MIC2292/93C High Frequency PWM White LED Drivers with Internal Schottky Diode and OVP General Description Features The MIC2292C and MIC2293C are high frequency, Pulse Width Modulator (PWM) boost regulators optimized for constant-current, white LED driver applications. Because of their constant PWM switching frequencies of 1.6MHz and 2MHz, respectively, the MIC2292/93C can use the smallest external components, allowing designers to avoid sensitive IF bands in their RF applications. The products feature an internal Schottky diode and two levels of output overvoltage protection allowing a small size and efficient DC/DC solution that requires only four external components. The 2.5V to 10V input voltage range of MIC2292/3C allows direct operation from 1- and 2-cell Li Ion as well as 3- to 4cell NiCad/NiMH/Alkaline batteries. The MIC2292/3C products are available in a small size 8-pin 2mm × 2mm MLF® package and have a junction temperature range of –40°C to +125°C. Data sheets and support documentation can be found on Micrel’s web site at www.micrel.com. • • • • • • • • • • • • • • • 2.5V to 10V input voltage Output voltage up to 34V Internal Schottky diode 1.6MHz PWM operation (MIC2292C) 2.0MHz PWM operation (MIC2293C) Stable with ceramic capacitors 15V and 34V output overvoltage protection options 500mA switch current rating 95mV feedback voltage <1% line and load regulation <1µA shutdown current Over-temperature protection UVLO 8-pin 2mm × 2mm MLF® package –40°C to +125°C junction temperature range Applications • White LED driver for backlighting: – Cell phones – PDAs – GPS systems – Digital cameras – MP3 players – IP phones • Constant current power supplies Typical Application 15µH 10µH MIC2293C-15BML MIC2292C-15BML VIN Li Ion 1µF VIN SW OUT FB EN 95mV 0.22µF 16V Li Ion 1µF SW OUT FB EN 95mV 0.22µF 16V GND GND 1.6MHz PWM White LED Driver with 15V OVP 2MHz PWM White LED Driver with 15V OVP MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com September 2006 1 M9999-090706 Micrel, Inc. MIC2292/93C Ordering Information Marking Code Part Number Overoltage Protection Junction Temp. Range Package 15V –40°C to +125°C 8-Pin 2mm x 2mm MLF® –40°C to +125°C 8-Pin 2mm x 2mm MLF ® Pb-Free 8-Pin 2mm x 2mm MLF ® Standard ® MIC2292C-15BML MIC2292C-15YML 15V MIC2292C-34BML 34V –40°C to +125°C Lead Finish Standard MIC2292C-34YML 34V –40°C to +125°C 8-Pin 2mm x 2mm MLF MIC2293C-15BML 15V –40°C to +125°C 8-Pin 2mm x 2mm MLF® Standard MIC2293C-15YML 15V –40°C to +125°C 8-Pin 2mm x 2mm MLF® Pb-Free ® MIC2293C-34BML 34V –40°C to +125°C 8-Pin 2mm x 2mm MLF MIC2293C-34YML 34V –40°C to +125°C 8-Pin 2mm x 2mm MLF® Pb-Free Standard Pb-Free Pin Configuration Denotes Pb-Free OUT 1 8 PGND VIN 2 7 SW EN 3 6 FB AGND 4 5 NC EP ??? Denotes MIC2292/93C ® 8-Pin MLF (ML) (Top View) Fused Lead Frame Pin Description Pin Number Pin Name 1 OUT Output Pin and Overvoltage Protection (Output): Connect to the output capacitor and LEDs. 2 VIN Supply (Input): Input Voltage. 3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator. 4 AGND 5 NC No connect (no internal connection to die). 6 FB Feedback (Input): Output voltage sense node. Connect the cathode of the LED to this pin. A resistor from this pin to ground sets the LED current. 7 SW Switch node (Input): Internal power transistor collector. 8 PGND EP GND September 2006 Pin Name Analog ground. Power ground. Ground (Return): Exposed backside pad. 2 M9999-090706 Micrel, Inc. MIC2292/93C Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) .......................................................12V Switch Voltage (VSW)....................................... –0.3V to 34V Enable Pin Voltage (VEN)................................... –0.3V to VIN FB Voltage (VFB)...............................................................6V Switch Current (ISW) .........................................................2A Ambient Storage Temperature (Ts) ...........