SYNC
DR1
GD1
SE1
VDHC
OutP
VLedFB
CDHC
Faultb
FAULT_CAP
VCC
DIM
Thermal
DMIN
Thermal_Cap
AGND PGND
EN VIN
PGND
DR2
GD2
SE2
DR3
GD3
SE3
DR4
GD4
SE4
CFLT
AGND
AGND
Primary power
supply Voltage
feedback pin
VRAIL
Voltage
output
Fault acknowledgement output
FAULTb
DIM PWM dimming input
CDHC
RFB1
RFB2
High Power LED Arrays
Q1
Q2
Q3
Q4
RISNS1 RISNS2 RISNS3 RISNS4
RDHC
RTHM1
CVCC
RTHM2
CTHM
RDMIN2
RDMIN1 PGND PGND PGND
PGND
PGND
NTC thermistor
couple to LED
arrays
To NTC thermal
sensor
A
B
To thermal
sensor
terminals
A
B
External voltage headroom control
VDHC
5V
0V
LM3464/64A
LM3464, LM3464A
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LED Driver with Dynamic Headroom Control and Thermal Control Interfaces
Check for Samples: LM3464,LM3464A
1FEATURES DESCRIPTION
The LM3464/64A is a 4-channel high voltage current
2• Wide Input Voltage Range regulator that provides a simple solution for LED
– 12V-80V (LM3464) lighting applications. The LM3464/64A provides four
– 12V-95V (LM3464A) individual current regulator channels and works in
conjunction with external N-channel MOSFETs and
• Dynamic Headroom Control Ensures Maximum sense resistors to give accurate driving current for
Efficiency every LED string. Additionally, the Dynamic
• 4 Output Channels With Individual Current Headroom Control (DHC) output can be interfaced to
Regulation the external power supply to adjust the LED supply
• High Channel to Channel Accuracy voltage to the lowest level that is adequate to
maintain all the string currents in regulation, yielding
• Digital PWM/Analog Dimming Control Interface the optimal overall efficiency.
• Resistor Programmable Dimming Frequency Digital PWM or analog voltage signals can be used to
and Minimum Duty Cycle (Analog Dimming control the duty cycle of the all the channels. When
Mode) analog control is used, the dimming frequency can be
• Direct Interface to Thermal Sensor programmed via an external capacitor. A minimum
• Fault Detection duty cycle control is provided in the conditions that
the analog dimming is configured as thermal
• Over Temperature Protection feedback.
• Thermal Shutdown Protection features include VIN under-voltage lock-
• Under Voltage Lockout out, LED open/short circuit and over-temperature fault
• Thermal Enhanced TSSOP-28 Package signaling to the system controller.
APPLICATIONS
• Streetlights
• Solid State Lighting Solutions
Typical Application
1Please 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.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2010–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LM3464, LM3464A
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Connection Diagram
Figure 1. Top View
28-Lead TSSOP-28
Package Number PWP
PIN DESCRIPTIONS
Pin Name Description Application Information
1 SYNC Synchronization signal output for Connect this pin to the DIM pin of other LM3464/64A to enable cascade
cascade operation operation (multiple device). This pin should leave open for single device
(Master-Slave configuration) operation.
2 DIM PWM dimming control Apply logic level PWM signal to this pin controls the average brightness of the
LED string. (<1.25V disable output).
3 Thermal Thermal sensor input Connect thermal sensor to this pin with bias accordingly to facilitate thermal
foldback and control the brightness of the LED array.
4 Thermal_Cap Thermal dimming ramp capacitor Connect a capacitor across this pin and GND to define the thermal dimming
frequency.
5 VDHC Head room control Apply external voltage across this pin and ground to define the minimum drain
voltage. This pin is internal biased at 0.9V.
6 DMIN Minimum thermal dimming duty The voltage across this pin and GND defines the minimum thermal dimming
control duty cycle.
7 Faultb Fault signal output Open Drain output, pull-down when FAULT condition occurred.
8 AGND Signal ground Analog ground connection for internal circuitry. Must be connected to PGND
external to the package.
9 FAULT_CAP Fault delay capacitor Connect to an external capacitor to program the fault response time.
10 CDHC DHC time constant capacitor An external capacitor to ground programs the Dynamic Headroom Control loop
response time
11 OutP DHC Output Connect this pin to the voltage feedback input of primary power supply to
facilitate dynamic headroom control.
12 VLedFB Output voltage sense input This pin senses the output voltage of the primary power supply.
13 VCC Internal regulator output This pin is the output terminal of the internal voltage regulator and should be
bypassed by a high quality 1uF ceramic capacitor.
14 EN Enable input This pin serves as device enable input when logic level signal is applied. (Active
high with internal pull-up)
15 VIN Supply voltage The input voltage should be in the range of 12V to 80V for LM3464, 12–95V for
LM3464A
16 DR4 Channel 4 drain sense input This pin senses the drain voltage of the external MOSFET of channel 4 to
facilitate DHC operation and fault detection.
17 DR3 Channel 3 drain sense input This pin senses the drain voltage of the external MOSFET of channel 3 to
facilitate DHC operation and fault detection.
18 DR2 Channel 2 drain sense input This pin senses the drain voltage of the external MOSFET of channel 2 to
facilitate DHC operation and fault detection.
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PIN DESCRIPTIONS (continued)
Pin Name Description Application Information
19 DR1 Channel 1 drain sense input This pin senses the drain voltage of the external MOSFET of channel 1 to
facilitate DHC operation and fault detection.
