step-up DC/DC Converter for White LED Applications 8-DSBGA -40 to 85
TI
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