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NCV7680 Linear Current Regulator and Controller for Automotive LED Rear Combination Lamps
The NCV7680 consists of eight linear programmable constant current sources. The part is designed for use in the regulation and control of LED based Rear Combination Lamps for automotive applications. System design with the NCV7680 allows for two brightness levels, one for stop and one for tail illumination, or optional PWM control can also be implemented. Discrete LED brightness levels are easily programmed (stop current value, tail duty cycle value) optional external ballast FET allows for power distribution on designs requiring high currents. Set back power limit reduces the drive current during overvoltage conditions. This is most useful for low current applications when no external FET is used.
Features http://onsemi.com MARKING DIAGRAM
SOIC-16 WB PW SUFFIX CASE 751AG
V7680 AWLYYWWG
* * * * * * * * * * * * * * * * * * *
Constant Current Outputs for LED String Drive LED Drive Current up to 75 mA per Channel Open LED String Diagnostic with Open-Drain Output Slew Rate Control Eliminates EMI Concerns Low Dropout Operation for Pre-Regulator Applications External Modulation Capable On-chip 1 kHz Tail PWM Dimming Single Resistor for Stop Current Set Point Single Resistor for Tail Dimming Set Point Overvoltage Set Back Power Limitation AEC Q100 Qualified 16 Lead SOICW Exposed Pad This is a Pb-Free Device Rear Combination Lamps (RCL) Daytime Running Lights (DRL) Fog Lights Center High Mounted Stop Lamps (CHMSL) Arrays Turn Signal and Other Externally Modulated Applications LCD Back Lighting
A WL YY WW G
= Assembly Location = Wafer Lot = Year = Work Week = Pb-Free Device
ORDERING INFORMATION
Device NCV7680PWR2G Package SOIC-16WB (Pb-Free) Shipping 1000 / Tape & Reel
For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D.
Applications
(c) Semiconductor Components Industries, LLC, 2010
January, 2010 - Rev. 1
1
Publication Order Number: NCV7680/D
NCV7680
VP
Ballast Drive Regulation Control Ballast Drive
Output Current Out1 Out2 Out3
1.05 V
STOP
Output Control Out7 Diagnostic Reporting (high reporting) Out8
DIAG
Open Circuit Rstop Current Limit Overvoltage Set Back Current (down 20%)
Figure 1. Simple Block Diagram
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2
+ -
FB
FET Drive
Out4 Out5 Out6
GND
Current Programming
RSTOP
RTAIL
NCV7680
VP Ballast Drive FB
5V 100k
Overvoltage
1 of 8
Soft Start, Bias, and Reference
FET Drive
OUT1 Channel Control
+
1.05 V
Output Disable Control Logic DIAG Interface
Setback Current -20%
200k
5V
Open Circuit Detect IRSTOP x 100
DIAG V-I Converter
Pin Current Limit
Oscillator and PWM
Vreg Irstop -
4.4 V 0.4 V
Rtail
RSTOP
RTAIL
Figure 2. Detailed Block Diagram
OUT1 VP Ballast Drive FB STOP/PWM DIAG RSTOP RTAIL
EP
OUT2 OUT3 OUT4 GND OUT5 OUT6 OUT7 OUT8
Figure 3. Pinout Diagram
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3
+
-
STOP
+
-
+ + -
-
OUT2 OUT3 OUT4
100 mV
Overtemperature & Overvoltage sense
OUT5 OUT6 OUT7
400 mV
OUT8
GND
NCV7680
TAIL Input STOP Input MRA4003T3G NTD2955 R3 1k C2 0.22mF C3 100nF
MRA4003T3G C1 0.1mF R1 10k
VSTRING
NCV7680 OUT2 OUT1 VP FB R4, 3.09k C4 10nF R5, 2.21k DIAG RSTOP RTAIL epad OUT3 GND OUT6 OUT7 OUT8 R6 8.87k Ballast Drive OUT4 STOP/PWM OUT5
Vref
R1 limits the current out of STOP/PWM during reverse battery condition. R6 and R7 values shown yield 10.5 V regulation on VSTRING. C1 is for line noise considerations. C3 is for EMS considerations. R7 1k
Figure 4. Application Diagram with External FET Ballast Transistor
TAIL Input
MRA4003T3G
STOP Input
MRA4003T3G C3 100nF
R1 10k
R8 10k
NCV7680 OUT2 OUT1 OUT3 VP Ballast Drive OUT4 FB R4, 3.09k C4 10nF R5, 2.21k DIAG RSTOP RTAIL epad GND OUT6 OUT7 OUT8 STOP/PWM OUT5
Figure 5. Application Diagram without the FET Ballast Transistor
When using the NCV7680 without the FET ballast transistor, tie the FB Pin to VP through a 10k resistor.