–65°C to +150°C Schottky Reverse Voltage (VDA).....................................34V EDS Rating(3) .................................................................. 2kV Supply Voltage (VIN)........................................ 2.5V to +10V Output Voltage (VIN) ............................................ VIN to VOVP Junction Temperature (TJ) ........................ –40°C to +125°C Package Thermal Resistance 2mm x 2mm MLF® (θJA).....................................93°C/W Electrical Characteristics(4) TA = 25°C, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 20mA, unless otherwise noted. Bold values indicate –40°C< TJ < +125°C. Symbol Parameter Condition Min VIN Supply Voltage Range 2.5 VUVLO Under Voltage Lockout 1.8 Typ 2.1 Max Units 10 V 2.4 V IVIN Quiescent Current VFB > 200mV, (not switching) 2.5 5 mA ISD Shutdown Current VEN = 0V(5) 0.1 1 µA VFB Feedback Voltage (±10%) 95 105 mV IFB 85 Feedback Input Current VFB = 95mV –450 nA Line Regulation(6) 3V ≤ VIN ≤ 5V 0.5 % 5mA ≤ IOUT ≤ 20mA 0.5 % 90 % Load Regulation (6) DMAX Maximum Duty Cycle ISW Switch Current Limit 750 mA VSW Switch Saturation Voltage ISW = 0.5A 450 mV ISW Switch Leakage Current VEN = 0V, VSW = 10V 0.01 VEN Enable Threshold TURN ON TURN OFF 85 IEN Enable Pin Current VEN = 10V fSW Oscillator Frequency MIC2292C MIC2293C VD Schottky Forward Drop ID = 150mA IRD Schottky Leakage Current VR = 30V VOVP Overvoltage Protection MIC2292/93C-15 MIC2292/93C-34 TJ Overtemperature Threshold Shutdown 5 µA 0.4 V V 20 40 µA 1.6 2.0 1.8 2.25 MHz MHz 0.8 1 V 4 µA 14 32 16.5 37 V V 1.5 1.4 1.75 11.4 27 150 10 Hysteresis °C °C Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model. 4. Specification for packaged product only. 5. ISD = IVIN. 6. Guaranteed by design September 2006 3 M9999-090706 Micrel, Inc. MIC2292/93C Typical Characteristics 95 94 93 92 91 8 10 0 12 0 2 4 Switch Frequency vs. Temperature 50 45 40 1.2 IENABLE (µA) 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Schottky Reverse Leakage Current 2 VR = 25V 1.5 1 VR = 16V 0.5 VR = 10V 0 30 2 40 50 60 70 80 90 100 TEMPERATURE (°C) Switch Frequency vs. Temperature 1.2 0.8 0.4 0 40 80 TEMPERATURE (°C) September 2006 0 2 4 120 EN Pin Bias Current vs. Temperature 100 700 8 10 12 500 400 300 200 100 0 SCHOTTKY FORWARD VOLTAGE DROP (mV) 900 500 450 400 350 IS W = 500mA 0 40 80 TEMPERATURE (°C) Schottky Forward Voltage Drop 600 Saturation Voltage vs. Temperature 300 -40 6 VIN (V) I = 3.6V EN 10 5 I = 3.0V EN 0 -50 0 50 TEMPERATURE (°C) 600 1.6 0 -40 0 12 35 I = 10V 30 E N 25 20 I = 4.2V 15 E N 550 SATURATION VOLTAGE (mV) 2.5 10 CURRENT LIMIT (mA) 1.4 8 VIN (V) SATURATION VOLTAGE (mV) SWITCHING FREQUENCY (MHz) SCHOTTKY LEAKAGE CURRENT (µA) SWITCHING FREQUENCY (MHz) VIN (V) 6 750 6 1 650 4 2 550 2 1 3 450 0 2 SCHOTTKY FORWARD CURRENT (mA) 90 3 4 1150 96 4 1050 97 950 98 Quiescent Current vs. Input Current 5 QUIESCENT CURRENT (mA) 5 SHUTDOWN CURRENT (µA) FB VOLTAGE (mV) 100 99 Shutdown Voltage vs. Input Voltage 850 Feedback Voltage vs. Input Voltage 120 Current Limit vs. Temperature 850 800 750 700 650 VIN = 2.5V 600 -40 0 40 80 TEMPERATURE (°C) 120 Switch Saturation Voltage vs. Current 500 400 VIN = 2.5V 300 VIN = 5V 200 100 0 0 100 200 300 ISW (mA) 4 400 500 M9999-090706 Micrel, Inc. MIC2292/93C Functional Characteristics September 2006 6-Series LED Circuit without External Soft-Start OUTPUT VOLTAGE INPUT CURRENT ENABLE (200mA/div) (2V/div) OUTPUT VOLTAGE INPUT CURRENT ENABLE (200mA/div) (2V/div) 6-Series LED Circuit with External Soft-Start L = 10µH CIN = 1µF COUT = 0.22µF VIN = 3.6V IOUT = 20mA 6 LEDs CSS = 2200pF 5 L = 10µH CIN = 1µF