TI1 LM3464MH/NOPB Led driver with dynamic headroom control and thermal control interface Datasheet

LM3464, LM3464A
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SNVS652F – APRIL 2010 – REVISED MAY 2013
LED Driver with Dynamic Headroom Control and Thermal Control Interfaces
Check for Samples: LM3464, LM3464A
FEATURES
DESCRIPTION
•
The LM3464/64A is a 4-channel high voltage current
regulator that provides a simple solution for LED
lighting applications. The LM3464/64A provides four
individual current regulator channels and works in
conjunction with external N-channel MOSFETs and
sense resistors to give accurate driving current for
every LED string. Additionally, the Dynamic
Headroom Control (DHC) output can be interfaced to
the external power supply to adjust the LED supply
voltage to the lowest level that is adequate to
maintain all the string currents in regulation, yielding
the optimal overall efficiency.
1
2
•
•
•
•
•
•
•
•
•
•
•
Wide Input Voltage Range
– 12V-80V (LM3464)
– 12V-95V (LM3464A)
Dynamic Headroom Control Ensures Maximum
Efficiency
4 Output Channels With Individual Current
Regulation
High Channel to Channel Accuracy
Digital PWM/Analog Dimming Control Interface
Resistor Programmable Dimming Frequency
and Minimum Duty Cycle (Analog Dimming
Mode)
Direct Interface to Thermal Sensor
Fault Detection
Over Temperature Protection
Thermal Shutdown
Under Voltage Lockout
Thermal Enhanced TSSOP-28 Package
Digital PWM or analog voltage signals can be used to
control the duty cycle of the all the channels. When
analog control is used, the dimming frequency can be
programmed via an external capacitor. A minimum
duty cycle control is provided in the conditions that
the analog dimming is configured as thermal
feedback.
Protection features include VIN under-voltage lockout, LED open/short circuit and over-temperature fault
signaling to the system controller.
APPLICATIONS
•
•
Streetlights
Solid State Lighting Solutions
Typical Application
High Power LED Arrays
VRAIL
NTC thermistor
couple to LED
arrays
RFB1
Voltage
output
B
EN
OutP
VLedFB
CDHC
Voltage
feedback pin
RFB2
CDHC
VIN
DR1
DR2
DR3
DR4
FAULT_CAP
CFLT
PGND
VDHC
FAULTb
Q2
GD2
SE2
AGND
External voltage headroom control
Q3
GD3
SE3
VDHC
Fault acknowledgement output
Faultb
DIM
Q4
GD4
SE4
RISNS1
RTHM1
PWM dimming input
RISNS2
RISNS3
RISNS4
Thermal
5V
0V
Q1
GD1
SE1
VCC
DIM
To thermal
sensor
terminals
LM3464/64A
RDHC
Primary power
supply
A
PGND
RDMIN1
RTHM2
A
To NTC thermal
sensor
RDMIN2
B
PGND
PGND
PGND
DMIN
CVCC
Thermal_Cap
SYNC
AGND
PGND
AGND
PGND
CTHM
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2010–2013, Texas Instruments Incorporated
LM3464, LM3464A
SNVS652F – APRIL 2010 – REVISED MAY 2013
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Connection Diagram
Figure 1. Top View
28-Lead TSSOP-28
Package Number PWP
PIN DESCRIPTIONS
2
Pin
Name
Description
Application Information
1
SYNC
Synchronization signal output for
cascade operation
(Master-Slave configuration)
Connect this pin to the DIM pin of other LM3464/64A to enable cascade
operation (multiple device). This pin should leave open for single device
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
control
The voltage across this pin and GND defines the minimum thermal dimming
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.
Fault delay capacitor
Connect to an external capacitor to program the fault response time.
DHC time constant capacitor
An external capacitor to ground programs the Dynamic Headroom Control loop
response time
DHC Output
Connect this pin to the voltage feedback input of primary power supply to
facilitate dynamic headroom control.
Output voltage sense input
This pin senses the output voltage of the primary power supply.
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.