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Table 1. APPLICATION I/O TRUTH TABLE (FB = Vref) (Reference Figure 2)
Stop Input 0 1 1 0 1 1 Tail Input 0 0 0 1 1 1 OUTX Current (1-8) OFF ISTOP ISTOP PWM ISTOP ISTOP Fault State* - NORMAL OPEN CIRCUIT*** DO NOT CARE NORMAL OPEN CIRCUIT*** DIAG State HIGHZ** LOW HIGH** HIGH** LOW HIGH**
* Open Circuit, RSTOP Current Limit, and Set Back Current Limit down 20% ** Pullup resistor to DIAG *** OPEN CIRCUIT = Any string open 0 = LOW 1 = HIGH
TAIL
STOP
HIGHZ
DIAG
Open String Occurs
Open String Removed
Open String Occurs
Figure 6. DIAG Timing Diagram
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Table 2. PIN FUNCTION DESCRIPTION (16 Pin SO Wide Exposed Pad Package)
Pin # 1 2 3 4 5 6 Label OUT1 VP Ballast Drive FB STOP/PWM DIAG Description Channel 1 constant current output to LED. Unused pin should be grounded. Supply Voltage Input. Gate drive for external power distribution PFET. Ground if not used. Feedback Sense node for VP regulation. Use feedback resistor divider or connect to VP with a 10k resistor. Stop Logic Input. External Modulation Input. Open-drain diagnostic output. Reporting Open Circuit, RSTOP Current Limit, and Overvoltage Set Back Current down 20%. Normal Operation = LOW. Ground if not used. Stop current bias program resistor. Tail current duty cycle PWM program resistor. Ground if using external modulation. Channel 8 constant current output to LED. Unused pin should be grounded. Channel 7 constant current output to LED. Unused pin should be grounded. Channel 6 constant current output to LED. Unused pin should be grounded. Channel 5 constant current output to LED. Unused pin should be grounded. Ground. Channel 4 constant current output to LED. Unused pin should be grounded. Channel 3 constant current output to LED. Unused pin should be grounded. Channel 2 constant current output to LED. Unused pin should be grounded. Ground. Do not connect to pcb traces other than GND.
7 8 9 10 11 12 13 14 15 16 epad*
RSTOP RTAIL OUT8 OUT7 OUT6 OUT5 GND OUT4 OUT3 OUT2 epad
*Grounding will provide better thermal and electrical performance.
MAXIMUM RATINGS (Voltages are with respect to device substrate)
Rating VP, Ballast Drive, STOP, DIAG DC Peak Transient Output Pin Voltage (OUTX) Output Pin Current (OUTX) Input Voltage (RTAIL, RSTOP, FB) Junction Temperature, TJ Peak Reflow Soldering Temperature: Pb-Free 60 to 150 seconds at 217C (Note 1) Value -0.3 to 45 45 -0.3 to 45 100 -0.3 to 5 -40 to 150 260 peak Unit V
V mA V C C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. For additional information, see or download ON Semiconductor's Soldering and Mounting Techniques Reference Manual, SOLDERRM/D, and Application Note AND8003/D.