20 SE4 Channel 4 sense input Connect to an external sense resistor to define the Channel 4 LED current.
21 GD4 Channel 4 gate driver output Connect to the gate of external NMOS to control the channel 4 LED current.
22 PGND Power Ground Ground for power circuitry. Reference point for all stated voltages. Must be
externally connected to EP and AGND
23 GD3 Channel 3 gate driver output Connect to the gate of external NMOS to control the channel 3 LED current.
24 SE3 Channel 3 sense input Connect to an external sense resistor to define the Channel 3 LED current.
25 GD2 Channel 2 gate driver output Connect to the gate of external NMOS to control the channel 2 LED current.
26 SE2 Channel 2 sense input Connect to an external sense resistor to define the Channel 2 LED current.
27 GD1 Channel 1 gate driver output Connect to the gate of external NMOS to control the channel 1 LED current.
28 SE1 Channel 1 sense input Connect to an external sense resistor to define the Channel 1 LED current.
EP EP Thermal Pad (Power Ground) Used to dissipate heat from the package during operation. Must be electrically
connected to PGND external to the package.
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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.
Absolute Maximum Ratings (LM3464/LM3464A) (1)(2)
VIN to GND -0.3V to 100V
DR1, DR2, DR3, DR4 to GND -0.3V to 100V
EN to GND -0.3V to 5.5V
All other inputs to GND -0.3V to 7V
ESD Rating (3), Human Body Model ±2 kV
Storage Temperature Range −65°C to + 150°C
Junction Temperature (TJ) + 150°C
(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which
operation of the device is intended to be functional. For ensured specifications and test conditions, see the Electrical Characteristics.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) The human body model is a 100 pF capacitor discharged through a 1.5 kΩresistor into each pin.
Operating Ratings (LM3464)
Supply Voltage Range (VIN) 12V to 80V
Junction Temperature Range (TJ)−40°C to + 125°C
Thermal Resistance (θJA)(1) 33.5°C/W
Thermal Resistance (θJC)(1) 6°C/W
(1) Measurements are performed on a 4 layer JEDEC board with 10 vias provided under the exposed pad. See JESD51-1 to JESD51-11.
The value of θJA is specifically dependent on the PCB trace area, trace material and the number of layers and thermal vias.
Operating Ratings (LM3464A)
Supply Voltage Range (VIN) 12V to 95V
Junction Temperature Range (TJ)−40°C to + 125°C
Thermal Resistance (θJA)(1) 33.5°C/W
Thermal Resistance (θJC)(1) 6°C/W
(1) Measurements are performed on a 4 layer JEDEC board with 10 vias provided under the exposed pad. See JESD51-1 to JESD51-11.
The value of θJA is specifically dependent on the PCB trace area, trace material and the number of layers and thermal vias.
Electrical Characteristics (LM3464/LM3464A)
Specification with standard type are for TA= TJ= +25°C only; limits in boldface type apply over the full Operating Junction
Temperature (TJ) range. Minimum and Maximum are specified through test, design or statistical correlation. Typical values
represent the most likely parametric norm at TJ= +25°C, and are provided for reference purposes only. Unless otherwise
stated the following conditions apply: VIN = 48V.
Symbol Parameter Conditions Min Typ Max Units
Vcc Regulator(1)
VIN-UVLO Vin under voltage lockout VIN increasing 8.5 V
VIN-UVLO-HYS Vin UVLO hysteresis VIN decreasing 95 mV
VCC VCC output voltage CVCC = 0.68 µF 6.15 6.3 6.51 V
No load
VCC-UVLO VCC under-voltage lockout threshold (UVLO) VCC increasing 4.98 5.28 V
VCC-UVLO-HYS VCC UVLO hysteresis VCC decreasing 250 mV
IIN Quiescent Current from VIN CVCC = 0.68 µF 1.65 2.3 3mA
No load
IVCC VCC Current limit VCC = 0V 18 mA
Device Enable
VEN-DISABLE Device disable voltage threshold VEN Decreasing 2.1 2.55 3V
(1) VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.
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Electrical Characteristics (LM3464/LM3464A) (continued)
Specification with standard type are for TA= TJ= +25°C only; limits in boldface type apply over the full Operating Junction
Temperature (TJ) range. Minimum and Maximum are specified through test, design or statistical correlation. Typical values
represent the most likely parametric norm at TJ= +25°C, and are provided for reference purposes only. Unless otherwise
stated the following conditions apply: VIN = 48V.
Symbol Parameter Conditions Min Typ Max Units
IEN-MAX EN pin internal pull current VEN = 0V 7.2 11 14.7 uA
Analog Dimming Control Interface
VCTHM-MAX Sawtooth max. voltage threshold at 2.95 3.25 3.3 V
Thermal_Cap pin
100% output duty cycle
VCTHM-MIN Sawtooth min. voltage threshold at 0.325 0.4 0.493 V
Thermal_Cap pin
0% output duty cycle
ICTHM Thermal_Cap pin output current 38.9 50 61 uA
PWM Dimming Control Interface
VDIM-LED-ON DIM pin voltage threshold at LED ON VDMIN = 0V 1.19 V
VTHERMAL = VCC
VDIM-LED-OFF DIM pin voltage threshold at LED OFF VDMIN = 0V 1.3 V
VTHERMAL = VCC
Dynamic Headroom Control Output
VOutP-MAX OutP pin max. output voltage VCC-0.5 V
VOutP-MIN OutP pin min. output voltage IoutP = 1 mA current sink 0.3 V
VLEDFB-LED-ON VLedFB pin voltage threshold at LED ON 2.4 2.5 2.58 V
VLEDFB-SYS-RST System restart VLedFB pin voltage threshold for Measure at VLedFB pin 1.2 V
system restart
LED Current Regulator
VGDx-MAX GDx gate driver max. output voltage 4.73 VCC–1 V
VGDx-MIN GDx gate driver min. output voltage 0.115 0.127 V
IGDx-MAX GDx gate driver short circuit current GDx short to GND 8 mA
IDRx DRx pin input current VDRx = 10V 25 29 μA
VDRx = 100V 55 70 μA
Fault Detection and Handling
VOVP-TH DRx Pin over-voltage protection threshold Measure at DRx pin 18 19 21 V
VSHORTFAULT DRx short fault threshold Any VDRx < 2.5V 8.35 8.4 9.75 V
VOPENFAULT SEx open fault threshold Measure at SEx pin 30 mV
IFAULT-CAP FAULT_CAP pin output current All VDRx < VOVP-TH 25 uA
IFAULT-CAP-OVP FAULT_CAP pin output current at DRx over- Any VDRx ≥VOVP-TH 105 uA
voltage
VFAULT-CAP FAULT-CAP pin voltage threshold at fault timer VFAULT-CAP rising 3.6 V
expire
RFaultb Faultb pin to GND resistance LED fault = TRUE 110 Ω
Thermal Protection
TOTM-TH Over Temperature Monitor Threshold 125 °C
TOTM-HYS Over Temperature Monitor Hysteresis 20 °C
TSD Thermal shutdown temperature TJrising 165 °C
TSD-HYS Thermal shutdown temperature hysteresis TJfalling 20 °C
Thermal Resistance
θJA Junction to Ambient (2) TSSOP-28 Package 33.5 °C/W
θJC Junction to Case (2) 6 °C/W
(2) Measurements are performed on a 4 layer JEDEC board with 10 vias provided under the exposed pad. See JESD51-1 to JESD51-11.
