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MIC2292/93
Micrel
MIC2292/93
High Frequency PWM White LED Drivers with Internal Schottky Diode and OVP
General Description
The MIC2292 and MIC2293 are high frequency, Pulse Width Modulator (PWM) boost regulators optimized for constantcurrent, white LED driver applications. Because of their constant PWM switching frequencies of 1.6MHz and 2MHz, respectively, the MIC2292/93 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 2.5V to 10V input voltage range of MIC2292/3 allows direct operation from 1- and 2-cell Li Ion as well as 3- to 4-cell NiCad/NiMH/Alkaline batteries. The MIC2292/3 products are available in a small size 2mm x 2mm 8-lead MLFTM package and have a junction temperature range of -40C to +125C. All support documentation can be found on Micrel's web site at www.micrel.com.
Features
* * * * * * * * * * * * * * * 2.5V to 10V input voltage Output voltage up to 34V Internal Schottky diode 1.6MHz PWM operation (MIC2292) 2.0MHz PWM operation (MIC2293) Stable with ceramic capacitors 15V and 34V output overvoltage protection options 500mA switch current rating 95mV feedback voltage <1% line and load regulation <1A shutdown current Over-temperature protection UVLO 8-lead (2mm x 2mm) MLFTMpackage -40C to +125C 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
15H
10H
MIC2292-15BML VIN Li Ion 1F EN GND SW OUT FB 95mV 6.3 0.22F 16V Li Ion 1F
MIC2293-15BML VIN SW OUT EN GND FB 95mV 6.3 0.22F 16V
1.6MHz PWM White LED Driver with 15V OVP
2MHz PWM White LED Driver with 15V OVP
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc. Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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Ordering Information
Part Number MIC2292-15BML MIC2292-15YML MIC2292-34BML MIC2292-34YML MIC2293-15BML MIC2293-15YML MIC2293-34BML MIC2293-34YML Marking Code SWA SWA SWC SWC SZA SZA SZC SZC Overvoltage Protection 15V 15V 34V 34V 15V 15V 34V 34V Frequency 1.6MHz 1.6MHz 1.6MHz 1.6MHz 2MHz 2MHz 2MHz 2MHz Junction Temp. Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM 8-lead MLFTM Lead Finish Standard Pb-Free Standard Pb-Free Standard Pb-Free Standard Pb-Free
Pin Configuration
OUT VIN EN GND
1 2 3 4
8 7 6
GND SW FB NC
EP
5
8-lead MLFTM (BML) (Top View) Fused Lead Frame
Pin Description
Pin Number 1 2 3 5 6 7 4,8 EP Pin Name OUT VIN EN NC FB SW GND GND Pin Function Output pin and overvoltage protection (Output): Connect to the output capacitor and LEDs. Supply (Input): Input voltage. Enable (Input): Logic high enables regulator. Logic low shuts down regulator. No connect (no internal connection to die). 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. Switch node (Input): Internal power transistor collector. Ground (Return): Ground. Ground (Return): Exposed backside pad.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ..................................................... 12V Switch Voltage (VSW) ..................................... -0.3V to 34V Enable Pin Voltage (VEN) ................................... -0.3 to VIN FB Voltage (VFB) ............................................................. 6V Switch Current (ISW) ....................................................... 2A Ambient Storage Temperature (TS) ......... -65C to +150C Schottky Reverse Voltage (VDA) ................................... 34V ESD Rating(3) ................................................................ 2kV
Operating Ratings(2)
Supply Voltage (VIN) ........................................ 2.5V to 10V Output Voltage (VOUT) ..................................... VIN to VOVP Junction Temperature Range (TJ) ........... -40C to +125C Package Thermal Impedance 8-lead MLFTM (JA) .............................................. 93C/W
Electrical Characteristics(4)
TA = 25C, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 20mA, unless otherwise noted. Bold values indicate -40C TJ +125C. Symbol VIN VUVLO IVIN ISD VFB IFB Parameter Supply Voltage Range Under Voltage Lockout Quiescent Current Shutdown Current Feedback Voltage Feedback Input Current Line Regulation Load Regulation DMAX ISW VSW ISW VEN IEN fSW VD IRD VOVP TJ
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, JA, 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. 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. ISD = IVIN. 6. Guaranteed by design.