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Table 3. ATTRIBUTES
Characteristics ESD Capability Human Body Model (RSTOP Pin) Human Body Model (All Remaining Pins) Machine Model (Note 2) Value > $1.8 kV > $2.0 kV > $200 V MSL 1 -55C to 150C 27C/W 78C/W 38C/W
Moisture Sensitivity Level Storage Temperature Package Thermal Resistance (Note 3) Junction-to-Board (RYJB) Junction-to-Ambient (RqJA) Junction-to-Pin (RYJL)
Meets or exceeds JEDEC Spec EIA/JESD78 IC Latchup Test 2. For additional information, see or download ON Semiconductor's Soldering and Mounting Techniques Reference Manual, SOLDERRM/D, and Application Note AND8003/D. 3. Values represent typical still air steady-state thermal performance on 1 oz. copper FR4 PCB with 650 mm2 copper area.
ELECTRICAL CHARACTERISTICS (6 V < VP < 16 V, VSTOP = VP, RSTOP = 3.09 kW, RTAIL = 2.21 kW, -40C v TJ v 150C, unless
otherwise specified) (Note 4) Characteristic GENERAL PARAMETERS Quiescent Current (IOUTx = 35 mA) STOP Mode, 8 Channel VP = 16 V STOP Mode, 4 Channel VP = 16 V, OUT5 = OUT6 = OUT7 = OUT8 = GND Tail Mode VP = 16 V Ground Pin Current CURRENT SOURCE OUTPUTS Output Current Maximum Regulated Output Current Current Matching -40C 25C 150C OUTX = 1.0 V, TJ = 25C, 150C OUTX = 1.0 V, TJ = -40C 31.5 30.8 75 35 35 - 0 0 0 38.5 39.2 - 7 6 5 mA mA % % % OUT1 to OUT8 = 35 mA - - - - 6.5 6.4 6.0 300 8.0 8.0 8.0 350 mA Conditions Min Typ Max Unit
mA
2I OUTx(min) I OUTx(min) ) I OUTx(max) 2I OUTx(max) I OUTx(min) ) I OUTx(max)
*1
100
-7 -6 -5
*1
100
- 0.3 0.6 0.4 6.0 18.7 94 80 100 3.0 0.5 25 24.5 - - 250 mA V mA/us V %IOUT %IOUT mV
Line Regulation Open Circuit Detection Threshold Current Slew Rate Overvoltage Set Back Threshold Overvoltage Set Back Current Diag Reporting of Set Back Current Output Disable Threshold FET DRIVER Ballast Drive Leakage Current Sink Current Ballast Drive Reference Voltage
6 V v VP v 16 V IOUT = 35 mA, 10% to 90% Points @ 99% IOUT VP = 20 V
- 16.0 - - -
FB = 1.5 V, Ballast Drive = 3 V FB = 0.5 V, Ballast Drive = 3 V
- 4 0.95
0 5 1.05
10 - 1.15
mA mA V
4. Designed to meet these characteristics over the stated voltage and temperature recommended operating ranges, though may not be 100% parametrically tested in production. 5. Guaranteed by design.
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ELECTRICAL CHARACTERISTICS (6 V < VP < 16 V, VSTOP = VP, RSTOP = 3.09 kW, RTAIL = 2.21 kW, -40C v TJ v 150C, unless
otherwise specified) (Note 4) Characteristic STOP LOGIC Input High Threshold Input Low Threshold VIN Hysteresis Input Bias Current PROGRAMMING RSTOP Bias Voltage RSTOP K multiplier RSTOP Current Limit RTAIL Bias Current Duty Cycle Tail Duty Cycle Programming Current RTAIL = 0.59 V RTAIL = 1.21 V RTAIL = 3.29 V Stop Current Programming Voltage IOUTX / IRSTOP 0.96 - - 300 3.5 17 59.5 1.08 100 1.8 350 5.0 20 70 1.21 - 2.2 450 6.5 23 80.5 V - mA mA % % % STOP = 14 V 1.6 0.7 - 0 1.9 0.85 1.05 150 2.2 1.1 - 300 V V V mA Conditions Min Typ Max Unit
DIAG OUTPUT Output Low Voltage Output Leakage Current THERMAL LIMIT Thermal Limit Temperature Thermal Shutdown Thermal Hysteresis OUTx Reduction Initiated @ 99% IOUT (Note 5) (Note 5) (Note 5) 150 150 - - 190 15 - - - C C C DIAG Active, IDIAG =1 mA VDIAG = 5 V - - 0.1 - 0.40 10 V mA
4. Designed to meet these characteristics over the stated voltage and temperature recommended operating ranges, though may not be 100% parametrically tested in production. 5. Guaranteed by design.