The value of θJA is specifically dependent on the PCB trace area, trace material and the number of layers and thermal vias.
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Typical Performance Characteristics
All curves taken at VIN = 48V with configuration in typical application for driving twelve power LEDs with four output channels
active and output current per channel = 350 mA. TA= 25°C, unless otherwise specified.
Channel 1 Current Sense Voltage (VSE1) Effifciency (%)
Figure 2. Figure 3.
Thermal_Cap Pin Output Current VCC Variation (%)
Figure 4. Figure 5.
Operating Current Shutdown Current
(EN pin floating) (EN pin = 0V)
Figure 6. Figure 7.
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Typical Performance Characteristics (continued)
All curves taken at VIN = 48V with configuration in typical application for driving twelve power LEDs with four output channels
active and output current per channel = 350 mA. TA= 25°C, unless otherwise specified.
Startup Waveforms PWM Dimming (DIM pin)
Figure 8. Figure 9.
PWM Dimming Delay Time PWM Dimming Delay Time
(VDIM) rising) (VDIM) falling)
Figure 10. Figure 11.
Thermal Foldback Dimming Thermal Foldback Dimming
(VTHERMAL) rising) (VTHERMAL) falling)
Figure 12. Figure 13.
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OVERVIEW
The LM3464/64A is a four channel linear current regulator designed for LED lighting systems with wide input
voltage range, high speed PWM and thermal foldback dimming control interface. The LM3464/64A incorporates a
Dynamic Headroom Control (DHC) technology which maximizes overall efficiency of the lighting system by
adjusting the output voltage of the primary power source dynamically. Linear current regulation secures high
accuracy output current, LED and system reliability. High speed PWM dimming provides the flexibility of
brightness control while maintaining constant color temperature of the light. The thermal foldback feature enables
the LM3464/64A to manage the temperature of the LED heat sink or system chassis with a simple NTC/PTC
temperature sensor. The thermal foldback input can also be used as an analog dimming control input to adapt to
other sensors easily, such as ambient light sensor.
Dynamic Headroom Control (DHC)
Operation Principles of DHC
Dynamic Headroom Control is a technology that aims at maximizing the overall system efficiency by altering the
supply voltage to the LED(s) dynamically in respect to the characteristics of the LED(s). In the LM3464/64A, DHC
is facilitated by connecting a resistor in between the OutP pin of the LM3464/64A and the voltage feedback node
of the primary power supply (AC/DC) as shown in Figure 15.
Figure 15. Circuitry of the DHC Mechanism
For example, in steady state, when all the output channels are in regulation and the forward voltage of any LED
string decreases due to temperature raise, the drain voltage of the corresponding channel (DRx) increases to
exceed the default 0.9V typical headroom voltage in order to maintain constant output current. As the drain
voltage increases, the voltage of CDHC increases and the current sink into the OutP pin decreases. This will
finally result in decrease of rail voltage (VRAIL) until the corresponding DRx voltage returns to minimum level.
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System Operation
In order to provide failure protection to the LEDs, the rail voltage is pulled up by the LM3464/64A from a
relatively low voltage level at system startup until the rail voltage reaches certain preset level. Figure 16 shows
the change of the rail voltage of the LM3464/64A LED lighting system upon the primary power source is
powered.
The Lm3464/64A can be interfaced to an off-the-shelf converter to form a LED lighting system with simple
connections. Figure 14 shows the typical application circuit of a lighting system using the LM3464/64A with a fly-
back AC/DC converter. In this application, the output voltage of the AC/DC converter is mainly governed by a
voltage reference IC, LM431 and a voltage divider consists of R1and R2. The LM3464/64A influences the output
voltage of the AC/DC converter by sinking current from the junction of the voltage divider (R1and R2) to realize
dynamic headroom control.
The operation of the LM3464/64A upon startup can be divided into several phases according to the changes of
the rail voltage as shown in Figure 16. When the AC/DC converter is powered, the rail voltage increases and
stays steady when its native nominal output voltage, VRAIL(nom) is reached. This voltage is defined by the output
voltage feedback resistor divider of the AC/DC converter. At this voltage level, the LM3464/64A is powered
already. After certain delay defined by CDHC, the LM3464/64A starts to push the rail voltage up by sinking current
into the OutP pin from the voltage feedback node of the AC/DC converter until the rail voltage reaches
VDHC_READY. VDHC_READY is the highest rail voltage in normal operation and should be enough to turn on all the
LED strings with current regulation (defined by RSNSx). As VRAIL reaches VDHC_READY, the LM3464/64A turns on all
the output channels. This discharges the output capacitor of the primary power supply and causes the rail
voltage to decrease to certain level that system efficiency is maximized (VLED).
