PAM2861CBR

A Product Line of Diodes Incorporated PAM2861 1A LED DRIVER WITH INTERNAL SWITCH Description Pin Assignments The PAM2861 is a continuous mode inductive step-down converter, Top View TSOT25 designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input supply between 6V and 40V and provides an externally adjustable output current of up to 1A. Depending upon supply voltage and external components, this can provide up to 30 watts of output power. The PAM2861 includes the output switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. Output current can be adjusted below the set value, by applying an external control signal to the VSET pin. The VSET pin will accept either a DC voltage or a PWM waveform. The soft-start time can be increased using an external capacitor from the VSET pin to ground. Applying a voltage of 0.2V or lower to the VSET pin turns the output off and switches the device into a low current standby state. Features Applications  Simple Low Parts Count  Internal 40V NDMOS Switch  1A Output Current  Single Pin On/Off and Brightness Control Using DC Voltage or PWM  Soft-Start  High Efficiency (up to 97%)  Wide Input Voltage Range: 6V to 40V  Output Shutdown  Open LED Protection  Short LED Protection  Up to 1MHz Switching Frequency  Inherent Open-Circuit LED Protection  Typical 5% Output Current Accuracy  Pb-free TSOT25 and SOT89-5 Packages PAM2861 Document number: DSxxxxx Rev. 1 - 1  Low voltage halogen replacement LEDs  Low voltage industrial lighting  LED back-side lighting  Illuminated signs 1 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Typical Applications Circuit Pin Descriptions Pin Number 1 2 Pin Name LX GND 3 VSET 4 ISENSE 5 VIN Function Drain of NDMOS switch. Ground (0V) • Multi-function On/Off and brightness control pin: • Leave floating for normal operation. • Drive to voltage below 0.2V to turn off output current • Drive with DC voltage (0.3V < VSET< 2.5V) to adjust output current from 12% to 100% of IOUTnom • Drive with PWM signal from open-collector or open-drain transistor, to adjust output current. Adjustment range 1% to 100% of IOUTnom for f < 500Hz • Connect a capacitor from this pin to ground to increase soft-start time. (Default soft-start time = 0.1ms. Additional soft-start time is approx.1.5ms/1nF) Connect resistor RS from this pin to VIN to define nominal average output current IOUTnom = 0.1/Rs Input voltage (6V to 40V). Decouple to ground with 10μF or higher X7R ceramic capacitor close to device. PAM2861 Document number: DSxxxxx Rev. 1 - 1 2 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Functional Block Diagram Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. Parameter Input Voltage Range Rating -0.3 to +40 Unit LX, ISENSE Pin Voltage VSET Pin Voltage Maximum Junction Temperature Storage Temperature Soldering Temperature -0.3 to +40 V -0.3 to +6.0 170 -65 to +170 300, 5sec °C Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Parameter Input Voltage Range Ambient Temperature Range Junction Temperature Range PAM2861 Document number: DSxxxxx Rev. 1 - 1 Rating 6 to 40 -40 to +85 -40 to +150 3 of 12 www.diodes.com Unit V °C July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Thermal Information Parameter Thermal Resistance (Junction to Ambient) Thermal Resistance (Junction to Case) Package TSOT25 SOT89-5 TSOT25 SOT89-5 Symbol θJA θJC Max 250 160 130 45 Unit °C/W Electrical Characteristics (@TA = +25°C, VIN = 16V, unless otherwise specified.) Parameter Input Voltage Symbol Test Conditions Min Typ 6 VIN 40 333 RS = 0.3Ω Output Current ILED RS = 0.1Ω 1 Shutdown Current ISD VSET Pin Grouded 20 Quiescent Current without Switching IQ VSET Pin Floating, VIN = 16V 0.6 VSENSE Measured on ISENSE Pin with Respect to VIN Mean Current Sense Threshold Voltage Sense Threshold Hysteresis Max 95 100 ISENSE Pin Input Current ISENSE VSENSE = VIN -0.1 VSET Range on VSET Pin VEN For DC Dimming A 40 µA mA 105 mV % 8 0.3 V mA ±13 VSENSE_HYS Units µA 2.5 V DC Voltage on VSET Pin to Enable VEN(ON) VEN Rising 0.25 DC Voltage on VSET Pin to Disable VEN(OFF) VEN Falling 0.2 V @ILX = 100mA 0.3 Ω LX Switch On Resistance LX Switch Leakage Current RLX V 5 ILX(LEAK) µA Soft Start Time TSS VIN = 16V, CEN = 1nF 1.5 ms Operating Frequency FLX VI = 16V, VO = 9.6V (3 LEDs) L = 47µF, ΔI = 0.25A (ILED = 1A) 233 kHz For 4% Accuracy 500 Recommended Minimum Switch ON Time TON_REC Recommended Maximum Switch Frequency FLX(MAX) Max Duty Circle Recommended Duty Cycle Range Internal Comparator Propagation Delay Over Temperature Protection Temp Protection Hysteresis Current Limit Note: Ns 1.0 MHz 75 % 98 25 DLX % TPD (Note 1) 45 ns TOTP 150 °C 40 °C TOTP_HYS IXL(MAX) Peak Inductor Current 1.5 A 1. Parameters are not tested at production, but guaranteed by design. VSENSE: level A: 95mV to 100mV; level B: 100mV to 105mV. PAM2861 Document number: DSxxxxx Rev. 1 - 1 4 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Typical Performance Characteristics (@TA = +25°C, VIN = 16V, unless otherwise specified.) PAM2861 Document number: DSxxxxx Rev. 1 - 1 5 