AC CHARACTERISTICS (6 V < VP < 16 V, VSTOP = VP, RSTOP = 3.09 kW, RTAIL = 2.21 kW, -40C v TJ v 150C, unless otherwise
specified) Characteristic Stop Turn-on Delay Time Stop Turn-off Delay Time PWM Frequency Conditions VSTOP/PWM 90% to IOUTX 90% VSTOP/PWM 10% to IOUTX 10% STOP = 0 V Min - - 0.5 - - Typ 14 21 1.0 2.0 4.0 Max 45 45 2.1 4.0 10 Unit ms ms kHz ms ms
Tail Frequency Stabilization Time VP step from 0 V to 6 V Open Circuit to DIAG Reporting
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TYPICAL PERFORMANCE CHARACTERISTICS
160 140 qJA MAXIMUM (C/W) 120 100 80 60 40 20 0 0 100 200 300 400 500 600 700 1 oz 2 oz
COPPER HEAT SPREADER AREA (2mm)
Figure 7. qJA vs. Copper Spreader Area
1000
R(t) MAXIMUM (C/W)
100
D = 0.5 0.2 0.1
10
0.05 0.02 0.01 SINGLE PULSE
1
0.1
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
PULSE TIME (s)
Figure 8. Thermal Duty Cycle Curves on 650 mm2 Spreader Test Board
1000 100 mm2 R(t) MAXIMUM (C/W) 100 50 mm2
10 500 mm2 1
0.1 0.000001
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
PULSE TIME (s)
Figure 9. Single Pulse Heating Curve
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36 70 IOUT, OUTPUT CURRENT (mA) IOUT, OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T = 25C 4.0 4.5 5.0 35.5 35 34.5 34 33.5 33 -40 -20 RSTOP = 3.09 kW 0 20 40 60 80 100 120 140 160
RSTOP (kW)
TEMPERATURE (C)
Figure 10. IOUT vs. RSTOP
70 60 DUTY CYCLE (%) DUTY CYCLE (%) 50 40 30 20 10 0 0 1 2 3 4 5 6 RSTOP = 3.09 kW 7 8 9 10 70 60 50 40 30 20 10 0 0 0.5
Figure 11. IOUT vs. Temperature
1
1.5
2
2.5
3
3.5
RTAIL (kW)
V(RTAIL)
Figure 12. Duty Cycle vs. RTAIL
35 30 DUTY CYCLE (%) 25 20 15 10 5 0 -40 -20 0 20 40 60 80 100 120 140 160 RTAIL = 3 kW 40 RTAIL = 4 kW IOUT, OUTPUT CURRENT (mA) 35 30 25 20 15 10 5 0 9 11
Figure 13. Duty Cycle vs. V(RTAIL)
RTAIL = 2 kW
RSTOP = 3.09 kW 13 15 17 19 21 23 25 27 VP (V)
TEMPERATURE (C)
Figure 14. Duty Cycle vs. Temperature
Figure 15. IOUT vs. VP
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36 IOUTx, OUTPUT CURRENT (mA) 35.8 35.6 35.4 VSTRING (V) 35.2 35 34.8 34.6 34.4 34.2 34 6 7 8 9 10 11 VP 12 13 OUTX = 1 V 14 15 16 14 12 10 8 6 4 2 0 0 2000 4000 6000 R6 (W) 8000 per eq. 1 R7 = 1K 10000 12000
Figure 16. VP Line Regulation
Figure 17. VSTRING vs. R6
120 100 80 IOUT (mA) 60 40 20 0
OUTx current is limited during short circuit events of RSTOP. The current rolls off per the diagram to prevent unexpected excessive power dissipation.