Figure 16. Changes of Rail Voltage Upon Power Up
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RDHC =1.7V
IR1 - 2.5V
R2
IR1 = VREF(AC/DC)
RD2 +VREF(AC/DC) - VD1 - VoutP(min)
RDHC
=2.5V
RD2 +2.5V - 0.5V - 0.3V
RDHC
IR1 = VRAIL(peak) - 2.5V
R1
2.5V = VDHC_READY x RFB2
RFB1 + RFB2
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APPLICATION INFORMATION
SETTING (VRAIL(nom))
The nominal rail voltage VRAIL(nom) is the nominal output voltage of the primary power supply (AC/DC) prior to
DHC begins. The selection of VRAIL(nom) is primarily depend on the forward voltages of the LED arrays and should
follow the equation shows below:
VRAIL(nom) ≤Vf(all_temp) + VVDHC (1)
In the equation, Vf(all_temp) is the lowest forward voltage among all the LED strings under all possible temperature.
And VVDHC is the voltage headroom which equals to the voltage at the VDHC pin. Normally, the forward voltage
of an LED drops as the ambient temperature increases. This could create large variation of total forward voltage
of a LED sting under different temperature. In order to ensure proper system startup, the variation of LED
forward voltage against temperature must be considered in calculations.
SETTING VDHC_READY AND VRAIL(peak)
DHC begins when the voltage at VLedFB pin reaches 2.5V, which is defined by the values of RFB1 and RFB2:
(2)
Where
VDHC_READY < VRAIL(peak) (3)
At this stage, the current of the LED strings are regulated and the rail voltage decreases in order to maintain
minimum voltage drop and power dissipation on the MOSFETs.
In case the OutP pin is accidentally shorten to ground, the rail voltage will increase and end up exceeds
VDHC_READY. To avoid damaging the AC/DC converter, the possible peak output voltage, VRAIL(peak) can be roughly
defined by the forward voltage of the LED strings and must set below the rated voltage of the components at the
output of the AC/DC converter. In order to limit the power dissipation on the external MOSFETs, VRAIL(peak) is set
to to no more than 10VDC higher than the forward voltage of the LED string. The following equations define the
maximum output voltage of the AC/DC converter that can be pushed up by the LM3464/64A:
VRAIL(peak) = VR1 + VREF(AC/DC) = (R1x IR1) + VREF(AC/DC) (4)
for VREF(AC/DC) = 2.5V
(5)
also since
(6)
(7)
As the system enters steady state, the rail voltage VRAIL decreases and finally settles to an optimal level that
maintains the maximum power efficiency of the system. The voltage level of VRAIL under steady state can be
calculated following this equation:
VRAIL = Vf(highest) + VVDHC (8)
In the equation, VRAIL is the rail voltage in steady state and Vf(highest) is the total forward voltage of the LED string
which carry the highest forward voltage among the LED stings.
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160 k: // RB + 1 M: //RAx VCC
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VVDHC is the voltage at the VDHC pin. This voltage decides the headroom voltage for the LM3464/64A driver
stage and equals to the minimum VDRx among the drain voltages of the MOSFETs under steady state. The
VDHC pin is internally biased to 0.9V which also set the default voltage headroom to 0.9V. In applications that
the output of the AC/DC converter contains more than 0.9V peak-to-peak ripple voltage, the voltage headroom
can be increased by applying external bias to the VDHC pin.
DEFINING VOLTAGE HEADROOM
The voltage headroom is the rail voltage margin that reserve for precision linear current regulation under steady
state. Under steady state, the voltage headroom is always minimized by the LM3464/64A to reduce power losses
on the MOSFETs till one of the drain voltage (VDRx) of the MOSFETs equals the voltage on VDHC pin (0.9V
typical).
With external bias, the voltage of the VDHC pin can be adjusted up or down to adapt to different types of primary
power supply. Figure 17 shows a simple resistor based biasing circuit that derives biasing voltage from the
output of the internal voltage regulator, the VCC pin.
Figure 17. Adjusting Voltage Headroom with Resistors
With the additional resistors, the VDHC pin voltage is adjustable in between 0.8V and 2V. The values of RAand
RBshould be at least 10 times lower than the typical values of the internal resistor divider of the VDHC pin (see
Figure 17). However, it is recommended not to set the voltage headroom too low because the ripple voltage of
the primary power supply output may cause visible flicker due to insufficient voltage headroom. Thus the voltage
headroom follows this equation:
where
• 0.8V < VVDHC < 2V (9)
SETTING LED CURRENT
The LED current regulating mechanism of the LM3464/64A driver stage contains four individual LED current
regulators. Every LED current regulator is composed of an external MOSFET (Q1-Q4), a current sensing resistor
(RISNS1-RISNS4) and an amplifier inside the LM3464/64A that monitors the feedback voltage from the current
sensing resistor. The integrated amplifier compares the voltage across current sensing resistors (RISNS1-RISNS4)
to a 200mV typical reference voltage and controls the gate voltage of the MOSFETs (Q1-Q4) to realize linear
current regulations. Figure 18 shows the simplified circuit of the linear LED current regulators.
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ILED = 200
RISNSx mA
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Figure 18. Linear LED Current Regulator
The driving currents of the LED strings are defined by the values of RISNS1 to RISNS4 individually. The LED current
and the value of RISNSx are related by the following equation:
(10)
Since the accuracy of the LED currents are dependent on the tolerance of RISNSx, the RISNSx to recommended to
be thick carbon file resistors with no more than 1% tolerance and adequate rated power to the desired LED
current.
