PR4101 PREMA | Alldatasheet

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Technical content

High Power LED Buck Driver The PR4101 is a LED buck driver for driving one or several high power LEDs in series. The supply voltage can be up to 40 V, with an output current of more than 1 A using an external n-channel MOSFET switching transistor. The PR4101A with additional PWM and power down input is delivered SOP14 packaged, while the PR4101B is offered SO8 packaged.

FEATURES

  • Adjustable output current of several amps
  • Supply voltage up to 40 V
  • Dimming with phase-cut dimmer
  • Brightness control with PWM (PR4101A only)
  • Output current temperature compensation
  • Delayed start possible (PR4101A only)
  • Over temperature protection
  • Frequency spreading for improved EMI
  • Low standby current of < 35 µA
  • Under voltage lockout

APPLICATIONS

  • Halogen lamp or filament bulb replacement by LEDs
  • General illumination
  • Warning lights
  • Automotive lighting
  • Indicator signs
  • LCD backlighting ABSOLUTE MAXIMUM RATINGS Parameter Min Max Units VCC, VDI (no damage) -0.3 50 [V] All other pins 14 [V] Operating Chip Temperature Range (over temperature protection) -20 125 [°C] Storage Temperature Range -55 150 [°C] Electrostatic Discharge (ESD) Protection 2 [kV] TYPICAL APPLICATION CIRCUIT Gnd Vsense PR4101 Vcc 7...40 V One or more LEDsSUB 5VHi NDRV Vcc VDI 5VLo CLEDD1 L RVsense Rsense CIN © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 1/24

PIN Configurations / PIN Descriptions Test PwrDwn 7 8 Delay PWM GND RTK Temp Vsense NDRV VDI VccSUB 5VHi 5VLo < version code> <lot code> <date code> PR4101A: Package SOP14 Topside marking: version code "PR4101" RTK GND Vsense NDRV VDI Vcc 5VHi 5VLo < version code> <lot code> <date code> PR4101B: Package SOP8 Topside marking: version code "PR4101B" Pin No. PR4101A Pin No. PR4101B Pin Name Pin Function Description 1 n.c. Test For test and internal use only 2 n.c. PwrDwn Power Down, sleep mode for min. power consumption. When connected to GND, NDRV is clamped to GND. 3 n.c. Delay Not connected: Delay Start is disabled connected to GND: Delay Start is enabled 4 n.c. PWM If VPWM < VrefPWM the buck converter is switched off. If VPWM > VrefPWM the buck converter is switched on. 5 2 GND Ground 6 2 SUB Substrate has to be connected to GND for PR4101A (internally connected to GND for PR4101B) 7 3 5VHi Internal 5V linear regulator output for high currents. Connect a capacitor of 100 nF to GND. Voltage is not for external use. 8 4 5VLo Internal 5V linear regulator output for low currents. Connect a capacitor of 100 nF to GND. Voltage is not for external use. 9 5 Vcc Supply voltage 10 6 VDI Undervoltage detection pin. If unused, connect to Vcc. For use with phase fired controllers (see application notes). 11 7 NDRV Gate connection for an external n-channel MOSFET. 12 8 VSense Feedback for controlling the output current. Connect this pin to the series resistor RVSENSE and the sense resistor RSENSE. The external MOSFET is switched off when the voltage at this pin is higher than VSENSE. 13 n.c. Temp Voltage output of the internal chip temperature sensor (over temperature protection). Please see „Electrical Characteristics“ for relationship between VTEMP and the chip temperature TCHIP. 14 1 RTK Softstart feature and temperature compensation of the output current. By connecting for example a NTC resistor from RTK to GND the sensing threshold voltage Vsense will be decreased depending on the NTC´s temperature. A capacitor CSOFT connected to GND offers a soft ramp up of the LED current. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 2/24

Electrical Characteristics

Vcc=12 VDC, Ta = 25°C, L=470 µH (unless otherwise noted) Symbol Parameter Conditions Min Typ Max Units Vcc Supply voltage 7 40 [V] VDI Undervoltage detection Start-up Shut-off 6.0 7.0 9.0 [V] [V] IsuppOFF Supply current, PwrDwn=0 V 30 [µA] IsuppON Supply current, PwrDwn=open 3.0 [mA] VNDRV Gate output voltage HIGH 3.0 3.8 [V] IOUTsource Output source current at NDRV 50 [mA] IOUTsink Output sink current at NDRV 20 [mA] fOP Operating center frequency 125 [kHz] fSP Frequency spreading 5 [%] VSENSE Threshold voltage at RSENSE Pin RTK not connected 200 [mV] tDELAY Delay start period (PR4101A only) 250 [µs] VRefPWM Threshold voltage PWM input (PR4101A only) 1000 [mV] fPWM Frequency of external PWM signal (PR4101A only) 500 [Hz] tPWM Min. pulse duration of PWM (PR4101A only) 2 [µs] VTEMP Output voltage of internal temperature sensor at pin TEMP (PR4101A only) Tchip = 100°C Tchip = 0°C 1.60 2.15 [V] [V] TOT Overtemperature protection junction temperature Shut-off Resume 125 [°C] [°C] © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 3/24