COUT = 0.22µF VIN = 3.6V IOUT = 20mA 6 LEDs M9999-090706 Micrel, Inc. MIC2292/93C Functional Diagram VIN FB EN OUT OVP SW PWM Generator gm VREF 95mV S 1.6MHz or 2.0MHz Oscillator GND Ramp Generator MIC2292/93C Block Diagram The gm error amplifier measures the LED current through the external sense resistor and amplifies the error between the detected signal and the 95mV reference voltage. The output of the gm error amplifier provides the voltage-loop signal that is fed to the other input of the PWM generator. When the current-loop signal exceeds the voltage-loop signal, the PWM generator turns off the bipolar output transistor. The next clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control. The LED is set by the feedback resistor: Functional Description The MIC2292/93C is a constant frequency, PWM current mode boost regulator. The block diagram is shown above. The MIC2292/93C is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, PWM generator, 500mA bipolar output transistor, and Schottky rectifier diode. The oscillator generates a 1.6MHz clock for the MIC2292C and a 2.0MHz clock for the MIC2293C. The clocks' two functions are to trigger the PWM generator that turns on the output transistor and to reset the slope compensation ramp generator. The current amplifier is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. The output of the current amplifier is summed with the output of the slope compensation ramp generator. This summed current-loop signal is fed to one of the inputs of the PWM generator. September 2006 ILED = 95mW R FB The Enable pin shuts down the output switching and disables control circuitry to reduce input current to leakage levels. Enable pin input current is zero at zero volts. 6 M9999-090706 Micrel, Inc. MIC2292/93C inductor and output capacitor values for various seriesLED applications. External Component Selection The MIC2292/93C can be used across a wide rage of applications. The table below shows recommended Series LEDs 2 L 22µH 15µH 10µH 6.8µH 4.7µH 3 22µH 15µH 10µH 6.8µH 4.7µH 4 22µH 15µH 10µH 6.8µH 4.7µH 5, 6 22µH 15µH 10µH 6.8µH 4.7µH 7, 8 22µH 15µH 10µH 6.8µH 4.7µH September 2006 Manufacturer LQH32CN220K21 (Murata) NLC453232T-220K(TDK) LQH32CN150K21 (Murata) NLC453232T-150K(TDK) LQH32CN100K21 (Murata) NLC453232T-100K(TDK) LQH32CN6R8K21 (Murata) NLC453232T-6R8K(TDK) LQH32CN4R7K21 (Murata) NLC453232T-4R7K(TDK) LQH43MN220K21 (Murata) NLC453232T-220K(TDK) LQH43MN 150K21 (Murata) NLC453232T-150K(TDK) LQH43MN 100K21 (Murata) NLC453232T-100K(TDK) LQH43MN 6R8K21 (Murata) NLC453232T-6R8K(TDK) LQH43MN 4R7K21 (Murata) NLC453232T-4R7K(TDK) LQH43MN220K21 (Murata) NLC453232T-220K(TDK) LQH43MN 150K21 (Murata) NLC453232T-150K(TDK) LQH43MN 100K21 (Murata) NLC453232T-100K(TDK) LQH43MN 6R8K21 (Murata) NLC453232T-6R8K(TDK) LQH43MN 4R7K21 (Murata) NLC453232T-4R7K(TDK) LQH43MN220K21 (Murata) NLC453232T-220K(TDK) LQH43MN 150K21 (Murata) NLC453232T-150K(TDK) LQH43MN 100K21 (Murata) NLC453232T-100K(TDK) LQH43MN 6R8K21 (Murata) NLC453232T-6R8K(TDK) LQH43MN 4R7K21 (Murata) NLC453232T-4R7K(TDK) LQH43MN220K21 (Murata) NLC453232T-220K(TDK) LQH43MN 150K21 (Murata) NLC453232T-150K(TDK) LQH43MN 100K21 (Murata) NLC453232T-100K(TDK) LQH43MN 6R8K21 (Murata) NLC453232T-6R8K(TDK) LQH43MN 4R7K21 (Murata) NLC453232T-4R7K(TDK) 7 Min COUT 2.2µF 1µF 0.22µF 0.22µF 0.22µF 2.2µF 1µF 0.22µF 0.22µF 0.27µF 1µF 1µF 0.27µF 0.27µF 0.27µF 0.22µF 0.22µF 0.27µF 0.27µF 0.27µF 0.22µF 0.22µF 0.27µF 0.27µF 0.27µF Manufacturer 0805ZD225KAT(AVX) GRM40X5R225K10(Murata) 0805ZD105KAT(AVX) GRM40X5R105K10(Murata) 0805ZD224KAT(AVX) GRM40X5R224K10(Murata) 0805ZD225KAT(AVX) GRM40X5R225K10(Murata) 0805ZD224KAT(AVX) GRM40X5R224K10(Murata) 0805YD225MAT(AVX) GRM40X5R225K16(Murata) 0805YD105MAT(AVX) GRM40X5R105K16(Murata) 