0
0.5
1.0
1.5
2.0
2.5
IRSTOP (mA)
Figure 18. IOUT vs. IRSTOP
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DETAILED OPERATING DESCRIPTION
General
The NCV7680 consists of eight linear programmable constant current sources. The part is designed for use in the regulation and control of LED based Rear Combination Lamps for automotive applications. System design with the NCV7680 allows for two brightness levels; one for stop, and one for tail illumination. Brightness levels are easily programmed (stop current absolute value, tail current duty cycle value) with two external resistors. The use of an external FET allows for power distribution on designs requiring high currents. Additionally, set back power limit reduces the drive current during overvoltage conditions. Set back power limit is most useful for low current applications when no external FET is used. The NCV7680 offers all of the built in protection normal to regulator systems, such as current limit, thermal limit, and provides an open load diagnostic that coincides with the STOP input signal.
Open String Reporting (DIAG)
Setback Current Limit is employed during high voltage. During a Setback Current Limit event, the drive current is reduced resulting in lower power dissipation on the IC. This occurs during high battery voltage (VP > 16 V). In this way the NCV7680 can operate in extreme conditions and still provide a controlled level of light output The Overvoltage condition is reported on the DIAG Pin. Reference Figures 19 and 20 for Power Limiting Behavior.
Only Voltage Effects DRIVER POWER DISSIPATION
Low Drop-out Area
Thermal Shutdown 180C (typ) Overvoltage Set Back Area Voltage
Constant Current Area
Figure 19. Ballast FET Power
IC POWER DISSIPATION
Open string detection is reported on the DIAG pin as a high with STOP Input high, or a combination of STOP Input high and TAIL Input high. Reference Table 1 on page 5 for more details. Open circuit is sensed on each of the 8 outputs. The typical threshold voltage for detection is 0.4 V. Care must be taken not to breach this voltage level under normal operation , or a false open will be reported. Make sure worst case system design focuses on the voltage level on top of the LED string (top anode) (VSTRING) and includes the worst case LED voltage drop while considering temperature effects.
Input Voltage and Set Back Current
Low Drop-out Area
Only Voltage Effects
Constant Current Area
Overvoltage Set Back Area
Thermal Shutdown 180C (typ) Voltage
Figure 20. IC Power Quiescent Current Power
Automotive battery systems have wide variations in line supply voltage. Low dropout is a key attribute for providing consistent LED light output at low line voltage. Unlike adjustable regulator based constant current source schemes where the set point resistor resides in the load path, the NCV7680's set point resistor lies outside the LED load path, and aids in the low dropout capability.
Further reduction in power to the NCV7680 can be achieved by moving the VP pin connection to the drain of the external FET. The contribution of power at the NCV7680 caused by the quiescent current into VP is lowered due to the lower operating voltage of VP with the new connection. Note also the addition of an external resistor Rsd in Figure 21. This will be required to insure startup of the system. A value for Rsd should be chosen low enough to provide current into VP and the current in the ILEDs & feedback string under all required input voltage input conditions.
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NCV7680
Rsd Vbat MRA4003T3G NTD2955 ILEDs & feedback C3 100 nF OUT1 VP Ballast Drive FB STOP DIAG RSTOP RTAIL
C1 0.1 mF
R3 1K
C2 0.22 mF
NCV7680 OUT2 OUT3 OUT4 GND OUT5 OUT6 OUT7 OUT8
Figure 21. Alternative VP Connection with Rsd Programmability
Strings of LEDs are a common configuration for RCL applications. The NCV7680 provides eight matched outputs allowing individual string drive with current set by a single resistor. Individual string drive is a benefit to ensure equal current distribution amongst all of the strings. Output currents are mirrored and matched within 5% at hot temperature. A high STOP condition sets the output current using equation 1 below. A low STOP condition, modulates the output currents at a duty cycle (DC) programmed using equation 2 below. Note, current limiting on RSTOP limits the current which can be referenced from the RSTOP Pin. Exceeding the RSTOP Current Limit will reduce the output current and the DIAG Pin will go high (reference Figure 18). This helps limit output current (brightness and power) for this type of fault. The average ISTOP Duty Cycle current provides the dimmed tail illumination function and assures a fixed brightness level for tail. The PWM generator's fixed frequency (1 kHz typ.) oscillator allows flicker-free illumination. PWM control is the preferred method for dimming LEDs. The diagnostic function allows the detection of an open in any one of the output circuits. The active-low diagnostic output (DIAG) is coincident with the STOP input. DIAG remains high (pulled up) if an open load is detected in any LED string when STOP is high.