Figure 19. LED Current vs RISNSx
RESPONSE OF THE LM3464/64A DRIVER STAGE
In order to ensure good operation stability of the entire system, the response of the LM3464/64A circuitry must
be set slower than the primary power supply. The response of the LM3464/64A is decided by the value of the
capacitor, CDHC. In general, a higher capacitance CDHC will result in slower response of the LM3464/64A driver
stage.
Generally, a first order integrator that consists of CDHC and a transconductance amplifier with gm= 76umho and
+/– 15uA current limit as shown in Figure 20 defines the frequency response of the LM3464/64A driver stage.
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fLM3464(-3 dB) = 1
2S(1.2 x 106) x CDHC
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Figure 20. Simplified Circuit of the Frequency Response Setting Mechanism
The transconductance amplifier serves as a voltage to current converter that charges CDHC with a current
proportional to the difference in voltage between the DRx and VDHC pins.
As the voltage of the OutP pin is equal to VCC – VCDHC, the capacitance of CDHCdecide the rate of change of the
OutP pin voltage and eventually limits the frequency response of the whole system . The higher capacitance the
CDHC has, the longer time the OutP pins takes for certain voltage change. Thus the value of CDHC decides the
response of the LM3464/64A driver stage.
If the response of the LM3464/64A driver stage is set faster than that of the primary power supply, the entire
system will suffer from unstable operation. However, setting the response of the LM3464/64A driver stage
unnecessarily slow will worsen transient performance of the system and false trigger the fault detection
mechanism of the LM3464/64A. Practically, the minimum value of the CDHC can be found out by means of ‘try
and error’. In most cases, a 1uF 16V ceramic capacitor is a good starting point that sets the response of the
LM3464/64A driver stage slow enough for initial trial.
The value of the CDHC capacitor can be reduced to speed up the response of the LM3464/64A driver stage.
Otherwise, in case the system is unstable with 1uF CDHC, the capacitance of the CDHC capacitor should be
increased until the entire system get into stable operation.
This approach is effectively setting the cut-off frequency of the LM3464/64A driver stage lower than that of the
primary power supply. Usually, setting the cut-off frequencies of the two stages apart can help avoiding unstable
operation. The cut-off frequency of the LM3464/64A driver stage is governed by the follow equation:
(11)
THERMAL FOLDBACK INTERFACE
The thermal foldback function of the LM3464/64A helps in reducing the average LED currents and prolonging the
LED lifetime under high temperature. By applying a DC voltage to the Thermal pin, the average output current is
adjustable from 100% down to a minimum value limited by the discharge time of the CTHM. The Thermal pin of
the LM3464/64A is an analog input for thermal foldback control that accepts a DC voltage in the range of 0V to
VCC. The thermal foldback control circuitry reduces the average LED currents by means of PWM dimming as
shown in Figure 21:
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Product Folder Links: LM3464 LM3464A
tTHM_MIN = 262 x CTHM in second
VCC
0V
3.25V
0.4V
VThermal
ILED (AVG)
Temperature
Thermal
foldback begin
100%
Approximately 0.5%
(Limited by tTHM_MIN)
LM3464, LM3464A
SNVS652F –APRIL 2010–REVISED MAY 2013
www.ti.com
Figure 21. Average LED Current Reduces According to VThermal
The dimming frequency is defined by a sawtooth waveform that generated by charging and discharging the
capacitor CTHM which connects across the Thermal_Cap pin and GND. The LM3464/64A charges the CTHM up to
3.25V with 50uA constant current and discharge the CTHM by pulling the Thermal_Cap pin to ground through a
125Ω(typ.) resistor until the pin voltage reaches 0.4V (VCTHM-MIN). When the voltages of the Thermal and DMIN
pins are both below 0.4V, the minimum dimming on time equals the discharge time of the CTHM following the
equation:
(12)
Thus the minimum dimming duty cycle for thermal foldback that being restricted by the discharge time of CTHM is
approximately 0.5%:
(13)
By comparing the voltage at the Thermal pin to the sawtooth voltage being generated at the Thermal_Cap pin of
the LM3464/64A, a PWM dimming signal for thermal foldback is generated as shown in Figure 22:
Figure 22. Signals Facilitating Thermal Foldback Control
16 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3464 LM3464A
VCC
0V
3.25V
VDMIN
0.4V
VThermal
ILED (AVG)
Temperature
Thermal
foldback begin Min. thermal
foldback dimming
100%
Min. ILED (AVG)
Approximately 0.5%
(Limited by tTHM_MIN)
fThermal-foldback = (3.25 - 0.4) x CTHM
50 PA
LM3464, LM3464A
www.ti.com
SNVS652F –APRIL 2010–REVISED MAY 2013
If the voltage at the Thermal pin is driven to exceed 3.25V, all output channels will be enabled with 100% thermal
dimming duty cycle. If the Thermal pin voltage is set below 0.4V, all output channels will be disabled with 0%
thermal dimming duty cycle. The dimming frequency and duty cycle with thermal foldback control are governed
by the following equations:
(14)
DThermal-foldback = (TLED_ON x fThermal-foldback) x 100% (15)
= [(VTHERMAL - 0.4) X 35]% (16)
for 0.4 ≤VTHERMAL ≤3.25V (17)
SETTING MINIMUM THERMAL DIMMING DUTY CYCLE
In applications that need to ensure minimum illumines under high temperature environments, the minimum
dimming duty cycle for thermal foldback may need to be limited. Such limit is defined by the voltage at the DMIN
pin. When the Thermal pin voltage falls below the voltage at the DMIN pin, the thermal foldback dimming duty
cycle will maintain at the level which set by the voltage of the DMIN pin (VDMIN), as shown in Figure 23.
Figure 23. Thermal Foldback Control with Minimum Dimming Duty Cycle Limit
To define the minimum thermal dimming duty cycle, VDMIN should be set in between 0.4V to 3.25V. The minimum
duty cycle is governed by the following equation:
DMINIMUM = [(VDMIN - 0.4) X 35]% (18)
for 0.4 ≤VDMIN ≤3.25V (19)
When VDMIN is below 0.4V (e.g. connect to GND), the minimum thermal dimming duty cycle limit is disabled. In
applications that thermal foldback control is not required, the DMIN pin can be tied to GND to reduce power
consumption.