0805YD224MAT(AVX) GRM40X5R224K16(Murata) 0805YD224MAT(AVX) GRM40X5R224K16(Murata) 0805YD274MAT(AVX) GRM40X5R224K16(Murata) 0805YD105MAT(AVX) GRM40X5R105K25(Murata) 0805YD105MAT(AVX) GRM40X5R105K25(Murata) 0805YD274MAT(AVX) GRM40X5R274K25(Murata) 0805YD274MAT(AVX) GRM40X5R274K25(Murata) 0805YD274MAT(AVX) GRM40X5R274K25(Murata) 08053D224MAT(AVX) GRM40X5R224K25(Murata) 08053D224MAT(AVX) GRM40X5R224K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) 08053D224MAT(AVX) GRM40X5R224K25(Murata) 08053D224MAT(AVX) GRM40X5R224K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) 08053D274MAT(AVX) GRM40X5R274K25(Murata) M9999-090706 Micrel, Inc. MIC2292/93C Dimming Control There are two techniques for dimming control. One is PWM dimming, and the other is continuous dimming. 1. PWM dimming control is implemented by applying a PWM signal on EN pin as shown in Figure 1. The MIC2292/93C is turned on and off by the PWM signal. With this method, the LEDs operate with either zero or full current. The average LED current is increased proportionally to the duty-cycle of the PWM signal. This technique has high-efficiency because the IC and the LEDs consume no current during the off cycle of the PWM signal. Typical frequency should be between 100Hz and 10kHz. 2. Continuous dimming control is implemented by applying a DC control voltage to the FB pin of the MIC2292/93C through a series resistor as shown in Figure 2. The LED current is decreased proportionally with the amplitude of the control voltage. The LED intensity (current) can be dynamically varied applying a DC voltage to the FB pin. The DC voltage can come from a DAC signal or a filtered PWM signal. The advantage of this approach is that a high frequency PWM signal (>10kHz) can be used to control LED intensity. Open-Circuit Protection If the LEDs are disconnected from the circuit, or in case an LED fails open, the sense resistor will pull the FB pin to ground. This will cause the MIC2292/93C to switch with a high duty-cycle resulting in output overvoltage. This may cause the SW pin voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components. To ensure the highest level of protection, the MIC2292/93C has three product options in the 8-pin MLF® with overvoltage protection, OVP. The extra pins of the 8-pin MLF® package allow the use of a dedicated OVP monitor with options for 15V or 34V (see Figure 3). The reason for the three OVP levels is to let users choose the suitable level of OVP for their application. For example, a 3-LED application would typically see an output voltage of no more than 12V, so a 15V OVP option would offer a suitable level of protection. This allows the user to select the output diode and capacitor with the lowest voltage ratings, and accordingly, smallest size and lowest cost. The OVP will clamp the output voltage to within the specified limits. VIN VIN VIN SW OUT FB EN GND VIN SW OUT EN PWM Figure 3. MLF® Package OVP Circuit FB Start-Up and Inrush Current During start-up, inrush current of approximately double the nominal current flows to set up the inductor current and the voltage on the output capacitor. If the inrush current needs to be limited, a soft-start circuit similar to Figure 4 could be implemented. The soft-start capacitor, Css, provides over-drive to the FB pin at start-up, resulting in gradual increase of switch duty cycle and limited inrush current. GND Figure 1. PWM Dimming Method VIN VIN VIN SW CSS 2200pF OUT FB EN GND 5.11k VIN 49.9k SW OUT EN DC Equivalent GND FB R 10k Figure 2. Continuous Dimming Figure 4. One of Soft-Start Circuit September 2006 8 M9999-090706 Micrel, Inc. MIC2292/93C Package Information 8-Pin MLF® (ML) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2006 Micrel, Incorporated. September 2006 9 M9999-090706