Output Current Programming
and RTAIL values. RSTOP should always be chosen first as the stop current is only dependent on this value. Alternatively, the equations below can be used to calculate a typical value and used for worst case analysis.
Set the Stop Current using RSTOP OUTX + 100 R STOP_Bias_Voltage R STOP
(eq. 1)
RSTOP Bias Voltage = 1.08 V (typ)
Set the Duty Cycle (DC) using RTAIL R TAIL + 4 R STOP(DC ) 0.1)
(eq. 2) DC = duty cycle expressed in fractional form. (e.g. 0.50 is equivalent to 50% duty cycle) (ground RTAIL when using external modulation)
Reference Figure 10 to choose programming resistor (RSTOP) value for stop current. Reference Figure 12 (Duty Cycle vs. RTAIL) to choose a typical value programming resistor for output duty cycle (with a typical RSTOP value of 3.09 kW). Note the duty cycle is dependent on both RSTOP
Output Current is directly tested per the electrical parameter table to be 10% (with RSTOP = 3.09 kW) or 31.5 mA (min), 35 mA (typ), 38.5 mA (max) at room and hot temperature. Duty Cycle will vary according to the changes in RTAIL Voltage and RTAIL Bias Current (generated form the current through RSTOP). Voltage errors encompass generator errors (0.4 V to 4.4 V) and comparator errors and are included in testing as the Duty Cycle. Typical duty cycle measurements are 5% with RTAIL = 0.59 V and 70% with RTAIL = 3.29 V. RTAIL Bias Current errors are measured as RTAIL Bias Current and vary as 300 mA (min), 350 mA (typ), and 450 mA (max) with RSTOP = 3.09 kW. The error duality and choice of duty cycle levels make it difficult to specify duty cycle minimum and maximum limits, but worst case conditions can be calculated when considering the variation in the voltage threshold and current source. Duty Cycle variation must include the direct
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duty cycle as specified in the electrical parameter table plus an additional error due to the Irstop current which generates this voltage in the system.
Vreg
Calculate system design VSTRING. Let VLED be the voltage drop across your LEDs (3 included in Figure 4). 9.5 V Choose a value for OUTx, 1 V
V STRING + V OUTx ) V LED
(eq. 5)
Oscillator and PWM
Using Equation 3
Irstop
-
V STRING + 1 V ) 9.5 V + 10.5 V
RTAIL
RTAIL
Figure 22. Duty Cycle Generator Circuitry Alternative Setup of Duty Cycle
Alternatively, the duty cycle can be controlled by providing a voltage to the RTAIL pin as per Figure 13 (Duty Cycle vs. V(RTAIL). Note the pull-up current source (Irstop) is still present on the RTAIL pin due to current setting resistor connected to RSTOP. For proper operation the system designer needs to insure there is sufficient loading on the RTAIL pin such that Irstop does not pull the referenced voltage higher than its regulated state. VSTRING should be set to a level to allow proper operation of the IC without detecting an open circuit (0.5 V max on OUTx) and to keep power to the IC at reduced levels below the 150C max die temperature thermal limit (die temperature will depend on printed circuit board composition, PCB size, thermal via number and placement, module component placement, and air flow). Example: VSTRING is set using resistors R6 and R7 (reference Figure 4).
