LM3429BKBSTEVAL/NOPB

User's Guide SNVA403C – July 2009 – Revised May 2013 AN-1985 LM3429 Buck-Boost Evaluation Board 1 Introduction This wide range evaluation board showcases the LM3429 NFET controller used with a buck-boost current regulator. It is designed to drive 4 to 8 LEDs at a maximum average LED current of 1A from a DC input voltage of 10 to 70V. The evaluation board showcases most features of the LM3429 including PWM dimming, overvoltage protection and input under-voltage lockout. It also has a right angle connector (J7) which can mate with an external LED load board allowing for the LEDs to be mounted close to the driver. Alternatively, the LED+ and LED- banana jacks can be used to connect the LED load. The buck-boost circuit can be easily redesigned for different specifications by changing only a few components (see Alternate Designs). Note that design modifications can change the system efficiency for better or worse. See the LM3429 LM3429Q1 N-Channel Controller for Constant Current LED Drivers (SNVS616) data sheet for a comprehensive explanation of the device and application information. 100 EFFICIENCY (%) 95 90 85 80 75 70 0 16 32 48 VIN (V) 64 80 Figure 1. Efficiency with 6 Series LEDS AT 1A All trademarks are the property of their respective owners. SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 1 Schematic 2 www.ti.com Schematic LED+ J4 TP3 TP7 TP1 L1 J1 VIN J7 D1 TP10 J2 C2, C3, C16, C18 R10 GND U1 C1 R3 1 VIN LM3429 VIN HSN 14 R7 13 R8 TP2 R2 C8 2 3 HSP COMP CSH IS RCT VCC GATE 13 3 12 4 11 5 10 6 9 7 8 C4, C6, C17, C19 J5 11 C12 C9 AGND 2 LED- C7 5 14 12 R1 4 1 10 Q1 R9 R20 R18 6 R13 OVP PGND 9 R6 VIN DAP R4 7 nDIM NC 8 TP11 R5 R11 Q3 PWM Q5 R12 TP12 Figure 2. Board Schematic 2 AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback Pin Descriptions www.ti.com 3 Pin Descriptions Pin Name Description Application Information 1 VIN Input Voltage Bypass with 100 nF capacitor to AGND as close to the device as possible in the circuit board layout. 2 COMP Compensation Connect a capacitor to AGND. 3 CSH Current Sense High 4 RCT Resistor Capacitor Timing 5 AGND Analog Ground 6 OVP Over-Voltage Protection 7 nDIM Not DIM input Connect a PWM signal for dimming as detailed in the PWM Dimming section and/or a resistor divider from VIN to program input under-voltage lockout (UVLO). Turn-on threshold is 1.24V and hysteresis for turn-off is provided by 20 µA current source. 8 NC No Connection Leave open. 9 PGND Power Ground Connect to AGND through the DAP copper circuit board pad to provide proper ground return for GATE. 10 GATE Gate Drive Output 11 VCC Internal Regulator Output 12 IS Main Switch Current Sense 13 HSP High-Side LED Current Sense Positive Connect through a series resistor to the positive side of the LED current sense resistor. 14 HSN High-Side LED Current Sense Negative Connect through a series resistor to the negative side of the LED current sense resistor. DAP (15) DAP Thermal pad on bottom of IC SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback Connect a resistor to AGND to set the signal current. For analog dimming, connect a controlled current source or a potentiometer to AGND as detailed in the Analog Dimming section. Connect a resistor from the switch node and a capacitor to AGND to set the switching frequency. Connect to PGND through the DAP copper circuit board pad to provide proper ground return for CSH, COMP, and RCT. Connect to a