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Characteristic Performance Curves 1 x 3 W LED operated by varied Rsense and Inductances (given in the caption) CIN=470 µF, RVSENSE = 1 kΩ , CLED = 100 µF, C5VHi/Lo = 220 nF, Ta = 25°C (unless otherwise noted) 5 10 15 20 25 30 35 40 45 50 55 60 100 200 300 400 500 600 700 800 900

0.25 Ohm / 100 µH

0.25 Ohm / 680 µH

0.33 Ohm / 100 µH

0.33 Ohm / 680 µH

0.50 Ohm / 100 µH

0.50 Ohm / 680 µH

1.00 Ohm / 100 µH

1.00 Ohm / 680 µH

Supply Voltage [V] ILED Current [mA] 3 x 3.5 W LED operated in series by varied Rsense and Inductances (given in the caption) CIN=470 µF, RVSENSE = 1 kΩ , CLED = 100 µF, C5VHi/Lo = 220 nF, Ta = 25°C (unless otherwise noted) 10 15 20 25 30 35 40 45 50 55 60 100 200 300 400 500 600 700 800 900 Supply Voltage [V] ILED Current [mA] 0 10 20 30 40 50 Supply Voltage [V] Supply Current [mA] 0 10 20 30 40 50 Supply Voltage [V] Quiescent Current [µA] © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 5/24

Characteristic Performance Curves EFFICIENCIES ARE GIVEN FOR VARIED CONDITIONS USING A FIXED INDUCTANCE OF 660 µH 10 15 20 25 30 35 40 45 50 60% 70% 80% 90% 100% 3LED / 0.25 Ohm 3LED / 0.33 Ohm 3LED / 0.50 Ohm 3LED / 1.00 Ohm 1LED / 0.25 Ohm 1LED / 0.33 Ohm 1LED / 0.50 Ohm 1LED / 1.00 Ohm Supply Voltage [V] Efficiency EFFICIENCIES ARE GIVEN FOR VARIED CONDITIONS USING A FIXED INDUCTANCE OF 330 µH 10 15 20 25 30 35 40 45 50 60% 70% 80% 90% 100% 3LED / 0.20 Ohm 3LED/ 0.25 Ohm 3LED / 0.33 Ohm 3LED / 0.50 Ohm 3LED / 1.00 Ohm 1LED / 0.20 Ohm 1LED / 0.25 Ohm 1LED / 0.33 Ohm 1LED / 0.50 Ohm 1LED / 1.00 Ohm Supply Voltage [V] Efficiency EFFICIENCIES ARE GIVEN FOR VARIED CONDITIONS USING A FIXED SUPPLY VOLTAGE OF 15 V 0 100 200 300 400 500 600 700 800 900 60% 70% 80% 90% 100% 1LED / 330µH 3LED / 330µH 1LED / 660µH 3LED / 660µH LED Current [mA] Efficiency © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 6/24

Examples for varying LED applications TYPICAL APPLICATION WITH 12/24 VAC SUPPLY FOR A MINIMUM BOARD SIZE The following circuit drives one LED from a 12...24 VAC supply. This circuit uses the PR4101B in SOP8 package and is optimized for a low number of small-sized external components to have a small PCB. LED and driver are supplied from the full-wave rectified and smoothed voltage. Ripples on the supply should be small enough to avoid a period in which the voltage becomes lower than the LED forward voltage, or below the undervoltage shut-off (see specification of VDI). The undervoltage detection pin VDI is connected to Vcc. With RSENSE = 0.24 Ω as in the diagram, the LED current is approx. 850 mA. For other currents see below Selection of RSENSE. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 7/24

