LDM24-xx-xxx Miniature, Wide Input Constant Current DC/DC LED Drivers Electrical Specifications Specifications typical @ +25°C, nominal input voltage & rated output current, unless otherwise noted. Specifications subject to change without notice. Key Features: Input Parameter • Constant Current Output Input Voltage Range • Wide 7V to 30V Input Range Maximum Input Voltage Input Filter • 95% Efficiency Output • Miniature MiniDIP Case Parameter • 500 mA to 700 mA Output Output Voltage Range Output Current • Meets EN 60950 Output Current Accuracy Output Power • 1.6 MHrs MTBF Efficiency • Digital & Analog Dimming! Capacitive Load Operating Frequency Ripple & Noise (20 MHz) Temperature Coefficient Thermal Impedance Output Short Circuit Environmental Parameter Conditions Typ. 24 Max. 30.0 40.0 Units VDC VDC Min. Typ. 2 VIN = 30V See Model Selection Guide See Model Selection Guide See Model Selection Guide See Model Selection Guide Max. 28 Units VDC 47 450 µF kHz ±0.05 %/ºC ºC/W Max. +71 +105 +125 Units 95 260 % ºC 0.5 Sec Internal Capacitor Conditions 70 See Model Selection Guide Natural Convection +40 Regulated At Rated Output Current Conditions Ambient Case Operating Temperature Range MicroPower Direct 292 Page Street Suite D Stoughton, MA 02072 USA T: (781) 344-8226 F: (781) 344-8481 E: [email protected] W: www.micropowerdirect.com Min. 7.0 Storage Temperature Range Cooling Humidity Lead Temperature (Solder) Physical Case Size Case Material Weight Remote On/Off Control Parameter DC/DC On DC/DC Off Remote Pin Drive Current Quiescent Input Current (Shutdown Mode) PWM Dimming Parameter Operation Frequency Switch On Time Switch Off Time Output Current Adjust Range Analog Dimming Parameter Input Voltage Range Output Current Adjustment Control Voltage Range Limits Drive Current EMC Compliance EMI/RFI Electrostatic Discharge (ESD) RF Field Susceptibility Electrical Fast Transients/Bursts On Mains EMS Immunity Reliability Specifications Parameter MTBF Min. -40 Typ. +25 -40 Free Air Convection RH, Non-condensing 1.5 mm From Case For 10 Sec ºC ºC 0.80 x 0.40 x 0.27 Inches (20.32 x 10.16 x 6.88 mm) Non-Conductive Black Plastic (UL94-V0) 0.092 Oz (2.6g) Conditions Min. VADJ = 1.25V VIN = 30V Conditions Recommended Maximum Min. Typ. Max. Units Open or 0.3V < VADJ <1.25V VADJ <0.15V 1 mA 25 µA Typ. 200 200 0 Conditions At VADJ Input (Pin 2) On Off VADJ = 1.25V Min. 0.0 25 0.30 0.0 Radiated/Conducted Class A Class A Class A Conditions MIL HDBK 217F, 25ºC, Gnd Benign Max. 1.0 100 Typ. Max. 1.25 100 1.25 0.15 1.0 Units kHz nS nS % Units VDC % VDC mA EN 55015 (CISPR22) IEC/EN 61000-4-2, -6, -8 IEC/EN 61000-4-3 IEC/EN 61000-4-4 EN61547 Min. 1.6 Typ. www.micropowerdirect.com Max. Units MHours www.micropowerdirect.com Model Selection Guide Input Model Number LDM24-14-500 LDM24-17-600 LDM24-20-700 Output Voltage (VDC) Range 7.0 - 30.0 7.0 - 30.0 7.0 - 30.0 Voltage (VDC) Range 2.0 - 28.0 2.0 - 28.0 2.0 - 28.0 Notes: 1. A reversed power source could damage the unit. 2. No connection should be made between input ground and the output. 3. These are step-down devices, the maximum output open voltage is equal to the input voltage. Current Max (mA) 300 500 700 Accuracy (%) ±10 ±10 ±10 Maximum Power Ripple & Noise (W) (mV P-P, Max) 14 17 20 Efficiency Package (%, Typ) 450 450 450 95 95 95 14 -Pin MiniDIP 14 -Pin MiniDIP 14 -Pin MiniDIP 4. The VADJ input should be left open if not used. Grounding VADJ will shut the unit down. Connecting VADJ to VIN may damage the unit. 5. Exceeding the specified maximum output power could cause damage to the unit. Typical Connection: DC/DC Input Connection Notes: To comply with EN61000-4-5, a TVS should be installed before the input filter components. A 3.0SMCJ24A or SMCJ24A is recommended. The TVS max clamping voltage (@max peak pulse current VC) must be ⬉40V. This will prevent any surge from exceeding the maximum input of the driver (40 VDC). Exceeding the maximum input rating could damage the driver. The filter shown (C1, C2, C3 and L1) will help to meet conducted emission requirements. With the addition of the filter, the unit should meet the levels of EN 55015. Typical Connection: AC/DC Input Connection Notes: This is a distributed (or two-stage) AC connection. In this configuration, the AC line in (85 to 264 VAC) is connected to the MPM-20S-24EPB, a compact 20W AC/DC power supply. The MPM-20S-24EPB provides a tightly regulated 24 VDC output at 833 mA. The 24 VDC output powers the LED driver. The two stage approach can simplify the safety approval process (most AC/DC power supplies on the market are approved to EN 60950) and may increase design flexibility. Besides the output voltage/current ratings, other specifications to consider when selecting the input AC/DC supply might include input range, case size, efficiency, EMI ratings and operating temperature range. Note: The output current adjustment circuit shown in both connection diagrams is discussed on page 4. 