resistor divider from VO to program output overvoltage lockout (OVLO). Turn-off threshold is 1.24V and hysteresis for turn-on is provided by 20 µA current source. Connect to the gate of the external NFET. Bypass with a 2.2 µF–3.3 µF, ceramic capacitor to PGND. Connect to the drain of the main N-channel MosFET switch for RDS-ON sensing or to a sense resistor installed in the source of the same device. Star ground, connecting AGND and PGND. AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 3 Bill of Materials 4 4 www.ti.com Bill of Materials Qty Part ID 2 C1, C4 0.1 µF X7R 10% 100V Part Value TDK 4 C2, C3, C16, C18 4.7 µF X7R 10% 100V MURATA 3 C6, C17, C19 2.2 µF X7R 10% 100V TDK 1 C7 1000 pF COG/NPO 5% 50V MURATA GRM2165C1H102JA01D 1 C8 1 µF X7R 10% 16V MURATA GRM21BR71C105KA01L 1 C9 2.2 µF X7R 10% 16V MURATA GRM21BR71C225KA12L 1 C12 0.1 µF X7R 10% 25V MURATA GRM21BR71E104KA01L 1 D1 Schottky 100V 12A VISHAY 12CWQ10FNPBF 4 J1, J2, J4, J5 1 J7 2 x 7 shrouded header 1 L1 33 µH 20% 6.3A 1 Q1 NMOS 100V 40A VISHAY SUD40N10-25 1 Q3 NMOS 60V 260 mA ON-SEMI 2N7002ET1G 1 Q5 PNP 150V 600 mA FAIRCHILD 1 R1 12.4 kΩ 1% VISHAY CRCW080512k4FKEA 1 R2 0Ω 1% VISHAY CRCW08050000Z0EA 2 R3, R20 10Ω 1% VISHAY CRCW080510R0FKEA 1 R4 16.9 kΩ 1% VISHAY CRCW080516k9FKEA 1 R5 1.43 kΩ 1% VISHAY CRCW08051k43FKEA 1 R6 0.05Ω 1% 1W VISHAY WSL2512R0500FEA 2 R7, R8 1.0 kΩ 1% VISHAY CRCW08051k00FKEA banana jack Manufacturer KEYSTONE SAMTEC COILCRAFT Part Number C2012X7R2A104K GRM55ER72A475KA01L C4532X7R2A225K 575-8 TSSH-107-01-SDRA MSS1278-333MLB MMBT5401 1 R9 0.1Ω 1% 1W VISHAY WSL2512R1000FEA 1 R10 35.7 kΩ 1% VISHAY CRCW080535k7FKEA 1 R11 15.8 kΩ 1% VISHAY CRCW080515k8FKEA 2 R12, R13 10.0 kΩ 1% VISHAY CRCW080510k0FKEA 1 R18 750 kΩ 1% VISHAY CRCW0805750kFKEA 7 TP1, TP2, TP3, TP7, TP10, TP11, TP12 1 U1 turret KEYSTONE 1502-2 TI LM3429 Buck-boost controller AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback PCB Layout www.ti.com 5 PCB Layout Figure 3. Top Layer Figure 4. Bottom Layer SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 5 Design Procedure 6 www.ti.com Design Procedure Refer to the LM3429 LM3429Q1 N-Channel Controller for Constant Current LED Drivers (SNVS616) data sheet for design considerations. 6.1 Specifications N=6 VLED = 3.5V rLED = 325 mΩ VIN = 24V VIN-MIN = 10V; VIN-MAX = 70V fSW = 700 kHz VSNS = 100 mV ILED = 1A ΔiL-PP = 500 mA ΔiLED-PP = 50 mA ΔvIN-PP = 100 mV ILIM = 5A VTURN-ON = 10V; VHYS = 3V VTURN-OFF = 60V; VHYSO = 15V 6.2 Operating Point Solve for VO and rD: VO = N x VLED = 6 x 3.5V = 21V rD = N x rLED = 6 x 325 m: = 1.95: (1) (2) Solve for D, D', DMAX, and DMIN: D= 6.3 VO VO + VIN = 21V = 0.467 21V + 24V (3) D' = 1 - D = 1 - 0.467 = 0.533 (4) VO 21V = = 0.231 DMIN = VO + VIN-MAX 21V + 70V (5) VO 21V = = 0.677 DMAX = VO + VIN-MIN 21V + 10V (6) Switching Frequency Assume C7 = 1 nF and solve for R10: R10 = 25 25 = = 35.7 k: fSW x C7 700 kHz x 1 nF (7) The closest standard resistor is actually 35.7 kΩ therefore the fSW is: fSW = 25 25 = 700 kHz = R10 x C7 35.7 k: x 1 nF (8) The chosen components from step 2 are: 6 AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback Design Procedure www.ti.com C7 = 1 nF R10 = 35.7 k: 6.4 (9) Average LED Current Solve for R9: R9 = VSNS = ILED 100 mV = 0.1: 1A (10) Assume R1 = 12.4 kΩ and solve for R8: 30100815 ILED x R1 x R9 1A x 12.4 k: x 0.1: = = 1.0 k: 1.24V 1.24V R8 = (11) The closest standard resistor for R9 is 0.1Ω and the closest for R8 (and R7) is actually 1 kΩ therefore ILED is: ILED = 1.24V x R8 1.24V x 1.0 k: = = 1.0A 0.1: x 12.4 k: R9 x R1 (12) The chosen components from step 3 are: R9 = 0.1: R1 = 12.4 k: R8 = R7 = 1 k: 6.5 (13) Inductor Ripple Current Solve for L1: L1 = VIN x D 'iL-PP x fSW = 24V x 0.467 = 32 PH 500 mA x 700 kHz (14) The closest standard inductor is 33 µH therefore the actual ΔiL-PP is: 'iL-PP = VIN x D L1 x fSW = 24V x 0.467 = 485 mA 33 PH x 700 kHz (15) Determine minimum allowable RMS current rating: ILED §'IL-PP x D' · ¸ x 1 + 1 x ¨¨ ¸ 12 © ILED D' ¹ IL-RMS = IL-RMS = 1A x 0.533 1+ 2 1 §¨485 mA x 0.533·¸ x ¸ 12 ¨© 1A ¹ 2 IL-RMS = 1.88A (16) The chosen component from step 4 is: L1 = 33 PH 6.6 (17) Output Capacitance Solve for CO: CO = CO = ILED x D rD x 'iLED-PP x fSW 1A x 0.467 = 6.84 PF 1.95: x 50 mA x 700 kHz (18) A total value of 6.6 µF (using 3 2.2 µF X7R ceramic capacitors) is chosen therefore the actual ΔiLED-PP is: SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 7 Design Procedure www.ti.com 'iLED-PP = 'iLED-PP = ILED x D rD x CO x fSW 1A x 0.467 = 52 mA 1.95: x 6.6 PF x 700 kHz (19) Determine minimum allowable RMS current rating: DMAX ICO-RMS = ILED x 1 - DMAX 0.677 = 1.45A 1- 0.677 = 1A x (20) The chosen components from step 5 are: C6 = C17 = C19 = 2.2 PF 6.7 (21) Peak Current Limit Solve for R6: R6 = 245 mV 245 mV = = 0.049: ILIM 5A (22) The closest standard resistor is 0.05 Ω therefore ILIM is: ILIM = 245 mV 245 mV = = 4.9A R6 0.05: (23) The chosen component from step 6 is: R6 = 0.05: 6.8 (24) Loop Compensation ωP1 is approximated: ZP1 = rad 1.467 1+D = = 110k sec rD x CO 1.95: x 6.8 PF (25) ωZ1 is approximated: rD x D'2 ZZ1 = D x L1 = rad 1.95: x 0.5332 = 36k sec 0.467 x 33 PH (26) TU0 is approximated: TU0 = D' x 620V 0.533 x 620V = = 4510 (1 + D) x ILED x R6 1.467 x 1A x 0.05: (27) To ensure stability, calculate ωP2: min(ZP1, ZZ1) ZP2 = 5 x TU0 rad rad sec = = = 1.596 sec 5 x 4510 5 x 4510 ZZ1 36k (28) Solve for C8: C8 = 1 = ZP2 x 5e6: 1 = 0.13 PF rad 1.596 x 5e6: sec (29) Since PWM dimming can be evaluated with this board, a much larger compensation capacitor C8 = 1.0 µF is chosen. To attenuate switching noise, calculate ωP3: 8 AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback Design Procedure www.ti.com ZP3 = max (ZP1, ZZ1) x 10 = ZP1 x 10 rad rad x 10 = 1.1M sec sec ZP3 = 110k (30) Assume R20 = 10Ω and solve for C12: C12 = 1 = 10: x ZP3 1 10: x 1.1M rad sec = 0.091 PF (31) The chosen components from step 7 are: C8 = 1.0 PF R20 = 10: C12 = 0.1 PF 6.9 (32) Input Capacitance Solve for the minimum CIN: CIN = ILED x D 'VIN-PP x fSW = 1A x 0.467 = 6.66 PF 100 mV x 700 kHz (33) To minimize power supply interaction a 3x larger capacitance of approximately 20 µF is used, therefore the actual ΔvIN-PP is much lower. Since high voltage ceramic capacitor selection is limited, four 4.7 µF X7R capacitors are chosen. Determine minimum allowable RMS current rating: IIN-RMS = ILED x DMAX 1 - DMAX = 1A x 0.677 = 1.45A 1- 0.677 (34) The chosen components from step 8 are: C2 = C3 = C16 = C18 = 4.7 PF (35) 6.10 NFET Determine minimum Q1 voltage rating and current rating: VT-MAX = VIN-MAX + VO = 70V + 21V = 91V IT-MAX = (36) 0.677 x 1A = 2.1A 1 - 0.677 (37) A 100V NFET is chosen with a current rating of 40A due to the low RDS-ON = 50 mΩ. Determine IT-RMS and PT: ILED IT-RMS = D' x D= 1A x 0.467 = 1.28A 0.533 2 (38) 2 PT = IT-RMS x RDSON = 1.28A x 50 m: = 82 mW (39) The chosen component