Examples for varying LED applications TYPICAL APPLICATION WITH 12 VDC SUPPLY The shown circuit drives 2 strings of 2 LEDs in series from a 12 VDC supply. The minimum supply voltage is given by the forward voltage of the LEDs, the DC resistance of the inductor, and the RDSon of the FET. As a rule of thumb, in most cases the supply voltage should be at least 2 V higher than the forward voltage of the LEDs. Assuming a V F of 3.5 V per LED, this means that the circuit will work with a supply of 9V and higher. As there are two strings of LEDs in parallel, the forward voltage of the LEDs must be matching to avoid an unequal current distribution. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 8/24

Examples for varying LED applications TYPICAL APPLICATION WITH 12 VAC SUPPLY The following circuit drives three LEDs in series from a 12...24 VAC supply. LED and driver are supplied from the full-wave rectified and smoothed voltage. Ideally, after the full-wave rectifier, Vcc is VAC x 1.41, which is sufficient to drive three LEDs in series from VAC = 12 V. Ripples on the supply should be small enough to avoid a period in which the voltage becomes lower than the LED forward voltage, or below the undervoltage shut-off (see specification of VDI). The undervoltage detection pin VDI is connected to Vcc. With R SENSE = (0.47/2) Ω as in the diagram, the LED current is approx. 850 mA. For other currents see below Selection of RSENSE. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 9/24

Examples for varying LED applications TYPICAL APPLICATION WITH 12 VAC SUPPLY AND PHASE CUT DIMMERS The circuit shown next allows dimming with phase-fired control by a conventional thyristor dimmer, operation with electronic dimmers and electronic transformers is also possible. The PR4101 is dimmable with leading and trailing edge phase control. In this application the undervoltage detection pin VDI is connected to the rectified, but unsmoothed AC, allowing to sense the pulse width of the phase-cut supply. In this way the converter is shut off in the phase cut out by the phase fired controller, even if the smoothed supply at Vcc holds a sufficient voltage level, and the LED brightness is dimmed in a way similar to that of a conventional filament bulb. Even without phase cutting, there is a period in which VDI falls below the undervoltage shut-off threshold, shutting the LED down in this period until the voltage reaches the startup threshold again. Therefore in the application shown the effective LED current is reduced against the circuit with VDI connected to the smoothed DC supply, e.g. at 12 VAC/50 Hz it is 68 % of the nominal brightness (theoretical value). C3/R3 serves as a filter for high frequencies, e.g. from power supplies with switching regulators, that would interfere with the regulator loop of PR4101. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 10/24

TYPICAL APPLICATION WITH 12 VAC SUPPLY AND PHASE CUT DIMMERS Supply from phase-fired SCR dimmer. Different duty cycles on VDI signal. --- Vcc --- VDI signal --- LED current (voltage at a 1Ω resistor) Measured with: Vcc = 12 VAC CLED = C4 = 100 µF C5VHi/Lo = 220 nF C3 = 2,2 nF, R3 = 100 kΩ CIN = C1 = 2000 µF L = 470 µH RSENSE = 0.25 Ω LED: 1 x 3W (Luxeon) Cutting at large phase angles reduces both the average supply voltage Vcc and also the VDI voltage. If it falls below the forward voltage of the LEDs, or below the undervoltage threshold, the circuit stops working. The right diagram shows the case at which the supply voltage and therefore also the VDI signal is close to the VDI threshold. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 11/24

A further Dimming Opportunity PWM CONTROL ( ONLY PR4101A) Brightness can also be controlled by an external PWM (pulse width modulation) signal via the PWM pin. In this way a wide dimming range can be achieved. The device will be turned off and on depending on the duty cycle of the control signal resulting in a proportional average output current. The PWM pin can be driven directly from a micro controller output or with a NPN transistor. The average output current will be ILEDAVG=ILED nom⋅D with the duty cycle D: D= TOFF TONTOFF A PWM frequency of 500 Hz, or lower is recommended, to minimize linearity errors due to the rise and fall times of the converter output. In the following, the LED mean current vs. PWM duty cycle at a PWM frequency of

500 Hz is shown for different values of Rsense:

800 0.25 Ohm

0.33 Ohm

0.50 Ohm

1.00 Ohm

PWM Duty Cycle [%] ILED Current [mA] 1 x 1 W LED; PWM @ Vcc = 40 V PWM controlled with L = 100 µH --- PWM --- LED current, voltage at a 1Ω resistor --- clock signal (test pin) Conditions: duty cycle = 50 % CIN = 470 µF CLED = 100 µF C5VHi/Lo = 220 nF Vcc = 15 V RSENSE = 0.25 Ω 1 x 3 W Luxeon LED PWM controlled with L = 330 µH Behaviour at a PWM frequency of 3000 Hz with two different inductors. The slow reaction, especially with the 330 µH inductance, causes a non-linearity in brightness vs. PWM duty cycle, limiting the recommended PWM frequencies to < 500 Hz, depending on the duty cycle range required. For operation with PWM control the inductance should be as small as possible, but on the other hand, also the LED current ripple will increase, as can be seen by comparison of the two graphs. Therefore it is important to find a compromise between current ripple, PWM frequency and duty cycle range. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 12/24

