MIC9/93 High Frequency PWM White LED Drivers with Internal Schottky Diode and OVP General Description The MIC9 and MIC93 are high frequency, Pulse Width Modulator (PWM) boost regulators optimized for constantcurrent, white LED driver applications. Because of their constant PWM switching frequencies of.6mhz and MHz, respectively, the MIC9/93 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.5V to V input voltage range of MIC9/3 allows direct operation from - and -cell Li Ion as well as 3- to 4-cell NiCad/NiMH/Alkaline batteries. The MIC9/3 products are available in a small size mm mm 8-lead MLF package and have a junction temperature range of 4 C to +5 C. All support documentation can be found on Micrel s web site at www.micrel.com. Features.5V to V input voltage Output voltage up to 34V Internal Schottky diode.6mhz PWM operation (MIC9).MHz PWM operation (MIC93) Stable with ceramic capacitors 5V and 34V output overvoltage protection options 5mA switch current rating 95mV feedback voltage <% line and load regulation <µa shutdown current Over-temperature protection UVLO 8-lead (mm mm) MLF package 4 C to +5 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 5µH µh MIC9-5BML MIC93-5BML Li Ion µf 95mV 6.3Ω.µF 6V Li Ion µf 95mV 6.3Ω.µF 6V.6MHz PWM White LED Driver with 5V OVP MHz PWM White LED Driver with 5V OVP MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. 8 Fortune Drive San Jose, CA 953 USA tel + (48) 944-8 fax + (48) 474- http://www.micrel.com July 5 M9999-75
Ordering Information Marking Overvoltage Junction Part Number Code Protection Frequency Temp. Range Package Lead Finish MIC9-5BML A 5V.6MHz 4 C to +5 C 8-lead MLF Standard MIC9-5YML A 5V.6MHz 4 C to +5 C 8-lead MLF Pb-Free MIC9-34BML C 34V.6MHz 4 C to +5 C 8-lead MLF Standard MIC9-34YML C 34V.6MHz 4 C to +5 C 8-lead MLF Pb-Free MIC93-5BML SZA 5V MHz 4 C to +5 C 8-lead MLF Standard MIC93-5YML SZA 5V MHz 4 C to +5 C 8-lead MLF Pb-Free MIC93-34BML SZC 34V MHz 4 C to +5 C 8-lead MLF Standard MIC93-34YML SZC 34V MHz 4 C to +5 C 8-lead MLF Pb-Free Pin Configuration 8 P 7 EN 3 6 FB A 4 EP 5 NC 8-lead MLF (BML) (Top View) Fused Lead Frame Pin Description Pin Number Pin Name Pin Function Output pin and overvoltage protection (Output): Connect to the output capacitor and LEDs. Supply (Input): Input voltage. 3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator. 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 Switch node (Input): Internal power transistor collector. 4,8 Ground (Return): Ground. EP Ground (Return): Exposed backside pad. M9999-75 July, 5
Absolute Maximum Ratings () Supply Voltage ( )... V Switch Voltage (V )....3V to 34V Enable Pin Voltage (V EN )....3 to FB Voltage (V FB )... 6V Switch Current (I )... A Ambient Storage Temperature (T S )... 65 C to +5 C Schottky Reverse Voltage (V DA )... 34V ESD Rating (3)... kv Operating Ratings () Supply Voltage ( )...5V to V Output Voltage (V )... to V OVP Junction Temperature Range (T J )... 4 C to +5 C Package Thermal Impedance 8-lead MLF (θ JA )... 