from step 9 is: Q1 o 40A, 100V, DPAK (40) 6.11 Diode Determine minimum D1 voltage rating and current rating: VRD-MAX = VIN-MAX + VO = 70V + 21V = 91V (41) ID-MAX = ILED = 1A (42) A 100V diode is chosen with a current rating of 12A and VD = 600 mV. Determine PD: SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 9 Design Procedure www.ti.com PD = ID x VFD = 1A x 600 mV = 600 mW (43) The chosen component from step 10 is: D1 o 12A, 100V, DPAK (44) 6.12 Input UVLO Since PWM dimming will be evaluated, a three resistor network will be used. Assume R13 = 10 kΩ and solve for R5: R5 = 1.24V x R13 1.24V x 10 k: = 1.42 k: = 10V - 1.24V VTURN-ON - 1.24V (45) The closest standard resistor is 1.43 kΩ therefore VTURN-ON is: VTURN-ON = 1.24V x (R5 + R13) R5 VTURN-ON = 1.24V x (1.43 k: + 10 k:) = 9.91V 1.43 k: (46) Solve for R4: R4 = R4 = R5 x (VHYS - 20 PA x R13) 20 PA x (R5 + R13) 1.43 k: x (2.9V - 20 PA x 10 k:) = 16.9 k: 20 PA x (1.43 k: + 10 k:) (47) The closest standard resistor is 16.9 kΩ making VHYS: VHYS = VHYS = 20 PA x R4 x (R5 + R13) + 20 PA x RUV2 R5 20 PA x 16.9 k: x (1.43 k: + 10 k:) 1.43 k: + 20 PA x 10 k: = 2.9V (48) The chosen components from step 11 are: R5 = 1.43 k: R13 = 10 k: R4 = 16.9 k: (49) 6.13 Output OVLO Solve for R18: VHYSO R18 = 20 PA = 15V = 750 k: 20 PA (50) The closest standard resistor is 750 kΩ therefore VHYSO is: VHYSO = R18 x 20 PA = 750 k: x 20 PA = 15V (51) Solve for R11: R11 = 1.24V x R18 1.24V x 750 k: = 15.8 k: = 60V - 1.24V VTURN-OFF - 1.24V (52) The closest standard resistor is 15.8 kΩ making VTURN-OFF: 10 AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback Design Procedure www.ti.com VTURN-OFF = 1.24V x (R11 + R18) R11 VTURN-OFF = 1.24V x (15.8 k: + 750 k:) = 60V 15.8 k: (53) The chosen components from step 12 are: R11 = 15.8 k: R18 = 750 k: SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback (54) AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 11 Typical Waveforms 7 www.ti.com Typical Waveforms TA = +25°C, VIN = 24V and VO = 21V. 40 0.0 20 ILED 0.0 -1.0 10 5 0 0 8 ILED (A) 0.5 VDIM (V) VSW (V) 60 ILED (A) 1.0 1.0 ILED VSW VDIM 2 Ps/DIV Figure 5. Standard Operation TP1 Switch Node Voltage (VSW) LED Current (ILED) 4 ms/DIV Figure 6. 200Hz 50% PWM Dimming TP11 Dim Voltage (VDIM) LED Current (ILED) Alternate Designs Alternate designs with the LM3429 evaluation board are possible with very few changes to the existing hardware. The evaluation board FETs and diodes are already rated higher than necessary for design flexibility. The input UVLO, output OVP, input and output capacitance can remain the same for the designs shown below. These alternate designs can be evaluated by changing only R9, R10, and L1. The table below gives the main specifications for four different designs and the corresponding values for R9, R10, and L1. PWM dimming can be evaluated with any of these designs. Table 1. Alternate Design Specification 12 Specification / Component Design 1 Design 2 Design 3 Design 4 VIN 10V - 45V 15V - 50V 20V - 55V 25V - 60V VO 14V 21V 28V 35V 700kHz fSW 600kHz 700kHz 500kHz ILED 2A 500mA 2.5A 1.25A R9 0.05Ω 0.2Ω 0.04Ω 0.08Ω R10 41.2 kΩ 35.7 kΩ 49.9 kΩ 35.7 kΩ L1 22µH 68µH 15µH 33µH AN-1985 LM3429 Buck-Boost Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA403C – July 2009 – Revised May 2013 Submit Documentation Feedback IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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