SELECTION OF THE INPUT CAPACITOR Cin The input capacitor is necessary in case of AC supply voltages to smooth the supply voltage. A value between 100 µF and 4700 µF for normal AC and of 470 µF up to 10000 µF for phase-cut supply voltages is recommended. In parallel a 100 nF capacitor should be placed close to the IC supply pins. Step-down regulators draw current from the input supply in pulses with very fast rise and fall times. The input capacitor is also required to reduce the resulting voltage ripple at the PR4101 input and to force this switching current into a tight local loop, minimizing EMI. The input capacitor must have a low impedance at the switching frequency to do this effectively, and it should have an adequate ripple current rating. SELECTION OF INDUCTOR AND CLED Selection of the inductor value depends a lot on the supply voltage, the number of connected LEDs, but also on the allowed current ripple and the desired efficiency. For a smaller LED current higher values above 660 µH should be used. In case that a minimized board size is desired inductor values around 100 µH may be selected but efficiency and LED current ripple are not optimized in this case. The saturation current of the inductors must be higher than the LED peak current. A low DC resistance of the coil avoids additional loss of efficiency. A capacitor value of CLED between 22 µF and 1000 µF in parallel to the LED is recommended to reduce the LED current ripple and avoid exceeding the LED current rating. SELECTION OF EXTERNAL MOSFET The n-channel MOSFET must have a gate threshold voltage of less than 3 V and a low ON resistance. A recommended transistor is the International Rectifier IRLL024N. To improve the behaviour of the module, long lines between the IC and the transistor should be avoided. SELECTION OF THE EXTERNAL DIODE A Schottky diode with fast recovery is needed to reduce the voltage drop. The diode must be able to carry the LED current flowing during the OFF time of the driver . The reverse voltage of the diode should be higher than the input voltage. DELAY START FEATURE (only PR4101A) A delayed start is possible by connecting the pin Delay to Gnd. Within the delay start period the output current is switched off. After the delay start period the output current rises to 100 % of the nominal current. The delay start period is fixed and cannot be changed by external components. SELECTION OF RVSENSE AND RSENSE The input V SENSE needs a series resistor RVSENSE = 1 kΩ while the LED current is defined by the selection of R SENSE. The nominal value of the current sense resistor can be calculated with the following formula: RSENSE= VSENSE ILED The value of VSENSE can be found in „Electrical Characteristics“. For example: With an LED current of 1 A and VSENSE =200 mV, RSENSE has a value of 200 mΩ. The following table gives some resistor values LED Current RSENSE 350 mA 0.571 Ω 700 mA 0.286 Ω 1000 mA 0.200 Ω © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 13/24

With an external capacitor at RTK the output current can ramp up continuously within a programmable period. The following table gives some capacitor values: Soft Start Time CSOFT 10 ms 100 nF 100 ms 1 µF 3 s 22 µF It is possible to combine temperature compensation and softstart functionality. A soft start is triggered by a reset that is initiated either by applying the supply voltage, or by starting the IC up with the PWRDWN signal. Passing the threshold at VDI does not trigger the soft start however, therefore supply by a phase-cut voltage from a dimmer does not interfere with soft start - see oscilloscope diagram. CORRESPONDING OSCILLOSCOPE IMAGES Softstart on RTK, C SOFT = 100 nF Softstart on RTK, C SOFT = 1 µF (phase-cut input voltage) --- Vcc --- PwrDwn --- LED current (voltage at a 1Ω resistor) --- clock signal (test pin) Measured with CIN = 470 µF CLED = 100 µF C5VHi/Lo = 220 nF L = 470 µH Vcc = 15 V RSENSE = 0.25 Ω 1 x 3 W Luxeon LED Supply by a phase-cut voltage from a dimmer does not interfere with soft start - see right diagram. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 14/24