PWM DIMMING
The LM3464/64A provides a DIM pin that accepts TTL logic level signal for PWM dimming. When the DIM pin is
pulled low, all LED current regulators will turn off while maintaining VCC regulator and part of the internal
circuitries operating. External pull up resistor is required if the DIM pin is driven by an open collector / drain
driver. PWM dimming ensures uniform color temperature of the light throughout the entire dimming range. The
average current of every output channel is decided by the dimming duty cycle and follows the equation below:
Copyright © 2010–2013, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LM3464 LM3464A
TFAULT = 25 PA
CFLT x 3.0V
LM3464, LM3464A
SNVS652F –APRIL 2010–REVISED MAY 2013
www.ti.com
ILED(AVG) = DPWM x ILED (20)
PWM DIMMING CONTROL WITH THERMAL FOLDBACK
The PWM dimming control can coexist with thermal foldback by applying PWM dimming control signal and
thermal control signal to the DIM and Thermal pins concurrently. Normally, the dimming frequency for thermal
foldback control should be much higher than the frequency of the PWM dimming control signal. Figure 24
presents the relationship among VThermal, VThermal_Cap, VDIM and ILED. As shown in the figure, when thermal
foldback is functioning, the average output current can be further decreased linearly according to the duty cycle
of the PWM dimming signal being applied to the DIM pin. In order to synchronize the dimming signals, the CTHM
is discharged on every rising edge of the PWM dimming signal on DIM pin, notice as t1, t2and t3in Figure 24.
Figure 24. Thermal Foldback + PWM Dimming Control
LOW POWER STANDBY
The LM3464/64A will enter low power standby mode when the EN pin is pulled to GND. The EN pin is internally
biased thus no external pull-up resistor or bias is required. Under standby mode, all the output channels are cut-
off and part of the internal circuitries are disabled to maintain low power consumption. Upon the EN pin is pulled
low, the OutP pin stopa sinking current from the feedback node of the primary power stage. This causes the rail
voltage fall back to VRAIL(nom) slowly as the output capacitors of the primary power supply are being discharged
by the LEDs. Pulling the EN pin low will not disable the VCC regulator. When the EN pin is released (floating), the
LM3464/64A exits low power standby mode and the startup sequence begins as described in Figure 16.
FAULT HANDLING and INDICATION
The LM3464/64A features a complete mechanism for fault handling and indication. The LM3464/64A detects
LED failures and raises fault indication signal at the Faultb pin upon open or short circuits of LED strings,
insufficient supply voltage and so on. In order to avoid false triggering the fault detection circuitry, the
LM3464/64A features a timer for fault recognition. When a fault condition arises and sustains longer than the
time constant preset by the capacitor , CFLT, a fault is confirmed. The Faultb pin is then pulled low as an
indication. The time constant for fault detection is defined by the value of the capacitor connects across the
FAULT_CAP pin and GND, CFLT. Normally, a 2.2 nF CFLT that set a 264 us delay time is suitable for most
application. For those applications with slow response primary power supply, the value of CFLT may need to
increase accordingly. The time delay for fault detection is governed by the following equation:
(21)
18 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
www.ti.com
SNVS652F –APRIL 2010–REVISED MAY 2013
OPEN CIRCUIT OF LED STRINGS
Detection of LED open circuit is achieved by detecting the voltages of the SEx pin and the internal gate control
signal being fed to the internal MOSFET gate driver. When a LED string is open circuit, the VSEx pin is pulled
down to below 30mV by the current sensing resistor. As VSEx falls below its regulated level, the LM3464/64A
increases the gate voltage of the corresponding MOSFET (VGDx) in order to maintain current regulation. Thus,
the requirement for LED open circuit is VSEx below 30mV and internal gate voltage reaches its maximum (at VGDx
about 5V). When the requirement of LED open fault is fulfilled, the LM3464/64A begins to charge up the CFLT.
When the voltage of the FAULT_CAP reaches 3V, and the condition of open fault retains, an open fault is
confirmed.
After an open fault is confirmed, the failed channel(s) will be disabled and excluded from DHC loop. To reactivate
the disabled channel(s), the EN pin can be pulled to GND for a soft reset or re-power the primary power supply
for a system reset. Either reset methods results in a system restart with startup sequence shows in Figure 16.
SHORT CIRCUIT OF LED STRINGS
If any LED string experiences partially short circuit after normal system startup, the drain voltage (DRx) of the
corresponding channel(s) will increase so as to maintain correct current regulation. When drain voltage increases
up to 8.4V higher than the drain voltages of any other channels, the shortened channel will be latched off and
excluded from the DHC loop to avoid further damages. Once a short fault is confirmed, the Faultb pin will be
pulled low no matter it is due to failure of the power source or shortening of LED strings. When a short circuit of
LED sting is confirmed, the failed channel(s) will be disabled and excluded from DHC loop. The disabled
channels can be reactivated by either pulling the EN pin to GND or system re-powering.
DRx PIN OVER-VOLTAGE PROTECTION
The LM3464/64A features a over-voltage protection function that prevents damaging of the external MOSFETs
due to short circuit of LED string(s). When the voltage of any DRx pin reaches 19V typical, the fault detection
timer is triggered with the output current of the FAULT_CAP pin increases by 4 times (IFAULT-CAP-OVP) and results
in fault detection time 4 times shorter. If a over-voltage of any DRx pin is confirmed, the particular channel will be
latched off and excluded from DHC loop until the EN pin is pulled low (soft reset) or system re-powering is
undertaken.