V STRING + V FB R6 R7 )1
(eq. 3)
Setting VSTRING
VFB = Ballast Drive Reference Voltage This simplifies to an equation for R6.
R6 + R7 V STRING * V FB V FB
(eq. 4)
+
4.4V 0.4V
Using Equation 4 Choose a value for R7. R7 = 1k
R6 + 1k 10.5 V * 1.08 V 1.08 V + 8.72k
The closest standard resistor value is 8.87k.
Reduced Channel Operation
The previously shown applications (Figures 4 and 5) show system operation using all 8 available channels of the NCV7680. When less than 8 channels are used, the unused OUTx pins can be grounded eliminating the unused OUTx drive current. This is accomplished by voltage threshold detection on OUTx (100 mV typ). A voltage less than 100 mV on OUTx turns the driver off, reducing quiescent current to the IC. This also helps reduce system power by eliminating the need for an external pullup resistor (from OUTx to VP) while maintaining open circuit detection. External pullup resistors may be used as an alternative.
Adding LED's to the String
The NCV7680 can function as a standalone device or in conjunction with additional support circuitry for more complex systems. Figure 23 shows the NCV7680 operating with a boost controller. This setup allows additional LEDs in a string to be increased. Eight are shown in the diagram. Consideration of the 45 V maximum limit on the OUTx Pin is the limitation of this configuration. The DC on voltage level on OUTx must also be considered for thermal reasons.
Electromagnetic Interference (EMI)
One of the key contributors to electromagnetic interference is the rise and fall times of the electrical signals. This is a concern with both the initial startup of a device, and the repeated turn on/off cycles of a device. The NCV7680 employs current slew rate control. Each output is rated at 6.0 mA/ms (typ). Slew rate control reduces overshoot and allows for a predictable electrical signal. Slew rate control is used in the stop mode for soft-start and in the tail mode for low EMI operation.
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NCV7680
TAIL Input
MRA4003T3G
STOP Input
MRA4003T3G
C3 1mF
+ -
NCV3163 Boost Controller
+ -
R1 10k
NCV7680 OUT2 OUT1 VP R8, 10k FB R4, 3.09k C4 10nF R5, 2.21k DIAG RSTOP RTAIL epad OUT3 GND OUT6 OUT7 OUT8 Ballast Drive OUT4 STOP/PWM OUT5
Figure 23. Boost Mode
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VSTRING
Cross-Coupled LEDs
The setup in Figure 24 shows the LEDs set up in a cross-coupled configuration connected to all the outputs of the NCV7680 in parallel. This allows the user to maintain illumination of all the remaining LEDs when one fails due to an open circuit (the most common form of LED failure). Comparatively, the standard setup shown in Figure 4 will result in a full string turning off when one LED is open. Be aware as LEDs fail as open circuits in the cross-coupled arrangement will cause the row of LEDs to run at a higher current level affected by the smaller number of LEDs in that row.
NCV7680 OUT1 VP Ballast Drive FB STOP DIAG RSTOP RTAIL epad OUT2 OUT3 OUT4 GND OUT5 OUT6 OUT7 OUT8
Figure 24. Cross Coupled LEDs
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TAIL Input STOP Input
MRA4003T3G NTD2955 R3 1k C2 0.22mF C3 100nF
MRA4003T3G
VSTRING
C1 0.1mF + - R1 10k
NCV7680 OUT2 OUT1 VP FB R4, 3.09k C4 10nF R5, 2.21k DIAG RSTOP RTAIL epad OUT3 GND OUT6 OUT7 OUT8 R6 8.87k Ballast Drive OUT4 STOP/PWM OUT5
Vref
R7 1k LED Module
Figure 25. No Tail Light, Stop Illuminated
MRA4003T3G TAIL Input MRA4003T3G STOP Input C1 0.1mF + - NCV7680 OUT2 OUT1 VP FB R4, 3.09k C4 10nF R5, 2.21k DIAG RSTOP RTAIL epad OUT3 GND OUT6 OUT7 OUT8 R6 8.87k Ballast Drive OUT4 STOP/PWM OUT5 R1 10k NTD2955 R3 1k C2 0.22mF C3 100nF
VSTRING
Vref
R7 1k LED Module
Figure 26. Tail Light Illuminated, No Stop
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VBAT or Boost Voltage MRA4003T3G
6V
C3 1mF
PWM
R1 10k
C5 1mF
NCV7680 OUT2 OUT1 VP FB R4, 3.09k DIAG RSTOP RTAIL epad OUT3 GND OUT6 OUT7 OUT8 Ballast Drive OUT4 STOP/PWM OUT5
C4* 10nF
* Optional for EMI considerations
Figure 27. PWM Operation (suggested LCD backlighting applications) External PWM Operation
Using the NCV7680 in a PWM setup requires RTAIL to be grounded. Grounding RTAIL disables the internal PWM circuitry. With RTAIL grounded, the STOP input pin can then be modulated externally with a microprocessor using the STOP logic input level thresholds.