93 C/W Electrical Characteristics (4) T A = 5ºC, = V EN = 3.6V, V = 5V, I = ma, unless otherwise noted. Bold values indicate 4ºC T J +5ºC. Symbol Parameter Condition Min Typ Max Units Supply Voltage Range.5 V V ULVO Under Voltage Lockout.8..4 V I Quiescent Current V FB > mv, (not switching).5 5 ma I SD Shutdown Current V EN = V (5). µa V FB Feedback Voltage (±5%) 9 95 mv I FB Feedback Input Current V FB = 95mV -45 na Line Regulation (6) 3V 5V.5 % Load Regulation (6) 5mA I ma.5 % D MAX Maximum Duty Cycle 85 9 % I Switch Current Limit 75 ma V Switch Saturation Voltage I =.5A 45 mv I Switch Leakage Current V EN = V, V = V. 5 µa V EN Enable Threshold TURN ON.5 V TURN OFF.4 V I EN Enable Pin Current V EN = V 4 µa f Oscillator Frequency MIC9 MIC93 V D Schottky Forward Drop I D = 5mA.8 V I RD Schottky Leakage Current V R = 3V 4 µa V OVP Overvoltage Protection MIC9/93-5 MIC9/93-34 T J Overtemperature Threshold Shutdown Hysteresis Notes:. 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, T J (max), the junction-to-ambient thermal resistance, θ JA, and the ambient temperature, T A. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.. This device is not guaranteed to operate beyond its specified operating ratings. 3. Devices are inherently ESD sensitive. Handling precautions required. Human body model. 4. Specification for packaged product only. 5. I SD = I. 6. Guaranteed by design..4.75 3 3.6. 4 3 5.8.5 6 34 MHz MHz V V C C July 5 3 M9999-75
Typical Characteristics FB VOLTAGE (mv) 99 98 97 96 95 94 93 9 9 Feedback Voltage vs. Input Voltage 9 4 6 8 (V) SHUTDOWN CURRENT (µa) 5 4 3 Shutdown Current vs. Input Voltage 4 6 8 (V) QUIESCENT CURRENT (ma) 5 4 3 Quiescent Current vs. Input Voltage 4 6 8 (V) ITCHING FREQUENCY (MHz).4..8.6.4. Switch Frequency -4-4 6 8 IENABLE (µa) 5 45 4 35 I = V 3 E N 5 I = 4.V 5 E N IE = 3.6V N EN Pin Bias Current 5 I = 3.V E N -5 5 SCHOTTKY FORWARD CURRENT (ma) 7 6 5 4 3 45 55 Schottky Forward Voltage Drop 65 75 85 95 5 5 SCHOTTKY FORWARD VOLTAGE DROP (mv) SCHOTTKY LEAKAGE CURRENT (µa).5.5.5 Schottky Reverse Leakage Current V R = 5V V R = 6V V R = V 3 4 5 6 7 8 9 SATURATION VOLTAGE (mv) 55 5 45 4 35 Saturation Voltage I S W = 5mA 3-4 4 8 CURRENT LIMIT (ma) 9 85 8 75 7 Current Limit 65 V =.5V IN 6-4 4 8 ITCHING FREQUENCY (MHz).6..8.4 Switch Frequency -4 4 8 SATURATION VOLTAGE (mv) 6 5 4 3 Switch Saturation Voltage vs. Current =.5V = 5V 3 4 5 I (ma) M9999-75 4 July, 5
Functional Diagram FB EN OVP* V REF 95mV g m PWM Generator S.6MHz or.mhz Oscillator Ramp Generator MIC9/93 Block Diagram Functional Description The MIC9/93 is a constant frequency, PWM current mode boost regulator. The block diagram is shown above. The MIC9/93 is composed of an oscillator, slope compensation ramp generator, current amplifier, g m error amplifier, PWM generator, 5mA bipolar output transistor, and Schottky rectifier diode. The oscillator generates a.6mhz clock for the MIC9 and a.mhz clock for the MIC93. 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. The g m 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 g m 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: I LED = 95mv 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. July 5 5 M9999-75
External Component Selection The MIC9/93 can be used across a wide rage of applica- tions. The table below shows recommended inductor and output capacitor values for various series-led applications: Series LEDs L Manufacturer Min C Manufacturer µh LQH3CNK (Murata).µF 85ZD5KAT(AVX) NLC4533T-K(TDK) GRM4X5R5K(Murata) 5µH LQH3CN5K (Murata) µf 85ZD5KAT(AVX) NLC4533T-5K(TDK) GRM4X5R5K(Murata) µh LQH3CNK (Murata).µF 85ZD4KAT(AVX) NLC4533T-K(TDK) GRM4X5R4K(Murata) 6.8µH LQH3CN6R8K (Murata).µF 85ZD5KAT(AVX) NLC4533T-6R8K(TDK) GRM4X5R5K(Murata) 4.7µH LQH3CN4R7K (Murata).µF 85ZD4KAT(AVX) NLC4533T-4R7K(TDK) GRM4X5R4K(Murata) 3 µh LQH43MNK (Murata).