DRIVING LESS THAN FOUR LED STRINGS
The LM3464/64A allows users to disable the unused output channels. Any output channel without a LED string
connected or with DRx and SEx pins floating will be disabled at system startup. A disabled channel will be
excluded from the DHC loop and will not contribute headroom control signal to the LM3464/64A. This function is
applicable to both single LM3464/64A and cascade operation modes.
EXPANDING NUMBER OF OUTPUT CHANNEL
The LM3464/64A can be cascaded to expand the number of output channel. Bases on the master-slave
architecture, one of the LM3464/64A in the system must be set to master mode and the rest must be set to slave
mode. Figure 27 shows an example application circuit that provides eight output channels.
To enable cascade operation, the SYNC pin of the master LM3464/64A should connect to the DIM pin of the first
slave device and similarly the SYNC pin of such slave device should connect to its down stream slave device for
startup synchronization. In addition, the OutP pins of all the LM3464/64A have to tie up though a diode and
resistor RDHC to the voltage feedback node of the primary power supply to accomplish dynamic headroom
control, as shown in Figure 27.
The slave devices can only be commanded by the master LM3464/64A. With the master and slave devices
linked up, the information of startup synchronization, thermal foldback and PWM dimming controls are gathered
by the master device and distribute stage by stage through the SYNC pin.
To set a LM3464/64A in master mode, the voltage of the VLedFB pin must be set below 3.25V. When the
VLedFB pin is connected to VCC, the device is in slave mode. In slave mode, local thermal foldback and PWM
controls are overridden by the packaged synchronization signal delivered from the master.
Copyright © 2010–2013, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
SNVS652F –APRIL 2010–REVISED MAY 2013
www.ti.com
CONNECTION TO LED ARRAYS
When LEDs are connected to the LM3464/64A driver stage through long cables, the parasitic components of the
cable harness and external MOSFETs may resonant and eventually lead to unstable system operation. In
applications that the cables between the LM3464/64A driver circuit and LED light engine are longer than 1 meter,
a 4.7kΩresistor should be added across the GDx pins to GND as shown in Figure 25.
Figure 25. Additional Resistor Across GDx and SEx for Cable Harness Over 1m Long
20 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
www.ti.com
SNVS652F –APRIL 2010–REVISED MAY 2013
Figure 26. Additional Voltage Clamping Circuits for VRAIL(peak) > 80V/95V (LM3464/64A)
APPLICATIONS WITH HIGH RAIL VOLTAGE
The normal operation voltage of the LM3464 and LM3464A are rated to 80V and 95V respectively, applying
voltage over the operation voltage limit to the LM3464/64A can damage the device permanently. In applications
that the rail voltage is higher than the operation voltage limited of the device (80V for LM3464, 95V for
LM3464A), voltage clamping circuits must be added externally to ensure the voltage limits of all the pins of the
LM3464/64A are not violated. Figure 26 shows a typical application circuit with 150V peak rail voltage.
Copyright © 2010–2013, Texas Instruments Incorporated Submit Documentation Feedback 21
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
SNVS652F –APRIL 2010–REVISED MAY 2013
www.ti.com
In Figure 26, Z1, Z2, Z3, Z4and ZIN are zener diodes for clamping the DRx pin voltage and input voltage (VIN pin)
of the LM3464/64A. The reverse voltage of the zener diodes must be below 80V for LM3464 and 95V for
LM3464A. The resistors RDR1, RDR2, RDR3, RDR4 and RIN are resistors for absorbing the voltage difference
between the clamping voltage of the zener diodes and the rail voltage.
Calculating the Values of Zxand RDRx:
The resistance of the RDRx must be properly selected according to the reverse current of the zener diode and
input current of the DRx pins of the LM3464/64A to secure the allowable pin voltages are not violated. For
instant, the DRx pins are required to clamp at 75V and a 500mW/75V zener diode CMHZ5267B from Central
Semiconductor is used. The reverse current of the CMHZ5267B is specified 1.7mA at 75V zener voltage. The
maximum allowable reverse current is 6.67mA as the power rating of the CMHZ5276B is 500mW.
Given that the input current of the DRx pins of the LM3464/64A at 100V is 63uA maximum, if the DRx pin voltage
is below 100V the current flows into the DRx pin (IDRx) is below 63uA. In order to reserve operation margin for
component variations, IDRx is assumed equal to 63uA in the following calculations.
Because VRAIL(peak) is the possible highest voltage at the DRx pins, the maximum resistance of RDRx can be
obtained following this equation:
(22)
Where VZand IZare the reverse voltage and current of the zener diode Zx respectively.
For VRAIL(peak) = 150V, the maximum value of RDRx is:
(23)
And the minimum value of RDRx is:
(24)
Thus, the value of RDRx must be selected in the range:
(25)
To minimize power dissipation on the zener diodes, a standard 42.2kΩresistor can be used for the RDRx.
Because the resistors, RDRx are used to absorb the power being introduced by the voltage difference between
VRAIL and VZx, the maximum power dissipation on every RDRx equals to:
(26)
Thus, a standard 42.2kΩresistor with 0.25W power rating (1206 package) and 1% tolerance can be used.
Calculating the Values of ZIN and RIN:
Similar to the requirements of selecting the Zx and RDRx, the voltage at the VIN pin of the LM3464/64A is
clamped to 75V by a voltage clamping circuit consists of ZIN and RIN. Because the maximum operating and shut-
down current (VEN < 2.1V) are 3mA and 700uA respectively, in order to ensure the voltage of the VIN pin is
clamped close to 75V even when the LM3464/64A is disabled, a 1.5W/75V zener diode CMZ5946B from Central
Semiconductor is used to ensure adequate conduction current for ZIN. The reverse current of the CMZ5946B is
specified 5mA at 75V, so the allowable current flows through ZIN is in between 5mA to 20mA.