292 Page Street Ste D Stoughton, MA 02072 • TEL: (781) 344-8226 • FAX: (781) 344-8481 • E-Mail: [email protected] PWM Output Current Control www.micropowerdirect.com An LED operates at its maximum efficiency when operated at the rated drive current specified by the manufacturer. Operating an LED at lower than its rated forward current not only decreases the system efficiency; but may cause color (or wavelength) shifting. In illumination applications, this could cause visible changes to lighting. A preferred method is using pulse width modulation (PWM). As shown at left, the output current is adjusted by applying a PWM signal to the VADJ input. By varying the signal duty cycle the average output current is adjusted up or down. To avoid visible flicker, the PWM signal should be greater than 200 Hz. For duty cycles (DPWM) between 0.1 and 1, the output current is derived by the formula: PWM Control Signals INOM = IMAX X DPWM The VADJ input may be driven via an open collector transistor (as shown). The diode and resistor suppress high amplitude negative spikes that may be caused by the drain-source capacitance of the transistor. Negative spikes on the control input of the unit could cause errors in output current or erratic operation. The VADJ input can also be driven by the open drain output of a microcontroller. Again, any high amplitude negative spikes that may be caused by the drainsource capacitance of the FET must be supressed. PWM Dimming Application A simple method of achieving digital (or PWM) dimming is by using a 555 timer again. The formulas for calculating the frequency and duty cycle are included to apply a series of pulses to the VADJ input, as illustrated above. Again, we are in the MPD application note “Driving LEDs”. powering the LED driver with the MPM-20S-24EPB AC power supply. The diodes (D1 and D2) allow duty cycles below 50% to be set. Diode D1 The 555 operates over a supply voltage range of 4.5 VDC to 18VDC. Here it is bypasses R2 while C6 is charging. Diode D2 is optional (but recommended), connected to the 15 VDC output of the SR7805 switching regulator (also driven essentially blocking R2 during the charge period. Theoretically, this circuit will by the MPM-20S-24EPB). Care should be taken to minimize ripple at the VCC allow for duty cycles over a range of approximately 5% to 95%. If manual input. Excess ripple could cause timing errors. adjustment is desired, a potentiometer may be substituted for R2 (with some adjustment of the circuit). The timer is connected for astable (free run) operation. The frequency is set by R1, R2 and C6. The timing capacitor (C6) charges through R1 and D2. When The size of C6 is generally not critical, but it should be as low leakage as posit reaches the level of 2/3 VCC, the discharge pin (pin 7) goes low and C6 will sible. In order to avoid excessive current flow through the internal discharge discharge through D1 and R2 to the internal discharge transistor. When the C6 transistor, it is recommended that R1 be at least 5 k⍀. voltage drops to 1/3 VCC, the discharge pin goes high and C6 begins to charge MicroPower Direct • 292 Page Street Ste D Stoughton, MA 02072 • TEL: (781) 344-8226 • FAX: (781) 344-8481 • E-Mail: [email protected] www.micropowerdirect.com Analog Output Current Control (VCNT = 5V) The output current of the unit can also be set by adjusting the voltage level on the VADJ input to a value between 0.3V to 1.25V (IOUT will vary from 25% to 100% of rated output current). Care must be taken not to exceed 1.25V on this input, or the driver may be damaged. The simple analog circuit at left uses a 15W DC/DC converter operating off a 12 VDC input line, to keep the input to the LED driver at 24 VDC. The POL regulator, driven off the same input line maintains the control voltage (for the VADJ input) at 5 VDC. The resister network of R1 and R2 can now be used to set the output current level of the LED driver. This level is equal to: VADJ = R2 X V CTRL R1 + R 2 In the second circuit, the input DC/DC has been changed to a higher power model, and the POL regulator is replaced by the shunt regulator (D1) circuit connected in parallel with the resistor network. The regulator will maintain the voltage across R2 and R3 at 2.5 VDC, insuring that the 1.25 VDC limit on the VADJ pin will not be exceeded. Analog Output Current Control (5 - 30 VIN) When using the analog control input, the nominal output current is equal to: INOM = IMAX x VADJ 1.25 The VADJ input should be left open if not used. Grounding VADJ will shut the unit down. Connecting VADJ to directly to +VIN may damage the unit. Mechanical Dimensions Pin Connections Pin Function 1 -VIN -DC Supply 2 VADJ PWM, On/Off 7 -LED LED Cathode Connection 8 +LED LED Anode Connection 14 +VIN +DC Supply Get a full explanation of the circuits in this datasheet and more in “Driving LEDs”. Available free at the MPD website MicroPower Direct We Power Your Success - For Less! 292 Page Street Ste D Stoughton, MA 02072 • TEL: (781) 344-8226 • Notes: • All dimensions are typical in inches (mm) • Tolerance x.xx = ±0.02 (±0.50) • Pin 1 is marked by a “dot” or indentation on the top of the unit FAX: (781) 344-8481 • E-Mail: [email protected]