Tail Frequency Stabilization Time requires 2 pulses from the internal oscillator. This is typically 2 ms (from the 1 kHz oscillator. Circuit limitations dictate the maximum output current (IOUTX) to be 60 mA when operated at VP = 5 V. Part capability increases up to the part maximum capability as VP is increased.
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Latch-Off on Open String Detection
Some LED lighting systems require the complete lighting system to shut down when the output intensity has diminished. This eliminates a slow degradation of output illumination. Figure 28 provides one solution for this requirement. The open circuit fault information provided on
TAIL Input STOP Input
MRA4003T3G NTD2955 MRA4003T3G C1 0.1uF R3 C2 1k 0.22uF C3 100nF
the DIAG pin coupled with external discrete transistors provides the feedback needed to the FB pin to turn off the ballast transistor drive removing the LED anode string from any power source. This condition is held until the input signal is toggled.
VSTRING
MRA4003T3G
R1 10k
NCV7680 OUT1 VP Ballast Drive FB R10 10k R11 10k R9 499 R4, 3.09k STOP DIAG RSTOP RTAIL OUT2 OUT3 OUT4 GND OUT5 OUT6 OUT7 OUT8
C4 10nF MUN2211
R5, 2.21k R2 4.99k C6 0.1uF
R6 8.87K
Vref
R7 1K
Note: Latch-off will be implemented under all conditions which cause DIAG to go high. Reference the pin function description table for a summary of DIAG performance.
Figure 28. Latch-Off Circuit
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NCV7680
PACKAGE DIMENSIONS
SOIC 16 LEAD WIDE BODY, EXPOSED PAD CASE 751AG-01 ISSUE A
A -U- M
16 1 8 9 NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE PROTRUSION SHALL BE 0.13 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. 6. 751R-01 OBSOLETE, NEW STANDARD 751R-02. MILLIMETERS MIN MAX 10.15 10.45 7.40 7.60 2.35 2.65 0.35 0.49 0.50 0.90 1.27 BSC 3.45 3.66 0.25 0.32 0.00 0.10 4.72 4.93 0_ 7_ 10.05 10.55 0.25 0.75 INCHES MIN MAX 0.400 0.411 0.292 0.299 0.093 0.104 0.014 0.019 0.020 0.035 0.050 BSC 0.136 0.144 0.010 0.012 0.000 0.004 0.186 0.194 0_ 7_ 0.395 0.415 0.010 0.029
P 0.25 (0.010)
M
W
M
B -W-
R x 45_
PIN 1 I.D.
G TOP SIDE
14 PL
DETAIL E
C -T- 0.10 (0.004) T D 16 PL 0.25 (0.010) H
1 8 M
F
K TU
S
SEATING PLANE
W
S
J DETAIL E
EXPOSED PAD
DIM A B C D F G H J K L M P R
L
16 9
SOLDERING FOOTPRINT*
0.350 0.175 0.050 Exposed Pad
BACK SIDE
C L 0.200 0.074
0.188 C L 0.376
0.024
0.150
DIMENSIONS: INCHES
*For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
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NCV7680/D

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