9
FAULT_CAP
10
CDHC
11
OutP
12
VLedFB
13
VCC
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
ESD Rating
-0.3V to 7V
(3)
, Human Body Model
±2 kV
−65°C to + 150°C
Storage Temperature Range
Junction Temperature (TJ)
(1)
(2)
(3)
+ 150°C
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.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Operating Ratings (LM3464)
Supply Voltage Range (VIN)
12V to 80V
−40°C to + 125°C
Junction Temperature Range (TJ)
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
−40°C to + 125°C
Junction Temperature Range (TJ)
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
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
No load
6.15
VCC-UVLO
VCC under-voltage lockout threshold (UVLO)
VCC increasing
4.98
VCC-UVLO-HYS
VCC UVLO hysteresis
VCC decreasing
IIN
Quiescent Current from VIN
CVCC = 0.68 µF
No load
IVCC
VCC Current limit
VCC = 0V
18
Device disable voltage threshold
VEN Decreasing
2.1
Vcc Regulator
Min
Typ
Max
Units
(1)
6.3
6.51
5.28
250
1.65
2.3
V
V
mV
3
mA
mA
Device Enable
VEN-DISABLE
(1)
4
2.55
3
V
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
Thermal_Cap pin
100% output duty cycle
2.95
3.25
3.3
V
VCTHM-MIN
Sawtooth min. voltage threshold at
Thermal_Cap pin
0% output duty cycle
0.325
0.4
0.493
V
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
VTHERMAL = VCC
VDIM-LED-OFF
DIM pin voltage threshold at LED OFF
VDMIN = 0V
VTHERMAL = VCC
1.19
V
1.3
V
Dynamic Headroom Control Output
VOutP-MAX
OutP pin max. output voltage
VOutP-MIN
OutP pin min. output voltage
VLEDFB-LED-ON
VLedFB pin voltage threshold at LED ON
VLEDFB-SYS-RST
System restart VLedFB pin voltage threshold for
system restart
IoutP = 1 mA current sink
2.4
Measure at VLedFB pin
VCC-0.5
V
0.3
V
2.5
2.58
1.2
V
V
LED Current Regulator
VGDx-MAX
GDx gate driver max. output voltage
VGDx-MIN
GDx gate driver min. output voltage
4.73
IGDx-MAX
GDx gate driver short circuit current
GDx short to GND
IDRx
DRx pin input current
VDRx = 10V
VDRx = 100V
VCC–1
0.115
V
0.127
V
8
mA
25
29
μA
55
70
μA
V
Fault Detection and Handling
VOVP-TH
DRx Pin over-voltage protection threshold
Measure at DRx pin
VSHORTFAULT
DRx short fault threshold
Any VDRx < 2.5V
18
19
21
8.35
8.4
9.75
VOPENFAULT
SEx open fault threshold
Measure at SEx pin
IFAULT-CAP
FAULT_CAP pin output current
All VDRx < VOVP-TH
25
uA
IFAULT-CAP-OVP
FAULT_CAP pin output current at DRx overvoltage
Any VDRx ≥ VOVP-TH
105
uA
VFAULT-CAP
FAULT-CAP pin voltage threshold at fault timer
expire
VFAULT-CAP rising
3.6
V
RFaultb
Faultb pin to GND resistance
LED fault = TRUE
110
Ω
125
°C
30
V
mV
Thermal Protection
TOTM-TH
Over Temperature Monitor Threshold
TOTM-HYS
Over Temperature Monitor Hysteresis
20
°C
TSD
Thermal shutdown temperature
TJ rising
165
°C
TSD-HYS
Thermal shutdown temperature hysteresis
TJ falling
20
°C
33.5
°C/W
6
°C/W
Thermal Resistance
θJA
Junction to Ambient
θJC
(2)
(2)
Junction to Case
(2)
TSSOP-28 Package
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.
6
Channel 1 Current Sense Voltage (VSE1)
Effifciency (%)
Figure 2.
Figure 3.
Thermal_Cap Pin Output Current
VCC Variation (%)
Figure 4.
Figure 5.
Operating Current
(EN pin floating)
Shutdown Current
(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
(VDIM) rising)
PWM Dimming Delay Time
(VDIM) falling)
Figure 10.
Figure 11.
Thermal Foldback Dimming
(VTHERMAL) rising)
Thermal Foldback Dimming
(VTHERMAL) falling)
Figure 12.
Figure 13.
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BLOCK DIAGRAM
8
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Figure 14. Typical Application Circuit with Fly-Back AC/DC Converter
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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.
10
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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 flyback 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 R1 and R2. The LM3464/64A influences the output
voltage of the AC/DC converter by sinking current from the junction of the voltage divider (R1 and 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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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:
2.5V = VDHC_READY x
RFB2
RFB1 + 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) = (R1 x IR1) + VREF(AC/DC)
(4)
for VREF(AC/DC) = 2.5V
IR1 =
VRAIL(peak) - 2.5V
R1
(5)
also since
IR1 =
=
VREF(AC/DC)
RD2
+
VREF(AC/DC) - VD1 - VoutP(min)
RDHC
2.5V - 0.5V - 0.3V
2.5V
+
RD2
RDHC
RDHC =
(6)
1.7V
IR1 -
2.5V
R2
(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.
12
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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 RA and
RB should 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:
160 k: // RB
x VCC
VDHC =
160 k: // RB + 1 M: //RA
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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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:
200
mA
ILED =
RISNSx
(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.
14
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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:
fLM3464(-3 dB) =
1
6
2S(1.2 x 10 ) x CDHC
(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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VThermal
www.ti.com
VCC
3.25V
ILED (AVG)
100%
0.4V
0V
Approximately 0.5%
(Limited by tTHM_MIN)
Temperature
Thermal
foldback begin
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:
tTHM_MIN = 262 x CTHM in second
(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
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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:
fThermal-foldback =
50 PA
(3.25 - 0.4) x CTHM
(14)
(15)
(16)
(17)
DThermal-foldback = (TLED_ON x fThermal-foldback) x 100%
= [(VTHERMAL - 0.4) X 35]%
for 0.4 ≤ VTHERMAL ≤ 3.25V
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.