µF 85YD5MAT(AVX) NLC4533T-K(TDK) GRM4X5R5K6(Murata) 5µH LQH43MN 5K (Murata) µf 85YD5MAT(AVX) NLC4533T-5K(TDK) GRM4X5R5K6(Murata) µh LQH43MN K (Murata).µF 85YD4MAT(AVX) NLC4533T-K(TDK) GRM4X5R4K6(Murata) 6.8µH LQH43MN 6R8K (Murata).µF 85YD4MAT(AVX) NLC4533T-6R8K(TDK) GRM4X5R4K6(Murata) 4.7µH LQH43MN 4R7K (Murata).7µF 85YD74MAT(AVX) NLC4533T-4R7K(TDK) GRM4X5R4K6(Murata) 4 µh LQH43MNK (Murata) µf 85YD5MAT(AVX) NLC4533T-K(TDK) GRM4X5R5K5(Murata) 5µH LQH43MN 5K (Murata) µf 85YD5MAT(AVX) NLC4533T-5K(TDK) GRM4X5R5K5(Murata) µh LQH43MN K (Murata).7µF 85YD74MAT(AVX) NLC4533T-K(TDK) 6.8µH LQH43MN 6R8K (Murata).7µF 85YD74MAT(AVX) NLC4533T-6R8K(TDK) 4.7µH LQH43MN 4R7K (Murata).7µF 85YD74MAT(AVX) NLC4533T-4R7K(TDK) 5, 6 µh LQH43MNK (Murata).µF 853D4MAT(AVX) NLC4533T-K(TDK) GRM4X5R4K5(Murata) 5µH LQH43MN 5K (Murata).µF 853D4MAT(AVX) NLC4533T-5K(TDK) GRM4X5R4K5(Murata) µh LQH43MN K (Murata).7µF 853D74MAT(AVX) NLC4533T-K(TDK) 6.8µH LQH43MN 6R8K (Murata).7µF 853D74MAT(AVX) NLC4533T-6R8K(TDK) 4.7µH LQH43MN 4R7K (Murata).7µF 853D74MAT(AVX) NLC4533T-4R7K(TDK) 7, 8 µh LQH43MNK (Murata).µF 853D4MAT(AVX) NLC4533T-K(TDK) GRM4X5R4K5(Murata) 5µH LQH43MN 5K (Murata).µF 853D4MAT(AVX) NLC4533T-5K(TDK) GRM4X5R4K5(Murata) µh LQH43MN K (Murata).7µF 853D74MAT(AVX) NLC4533T-K(TDK) 6.8µH LQH43MN 6R8K (Murata).7µF 853D74MAT(AVX) NLC4533T-6R8K(TDK) 4.7µH LQH43MN 4R7K (Murata).7µF 853D74MAT(AVX) NLC4533T-4R7K(TDK) M9999-75 6 July, 5
Dimming Control There are two techniques for dimming control. One is PWM dimming and the other is continuous dimming.. PWM dimming control is implemented by applying a PWM signal on EN pin as shown in Figure. The MIC9/93 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 Hz and khz.. Continuous dimming control is implemented by applying a DC control voltage to the FB pin of the MIC9/93 through a series resistor as shown in Figure. 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 (>khz) 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 MIC9/93 to switch with a high duty-cycle resulting in output overvoltage. This may cause the pin voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components. To ensure the highest level of protection, the MIC9/93 has three product options in the 8-lead MLF with overvoltage protection, OVP. The extra pins of the 8-leadMLF package allow the use of a dedicated OVP monitor with options for 5V 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 V, so a 5V 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. PWM Figure. PWM Dimming Method Figure 3. MLF Package OVP Circuit 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, C ss, provides overdrive to the FB pin at start-up, resulting in gradual increase of switch duty cycle and limited inrush current. 5.k 49.9k C SS pf DC Equivalent Figure. Continuous Dimming R k Figure 4. Soft-Start Circuit July 5 7 M9999-75
Functional Characteristics 6-Series LED Circuit with External Soft-Start 6-Series LED Circuit without External Soft-Start PUT VOL AGE INPUT CURRENT ENABLE (ma/div) (V/div) L = µh C IN = µf C =.µf = 3.6V I = ma 6 LEDs C SS = pf R = kω PUT VOL AGE INPUT CURRENT ENABLE (ma/div) (V/div) L = µh C IN = µf C =.µf = 3.6V I = ma 6 LEDs TIME (µs/div.) TIME (µs/div.) M9999-75 8 July, 5
Package Information 8-lead MLF (BML) MICREL INC. 8 FORTUNE DRIVE SAN JOSE, CA 953 USA TEL + (48) 944-8 FAX + (48) 474- WEB http://www.micrel.com This 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. 4 July 5 9 M9999-75