22 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
www.ti.com
SNVS652F –APRIL 2010–REVISED MAY 2013
The value of RIN is governed by the following equations:
(27)
Maximum value of RIN:
(28)
Minimum value of RIN:
(29)
So the value of RIN must be in the range:
(30)
To minimize power dissipations on both the ZIN and RIN, a standard 9.31kΩresistor can be selected for the RIN.
Then the maximum power dissipation on RIN is:
(31)
Thus, a standard 9.38kΩresistor with 2512 package (1W) and 1% tolerance can be used.
Copyright © 2010–2013, Texas Instruments Incorporated Submit Documentation Feedback 23
Product Folder Links: LM3464 LM3464A
LM3464, LM3464A
www.ti.com
SNVS652F –APRIL 2010–REVISED MAY 2013
REVISION HISTORY
Changes from Revision E (May 2013) to Revision F Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 24
Copyright © 2010–2013, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Links: LM3464 LM3464A
PACKAGE OPTION ADDENDUM
www.ti.com 28-Aug-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM3464AMH/NOPB ACTIVE HTSSOP PWP 28 48 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3464AMH
LM3464AMHX/NOPB ACTIVE HTSSOP PWP 28 2500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3464AMH
LM3464MH/NOPB ACTIVE HTSSOP PWP 28 48 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3464MH
LM3464MHX/NOPB ACTIVE HTSSOP PWP 28 2500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LM3464MH
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
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
PACKAGE OPTION ADDENDUM
www.ti.com 28-Aug-2013
Addendum-Page 2
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.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM3464AMHX/NOPB HTSSOP PWP 28 2500 330.0 16.4 6.8 10.2 1.6 8.0 16.0 Q1
LM3464MHX/NOPB HTSSOP PWP 28 2500 330.0 16.4 6.8 10.2 1.6 8.0 16.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 8-May-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM3464AMHX/NOPB HTSSOP PWP 28 2500 367.0 367.0 35.0
LM3464MHX/NOPB HTSSOP PWP 28 2500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 8-May-2013
Pack Materials-Page 2
www.ti.com
PACKAGE OUTLINE
C
TYP
6.6
6.2
1.1 MAX
26X 0.65
28X 0.30
0.19
2X
8.45
TYP
0.20
0.09
0 - 8
0.10
0.02
5.65
5.25
3.15
2.75
(1)
0.25
GAGE PLANE
0.7
0.5
A
NOTE 3
9.8
9.6
B
NOTE 4
4.5
4.3
4214870/A 10/2014
PowerPAD - 1.1 mm max heightPWP0028A
PLASTIC SMALL OUTLINE
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. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not
exceed 0.15 mm, per side.
4. This dimension does not include interlead flash. Interlead flash shall not exceed 0.25 mm, per side.
5. Reference JEDEC registration MO-153, variation AET.
PowerPAD is a trademark of Texas Instruments.
TM
128
0.1 C A B
15
14
PIN 1 ID
AREA
SEATING PLANE
0.1 C
SEE DETAIL A
DETAIL A
TYPICAL
SCALE 1.800
THERMAL
PAD
www.ti.com
EXAMPLE BOARD LAYOUT
0.05 MAX
ALL AROUND
0.05 MIN
ALL AROUND
28X (1.3)
(6.1)
28X (0.45)
(0.9) TYP
28X (1.5)
28X (0.45)
26X
(0.65)
(3)
(3.4)
NOTE 9
(5.5)
SOLDER
MASK
OPENING
(9.7)
(1.3)
(1.3) TYP
(5.8)
( ) TYP
VIA
0.2
(0.65) TYP
4214870/A 10/2014
PowerPAD - 1.1 mm max heightPWP0028A
PLASTIC SMALL OUTLINE
SOLDER MASK
DEFINED PAD
LAND PATTERN EXAMPLE
SCALE:6X
HV / ISOLATION OPTION
0.9 CLEARANCE CREEPAGE
OTHER DIMENSIONS IDENTICAL TO IPC-7351
TM
NOTES: (continued)
6. Publication IPC-7351 may have alternate designs.
7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.
8. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
numbers SLMA002 (www.ti.com/lit/slma002) and SLMA004 (www.ti.com/lit/slma004).
9. Size of metal pad may vary due to creepage requirement.
METAL
SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
SOLDER MASK DETAILS
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
SOLDER MASK
DEFINED
SYMM
SYMM
SEE DETAILS
1
14 15
28
METAL COVERED
BY SOLDER MASK
SOLDER
MASK
OPENING
IPC-7351 NOMINAL
0.65 CLEARANCE CREEPAGE
www.ti.com
EXAMPLE STENCIL DESIGN
28X (1.3)
28X (0.45)
(6.1)
28X (1.5)
28X (0.45)
26X (0.65)
(3)
(5.5)
BASED ON
0.127 THICK
STENCIL
(5.8)
4214870/A 10/2014
PowerPAD - 1.1 mm max heightPWP0028A
PLASTIC SMALL OUTLINE
2.66 X 4.770.178
2.88 X 5.160.152
3.0 X 5.5 (SHOWN)0.127
3.55 X 6.370.1
SOLDER STENCIL
OPENING
STENCIL
THICKNESS
SEE TABLE FOR
DIFFERENT OPENINGS
FOR OTHER STENCIL
THICKNESSES
NOTES: (continued)
10. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
11. Board assembly site may have different recommendations for stencil design.
TM
SOLDER PASTE EXAMPLE
EXPOSED PAD
100% PRINTED SOLDER COVERAGE AREA
SCALE:6X
HV / ISOLATION OPTION
0.9 CLEARANCE CREEPAGE
OTHER DIMENSIONS IDENTICAL TO IPC-7351
SYMM
SYMM
1
14 15
28
BASED ON
0.127 THICK
STENCIL BY SOLDER MASK
METAL COVERED
IPC-7351 NOMINAL
0.65 CLEARANCE CREEPAGE
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