VThermal
VCC
3.25V
VDMIN
100%
ILED (AVG)
0.4V
0V
Min. ILED (AVG)
Approximately 0.5%
(Limited by tTHM_MIN)
Temperature
Thermal
foldback begin
Min. thermal
foldback dimming
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]%
for 0.4 ≤ VDMIN ≤ 3.25V
(18)
(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:
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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, t2 and t3 in 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 cutoff 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:
TFAULT =
18
CFLT x 3.0V
25 PA
(21)
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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.
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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 4.7kΩ resistor 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
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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.
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In Figure 26, Z1, Z2, Z3, Z4 and 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 Zx and 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 VZ and IZ are 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 42.2kΩ resistor 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 42.2kΩ resistor 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 shutdown 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
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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 9.31kΩ resistor can be selected for the RIN.
Then the maximum power dissipation on RIN is:
(31)
Thus, a standard 9.38kΩ resistor with 2512 package (1W) and 1% tolerance can be used.
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Additional Application Circuit
Figure 27. Cascade Operation with Thermal Foldback Control
24
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REVISION HISTORY
Changes from Revision E (May 2013) to Revision F
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 24
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PACKAGE OPTION ADDENDUM
www.ti.com
28-Aug-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
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
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
28-Aug-2013
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 2
PACKAGE MATERIALS INFORMATION
www.ti.com
8-May-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
LM3464AMHX/NOPB
HTSSOP
PWP
28
2500
330.0
16.4
LM3464MHX/NOPB
HTSSOP
PWP
28
2500
330.0
16.4
Pack Materials-Page 1
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
6.8
10.2
1.6
8.0
16.0
Q1
6.8
10.2
1.6
8.0
16.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
8-May-2013
*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
Pack Materials-Page 2
PACKAGE OUTLINE
PWP0028A
PowerPAD TM - 1.1 mm max height
SCALE 1.800
PLASTIC SMALL OUTLINE
C
6.6
TYP
6.2
A
SEATING PLANE
PIN 1 ID
AREA
28
1
9.8
9.6
NOTE 3
0.1 C
26X 0.65
2X
8.45
14
B
15
4.5
4.3
NOTE 4
0.30
0.19
0.1
C A
28X
1.1 MAX
B
0.20
TYP
0.09
SEE DETAIL A
3.15
2.75
0.25
GAGE PLANE
5.65
5.25
THERMAL
PAD
0 -8
0.10
0.02
0.7
0.5
(1)
DETAIL A
TYPICAL
4214870/A 10/2014
PowerPAD is a trademark of Texas Instruments.
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.
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EXAMPLE BOARD LAYOUT
PWP0028A
PowerPAD TM - 1.1 mm max height
PLASTIC SMALL OUTLINE
(3.4)
NOTE 9
(3)
SOLDER
MASK
OPENING
28X (1.5)
28X (0.45)
SOLDER MASK
DEFINED PAD
1
28X (0.45)
28X (1.3)
28
26X
(0.65)
SYMM
(5.5)
(9.7)
SOLDER
MASK
OPENING
(1.3) TYP
14
15
( 0.2) TYP
VIA
(1.3)
SEE DETAILS
SYMM
(0.9) TYP
METAL COVERED
BY SOLDER MASK
(0.65) TYP
(5.8)
(6.1)
HV / ISOLATION OPTION
0.9 CLEARANCE CREEPAGE
OTHER DIMENSIONS IDENTICAL TO IPC-7351
IPC-7351 NOMINAL
0.65 CLEARANCE CREEPAGE
LAND PATTERN EXAMPLE
SCALE:6X
SOLDER MASK
OPENING
METAL
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
0.05 MAX
ALL AROUND
0.05 MIN
ALL AROUND
SOLDER MASK
DEFINED
NON SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4214870/A 10/2014
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.
www.ti.com
EXAMPLE STENCIL DESIGN
PWP0028A
PowerPAD TM - 1.1 mm max height
PLASTIC SMALL OUTLINE
(3)
BASED ON
0.127 THICK
STENCIL
28X (1.5)
28X (0.45)
METAL COVERED
BY SOLDER MASK
1
28X (1.3)
28
26X (0.65)
28X (0.45)
(5.5)
BASED ON
0.127 THICK
STENCIL
SYMM
14
15
SEE TABLE FOR
DIFFERENT OPENINGS
FOR OTHER STENCIL
THICKNESSES
SYMM
(5.8)
(6.1)
HV / ISOLATION OPTION
0.9 CLEARANCE CREEPAGE
OTHER DIMENSIONS IDENTICAL TO IPC-7351
IPC-7351 NOMINAL
0.65 CLEARANCE CREEPAGE
SOLDER PASTE EXAMPLE
EXPOSED PAD
100% PRINTED SOLDER COVERAGE AREA
SCALE:6X
STENCIL
THICKNESS
SOLDER STENCIL
OPENING
0.1
0.127
0.152
0.178
3.55 X 6.37
3.0 X 5.5 (SHOWN)
2.88 X 5.16
2.66 X 4.77
4214870/A 10/2014
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.
www.ti.com
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