Condition
Min 2.5 1.8
Typ
Max 10
Units V V mA A mV nA % % % mA mV A V V A MHz MHz V A V V C C
2.1 2.5 0.1
2.4 5 1 100 1 2
VFB > 200mV, (not switching) VEN = 0V(5) 90 (5%) VFB = 95mV 3V VIN 5V 5mA IOUT 20mA 85
95 -450 0.5 0.5 90 750
Maximum Duty Cycle Switch Current Limit Switch Saturation Voltage Switch Leakage Current Enable Threshold Enable Pin Current Oscillator Frequency Schottky Forward Drop Schottky Leakage Current Overvoltage Protection Overtemperature Threshold Shutdown ISW = 0.5A VEN = 0V, VSW = 10V TURN ON TURN OFF VEN = 10V MIC2292 MIC2293 ID = 150mA VR = 30V MIC2292/93-15 MIC2292/93-34 Hysteresis
450 0.01 1.5 0.4 20 1.4 1.75 1.6 2.0 0.8 40 1.8 2.25 1 4 13 30 14 32 150 10 16 34 5
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Typical Characteristics
Feedback Voltage vs. Input Voltage
100 99 98 97 96 95 94 93 92 91 90 0 2 4 6 VIN (V) 8 10 12
SHUTDOWN CURRENT (A)
Shutdown Current vs. Input Voltage
5 4 3 2 1 0
5
Quiescent Current vs. Input Voltage
QUIESCENT CURRENT (mA)
FB VOLTAGE (mV)
4 3 2 1 0
0
2
4
6 VIN (V)
8
10
12
0
2
4
6 VIN (V)
8
10
12
SWITCHING FREQUENCY (MHz)
1.4 1.2
IENABLE (A)
SCHOTTKY FORWARD CURRENT (mA)
Switch Frequency vs. Temperature
EN Pin Bias Current vs. Temperature
50 45 40 35 30 I EN = 10V 25 20 15 IEN = 4.2V = 3.6V EN 10 5 I = 3.0V 0 EN 0 50 -50 TEMPERATURE (C) I
Schottky Forward Voltage Drop
700 600 500 400 300 200 100
1 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
1050
SCHOTTKY FORWARD VOLTAGE DROP (mV)
SCHOTTKY LEAKAGE CURRENT (A)
Schottky Reverse Leakage Current
2.5 SATURATION VOLTAGE (mV) 2 1.5 1 0.5 VR = 10V 0 30 40 50 60 70 80 90 100 TEMPERATURE (C) VR = 25V 550 500 450 400 350 300 -40
Saturation Voltage vs. Temperature
900
Current Limit vs. Temperature
850 800 750 700 650 600 -40 VIN = 2.5V 0 40 80 TEMPERATURE (C) 120
VR = 16V
ISW = 500mA 0 40 80 TEMPERATURE (C) 120
Switch Frequency vs. Temperature
SWITCHING FREQUENCY (MHz)
Switch Saturation Voltage vs. Current
600 SATURATION VOLTAGE (mV) 500 400 300 200 100 0 0 100 200 300 ISW (mA) 400 500 VIN = 5V VIN = 2.5V
2 1.6 1.2 0.8 0.4 0 -40
0 40 80 TEMPERATURE (C)
120
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CURRENT LIMIT (mA)
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1150
450
550
650
750
850
950
100
0
MIC2292/93
Micrel
Functional Diagram
VIN
FB
OVP*
EN
OVP* SW gm VREF 95mV 1.6MHz or 2.0MHz Oscillator *OVP available on MLFTM package option only PWM Generator
Ramp Generator
GND
MIC2292/93 Block Diagram
Functional Description
The MIC2292/93 is a constant frequency, PWM current mode boost regulator. The block diagram is shown above. The MIC2292/93 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 MIC2292 and a 2.0MHz clock for the MIC2293. 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 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:
95mv
ILED =
RFB
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. 5
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tions. The table below shows recommended inductor and output capacitor values for various series-LED applications:
External Component Selection
The MIC2292/93 can be used across a wide rage of applicaSeries LEDs 2 L 22H 15H 10H 6.8H 4.7H 3 22H 15H 10H 6.8H 4.7H 4 22H 15H 10H 6.8H 4.7H 5, 6 22H 15H 10H 6.8H 4.7H 7, 8 22H 15H 10H 6.8H 4.7H Manufacturer
Min COUT 2.2F 1F 0.22F 0.22F 0.22F 2.2F 1F 0.22F 0.22F 0.27F 1F 1F 0.27F 0.27F 0.27F 0.22F 0.22F 0.27F 0.27F 0.27F 0.22F 0.22F 0.27F 0.27F 0.27F
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)
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)
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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 MIC2292/93 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 100Hz and 10kHz. 2. Continuous dimming control is implemented by applying a DC control voltage to the FB pin of the MIC2292/93 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.
VIN EN GND VIN SW OUT PWM EN GND FB
Micrel
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 MIC2292/93 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 MIC2292/93 has three product options in the 8-lead MLFTMwith overvoltage protection, OVP. The extra pins of the 8-leadMLFTM 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
SW OUT FB
Figure 3. MLFTM 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, Css, provides overdrive to the FB pin at start-up, resulting in gradual increase of switch duty cycle and limited inrush current.
VIN
5.11k 49.9k
Figure 1. PWM Dimming Method
VIN
VIN
SW OUT
EN GND
FB
CSS
2200pF
VIN
DC Equivalent
SW OUT
Figure 2. Continuous Dimming
EN GND
FB R 10k
Figure 4. Soft-Start Circuit
Functional Characteristics
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6-Series LED Circuit with External Soft-Start
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)
L = 10H CIN = 1F COUT = 0.22F VIN = 3.6V IOUT = 20mA 6 LEDs CSS = 2200pF R = 10k TIME (100s/div.)
L = 10H CIN = 1F COUT = 0.22F VIN = 3.6V IOUT = 20mA 6 LEDs
TIME (100s/div.)
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Package Information
8-lead MLFTM (BML)
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 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 at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2004 Micrel, Incorporated.
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