TEMPERATURE COMPENSATION OF THE OUTPUT CURRENT The NTC changes the voltage at RTK, thus influencing the VSense threshold and the LED current. High brightness LEDs often need to be supplied by a temperature compensated current in order to get a stable and reliable operation also at higher temperatures. This is normally achieved by reducing the LED current proportionally from its nominal set value when the LED temperature rises above a predefined threshold. For this thermal compensation an NTC resistor at the RTK pin can be used to sense the temperature. The NTC value has to be selected according to the application requirements. For many purposes a nominal value around 470 kΩ is suitable. The relationship between the voltage at RTK and the LED current (1 x 1 W) for Rsense = 0.25 Ω is shown. The nominal RTK voltage without NTC is 200 mV OVER TEMPERATURE PROTECTION (only PR4101) An internal temperature sensor detects the chip temperature. Over temperature is detected at TOFF, then the NDRV and the 5VHi-regulators are switched off and switched on again at a chip temperature of TON. The voltage VTEMP at the pin TEMP relates to the internal chip temperature, please see „Electrical Characteristics“. FREQUENCY SPREADING To reduce the EMI of the converter the switching frequency is varied in a range around the center frequency. This decreases the EMI power density that is otherwise concentrated at a single clock frequency. OPERATION WITH INSUFFICIENT VOLTAGE In operation with several LEDs in series, it is possible that the supply voltage is higher than the undervoltage detection threshold, but insufficient to drive the programmed LED current because of the LED forward voltage. Then the desired LED current can obviously not be reached. In this case the MOSFET is permanently switched through, allowing the maximum LED current possible, but always less than the current setpoint. PWM control does not work in this mode. When the supply rises, the converter will resume normal operation. In any mode the converter can be safely switched off with the PwrDwn signal. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 15/24 0 20 40 60 80 100 120 140 160 180 200 200 400 600 800 V_RTK [mV] ILED current [mA]

For PR4101 a demoboard is available that shows the operation of the components. Here, a LED driver and several power LEDs are replacing halogen lamps. At the pins IN+ and IN- an AC voltage up to 24 V or a DC voltage from 9 V up to 35 V can be supplied. Several LEDs can be connected, the potental number depends on the input voltage. The demoboard includes a bridge rectifier, necessary capacities, an external MOS transistor, a sense resistor and an inductor. The size of the board is 35 x 35 ± 2 mm. SCHEMATIC DIAGRAM LIST OF COMPONENTS Name Value Descriptions D1 – D7 40 V / 1 A Schottky diode MBRS140 C1 100 nF /100 V Cin C3 / C5 100 nF/63 V C8 / C9 100 µF/35 V electrolytic capacitors if higher current ripples are allowed, C9 (Cled) is not needed C10 2.2 nF © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 16/24

R2 / R4 R1 / R3 1.2 Ω / 1 % 1 Ω / 1 % Rsense R5 10 Ω 10 Ω resistor as a shunt for current measurements R6 1 kΩ Rvsense R8 120 kΩ Together with C10 a low pass filter for operation with electronic transformers L1 220 µH, WE-PD Type L (Würth) IC1 PR4101A (PREMA) SO14 package T1 IRLL024N (International Rectifier) External NDMOS switch J1 Sets Rsense Solder bridge (open) Open: Iled around 350 mA* (Rsense = 0.54 Ω) Closed: Iled around 700 mA* (Rsense =0.27 Ω) J2 Activates PwrDwn Solder bridge (open) J3 Activates Delay Solder bridge (open) J4 Dimming operation Solder bridge (open), close for deactivate dimming operation * LED current can vary and depends on supply voltage and number of LEDs DEMOBOARD 1st SIDE © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 17/24

IN + / IN - Connect Vac up to 24 V or Vdc from 9 V up to 35 V LED + / A Connect the anode of the LED LED - / K Connect the cathode of the LED © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 18/24

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Delivery in die form upon request. Package D E H A A1 e b L Copl. w SOP 08L PR4101B Nom max 0.10 SOP 14L PR4101A Nom max 0.10 ALL PARTS DELIVERED, COMPLY WITH RoHS. FINISH IS PURE TIN. © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 20/24

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Information provided by PREMA is believed to be accurate and correct. However, no responsibility is assumed by PREMA for its use, nor for any infringements of patents or other rights of third parties which may result from its use. PREMA reserves the right at any time without notice to change circuitry and specifications. Life Support Policy PREMA Semiconductors products are not authorized for use as critical components in life support devices or systems without the express written approval of PREMA Semiconductor. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. PREMA Semiconductor GmbH Robert-Bosch-Str. 6

55129 Mainz Germany

Phone: +49-6131-5062-0 Fax: +49-6131-5062-220 Email: prema@prema.com Web site: www.prema.com © PREMA Semiconductor GmbH 2006-2014 I rev. 1014 Page 24/24