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Typical Performance Characteristics (cont.) (@TA = +25°C, VIN = 16V, unless otherwise specified.) PAM2861 Document number: DSxxxxx Rev. 1 - 1 6 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Typical Performance Characteristics (cont.) (@TA = +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.) PAM2861 Document number: DSxxxxx Rev. 1 - 1 7 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Application Information Setting Nominal Average Output Current with External Resistor RS The nominal average output current in the LED(s) is determined by the value of the external current sense resistor (RS) connected between VIN and ISENSE and is given by: IOUT(NOM)  0 .1 RS The table below gives values of nominal average output current for several preferred values of current setting resistor (RS) in the typical application circuit shown on page 1. Nominal Average Output Current (mA) 1000 760 667 333 RS (Ω) 0.1 0.13 0.15 0.3 The above values assume that the VSET pin is floating and at a nominal voltage of VREF (1.25V). Note that RS = 0.1Ω is the minimum allowed value of sense resistor under these conditions to maintain switch current below the specified maximum value. It is possible to use different values of RS if the VSET pin is driven from an external voltage. Capacitor Selection A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in series with the supply source impedance and lowers overall efficiency. This capacitor has to supply the relatively high peak current to the coil and smooth the current ripple on the input supply. A minimum value of 4.7µF is acceptable if the input source is close to the device, but higher values will improve performance at lower input voltages, especially when the source impedance is high. The input capacitor should be placed as close as possible to the IC. For maximum stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric are recommended. Capacitors with Y5Vdielectric are not suitable for decoupling in this application and should NOT be used. Inductor Selection Recommended inductor values for the PAM2861 are in the range 33µH to 100µH. Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which in increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range. The inductor should be mounted as close to the device as possilbe with low resistance connections to the LX and VIN pins. The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean output current. The inductor value should be chosen to maintain operating duty cycle and switch ‘on’/’off’ times within the specified limits over the supply voltage and load current range. The following equations can be used as a guide. LX Switch ‘On’ time TON  LI   VIN VLED ILED (RS  RL  RLX ) Lx Switch ‘Off’ time TOFF  LI   VLED VD ILED (RS  RL ) Where: L is the coil inductance; RL is the coil resistance; RS is the current sense resistance ILED is the required LED current; ΔI is the coil peakpeak ripple current (Internally set to 0.25 x ILED); VIN is the supply voltage; VLED is the total LED forward voltage; RLX is the switch resistance (0.3Ω nominal); VD is the diode forward voltage at the required load current PAM2861 Document number: DSxxxxx Rev. 1 - 1 8 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Application Information (cont.) Diode Selection For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode with low reverse leakage at the maximum operating voltage and temperature. They also provide better efficiency than silicon diodes, due to a combination of lower forward voltage and reduced recovery time. It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum output load current. It is very important to consider the reverse leakage of the diode when operating above +85°C. Excess leakage will increase the power dissipation in the device and if close to the load may create a thermal runaway condition. The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the LX output. If a silicon diode is used, care should be taken to ensure that the total voltage appearing on the LX pin including supply ripple, does not exceed the specified maximum value. Ordering Information Part Number PAM2861ABR PAM2861CBR Part Marking EQXYW P2861 XXXYW Package Type TSOT25 Standard Package 3000 Units/ Tape&Reel SOT89-5 1000 Units/ Tape&Reel Marking Information Top View TSOT25 PAM2861 Document number: DSxxxxx Rev. 1 - 1 9 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Package Outline Dimensions (All dimensions in mm.) TSOT25 PAM2861 Document number: DSxxxxx Rev. 1 - 1 10 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 Package Outline Dimensions (cont.) (All dimensions in mm.) SOT89-5 PAM2861 Document number: DSxxxxx Rev. 1 - 1 11 of 12 www.diodes.com July 2013 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2861 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. 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Copyright © 2013, Diodes Incorporated www.diodes.com PAM2861 Document number: DSxxxxx Rev. 1 - 1 12 of 12 www.diodes.com July 2013 © Diodes Incorporated